[Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Vladimir Sementsov-Ogievskiy]

Hi all!

Here is new parameter qiov_offset for io path, to avoid
a lot of places with same pattern of creating local_qiov or hd_qiov
variables.

These series also includes my
"[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
with some changes [described in 01 and 03 emails]

Vladimir Sementsov-Ogievskiy (12):
  util/iov: introduce qemu_iovec_init_extended
  util/iov: improve qemu_iovec_is_zero
  block/io: refactor padding
  block: define .*_part io handlers in BlockDriver
  block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
  block/io: bdrv_co_do_copy_on_readv: lazy allocation
  block/io: bdrv_aligned_preadv: use and support qiov_offset
  block/io: bdrv_aligned_pwritev: use and support qiov_offset
  block/io: introduce bdrv_co_p{read,write}v_part
  block/qcow2: refactor qcow2_co_preadv to use buffer-based io
  block/qcow2: implement .bdrv_co_preadv_part
  block/qcow2: implement .bdrv_co_pwritev(_compressed)_part

 block/qcow2.h             |   1 +
 include/block/block_int.h |  21 ++
 include/qemu/iov.h        |  10 +-
 block/backup.c            |   2 +-
 block/io.c                | 532 ++++++++++++++++++++++----------------
 block/qcow2-cluster.c     |  14 +-
 block/qcow2.c             | 131 +++++-----
 qemu-img.c                |   4 +-
 util/iov.c                | 153 +++++++++--
 9 files changed, 559 insertions(+), 309 deletions(-)

-- 
2.18.0

[Qemu-devel] [PATCH v2 01/12] util/iov: introduce qemu_iovec_init_extended

[Vladimir Sementsov-Ogievskiy]

Introduce new initialization API, to create requests with padding. Will
be used in the following patch. New API uses qemu_iovec_init_buf if
resulting io vector has only one element, to avoid extra allocations.
So, we need to update qemu_iovec_destroy to support destroying such
QIOVs.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 include/qemu/iov.h |   7 +++
 util/iov.c         | 112 +++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 114 insertions(+), 5 deletions(-)

diff --git a/include/qemu/iov.h b/include/qemu/iov.h
index 48b45987b7..f3787a0cf7 100644
--- a/include/qemu/iov.h
+++ b/include/qemu/iov.h
@@ -199,6 +199,13 @@ static inline void *qemu_iovec_buf(QEMUIOVector *qiov)
 
 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);
 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov);
+void qemu_iovec_init_extended(
+        QEMUIOVector *qiov,
+        void *head_buf, size_t head_len,
+        QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,
+        void *tail_buf, size_t tail_len);
+void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
+                           size_t offset, size_t len);
 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);
 void qemu_iovec_concat(QEMUIOVector *dst,
                        QEMUIOVector *src, size_t soffset, size_t sbytes);
diff --git a/util/iov.c b/util/iov.c
index 74e6ca8ed7..39b6e31494 100644
--- a/util/iov.c
+++ b/util/iov.c
@@ -353,6 +353,103 @@ void qemu_iovec_concat(QEMUIOVector *dst,
     qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
 }
 
+/*
+ * qiov_find_iov
+ *
+ * Return pointer to iovec structure, where byte at @offset in original vector
+ * @iov exactly is.
+ * Set @remaining_offset to be offset inside that iovec to the same byte.
+ */
+static struct iovec *iov_skip_offset(struct iovec *iov, size_t offset,
+                                     size_t *remaining_offset)
+{
+    while (offset > 0 && offset >= iov->iov_len) {
+        offset -= iov->iov_len;
+        iov++;
+    }
+    *remaining_offset = offset;
+
+    return iov;
+}
+
+/*
+ * qiov_slice
+ *
+ * Find subarray of iovec's, containing requested range. @head would
+ * be offset in first iov (returned by the function), @tail would be
+ * count of extra bytes in last iovec (returned iov + @niov - 1).
+ */
+static struct iovec *qiov_slice(QEMUIOVector *qiov,
+                                size_t offset, size_t len,
+                                size_t *head, size_t *tail, int *niov)
+{
+    struct iovec *iov, *end_iov;
+
+    assert(offset + len <= qiov->size);
+
+    iov = iov_skip_offset(qiov->iov, offset, head);
+    end_iov = iov_skip_offset(iov, *head + len, tail);
+
+    if (*tail > 0) {
+        assert(*tail < end_iov->iov_len);
+        *tail = end_iov->iov_len - *tail;
+        end_iov++;
+    }
+
+    *niov = end_iov - iov;
+
+    return iov;
+}
+
+/*
+ * Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov,
+ * and @tail_buf buffer into new qiov.
+ */
+void qemu_iovec_init_extended(
+        QEMUIOVector *qiov,
+        void *head_buf, size_t head_len,
+        QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,
+        void *tail_buf, size_t tail_len)
+{
+    size_t mid_head, mid_tail;
+    int total_niov, mid_niov;
+    struct iovec *p, *mid_iov;
+
+    if (mid_len) {
+        mid_iov = qiov_slice(mid_qiov, mid_offset, mid_len,
+                             &mid_head, &mid_tail, &mid_niov);
+    }
+
+    total_niov = !!head_len + mid_niov + !!tail_len;
+    if (total_niov == 1) {
+        qemu_iovec_init_buf(qiov, NULL, 0);
+        p = &qiov->local_iov;
+    } else {
+        qiov->niov = qiov->nalloc = total_niov;
+        qiov->size = head_len + mid_len + tail_len;
+        p = qiov->iov = g_new(struct iovec, qiov->niov);
+    }
+
+    if (head_len) {
+        p->iov_base = head_buf;
+        p->iov_len = head_len;
+        p++;
+    }
+
+    if (mid_len) {
+        memcpy(p, mid_iov, mid_niov * sizeof(*p));
+        p[0].iov_base = (uint8_t *)p[0].iov_base + mid_head;
+        p[0].iov_len -= mid_head;
+        p[mid_niov - 1].iov_len -= mid_tail;
+        p += mid_niov;
+    }
+
+    if (tail_len) {
+        p->iov_base = tail_buf;
+        p->iov_len = tail_len;
+    }
+}
+
 /*
  * Check if the contents of the iovecs are all zero
  */
@@ -374,14 +471,19 @@ bool qemu_iovec_is_zero(QEMUIOVector *qiov)
     return true;
 }
 
+void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
+                           size_t offset, size_t len)
+{
+    qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0);
+}
+
 void qemu_iovec_destroy(QEMUIOVector *qiov)
 {
-    assert(qiov->nalloc != -1);
+    if (qiov->nalloc != -1) {
+        g_free(qiov->iov);
+    }
 
-    qemu_iovec_reset(qiov);
-    g_free(qiov->iov);
-    qiov->nalloc = 0;
-    qiov->iov = NULL;
+    memset(qiov, 0, sizeof(*qiov));
 }
 
 void qemu_iovec_reset(QEMUIOVector *qiov)
-- 
2.18.0

[Qemu-devel] [PATCH v2 02/12] util/iov: improve qemu_iovec_is_zero

[Vladimir Sementsov-Ogievskiy]

We'll need to check a part of qiov soon, so implement it now.

Optimization with align down to 4 * sizeof(long) is dropped due to:
1. It is strange: it aligns length of the buffer, but where is a
   guarantee that buffer pointer is aligned itself?
2. buffer_is_zero() is a better place for optimizations and it has
   them.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 include/qemu/iov.h |  2 +-
 block/io.c         |  2 +-
 util/iov.c         | 31 +++++++++++++++++++------------
 3 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/include/qemu/iov.h b/include/qemu/iov.h
index f3787a0cf7..29957c8a72 100644
--- a/include/qemu/iov.h
+++ b/include/qemu/iov.h
@@ -212,7 +212,7 @@ void qemu_iovec_concat(QEMUIOVector *dst,
 size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
                              struct iovec *src_iov, unsigned int src_cnt,
                              size_t soffset, size_t sbytes);
-bool qemu_iovec_is_zero(QEMUIOVector *qiov);
+bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t qiov_offeset, size_t bytes);
 void qemu_iovec_destroy(QEMUIOVector *qiov);
 void qemu_iovec_reset(QEMUIOVector *qiov);
 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
diff --git a/block/io.c b/block/io.c
index 3134a60a48..d02fded3b1 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1651,7 +1651,7 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
 
     if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF &&
         !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
-        qemu_iovec_is_zero(qiov)) {
+        qemu_iovec_is_zero(qiov, 0, qiov->size)) {
         flags |= BDRV_REQ_ZERO_WRITE;
         if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
             flags |= BDRV_REQ_MAY_UNMAP;
diff --git a/util/iov.c b/util/iov.c
index 39b6e31494..d988a533ce 100644
--- a/util/iov.c
+++ b/util/iov.c
@@ -451,23 +451,30 @@ void qemu_iovec_init_extended(
 }
 
 /*
- * Check if the contents of the iovecs are all zero
+ * Check if the contents of subrange of qiov data is all zeroes.
  */
-bool qemu_iovec_is_zero(QEMUIOVector *qiov)
+bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t offset, size_t bytes)
 {
-    int i;
-    for (i = 0; i < qiov->niov; i++) {
-        size_t offs = QEMU_ALIGN_DOWN(qiov->iov[i].iov_len, 4 * sizeof(long));
-        uint8_t *ptr = qiov->iov[i].iov_base;
-        if (offs && !buffer_is_zero(qiov->iov[i].iov_base, offs)) {
+    struct iovec *iov;
+    size_t current_offset;
+
+    assert(offset + bytes <= qiov->size);
+
+    iov = iov_skip_offset(qiov->iov, offset, &current_offset);
+
+    while (bytes) {
+        uint8_t *base = (uint8_t *)iov->iov_base + current_offset;
+        size_t len = MIN(iov->iov_len - current_offset, bytes);
+
+        if (!buffer_is_zero(base, len)) {
             return false;
         }
-        for (; offs < qiov->iov[i].iov_len; offs++) {
-            if (ptr[offs]) {
-                return false;
-            }
-        }
+
+        current_offset = 0;
+        bytes -= len;
+        iov++;
     }
+
     return true;
 }
 
-- 
2.18.0

[Qemu-devel] [PATCH v2 03/12] block/io: refactor padding

[Vladimir Sementsov-Ogievskiy]

We have similar padding code in bdrv_co_pwritev,
bdrv_co_do_pwrite_zeroes and bdrv_co_preadv. Let's combine and unify
it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 355 ++++++++++++++++++++++++++++-------------------------
 1 file changed, 190 insertions(+), 165 deletions(-)

diff --git a/block/io.c b/block/io.c
index d02fded3b1..ddd5902dc1 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1344,28 +1344,167 @@ out:
 }
 
 /*
- * Handle a read request in coroutine context
+ * Request padding
+ *
+ *  |<---- align ----->|                     |<----- align ---->|
+ *  |<- head ->|<------------- bytes ------------->|<-- tail -->|
+ *  |          |       |                     |     |            |
+ * -*----------$-------*-------- ... --------*-----$------------*---
+ *  |          |       |                     |     |            |
+ *  |          offset  |                     |     end          |
+ *  ALIGN_DOWN(offset) ALIGN_UP(offset)      ALIGN_DOWN(end)   ALIGN_UP(end)
+ *  [buf   ... )                             [tail_buf          )
+ *
+ * @buf is an aligned allocation needed to store @head and @tail paddings. @head
+ * is placed at the beginning of @buf and @tail at the @end.
+ *
+ * @tail_buf is a pointer to sub-buffer, corresponding to align-sized chunk
+ * around tail, if tail exists.
+ *
+ * @merge_reads is true for small requests,
+ * if @buf_len == @head + bytes + @tail. In this case it is possible that both
+ * head and tail exist but @buf_len == align and @tail_buf == @buf.
  */
+typedef struct BdrvRequestPadding {
+    uint8_t *buf;
+    size_t buf_len;
+    uint8_t *tail_buf;
+    size_t head;
+    size_t tail;
+    bool merge_reads;
+    QEMUIOVector local_qiov;
+} BdrvRequestPadding;
+
+static bool bdrv_init_padding(BlockDriverState *bs,
+                              int64_t offset, int64_t bytes,
+                              BdrvRequestPadding *pad)
+{
+    uint64_t align = bs->bl.request_alignment;
+    size_t sum;
+
+    memset(pad, 0, sizeof(*pad));
+
+    pad->head = offset & (align - 1);
+    pad->tail = ((offset + bytes) & (align - 1));
+    if (pad->tail) {
+        pad->tail = align - pad->tail;
+    }
+
+    if ((!pad->head && !pad->tail) || !bytes) {
+        return false;
+    }
+
+    sum = pad->head + bytes + pad->tail;
+    pad->buf_len = (sum > align && pad->head && pad->tail) ? 2 * align : align;
+    pad->buf = qemu_blockalign(bs, pad->buf_len);
+    pad->merge_reads = sum == pad->buf_len;
+    if (pad->tail) {
+        pad->tail_buf = pad->buf + pad->buf_len - align;
+    }
+
+    return true;
+}
+
+static int bdrv_padding_rmw_read(BdrvChild *child,
+                                 BdrvTrackedRequest *req,
+                                 BdrvRequestPadding *pad,
+                                 bool zero_middle)
+{
+    QEMUIOVector local_qiov;
+    BlockDriverState *bs = child->bs;
+    uint64_t align = bs->bl.request_alignment;
+    int ret;
+
+    assert(req->serialising && pad->buf);
+
+    if (pad->head || pad->merge_reads) {
+        uint64_t bytes = pad->merge_reads ? pad->buf_len : align;
+
+        qemu_iovec_init_buf(&local_qiov, pad->buf, bytes);
+
+        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
+        ret = bdrv_aligned_preadv(child, req, req->overlap_offset, bytes,
+                                  align, &local_qiov, 0);
+        if (ret < 0) {
+            return ret;
+        }
+        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
+
+        if (pad->merge_reads) {
+            goto zero_mem;
+        }
+    }
+
+    if (pad->tail) {
+        qemu_iovec_init_buf(&local_qiov, pad->tail_buf, align);
+
+        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
+        ret = bdrv_aligned_preadv(
+                child, req,
+                req->overlap_offset + req->overlap_bytes - align,
+                align, align, &local_qiov, 0);
+        if (ret < 0) {
+            return ret;
+        }
+        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
+    }
+
+zero_mem:
+    if (zero_middle) {
+        memset(pad->buf + pad->head, 0, pad->buf_len - pad->head - pad->tail);
+    }
+
+    return 0;
+}
+
+static void bdrv_padding_destroy(BdrvRequestPadding *pad)
+{
+    if (pad->buf) {
+        qemu_vfree(pad->buf);
+        qemu_iovec_destroy(&pad->local_qiov);
+    }
+}
+
+/*
+ * bdrv_pad_request
+ *
+ * Exchange request parameters with padded request if needed. Don't include RMW
+ * read of padding, bdrv_padding_rmw_read() should be called separately if
+ * needed.
+ *
+ * All parameters except @bs are in-out: they represent original request at
+ * function call and padded (if padding needed) at function finish.
+ *
+ * Function always succeeds.
+ */
+static bool bdrv_pad_request(BlockDriverState *bs, QEMUIOVector **qiov,
+                             int64_t *offset, unsigned int *bytes,
+                             BdrvRequestPadding *pad)
+{
+    if (!bdrv_init_padding(bs, *offset, *bytes, pad)) {
+        return false;
+    }
+
+    qemu_iovec_init_extended(&pad->local_qiov, pad->buf, pad->head,
+                             *qiov, 0, *bytes,
+                             pad->buf + pad->buf_len - pad->tail, pad->tail);
+    *bytes += pad->head + pad->tail;
+    *offset -= pad->head;
+    *qiov = &pad->local_qiov;
+
+    return true;
+}
+
 int coroutine_fn bdrv_co_preadv(BdrvChild *child,
     int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
     BdrvRequestFlags flags)
 {
     BlockDriverState *bs = child->bs;
-    BlockDriver *drv = bs->drv;
     BdrvTrackedRequest req;
-
-    uint64_t align = bs->bl.request_alignment;
-    uint8_t *head_buf = NULL;
-    uint8_t *tail_buf = NULL;
-    QEMUIOVector local_qiov;
-    bool use_local_qiov = false;
+    BdrvRequestPadding pad;
     int ret;
 
-    trace_bdrv_co_preadv(child->bs, offset, bytes, flags);
-
-    if (!drv) {
-        return -ENOMEDIUM;
-    }
+    trace_bdrv_co_preadv(bs, offset, bytes, flags);
 
     ret = bdrv_check_byte_request(bs, offset, bytes);
     if (ret < 0) {
@@ -1379,43 +1518,16 @@ int coroutine_fn bdrv_co_preadv(BdrvChild *child,
         flags |= BDRV_REQ_COPY_ON_READ;
     }
 
-    /* Align read if necessary by padding qiov */
-    if (offset & (align - 1)) {
-        head_buf = qemu_blockalign(bs, align);
-        qemu_iovec_init(&local_qiov, qiov->niov + 2);
-        qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
-        qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
-        use_local_qiov = true;
-
-        bytes += offset & (align - 1);
-        offset = offset & ~(align - 1);
-    }
-
-    if ((offset + bytes) & (align - 1)) {
-        if (!use_local_qiov) {
-            qemu_iovec_init(&local_qiov, qiov->niov + 1);
-            qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
-            use_local_qiov = true;
-        }
-        tail_buf = qemu_blockalign(bs, align);
-        qemu_iovec_add(&local_qiov, tail_buf,
-                       align - ((offset + bytes) & (align - 1)));
-
-        bytes = ROUND_UP(bytes, align);
-    }
+    bdrv_pad_request(bs, &qiov, &offset, &bytes, &pad);
 
     tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ);
-    ret = bdrv_aligned_preadv(child, &req, offset, bytes, align,
-                              use_local_qiov ? &local_qiov : qiov,
-                              flags);
+    ret = bdrv_aligned_preadv(child, &req, offset, bytes,
+                              bs->bl.request_alignment,
+                              qiov, flags);
     tracked_request_end(&req);
     bdrv_dec_in_flight(bs);
 
-    if (use_local_qiov) {
-        qemu_iovec_destroy(&local_qiov);
-        qemu_vfree(head_buf);
-        qemu_vfree(tail_buf);
-    }
+    bdrv_padding_destroy(&pad);
 
     return ret;
 }
@@ -1711,44 +1823,34 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
                                                 BdrvTrackedRequest *req)
 {
     BlockDriverState *bs = child->bs;
-    uint8_t *buf = NULL;
     QEMUIOVector local_qiov;
     uint64_t align = bs->bl.request_alignment;
-    unsigned int head_padding_bytes, tail_padding_bytes;
     int ret = 0;
+    bool padding;
+    BdrvRequestPadding pad;
 
-    head_padding_bytes = offset & (align - 1);
-    tail_padding_bytes = (align - (offset + bytes)) & (align - 1);
-
-
-    assert(flags & BDRV_REQ_ZERO_WRITE);
-    if (head_padding_bytes || tail_padding_bytes) {
-        buf = qemu_blockalign(bs, align);
-        qemu_iovec_init_buf(&local_qiov, buf, align);
-    }
-    if (head_padding_bytes) {
-        uint64_t zero_bytes = MIN(bytes, align - head_padding_bytes);
-
-        /* RMW the unaligned part before head. */
+    padding = bdrv_init_padding(bs, offset, bytes, &pad);
+    if (padding) {
         mark_request_serialising(req, align);
         wait_serialising_requests(req);
-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
-        ret = bdrv_aligned_preadv(child, req, offset & ~(align - 1), align,
-                                  align, &local_qiov, 0);
-        if (ret < 0) {
-            goto fail;
-        }
-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
 
-        memset(buf + head_padding_bytes, 0, zero_bytes);
-        ret = bdrv_aligned_pwritev(child, req, offset & ~(align - 1), align,
-                                   align, &local_qiov,
-                                   flags & ~BDRV_REQ_ZERO_WRITE);
-        if (ret < 0) {
-            goto fail;
+        bdrv_padding_rmw_read(child, req, &pad, true);
+
+        if (pad.head || pad.merge_reads) {
+            int64_t aligned_offset = offset & ~(align - 1);
+            int64_t write_bytes = pad.merge_reads ? pad.buf_len : align;
+
+            qemu_iovec_init_buf(&local_qiov, pad.buf, write_bytes);
+            ret = bdrv_aligned_pwritev(child, req, aligned_offset, write_bytes,
+                                       align, &local_qiov,
+                                       flags & ~BDRV_REQ_ZERO_WRITE);
+            if (ret < 0 || pad.merge_reads) {
+                /* Error or all work is done */
+                goto out;
+            }
+            offset += write_bytes - pad.head;
+            bytes -= write_bytes - pad.head;
         }
-        offset += zero_bytes;
-        bytes -= zero_bytes;
     }
 
     assert(!bytes || (offset & (align - 1)) == 0);
@@ -1758,7 +1860,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
         ret = bdrv_aligned_pwritev(child, req, offset, aligned_bytes, align,
                                    NULL, flags);
         if (ret < 0) {
-            goto fail;
+            goto out;
         }
         bytes -= aligned_bytes;
         offset += aligned_bytes;
@@ -1766,26 +1868,17 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
 
     assert(!bytes || (offset & (align - 1)) == 0);
     if (bytes) {
-        assert(align == tail_padding_bytes + bytes);
-        /* RMW the unaligned part after tail. */
-        mark_request_serialising(req, align);
-        wait_serialising_requests(req);
-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
-        ret = bdrv_aligned_preadv(child, req, offset, align,
-                                  align, &local_qiov, 0);
-        if (ret < 0) {
-            goto fail;
-        }
-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
+        assert(align == pad.tail + bytes);
 
-        memset(buf, 0, bytes);
+        qemu_iovec_init_buf(&local_qiov, pad.tail_buf, align);
         ret = bdrv_aligned_pwritev(child, req, offset, align, align,
                                    &local_qiov, flags & ~BDRV_REQ_ZERO_WRITE);
     }
-fail:
-    qemu_vfree(buf);
-    return ret;
 
+out:
+    bdrv_padding_destroy(&pad);
+
+    return ret;
 }
 
 /*
@@ -1798,10 +1891,7 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
     BlockDriverState *bs = child->bs;
     BdrvTrackedRequest req;
     uint64_t align = bs->bl.request_alignment;
-    uint8_t *head_buf = NULL;
-    uint8_t *tail_buf = NULL;
-    QEMUIOVector local_qiov;
-    bool use_local_qiov = false;
+    BdrvRequestPadding pad;
     int ret;
 
     trace_bdrv_co_pwritev(child->bs, offset, bytes, flags);
@@ -1828,86 +1918,21 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
         goto out;
     }
 
-    if (offset & (align - 1)) {
-        QEMUIOVector head_qiov;
-
+    if (bdrv_pad_request(bs, &qiov, &offset, &bytes, &pad)) {
         mark_request_serialising(&req, align);
         wait_serialising_requests(&req);
-
-        head_buf = qemu_blockalign(bs, align);
-        qemu_iovec_init_buf(&head_qiov, head_buf, align);
-
-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
-        ret = bdrv_aligned_preadv(child, &req, offset & ~(align - 1), align,
-                                  align, &head_qiov, 0);
-        if (ret < 0) {
-            goto fail;
-        }
-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
-
-        qemu_iovec_init(&local_qiov, qiov->niov + 2);
-        qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
-        qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
-        use_local_qiov = true;
-
-        bytes += offset & (align - 1);
-        offset = offset & ~(align - 1);
-
-        /* We have read the tail already if the request is smaller
-         * than one aligned block.
-         */
-        if (bytes < align) {
-            qemu_iovec_add(&local_qiov, head_buf + bytes, align - bytes);
-            bytes = align;
-        }
-    }
-
-    if ((offset + bytes) & (align - 1)) {
-        QEMUIOVector tail_qiov;
-        size_t tail_bytes;
-        bool waited;
-
-        mark_request_serialising(&req, align);
-        waited = wait_serialising_requests(&req);
-        assert(!waited || !use_local_qiov);
-
-        tail_buf = qemu_blockalign(bs, align);
-        qemu_iovec_init_buf(&tail_qiov, tail_buf, align);
-
-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
-        ret = bdrv_aligned_preadv(child, &req, (offset + bytes) & ~(align - 1),
-                                  align, align, &tail_qiov, 0);
-        if (ret < 0) {
-            goto fail;
-        }
-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
-
-        if (!use_local_qiov) {
-            qemu_iovec_init(&local_qiov, qiov->niov + 1);
-            qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
-            use_local_qiov = true;
-        }
-
-        tail_bytes = (offset + bytes) & (align - 1);
-        qemu_iovec_add(&local_qiov, tail_buf + tail_bytes, align - tail_bytes);
-
-        bytes = ROUND_UP(bytes, align);
+        bdrv_padding_rmw_read(child, &req, &pad, false);
     }
 
     ret = bdrv_aligned_pwritev(child, &req, offset, bytes, align,
-                               use_local_qiov ? &local_qiov : qiov,
-                               flags);
+                               qiov, flags);
 
-fail:
+    bdrv_padding_destroy(&pad);
 
-    if (use_local_qiov) {
-        qemu_iovec_destroy(&local_qiov);
-    }
-    qemu_vfree(head_buf);
-    qemu_vfree(tail_buf);
 out:
     tracked_request_end(&req);
     bdrv_dec_in_flight(bs);
+
     return ret;
 }
 
-- 
2.18.0

[Qemu-devel] [PATCH v2 04/12] block: define .*_part io handlers in BlockDriver

[Vladimir Sementsov-Ogievskiy]

Add handlers supporting qiov_offset parameter:
    bdrv_co_preadv_part
    bdrv_co_pwritev_part
    bdrv_co_pwritev_compressed_part
This is used to reduce need of defining local_qiovs and hd_qiovs in all
corners of block layer code. The following patches will increase usage
of this new API part by part.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 include/block/block_int.h | 15 ++++++
 block/backup.c            |  2 +-
 block/io.c                | 96 +++++++++++++++++++++++++++++++--------
 qemu-img.c                |  4 +-
 4 files changed, 95 insertions(+), 22 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 1eebc7c8f3..46e17d2e2f 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -211,6 +211,9 @@ struct BlockDriver {
      */
     int coroutine_fn (*bdrv_co_preadv)(BlockDriverState *bs,
         uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags);
+    int coroutine_fn (*bdrv_co_preadv_part)(BlockDriverState *bs,
+        uint64_t offset, uint64_t bytes,
+        QEMUIOVector *qiov, size_t qiov_offset, int flags);
     int coroutine_fn (*bdrv_co_writev)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, QEMUIOVector *qiov, int flags);
     /**
@@ -230,6 +233,9 @@ struct BlockDriver {
      */
     int coroutine_fn (*bdrv_co_pwritev)(BlockDriverState *bs,
         uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags);
+    int coroutine_fn (*bdrv_co_pwritev_part)(BlockDriverState *bs,
+        uint64_t offset, uint64_t bytes,
+        QEMUIOVector *qiov, size_t qiov_offset, int flags);
 
     /*
      * Efficiently zero a region of the disk image.  Typically an image format
@@ -340,6 +346,9 @@ struct BlockDriver {
 
     int coroutine_fn (*bdrv_co_pwritev_compressed)(BlockDriverState *bs,
         uint64_t offset, uint64_t bytes, QEMUIOVector *qiov);
+    int coroutine_fn (*bdrv_co_pwritev_compressed_part)(BlockDriverState *bs,
+        uint64_t offset, uint64_t bytes, QEMUIOVector *qiov,
+        size_t qiov_offset);
 
     int (*bdrv_snapshot_create)(BlockDriverState *bs,
                                 QEMUSnapshotInfo *sn_info);
@@ -564,6 +573,12 @@ struct BlockDriver {
     const char *const *strong_runtime_opts;
 };
 
+static inline bool block_driver_can_compress(BlockDriver *drv)
+{
+    return drv->bdrv_co_pwritev_compressed ||
+           drv->bdrv_co_pwritev_compressed_part;
+}
+
 typedef struct BlockLimits {
     /* Alignment requirement, in bytes, for offset/length of I/O
      * requests. Must be a power of 2 less than INT_MAX; defaults to
diff --git a/block/backup.c b/block/backup.c
index 00f4f8af53..af821b8990 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -569,7 +569,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
         return NULL;
     }
 
-    if (compress && target->drv->bdrv_co_pwritev_compressed == NULL) {
+    if (compress && !block_driver_can_compress(target->drv)) {
         error_setg(errp, "Compression is not supported for this drive %s",
                    bdrv_get_device_name(target));
         return NULL;
diff --git a/block/io.c b/block/io.c
index ddd5902dc1..7e53a11492 100644
--- a/block/io.c
+++ b/block/io.c
@@ -128,7 +128,8 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
 
     /* Default alignment based on whether driver has byte interface */
     bs->bl.request_alignment = (drv->bdrv_co_preadv ||
-                                drv->bdrv_aio_preadv) ? 1 : 512;
+                                drv->bdrv_aio_preadv ||
+                                drv->bdrv_co_preadv_part) ? 1 : 512;
 
     /* Take some limits from the children as a default */
     if (bs->file) {
@@ -979,11 +980,14 @@ static void bdrv_co_io_em_complete(void *opaque, int ret)
 
 static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
                                            uint64_t offset, uint64_t bytes,
-                                           QEMUIOVector *qiov, int flags)
+                                           QEMUIOVector *qiov,
+                                           size_t qiov_offset, int flags)
 {
     BlockDriver *drv = bs->drv;
     int64_t sector_num;
     unsigned int nb_sectors;
+    QEMUIOVector local_qiov;
+    int ret;
 
     assert(!(flags & ~BDRV_REQ_MASK));
     assert(!(flags & BDRV_REQ_NO_FALLBACK));
@@ -992,8 +996,19 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
         return -ENOMEDIUM;
     }
 
+    if (drv->bdrv_co_preadv_part) {
+        return drv->bdrv_co_preadv_part(bs, offset, bytes, qiov, qiov_offset,
+                                        flags);
+    }
+
+    if (qiov_offset > 0 || bytes != qiov->size) {
+        qemu_iovec_init_slice(&local_qiov, qiov, qiov_offset, bytes);
+        qiov = &local_qiov;
+    }
+
     if (drv->bdrv_co_preadv) {
-        return drv->bdrv_co_preadv(bs, offset, bytes, qiov, flags);
+        ret = drv->bdrv_co_preadv(bs, offset, bytes, qiov, flags);
+        goto out;
     }
 
     if (drv->bdrv_aio_preadv) {
@@ -1005,10 +1020,12 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
         acb = drv->bdrv_aio_preadv(bs, offset, bytes, qiov, flags,
                                    bdrv_co_io_em_complete, &co);
         if (acb == NULL) {
-            return -EIO;
+            ret = -EIO;
+            goto out;
         } else {
             qemu_coroutine_yield();
-            return co.ret;
+            ret = co.ret;
+            goto out;
         }
     }
 
@@ -1020,16 +1037,25 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
     assert(bytes <= BDRV_REQUEST_MAX_BYTES);
     assert(drv->bdrv_co_readv);
 
-    return drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
+    ret = drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
+
+out:
+    if (qiov == &local_qiov) {
+        qemu_iovec_destroy(&local_qiov);
+    }
+
+    return ret;
 }
 
 static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
                                             uint64_t offset, uint64_t bytes,
-                                            QEMUIOVector *qiov, int flags)
+                                            QEMUIOVector *qiov,
+                                            size_t qiov_offset, int flags)
 {
     BlockDriver *drv = bs->drv;
     int64_t sector_num;
     unsigned int nb_sectors;
+    QEMUIOVector local_qiov;
     int ret;
 
     assert(!(flags & ~BDRV_REQ_MASK));
@@ -1039,6 +1065,18 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
         return -ENOMEDIUM;
     }
 
+    if (drv->bdrv_co_pwritev_part) {
+        ret = drv->bdrv_co_pwritev_part(bs, offset, bytes, qiov, qiov_offset,
+                                        flags & bs->supported_write_flags);
+        flags &= ~bs->supported_write_flags;
+        goto emulate_flags;
+    }
+
+    if (qiov_offset > 0 || bytes != qiov->size) {
+        qemu_iovec_init_slice(&local_qiov, qiov, qiov_offset, bytes);
+        qiov = &local_qiov;
+    }
+
     if (drv->bdrv_co_pwritev) {
         ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov,
                                    flags & bs->supported_write_flags);
@@ -1082,24 +1120,44 @@ emulate_flags:
         ret = bdrv_co_flush(bs);
     }
 
+    if (qiov == &local_qiov) {
+        qemu_iovec_destroy(&local_qiov);
+    }
+
     return ret;
 }
 
 static int coroutine_fn
 bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
-                               uint64_t bytes, QEMUIOVector *qiov)
+                               uint64_t bytes, QEMUIOVector *qiov,
+                               size_t qiov_offset)
 {
     BlockDriver *drv = bs->drv;
+    QEMUIOVector local_qiov;
+    int ret;
 
     if (!drv) {
         return -ENOMEDIUM;
     }
 
-    if (!drv->bdrv_co_pwritev_compressed) {
+    if (!block_driver_can_compress(drv)) {
         return -ENOTSUP;
     }
 
-    return drv->bdrv_co_pwritev_compressed(bs, offset, bytes, qiov);
+    if (drv->bdrv_co_pwritev_compressed_part) {
+        return drv->bdrv_co_pwritev_compressed_part(bs, offset, bytes,
+                                                    qiov, qiov_offset);
+    }
+
+    if (qiov_offset == 0) {
+        return drv->bdrv_co_pwritev_compressed(bs, offset, bytes, qiov);
+    }
+
+    qemu_iovec_init_slice(&local_qiov, qiov, qiov_offset, bytes);
+    ret = drv->bdrv_co_pwritev_compressed(bs, offset, bytes, &local_qiov);
+    qemu_iovec_destroy(&local_qiov);
+
+    return ret;
 }
 
 static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
@@ -1183,7 +1241,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
             qemu_iovec_init_buf(&local_qiov, bounce_buffer, pnum);
 
             ret = bdrv_driver_preadv(bs, cluster_offset, pnum,
-                                     &local_qiov, 0);
+                                     &local_qiov, 0, 0);
             if (ret < 0) {
                 goto err;
             }
@@ -1201,7 +1259,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
                  * necessary to flush even in cache=writethrough mode.
                  */
                 ret = bdrv_driver_pwritev(bs, cluster_offset, pnum,
-                                          &local_qiov,
+                                          &local_qiov, 0,
                                           BDRV_REQ_WRITE_UNCHANGED);
             }
 
@@ -1221,7 +1279,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
             qemu_iovec_init(&local_qiov, qiov->niov);
             qemu_iovec_concat(&local_qiov, qiov, progress, pnum - skip_bytes);
             ret = bdrv_driver_preadv(bs, offset + progress, local_qiov.size,
-                                     &local_qiov, 0);
+                                     &local_qiov, 0, 0);
             qemu_iovec_destroy(&local_qiov);
             if (ret < 0) {
                 goto err;
@@ -1309,7 +1367,7 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
 
     max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
     if (bytes <= max_bytes && bytes <= max_transfer) {
-        ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0);
+        ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0, 0);
         goto out;
     }
 
@@ -1325,7 +1383,7 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
             qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num);
 
             ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining,
-                                     num, &local_qiov, 0);
+                                     num, &local_qiov, 0, 0);
             max_bytes -= num;
             qemu_iovec_destroy(&local_qiov);
         } else {
@@ -1620,7 +1678,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
             }
             qemu_iovec_init_buf(&qiov, buf, num);
 
-            ret = bdrv_driver_pwritev(bs, offset, num, &qiov, write_flags);
+            ret = bdrv_driver_pwritev(bs, offset, num, &qiov, 0, write_flags);
 
             /* Keep bounce buffer around if it is big enough for all
              * all future requests.
@@ -1776,10 +1834,10 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
         bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO);
         ret = bdrv_co_do_pwrite_zeroes(bs, offset, bytes, flags);
     } else if (flags & BDRV_REQ_WRITE_COMPRESSED) {
-        ret = bdrv_driver_pwritev_compressed(bs, offset, bytes, qiov);
+        ret = bdrv_driver_pwritev_compressed(bs, offset, bytes, qiov, 0);
     } else if (bytes <= max_transfer) {
         bdrv_debug_event(bs, BLKDBG_PWRITEV);
-        ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, flags);
+        ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, 0, flags);
     } else {
         bdrv_debug_event(bs, BLKDBG_PWRITEV);
         while (bytes_remaining) {
@@ -1798,7 +1856,7 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
             qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num);
 
             ret = bdrv_driver_pwritev(bs, offset + bytes - bytes_remaining,
-                                      num, &local_qiov, local_flags);
+                                      num, &local_qiov, 0, local_flags);
             qemu_iovec_destroy(&local_qiov);
             if (ret < 0) {
                 break;
diff --git a/qemu-img.c b/qemu-img.c
index b0535919b1..8a62a75a71 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2329,7 +2329,7 @@ static int img_convert(int argc, char **argv)
         const char *preallocation =
             qemu_opt_get(opts, BLOCK_OPT_PREALLOC);
 
-        if (drv && !drv->bdrv_co_pwritev_compressed) {
+        if (drv && !block_driver_can_compress(drv)) {
             error_report("Compression not supported for this file format");
             ret = -1;
             goto out;
@@ -2398,7 +2398,7 @@ static int img_convert(int argc, char **argv)
     }
     out_bs = blk_bs(s.target);
 
-    if (s.compressed && !out_bs->drv->bdrv_co_pwritev_compressed) {
+    if (s.compressed && !block_driver_can_compress(out_bs->drv)) {
         error_report("Compression not supported for this file format");
         ret = -1;
         goto out;
-- 
2.18.0

[Qemu-devel] [PATCH v2 05/12] block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset

[Vladimir Sementsov-Ogievskiy]

Use and support new API in bdrv_co_do_copy_on_readv. Note that in case
of allocated-in-top we need to shrink read size to MIN(..) by hand, as
pre-patch this was actually done implicitly by qemu_iovec_concat (and
we used local_qiov.size).

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/block/io.c b/block/io.c
index 7e53a11492..efd2b80293 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1161,7 +1161,8 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
 }
 
 static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
-        int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
+        int64_t offset, unsigned int bytes,
+        QEMUIOVector *qiov, size_t qiov_offset)
 {
     BlockDriverState *bs = child->bs;
 
@@ -1173,7 +1174,6 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
     void *bounce_buffer;
 
     BlockDriver *drv = bs->drv;
-    QEMUIOVector local_qiov;
     int64_t cluster_offset;
     int64_t cluster_bytes;
     size_t skip_bytes;
@@ -1236,6 +1236,8 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
         assert(skip_bytes < pnum);
 
         if (ret <= 0) {
+            QEMUIOVector local_qiov;
+
             /* Must copy-on-read; use the bounce buffer */
             pnum = MIN(pnum, MAX_BOUNCE_BUFFER);
             qemu_iovec_init_buf(&local_qiov, bounce_buffer, pnum);
@@ -1272,15 +1274,14 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
                 goto err;
             }
 
-            qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_bytes,
+            qemu_iovec_from_buf(qiov, qiov_offset + progress,
+                                bounce_buffer + skip_bytes,
                                 pnum - skip_bytes);
         } else {
             /* Read directly into the destination */
-            qemu_iovec_init(&local_qiov, qiov->niov);
-            qemu_iovec_concat(&local_qiov, qiov, progress, pnum - skip_bytes);
-            ret = bdrv_driver_preadv(bs, offset + progress, local_qiov.size,
-                                     &local_qiov, 0, 0);
-            qemu_iovec_destroy(&local_qiov);
+            ret = bdrv_driver_preadv(bs, offset + progress,
+                                     MIN(pnum - skip_bytes, bytes - progress),
+                                     qiov, qiov_offset + progress, 0);
             if (ret < 0) {
                 goto err;
             }
@@ -1353,7 +1354,7 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
         }
 
         if (!ret || pnum != bytes) {
-            ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov);
+            ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov, 0);
             goto out;
         }
     }
-- 
2.18.0

[Qemu-devel] [PATCH v2 06/12] block/io: bdrv_co_do_copy_on_readv: lazy allocation

[Vladimir Sementsov-Ogievskiy]

Allocate bounce_buffer only if it is really needed. Also, sub-optimize
allocation size (why not?).

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/block/io.c b/block/io.c
index efd2b80293..a4f67aca47 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1171,7 +1171,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
      * modifying the image file.  This is critical for zero-copy guest I/O
      * where anything might happen inside guest memory.
      */
-    void *bounce_buffer;
+    void *bounce_buffer = NULL;
 
     BlockDriver *drv = bs->drv;
     int64_t cluster_offset;
@@ -1206,14 +1206,6 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
     trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
                                    cluster_offset, cluster_bytes);
 
-    bounce_buffer = qemu_try_blockalign(bs,
-                                        MIN(MIN(max_transfer, cluster_bytes),
-                                            MAX_BOUNCE_BUFFER));
-    if (bounce_buffer == NULL) {
-        ret = -ENOMEM;
-        goto err;
-    }
-
     while (cluster_bytes) {
         int64_t pnum;
 
@@ -1240,6 +1232,17 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
 
             /* Must copy-on-read; use the bounce buffer */
             pnum = MIN(pnum, MAX_BOUNCE_BUFFER);
+            if (!bounce_buffer) {
+                int64_t max_we_need = MAX(pnum, cluster_bytes - pnum);
+                int64_t max_allowed = MIN(max_transfer, MAX_BOUNCE_BUFFER);
+                int64_t bounce_buffer_len = MIN(max_we_need, max_allowed);
+
+                bounce_buffer = qemu_try_blockalign(bs, bounce_buffer_len);
+                if (!bounce_buffer) {
+                    ret = -ENOMEM;
+                    goto err;
+                }
+            }
             qemu_iovec_init_buf(&local_qiov, bounce_buffer, pnum);
 
             ret = bdrv_driver_preadv(bs, cluster_offset, pnum,
-- 
2.18.0

[Qemu-devel] [PATCH v2 07/12] block/io: bdrv_aligned_preadv: use and support qiov_offset

[Vladimir Sementsov-Ogievskiy]

Use and support new API in bdrv_co_do_copy_on_readv.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/block/io.c b/block/io.c
index a4f67aca47..0cc80e2d5a 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1309,7 +1309,7 @@ err:
  */
 static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
     BdrvTrackedRequest *req, int64_t offset, unsigned int bytes,
-    int64_t align, QEMUIOVector *qiov, int flags)
+    int64_t align, QEMUIOVector *qiov, size_t qiov_offset, int flags)
 {
     BlockDriverState *bs = child->bs;
     int64_t total_bytes, max_bytes;
@@ -1320,7 +1320,6 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
     assert(is_power_of_2(align));
     assert((offset & (align - 1)) == 0);
     assert((bytes & (align - 1)) == 0);
-    assert(!qiov || bytes == qiov->size);
     assert((bs->open_flags & BDRV_O_NO_IO) == 0);
     max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
                                    align);
@@ -1357,7 +1356,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
         }
 
         if (!ret || pnum != bytes) {
-            ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov, 0);
+            ret = bdrv_co_do_copy_on_readv(child, offset, bytes,
+                                           qiov, qiov_offset);
             goto out;
         }
     }
@@ -1371,7 +1371,7 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
 
     max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
     if (bytes <= max_bytes && bytes <= max_transfer) {
-        ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0, 0);
+        ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset, 0);
         goto out;
     }
 
@@ -1379,17 +1379,12 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
         int num;
 
         if (max_bytes) {
-            QEMUIOVector local_qiov;
-
             num = MIN(bytes_remaining, MIN(max_bytes, max_transfer));
             assert(num);
-            qemu_iovec_init(&local_qiov, qiov->niov);
-            qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num);
 
             ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining,
-                                     num, &local_qiov, 0, 0);
+                                     num, qiov, bytes - bytes_remaining, 0);
             max_bytes -= num;
-            qemu_iovec_destroy(&local_qiov);
         } else {
             num = bytes_remaining;
             ret = qemu_iovec_memset(qiov, bytes - bytes_remaining, 0,
@@ -1486,7 +1481,7 @@ static int bdrv_padding_rmw_read(BdrvChild *child,
 
         bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
         ret = bdrv_aligned_preadv(child, req, req->overlap_offset, bytes,
-                                  align, &local_qiov, 0);
+                                  align, &local_qiov, 0, 0);
         if (ret < 0) {
             return ret;
         }
@@ -1504,7 +1499,7 @@ static int bdrv_padding_rmw_read(BdrvChild *child,
         ret = bdrv_aligned_preadv(
                 child, req,
                 req->overlap_offset + req->overlap_bytes - align,
-                align, align, &local_qiov, 0);
+                align, align, &local_qiov, 0, 0);
         if (ret < 0) {
             return ret;
         }
@@ -1585,7 +1580,7 @@ int coroutine_fn bdrv_co_preadv(BdrvChild *child,
     tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ);
     ret = bdrv_aligned_preadv(child, &req, offset, bytes,
                               bs->bl.request_alignment,
-                              qiov, flags);
+                              qiov, 0, flags);
     tracked_request_end(&req);
     bdrv_dec_in_flight(bs);
 
-- 
2.18.0

[Qemu-devel] [PATCH v2 08/12] block/io: bdrv_aligned_pwritev: use and support qiov_offset

[Vladimir Sementsov-Ogievskiy]

Use and support new API in bdrv_aligned_pwritev.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/block/io.c b/block/io.c
index 0cc80e2d5a..660c96527d 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1792,7 +1792,7 @@ bdrv_co_write_req_finish(BdrvChild *child, int64_t offset, uint64_t bytes,
  */
 static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
     BdrvTrackedRequest *req, int64_t offset, unsigned int bytes,
-    int64_t align, QEMUIOVector *qiov, int flags)
+    int64_t align, QEMUIOVector *qiov, size_t qiov_offset, int flags)
 {
     BlockDriverState *bs = child->bs;
     BlockDriver *drv = bs->drv;
@@ -1812,7 +1812,7 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
     assert(is_power_of_2(align));
     assert((offset & (align - 1)) == 0);
     assert((bytes & (align - 1)) == 0);
-    assert(!qiov || bytes == qiov->size);
+    assert(!qiov || qiov_offset + bytes <= qiov->size);
     max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
                                    align);
 
@@ -1820,7 +1820,7 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
 
     if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF &&
         !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
-        qemu_iovec_is_zero(qiov, 0, qiov->size)) {
+        qemu_iovec_is_zero(qiov, qiov_offset, bytes)) {
         flags |= BDRV_REQ_ZERO_WRITE;
         if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
             flags |= BDRV_REQ_MAY_UNMAP;
@@ -1833,15 +1833,15 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
         bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO);
         ret = bdrv_co_do_pwrite_zeroes(bs, offset, bytes, flags);
     } else if (flags & BDRV_REQ_WRITE_COMPRESSED) {
-        ret = bdrv_driver_pwritev_compressed(bs, offset, bytes, qiov, 0);
+        ret = bdrv_driver_pwritev_compressed(bs, offset, bytes,
+                                             qiov, qiov_offset);
     } else if (bytes <= max_transfer) {
         bdrv_debug_event(bs, BLKDBG_PWRITEV);
-        ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, 0, flags);
+        ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, qiov_offset, flags);
     } else {
         bdrv_debug_event(bs, BLKDBG_PWRITEV);
         while (bytes_remaining) {
             int num = MIN(bytes_remaining, max_transfer);
-            QEMUIOVector local_qiov;
             int local_flags = flags;
 
             assert(num);
@@ -1851,12 +1851,10 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
                  * need to flush on the last iteration */
                 local_flags &= ~BDRV_REQ_FUA;
             }
-            qemu_iovec_init(&local_qiov, qiov->niov);
-            qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num);
 
             ret = bdrv_driver_pwritev(bs, offset + bytes - bytes_remaining,
-                                      num, &local_qiov, 0, local_flags);
-            qemu_iovec_destroy(&local_qiov);
+                                      num, qiov, bytes - bytes_remaining,
+                                      local_flags);
             if (ret < 0) {
                 break;
             }
@@ -1899,7 +1897,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
 
             qemu_iovec_init_buf(&local_qiov, pad.buf, write_bytes);
             ret = bdrv_aligned_pwritev(child, req, aligned_offset, write_bytes,
-                                       align, &local_qiov,
+                                       align, &local_qiov, 0,
                                        flags & ~BDRV_REQ_ZERO_WRITE);
             if (ret < 0 || pad.merge_reads) {
                 /* Error or all work is done */
@@ -1915,7 +1913,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
         /* Write the aligned part in the middle. */
         uint64_t aligned_bytes = bytes & ~(align - 1);
         ret = bdrv_aligned_pwritev(child, req, offset, aligned_bytes, align,
-                                   NULL, flags);
+                                   NULL, 0, flags);
         if (ret < 0) {
             goto out;
         }
@@ -1929,7 +1927,8 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
 
         qemu_iovec_init_buf(&local_qiov, pad.tail_buf, align);
         ret = bdrv_aligned_pwritev(child, req, offset, align, align,
-                                   &local_qiov, flags & ~BDRV_REQ_ZERO_WRITE);
+                                   &local_qiov, 0,
+                                   flags & ~BDRV_REQ_ZERO_WRITE);
     }
 
 out:
@@ -1982,7 +1981,7 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
     }
 
     ret = bdrv_aligned_pwritev(child, &req, offset, bytes, align,
-                               qiov, flags);
+                               qiov, 0, flags);
 
     bdrv_padding_destroy(&pad);
 
-- 
2.18.0

[Qemu-devel] [PATCH v2 09/12] block/io: introduce bdrv_co_p{read, write}v_part

[Vladimir Sementsov-Ogievskiy]

Introduce extended variants of bdrv_co_preadv and bdrv_co_pwritev
with qiov_offset parameter.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 include/block/block_int.h |  6 ++++++
 block/io.c                | 29 +++++++++++++++++++++++------
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 46e17d2e2f..8b7b5d5b84 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -940,9 +940,15 @@ extern BlockDriver bdrv_qcow2;
 int coroutine_fn bdrv_co_preadv(BdrvChild *child,
     int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
     BdrvRequestFlags flags);
+int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
+    int64_t offset, unsigned int bytes,
+    QEMUIOVector *qiov, size_t qiov_offset, BdrvRequestFlags flags);
 int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
     int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
     BdrvRequestFlags flags);
+int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
+    int64_t offset, unsigned int bytes,
+    QEMUIOVector *qiov, size_t qiov_offset, BdrvRequestFlags flags);
 
 static inline int coroutine_fn bdrv_co_pread(BdrvChild *child,
     int64_t offset, unsigned int bytes, void *buf, BdrvRequestFlags flags)
diff --git a/block/io.c b/block/io.c
index 660c96527d..82051730fd 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1534,7 +1534,8 @@ static void bdrv_padding_destroy(BdrvRequestPadding *pad)
  *
  * Function always succeeds.
  */
-static bool bdrv_pad_request(BlockDriverState *bs, QEMUIOVector **qiov,
+static bool bdrv_pad_request(BlockDriverState *bs,
+                             QEMUIOVector **qiov, size_t *qiov_offset,
                              int64_t *offset, unsigned int *bytes,
                              BdrvRequestPadding *pad)
 {
@@ -1543,11 +1544,12 @@ static bool bdrv_pad_request(BlockDriverState *bs, QEMUIOVector **qiov,
     }
 
     qemu_iovec_init_extended(&pad->local_qiov, pad->buf, pad->head,
-                             *qiov, 0, *bytes,
+                             *qiov, *qiov_offset, *bytes,
                              pad->buf + pad->buf_len - pad->tail, pad->tail);
     *bytes += pad->head + pad->tail;
     *offset -= pad->head;
     *qiov = &pad->local_qiov;
+    *qiov_offset = 0;
 
     return true;
 }
@@ -1555,6 +1557,14 @@ static bool bdrv_pad_request(BlockDriverState *bs, QEMUIOVector **qiov,
 int coroutine_fn bdrv_co_preadv(BdrvChild *child,
     int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
     BdrvRequestFlags flags)
+{
+    return bdrv_co_preadv_part(child, offset, bytes, qiov, 0, flags);
+}
+
+int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
+    int64_t offset, unsigned int bytes,
+    QEMUIOVector *qiov, size_t qiov_offset,
+    BdrvRequestFlags flags)
 {
     BlockDriverState *bs = child->bs;
     BdrvTrackedRequest req;
@@ -1575,12 +1585,12 @@ int coroutine_fn bdrv_co_preadv(BdrvChild *child,
         flags |= BDRV_REQ_COPY_ON_READ;
     }
 
-    bdrv_pad_request(bs, &qiov, &offset, &bytes, &pad);
+    bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad);
 
     tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ);
     ret = bdrv_aligned_preadv(child, &req, offset, bytes,
                               bs->bl.request_alignment,
-                              qiov, 0, flags);
+                              qiov, qiov_offset, flags);
     tracked_request_end(&req);
     bdrv_dec_in_flight(bs);
 
@@ -1943,6 +1953,13 @@ out:
 int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
     int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
     BdrvRequestFlags flags)
+{
+    return bdrv_co_pwritev_part(child, offset, bytes, qiov, 0, flags);
+}
+
+int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
+    int64_t offset, unsigned int bytes, QEMUIOVector *qiov, size_t qiov_offset,
+    BdrvRequestFlags flags)
 {
     BlockDriverState *bs = child->bs;
     BdrvTrackedRequest req;
@@ -1974,14 +1991,14 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
         goto out;
     }
 
-    if (bdrv_pad_request(bs, &qiov, &offset, &bytes, &pad)) {
+    if (bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad)) {
         mark_request_serialising(&req, align);
         wait_serialising_requests(&req);
         bdrv_padding_rmw_read(child, &req, &pad, false);
     }
 
     ret = bdrv_aligned_pwritev(child, &req, offset, bytes, align,
-                               qiov, 0, flags);
+                               qiov, qiov_offset, flags);
 
     bdrv_padding_destroy(&pad);
 
-- 
2.18.0

[Qemu-devel] [PATCH v2 10/12] block/qcow2: refactor qcow2_co_preadv to use buffer-based io

[Vladimir Sementsov-Ogievskiy]

Use buffer based io in encrypted case.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index f2cb131048..8a033ae08c 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2047,19 +2047,15 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
                 }
 
                 assert(cur_bytes <= QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
-                qemu_iovec_reset(&hd_qiov);
-                qemu_iovec_add(&hd_qiov, cluster_data, cur_bytes);
-            }
 
-            BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
-            ret = bdrv_co_preadv(s->data_file,
-                                 cluster_offset + offset_in_cluster,
-                                 cur_bytes, &hd_qiov, 0);
-            if (ret < 0) {
-                goto fail;
-            }
-            if (bs->encrypted) {
-                assert(s->crypto);
+                BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
+                ret = bdrv_co_pread(s->data_file,
+                                    cluster_offset + offset_in_cluster,
+                                    cur_bytes, cluster_data, 0);
+                if (ret < 0) {
+                    goto fail;
+                }
+
                 assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
                 assert((cur_bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
                 if (qcow2_co_decrypt(bs, cluster_offset, offset,
@@ -2068,6 +2064,14 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
                     goto fail;
                 }
                 qemu_iovec_from_buf(qiov, bytes_done, cluster_data, cur_bytes);
+            } else {
+                BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
+                ret = bdrv_co_preadv(s->data_file,
+                                     cluster_offset + offset_in_cluster,
+                                     cur_bytes, &hd_qiov, 0);
+                if (ret < 0) {
+                    goto fail;
+                }
             }
             break;
 
-- 
2.18.0

[Qemu-devel] [PATCH v2 11/12] block/qcow2: implement .bdrv_co_preadv_part

[Vladimir Sementsov-Ogievskiy]

Implement and use new interface to get rid of hd_qiov.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2-cluster.c |  5 +++--
 block/qcow2.c         | 49 +++++++++++++++++++------------------------
 2 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index cf892f37a8..1159d6ed2f 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -453,8 +453,9 @@ static int coroutine_fn do_perform_cow_read(BlockDriverState *bs,
      * interface.  This avoids double I/O throttling and request tracking,
      * which can lead to deadlock when block layer copy-on-read is enabled.
      */
-    ret = bs->drv->bdrv_co_preadv(bs, src_cluster_offset + offset_in_cluster,
-                                  qiov->size, qiov, 0);
+    ret = bs->drv->bdrv_co_preadv_part(bs,
+                                       src_cluster_offset + offset_in_cluster,
+                                       qiov->size, qiov, 0, 0);
     if (ret < 0) {
         return ret;
     }
diff --git a/block/qcow2.c b/block/qcow2.c
index 8a033ae08c..c389ef07b0 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -75,7 +75,8 @@ qcow2_co_preadv_compressed(BlockDriverState *bs,
                            uint64_t file_cluster_offset,
                            uint64_t offset,
                            uint64_t bytes,
-                           QEMUIOVector *qiov);
+                           QEMUIOVector *qiov,
+                           size_t qiov_offset);
 
 static int qcow2_probe(const uint8_t *buf, int buf_size, const char *filename)
 {
@@ -1955,21 +1956,18 @@ out:
     return ret;
 }
 
-static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
-                                        uint64_t bytes, QEMUIOVector *qiov,
-                                        int flags)
+static coroutine_fn int qcow2_co_preadv_part(BlockDriverState *bs,
+                                             uint64_t offset, uint64_t bytes,
+                                             QEMUIOVector *qiov,
+                                             size_t qiov_offset, int flags)
 {
     BDRVQcow2State *s = bs->opaque;
     int offset_in_cluster;
     int ret;
     unsigned int cur_bytes; /* number of bytes in current iteration */
     uint64_t cluster_offset = 0;
-    uint64_t bytes_done = 0;
-    QEMUIOVector hd_qiov;
     uint8_t *cluster_data = NULL;
 
-    qemu_iovec_init(&hd_qiov, qiov->niov);
-
     while (bytes != 0) {
 
         /* prepare next request */
@@ -1988,34 +1986,31 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
 
         offset_in_cluster = offset_into_cluster(s, offset);
 
-        qemu_iovec_reset(&hd_qiov);
-        qemu_iovec_concat(&hd_qiov, qiov, bytes_done, cur_bytes);
-
         switch (ret) {
         case QCOW2_CLUSTER_UNALLOCATED:
 
             if (bs->backing) {
                 BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO);
-                ret = bdrv_co_preadv(bs->backing, offset, cur_bytes,
-                                     &hd_qiov, 0);
+                ret = bdrv_co_preadv_part(bs->backing, offset, cur_bytes,
+                                          qiov, qiov_offset, 0);
                 if (ret < 0) {
                     goto fail;
                 }
             } else {
                 /* Note: in this case, no need to wait */
-                qemu_iovec_memset(&hd_qiov, 0, 0, cur_bytes);
+                qemu_iovec_memset(qiov, qiov_offset, 0, cur_bytes);
             }
             break;
 
         case QCOW2_CLUSTER_ZERO_PLAIN:
         case QCOW2_CLUSTER_ZERO_ALLOC:
-            qemu_iovec_memset(&hd_qiov, 0, 0, cur_bytes);
+            qemu_iovec_memset(qiov, qiov_offset, 0, cur_bytes);
             break;
 
         case QCOW2_CLUSTER_COMPRESSED:
             ret = qcow2_co_preadv_compressed(bs, cluster_offset,
                                              offset, cur_bytes,
-                                             &hd_qiov);
+                                             qiov, qiov_offset);
             if (ret < 0) {
                 goto fail;
             }
@@ -2063,12 +2058,12 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
                     ret = -EIO;
                     goto fail;
                 }
-                qemu_iovec_from_buf(qiov, bytes_done, cluster_data, cur_bytes);
+                qemu_iovec_from_buf(qiov, qiov_offset, cluster_data, cur_bytes);
             } else {
                 BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
-                ret = bdrv_co_preadv(s->data_file,
-                                     cluster_offset + offset_in_cluster,
-                                     cur_bytes, &hd_qiov, 0);
+                ret = bdrv_co_preadv_part(s->data_file,
+                                          cluster_offset + offset_in_cluster,
+                                          cur_bytes, qiov, qiov_offset, 0);
                 if (ret < 0) {
                     goto fail;
                 }
@@ -2083,12 +2078,11 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
 
         bytes -= cur_bytes;
         offset += cur_bytes;
-        bytes_done += cur_bytes;
+        qiov_offset += cur_bytes;
     }
     ret = 0;
 
 fail:
-    qemu_iovec_destroy(&hd_qiov);
     qemu_vfree(cluster_data);
 
     return ret;
@@ -4087,7 +4081,8 @@ qcow2_co_preadv_compressed(BlockDriverState *bs,
                            uint64_t file_cluster_offset,
                            uint64_t offset,
                            uint64_t bytes,
-                           QEMUIOVector *qiov)
+                           QEMUIOVector *qiov,
+                           size_t qiov_offset)
 {
     BDRVQcow2State *s = bs->opaque;
     int ret = 0, csize, nb_csectors;
@@ -4118,7 +4113,7 @@ qcow2_co_preadv_compressed(BlockDriverState *bs,
         goto fail;
     }
 
-    qemu_iovec_from_buf(qiov, 0, out_buf + offset_in_cluster, bytes);
+    qemu_iovec_from_buf(qiov, qiov_offset, out_buf + offset_in_cluster, bytes);
 
 fail:
     qemu_vfree(out_buf);
@@ -4638,8 +4633,8 @@ static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
     BDRVQcow2State *s = bs->opaque;
 
     BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_LOAD);
-    return bs->drv->bdrv_co_preadv(bs, qcow2_vm_state_offset(s) + pos,
-                                   qiov->size, qiov, 0);
+    return bs->drv->bdrv_co_preadv_part(bs, qcow2_vm_state_offset(s) + pos,
+                                        qiov->size, qiov, 0, 0);
 }
 
 /*
@@ -5179,7 +5174,7 @@ BlockDriver bdrv_qcow2 = {
     .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_co_block_status = qcow2_co_block_status,
 
-    .bdrv_co_preadv         = qcow2_co_preadv,
+    .bdrv_co_preadv_part    = qcow2_co_preadv_part,
     .bdrv_co_pwritev        = qcow2_co_pwritev,
     .bdrv_co_flush_to_os    = qcow2_co_flush_to_os,
 
-- 
2.18.0

[Qemu-devel] [PATCH v2 12/12] block/qcow2: implement .bdrv_co_pwritev(_compressed)_part

[Vladimir Sementsov-Ogievskiy]

Implement and use new interface to get rid of hd_qiov.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2.h         |  1 +
 include/qemu/iov.h    |  1 +
 block/qcow2-cluster.c |  9 ++++---
 block/qcow2.c         | 60 +++++++++++++++++++++----------------------
 util/iov.c            | 10 ++++++++
 5 files changed, 48 insertions(+), 33 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index 567375e56c..ea3bdb0699 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -417,6 +417,7 @@ typedef struct QCowL2Meta
      * from @cow_start and @cow_end into one single write operation.
      */
     QEMUIOVector *data_qiov;
+    size_t data_qiov_offset;
 
     /** Pointer to next L2Meta of the same write request */
     struct QCowL2Meta *next;
diff --git a/include/qemu/iov.h b/include/qemu/iov.h
index 29957c8a72..bffc151282 100644
--- a/include/qemu/iov.h
+++ b/include/qemu/iov.h
@@ -206,6 +206,7 @@ void qemu_iovec_init_extended(
         void *tail_buf, size_t tail_len);
 void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
                            size_t offset, size_t len);
+int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len);
 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);
 void qemu_iovec_concat(QEMUIOVector *dst,
                        QEMUIOVector *src, size_t soffset, size_t sbytes);
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 1159d6ed2f..00b1a9ab8d 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -830,7 +830,6 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta *m)
     assert(start->nb_bytes <= UINT_MAX - end->nb_bytes);
     assert(start->nb_bytes + end->nb_bytes <= UINT_MAX - data_bytes);
     assert(start->offset + start->nb_bytes <= end->offset);
-    assert(!m->data_qiov || m->data_qiov->size == data_bytes);
 
     if ((start->nb_bytes == 0 && end->nb_bytes == 0) || m->skip_cow) {
         return 0;
@@ -862,7 +861,11 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta *m)
     /* The part of the buffer where the end region is located */
     end_buffer = start_buffer + buffer_size - end->nb_bytes;
 
-    qemu_iovec_init(&qiov, 2 + (m->data_qiov ? m->data_qiov->niov : 0));
+    qemu_iovec_init(&qiov, 2 + (m->data_qiov ?
+                                qemu_iovec_subvec_niov(m->data_qiov,
+                                                       m->data_qiov_offset,
+                                                       data_bytes)
+                                : 0));
 
     qemu_co_mutex_unlock(&s->lock);
     /* First we read the existing data from both COW regions. We
@@ -905,7 +908,7 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta *m)
         if (start->nb_bytes) {
             qemu_iovec_add(&qiov, start_buffer, start->nb_bytes);
         }
-        qemu_iovec_concat(&qiov, m->data_qiov, 0, data_bytes);
+        qemu_iovec_concat(&qiov, m->data_qiov, m->data_qiov_offset, data_bytes);
         if (end->nb_bytes) {
             qemu_iovec_add(&qiov, end_buffer, end->nb_bytes);
         }
diff --git a/block/qcow2.c b/block/qcow2.c
index c389ef07b0..850117cfa2 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2091,7 +2091,8 @@ fail:
 /* Check if it's possible to merge a write request with the writing of
  * the data from the COW regions */
 static bool merge_cow(uint64_t offset, unsigned bytes,
-                      QEMUIOVector *hd_qiov, QCowL2Meta *l2meta)
+                      QEMUIOVector *qiov, size_t qiov_offset,
+                      QCowL2Meta *l2meta)
 {
     QCowL2Meta *m;
 
@@ -2120,11 +2121,12 @@ static bool merge_cow(uint64_t offset, unsigned bytes,
 
         /* Make sure that adding both COW regions to the QEMUIOVector
          * does not exceed IOV_MAX */
-        if (hd_qiov->niov > IOV_MAX - 2) {
+        if (qemu_iovec_subvec_niov(qiov, qiov_offset, bytes) > IOV_MAX - 2) {
             continue;
         }
 
-        m->data_qiov = hd_qiov;
+        m->data_qiov = qiov;
+        m->data_qiov_offset = qiov_offset;
         return true;
     }
 
@@ -2205,24 +2207,22 @@ static int handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta)
     return 0;
 }
 
-static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
-                                         uint64_t bytes, QEMUIOVector *qiov,
-                                         int flags)
+static coroutine_fn int qcow2_co_pwritev_part(
+        BlockDriverState *bs, uint64_t offset, uint64_t bytes,
+        QEMUIOVector *qiov, size_t qiov_offset, int flags)
 {
     BDRVQcow2State *s = bs->opaque;
     int offset_in_cluster;
     int ret;
     unsigned int cur_bytes; /* number of sectors in current iteration */
     uint64_t cluster_offset;
-    QEMUIOVector hd_qiov;
+    QEMUIOVector encrypted_qiov;
     uint64_t bytes_done = 0;
     uint8_t *cluster_data = NULL;
     QCowL2Meta *l2meta = NULL;
 
     trace_qcow2_writev_start_req(qemu_coroutine_self(), offset, bytes);
 
-    qemu_iovec_init(&hd_qiov, qiov->niov);
-
     qemu_co_mutex_lock(&s->lock);
 
     while (bytes != 0) {
@@ -2255,9 +2255,6 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
 
         qemu_co_mutex_unlock(&s->lock);
 
-        qemu_iovec_reset(&hd_qiov);
-        qemu_iovec_concat(&hd_qiov, qiov, bytes_done, cur_bytes);
-
         if (bs->encrypted) {
             assert(s->crypto);
             if (!cluster_data) {
@@ -2270,9 +2267,9 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
                 }
             }
 
-            assert(hd_qiov.size <=
-                   QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
-            qemu_iovec_to_buf(&hd_qiov, 0, cluster_data, hd_qiov.size);
+            assert(cur_bytes <= QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
+            qemu_iovec_to_buf(qiov, qiov_offset + bytes_done,
+                              cluster_data, cur_bytes);
 
             if (qcow2_co_encrypt(bs, cluster_offset, offset,
                                  cluster_data, cur_bytes) < 0) {
@@ -2280,8 +2277,7 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
                 goto out_unlocked;
             }
 
-            qemu_iovec_reset(&hd_qiov);
-            qemu_iovec_add(&hd_qiov, cluster_data, cur_bytes);
+            qemu_iovec_init_buf(&encrypted_qiov, cluster_data, cur_bytes);
         }
 
         /* Try to efficiently initialize the physical space with zeroes */
@@ -2294,13 +2290,17 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
          * writing of the guest data together with that of the COW regions.
          * If it's not possible (or not necessary) then write the
          * guest data now. */
-        if (!merge_cow(offset, cur_bytes, &hd_qiov, l2meta)) {
+        if (!merge_cow(offset, cur_bytes,
+                       bs->encrypted ? &encrypted_qiov : qiov,
+                       bs->encrypted ? 0 : qiov_offset + bytes_done, l2meta))
+        {
             BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
             trace_qcow2_writev_data(qemu_coroutine_self(),
                                     cluster_offset + offset_in_cluster);
-            ret = bdrv_co_pwritev(s->data_file,
-                                  cluster_offset + offset_in_cluster,
-                                  cur_bytes, &hd_qiov, 0);
+            ret = bdrv_co_pwritev_part(
+                    s->data_file, cluster_offset + offset_in_cluster, cur_bytes,
+                    bs->encrypted ? &encrypted_qiov : qiov,
+                    bs->encrypted ? 0 : qiov_offset + bytes_done, 0);
             if (ret < 0) {
                 goto out_unlocked;
             }
@@ -2329,7 +2329,6 @@ out_locked:
 
     qemu_co_mutex_unlock(&s->lock);
 
-    qemu_iovec_destroy(&hd_qiov);
     qemu_vfree(cluster_data);
     trace_qcow2_writev_done_req(qemu_coroutine_self(), ret);
 
@@ -3993,8 +3992,9 @@ fail:
 /* XXX: put compressed sectors first, then all the cluster aligned
    tables to avoid losing bytes in alignment */
 static coroutine_fn int
-qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
-                            uint64_t bytes, QEMUIOVector *qiov)
+qcow2_co_pwritev_compressed_part(BlockDriverState *bs,
+                                 uint64_t offset, uint64_t bytes,
+                                 QEMUIOVector *qiov, size_t qiov_offset)
 {
     BDRVQcow2State *s = bs->opaque;
     int ret;
@@ -4031,7 +4031,7 @@ qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
         /* Zero-pad last write if image size is not cluster aligned */
         memset(buf + bytes, 0, s->cluster_size - bytes);
     }
-    qemu_iovec_to_buf(qiov, 0, buf, bytes);
+    qemu_iovec_to_buf(qiov, qiov_offset, buf, bytes);
 
     out_buf = g_malloc(s->cluster_size);
 
@@ -4039,7 +4039,7 @@ qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
                                 buf, s->cluster_size);
     if (out_len == -ENOMEM) {
         /* could not compress: write normal cluster */
-        ret = qcow2_co_pwritev(bs, offset, bytes, qiov, 0);
+        ret = qcow2_co_pwritev_part(bs, offset, bytes, qiov, qiov_offset, 0);
         if (ret < 0) {
             goto fail;
         }
@@ -4623,8 +4623,8 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
     BDRVQcow2State *s = bs->opaque;
 
     BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
-    return bs->drv->bdrv_co_pwritev(bs, qcow2_vm_state_offset(s) + pos,
-                                    qiov->size, qiov, 0);
+    return bs->drv->bdrv_co_pwritev_part(bs, qcow2_vm_state_offset(s) + pos,
+                                         qiov->size, qiov, 0, 0);
 }
 
 static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
@@ -5175,7 +5175,7 @@ BlockDriver bdrv_qcow2 = {
     .bdrv_co_block_status = qcow2_co_block_status,
 
     .bdrv_co_preadv_part    = qcow2_co_preadv_part,
-    .bdrv_co_pwritev        = qcow2_co_pwritev,
+    .bdrv_co_pwritev_part   = qcow2_co_pwritev_part,
     .bdrv_co_flush_to_os    = qcow2_co_flush_to_os,
 
     .bdrv_co_pwrite_zeroes  = qcow2_co_pwrite_zeroes,
@@ -5183,7 +5183,7 @@ BlockDriver bdrv_qcow2 = {
     .bdrv_co_copy_range_from = qcow2_co_copy_range_from,
     .bdrv_co_copy_range_to  = qcow2_co_copy_range_to,
     .bdrv_co_truncate       = qcow2_co_truncate,
-    .bdrv_co_pwritev_compressed = qcow2_co_pwritev_compressed,
+    .bdrv_co_pwritev_compressed_part = qcow2_co_pwritev_compressed_part,
     .bdrv_make_empty        = qcow2_make_empty,
 
     .bdrv_snapshot_create   = qcow2_snapshot_create,
diff --git a/util/iov.c b/util/iov.c
index d988a533ce..0ed75e764c 100644
--- a/util/iov.c
+++ b/util/iov.c
@@ -401,6 +401,16 @@ static struct iovec *qiov_slice(QEMUIOVector *qiov,
     return iov;
 }
 
+int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len)
+{
+    size_t head, tail;
+    int niov;
+
+    qiov_slice(qiov, offset, len, &head, &tail, &niov);
+
+    return niov;
+}
+
 /*
  * Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov,
  * and @tail_buf buffer into new qiov.
-- 
2.18.0

Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[no-reply]

Patchew URL: https://patchew.org/QEMU/20190604161514.262241-1-vsementsov@virtuozzo.com/



Hi,

This series failed the asan build test. Please find the testing commands and
their output below. If you have Docker installed, you can probably reproduce it
locally.

=== TEST SCRIPT BEGIN ===
#!/bin/bash
time make docker-test-debug@fedora TARGET_LIST=x86_64-softmmu J=14 NETWORK=1
=== TEST SCRIPT END ===

  CC      accel/tcg/trace.o
  CC      crypto/trace.o
  CC      authz/trace.o
/tmp/qemu-test/src/util/iov.c:428:9: error: variable 'mid_niov' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
    if (mid_len) {
        ^~~~~~~
/tmp/qemu-test/src/util/iov.c:433:31: note: uninitialized use occurs here


The full log is available at
http://patchew.org/logs/20190604161514.262241-1-vsementsov@virtuozzo.com/testing.asan/?type=message.
---
Email generated automatically by Patchew [https://patchew.org/].
Please send your feedback to patchew-devel@redhat.com

Re: [Qemu-devel] [PATCH v2 01/12] util/iov: introduce qemu_iovec_init_extended

[Vladimir Sementsov-Ogievskiy]

04.06.2019 19:15, Vladimir Sementsov-Ogievskiy wrote:
> Introduce new initialization API, to create requests with padding. Will
> be used in the following patch. New API uses qemu_iovec_init_buf if
> resulting io vector has only one element, to avoid extra allocations.
> So, we need to update qemu_iovec_destroy to support destroying such
> QIOVs.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>   include/qemu/iov.h |   7 +++
>   util/iov.c         | 112 +++++++++++++++++++++++++++++++++++++++++++--
>   2 files changed, 114 insertions(+), 5 deletions(-)
> 
> diff --git a/include/qemu/iov.h b/include/qemu/iov.h
> index 48b45987b7..f3787a0cf7 100644
> --- a/include/qemu/iov.h
> +++ b/include/qemu/iov.h
> @@ -199,6 +199,13 @@ static inline void *qemu_iovec_buf(QEMUIOVector *qiov)
>   
>   void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);
>   void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov);
> +void qemu_iovec_init_extended(
> +        QEMUIOVector *qiov,
> +        void *head_buf, size_t head_len,
> +        QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,
> +        void *tail_buf, size_t tail_len);
> +void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
> +                           size_t offset, size_t len);
>   void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);
>   void qemu_iovec_concat(QEMUIOVector *dst,
>                          QEMUIOVector *src, size_t soffset, size_t sbytes);
> diff --git a/util/iov.c b/util/iov.c
> index 74e6ca8ed7..39b6e31494 100644
> --- a/util/iov.c
> +++ b/util/iov.c
> @@ -353,6 +353,103 @@ void qemu_iovec_concat(QEMUIOVector *dst,
>       qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
>   }
>   
> +/*
> + * qiov_find_iov
> + *
> + * Return pointer to iovec structure, where byte at @offset in original vector
> + * @iov exactly is.
> + * Set @remaining_offset to be offset inside that iovec to the same byte.
> + */
> +static struct iovec *iov_skip_offset(struct iovec *iov, size_t offset,
> +                                     size_t *remaining_offset)
> +{
> +    while (offset > 0 && offset >= iov->iov_len) {
> +        offset -= iov->iov_len;
> +        iov++;
> +    }
> +    *remaining_offset = offset;
> +
> +    return iov;
> +}
> +
> +/*
> + * qiov_slice
> + *
> + * Find subarray of iovec's, containing requested range. @head would
> + * be offset in first iov (returned by the function), @tail would be
> + * count of extra bytes in last iovec (returned iov + @niov - 1).
> + */
> +static struct iovec *qiov_slice(QEMUIOVector *qiov,
> +                                size_t offset, size_t len,
> +                                size_t *head, size_t *tail, int *niov)
> +{
> +    struct iovec *iov, *end_iov;
> +
> +    assert(offset + len <= qiov->size);
> +
> +    iov = iov_skip_offset(qiov->iov, offset, head);
> +    end_iov = iov_skip_offset(iov, *head + len, tail);
> +
> +    if (*tail > 0) {
> +        assert(*tail < end_iov->iov_len);
> +        *tail = end_iov->iov_len - *tail;
> +        end_iov++;
> +    }
> +
> +    *niov = end_iov - iov;
> +
> +    return iov;
> +}
> +
> +/*
> + * Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov,
> + * and @tail_buf buffer into new qiov.
> + */
> +void qemu_iovec_init_extended(
> +        QEMUIOVector *qiov,
> +        void *head_buf, size_t head_len,
> +        QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,
> +        void *tail_buf, size_t tail_len)
> +{
> +    size_t mid_head, mid_tail;
> +    int total_niov, mid_niov;

Oops, clang is right, mid_niov may be uninitialized. So, here should be "mid_niov = 0".

> +    struct iovec *p, *mid_iov;
> +
> +    if (mid_len) {
> +        mid_iov = qiov_slice(mid_qiov, mid_offset, mid_len,
> +                             &mid_head, &mid_tail, &mid_niov);
> +    }
> +
> +    total_niov = !!head_len + mid_niov + !!tail_len;
> +    if (total_niov == 1) {
> +        qemu_iovec_init_buf(qiov, NULL, 0);
> +        p = &qiov->local_iov;
> +    } else {
> +        qiov->niov = qiov->nalloc = total_niov;
> +        qiov->size = head_len + mid_len + tail_len;
> +        p = qiov->iov = g_new(struct iovec, qiov->niov);
> +    }
> +
> +    if (head_len) {
> +        p->iov_base = head_buf;
> +        p->iov_len = head_len;
> +        p++;
> +    }
> +
> +    if (mid_len) {
> +        memcpy(p, mid_iov, mid_niov * sizeof(*p));
> +        p[0].iov_base = (uint8_t *)p[0].iov_base + mid_head;
> +        p[0].iov_len -= mid_head;
> +        p[mid_niov - 1].iov_len -= mid_tail;
> +        p += mid_niov;
> +    }
> +
> +    if (tail_len) {
> +        p->iov_base = tail_buf;
> +        p->iov_len = tail_len;
> +    }
> +}
> +
>   /*
>    * Check if the contents of the iovecs are all zero
>    */
> @@ -374,14 +471,19 @@ bool qemu_iovec_is_zero(QEMUIOVector *qiov)
>       return true;
>   }
>   
> +void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
> +                           size_t offset, size_t len)
> +{
> +    qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0);
> +}
> +
>   void qemu_iovec_destroy(QEMUIOVector *qiov)
>   {
> -    assert(qiov->nalloc != -1);
> +    if (qiov->nalloc != -1) {
> +        g_free(qiov->iov);
> +    }
>   
> -    qemu_iovec_reset(qiov);
> -    g_free(qiov->iov);
> -    qiov->nalloc = 0;
> -    qiov->iov = NULL;
> +    memset(qiov, 0, sizeof(*qiov));
>   }
>   
>   void qemu_iovec_reset(QEMUIOVector *qiov)
> 


-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 1892 bytes --]

On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
> 
> Here is new parameter qiov_offset for io path, to avoid
> a lot of places with same pattern of creating local_qiov or hd_qiov
> variables.
> 
> These series also includes my
> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
> with some changes [described in 01 and 03 emails]
> 
> Vladimir Sementsov-Ogievskiy (12):
>   util/iov: introduce qemu_iovec_init_extended
>   util/iov: improve qemu_iovec_is_zero
>   block/io: refactor padding
>   block: define .*_part io handlers in BlockDriver
>   block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>   block/io: bdrv_co_do_copy_on_readv: lazy allocation
>   block/io: bdrv_aligned_preadv: use and support qiov_offset
>   block/io: bdrv_aligned_pwritev: use and support qiov_offset
>   block/io: introduce bdrv_co_p{read,write}v_part
>   block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>   block/qcow2: implement .bdrv_co_preadv_part
>   block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
> 
>  block/qcow2.h             |   1 +
>  include/block/block_int.h |  21 ++
>  include/qemu/iov.h        |  10 +-
>  block/backup.c            |   2 +-
>  block/io.c                | 532 ++++++++++++++++++++++----------------
>  block/qcow2-cluster.c     |  14 +-
>  block/qcow2.c             | 131 +++++-----
>  qemu-img.c                |   4 +-
>  util/iov.c                | 153 +++++++++--
>  9 files changed, 559 insertions(+), 309 deletions(-)
> 
> -- 
> 2.18.0
> 
> 

I don't see a significant advantage after taking into account more
complex code (e.g. additional block driver interfaces) and the risk of
introducing new bugs.  A measurable performance improvement would make
this refactoring more attractive.  Still:

Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Vladimir Sementsov-Ogievskiy]

28.06.2019 11:43, Stefan Hajnoczi wrote:
> On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> Here is new parameter qiov_offset for io path, to avoid
>> a lot of places with same pattern of creating local_qiov or hd_qiov
>> variables.
>>
>> These series also includes my
>> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
>> with some changes [described in 01 and 03 emails]
>>
>> Vladimir Sementsov-Ogievskiy (12):
>>    util/iov: introduce qemu_iovec_init_extended
>>    util/iov: improve qemu_iovec_is_zero
>>    block/io: refactor padding
>>    block: define .*_part io handlers in BlockDriver
>>    block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>>    block/io: bdrv_co_do_copy_on_readv: lazy allocation
>>    block/io: bdrv_aligned_preadv: use and support qiov_offset
>>    block/io: bdrv_aligned_pwritev: use and support qiov_offset
>>    block/io: introduce bdrv_co_p{read,write}v_part
>>    block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>>    block/qcow2: implement .bdrv_co_preadv_part
>>    block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
>>
>>   block/qcow2.h             |   1 +
>>   include/block/block_int.h |  21 ++
>>   include/qemu/iov.h        |  10 +-
>>   block/backup.c            |   2 +-
>>   block/io.c                | 532 ++++++++++++++++++++++----------------
>>   block/qcow2-cluster.c     |  14 +-
>>   block/qcow2.c             | 131 +++++-----
>>   qemu-img.c                |   4 +-
>>   util/iov.c                | 153 +++++++++--
>>   9 files changed, 559 insertions(+), 309 deletions(-)
>>
>> -- 
>> 2.18.0
>>
>>
> 
> I don't see a significant advantage after taking into account more
> complex code (e.g. additional block driver interfaces) and the risk of
> introducing new bugs.  A measurable performance improvement would make
> this refactoring more attractive.  Still:
> 
> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
> 

Hmm, I understand your doubt. And I doubt that there will be some significant performance
gain.

What will you say if instead of adding new interfaces I just add qiov_offset parameter to
old ones, and add one boolean field to BlockDriver like .supports_qiov_offset, so, generic
code will use non-zero qiov_offset only for drivers supporting it? And, maybe, add corresponding
asserts to all not-supporting driver handlers?

-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 1671 bytes --]

On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
> 
> Here is new parameter qiov_offset for io path, to avoid
> a lot of places with same pattern of creating local_qiov or hd_qiov
> variables.
> 
> These series also includes my
> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
> with some changes [described in 01 and 03 emails]
> 
> Vladimir Sementsov-Ogievskiy (12):
>   util/iov: introduce qemu_iovec_init_extended
>   util/iov: improve qemu_iovec_is_zero
>   block/io: refactor padding
>   block: define .*_part io handlers in BlockDriver
>   block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>   block/io: bdrv_co_do_copy_on_readv: lazy allocation
>   block/io: bdrv_aligned_preadv: use and support qiov_offset
>   block/io: bdrv_aligned_pwritev: use and support qiov_offset
>   block/io: introduce bdrv_co_p{read,write}v_part
>   block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>   block/qcow2: implement .bdrv_co_preadv_part
>   block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
> 
>  block/qcow2.h             |   1 +
>  include/block/block_int.h |  21 ++
>  include/qemu/iov.h        |  10 +-
>  block/backup.c            |   2 +-
>  block/io.c                | 532 ++++++++++++++++++++++----------------
>  block/qcow2-cluster.c     |  14 +-
>  block/qcow2.c             | 131 +++++-----
>  qemu-img.c                |   4 +-
>  util/iov.c                | 153 +++++++++--
>  9 files changed, 559 insertions(+), 309 deletions(-)
> 
> -- 
> 2.18.0

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

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Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Vladimir Sementsov-Ogievskiy]

29.07.2019 18:24, Stefan Hajnoczi wrote:
> On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> Here is new parameter qiov_offset for io path, to avoid
>> a lot of places with same pattern of creating local_qiov or hd_qiov
>> variables.
>>
>> These series also includes my
>> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
>> with some changes [described in 01 and 03 emails]
>>
>> Vladimir Sementsov-Ogievskiy (12):
>>    util/iov: introduce qemu_iovec_init_extended
>>    util/iov: improve qemu_iovec_is_zero
>>    block/io: refactor padding
>>    block: define .*_part io handlers in BlockDriver
>>    block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>>    block/io: bdrv_co_do_copy_on_readv: lazy allocation
>>    block/io: bdrv_aligned_preadv: use and support qiov_offset
>>    block/io: bdrv_aligned_pwritev: use and support qiov_offset
>>    block/io: introduce bdrv_co_p{read,write}v_part
>>    block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>>    block/qcow2: implement .bdrv_co_preadv_part
>>    block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
>>
>>   block/qcow2.h             |   1 +
>>   include/block/block_int.h |  21 ++
>>   include/qemu/iov.h        |  10 +-
>>   block/backup.c            |   2 +-
>>   block/io.c                | 532 ++++++++++++++++++++++----------------
>>   block/qcow2-cluster.c     |  14 +-
>>   block/qcow2.c             | 131 +++++-----
>>   qemu-img.c                |   4 +-
>>   util/iov.c                | 153 +++++++++--
>>   9 files changed, 559 insertions(+), 309 deletions(-)
>>
>> -- 
>> 2.18.0
> 
> Thanks, applied to my block tree:
> https://github.com/stefanha/qemu/commits/block
> 
> Stefan
> 

Thanks! Than I can base my further work on parallelizing qcow2
read/write loops  on it, great! (long ago v1 was
[PATCH 0/7] qcow2: async handling of fragmented io)

-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Vladimir Sementsov-Ogievskiy]

29.07.2019 18:24, Stefan Hajnoczi wrote:
> On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> Here is new parameter qiov_offset for io path, to avoid
>> a lot of places with same pattern of creating local_qiov or hd_qiov
>> variables.
>>
>> These series also includes my
>> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
>> with some changes [described in 01 and 03 emails]
>>
>> Vladimir Sementsov-Ogievskiy (12):
>>    util/iov: introduce qemu_iovec_init_extended
>>    util/iov: improve qemu_iovec_is_zero
>>    block/io: refactor padding
>>    block: define .*_part io handlers in BlockDriver
>>    block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>>    block/io: bdrv_co_do_copy_on_readv: lazy allocation
>>    block/io: bdrv_aligned_preadv: use and support qiov_offset
>>    block/io: bdrv_aligned_pwritev: use and support qiov_offset
>>    block/io: introduce bdrv_co_p{read,write}v_part
>>    block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>>    block/qcow2: implement .bdrv_co_preadv_part
>>    block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
>>
>>   block/qcow2.h             |   1 +
>>   include/block/block_int.h |  21 ++
>>   include/qemu/iov.h        |  10 +-
>>   block/backup.c            |   2 +-
>>   block/io.c                | 532 ++++++++++++++++++++++----------------
>>   block/qcow2-cluster.c     |  14 +-
>>   block/qcow2.c             | 131 +++++-----
>>   qemu-img.c                |   4 +-
>>   util/iov.c                | 153 +++++++++--
>>   9 files changed, 559 insertions(+), 309 deletions(-)
>>
>> -- 
>> 2.18.0
> 
> Thanks, applied to my block tree:
> https://github.com/stefanha/qemu/commits/block
> 
> Stefan
> 

Could you please squash this into 01:

diff --git a/util/iov.c b/util/iov.c
index 0ed75e764c..5059e10431 100644
--- a/util/iov.c
+++ b/util/iov.c
@@ -422,7 +422,7 @@ void qemu_iovec_init_extended(
          void *tail_buf, size_t tail_len)
  {
      size_t mid_head, mid_tail;
-    int total_niov, mid_niov;
+    int total_niov, mid_niov = 0;
      struct iovec *p, *mid_iov;

      if (mid_len) {



-- 
Best regards,
Vladimir

Re: [Qemu-devel] [Qemu-block] [PATCH v2 00/12] block: qiov_offset parameter for io

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 2451 bytes --]

On Thu, Aug 15, 2019 at 11:12:35AM +0000, Vladimir Sementsov-Ogievskiy wrote:
> 29.07.2019 18:24, Stefan Hajnoczi wrote:
> > On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> >> Hi all!
> >>
> >> Here is new parameter qiov_offset for io path, to avoid
> >> a lot of places with same pattern of creating local_qiov or hd_qiov
> >> variables.
> >>
> >> These series also includes my
> >> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
> >> with some changes [described in 01 and 03 emails]
> >>
> >> Vladimir Sementsov-Ogievskiy (12):
> >>    util/iov: introduce qemu_iovec_init_extended
> >>    util/iov: improve qemu_iovec_is_zero
> >>    block/io: refactor padding
> >>    block: define .*_part io handlers in BlockDriver
> >>    block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
> >>    block/io: bdrv_co_do_copy_on_readv: lazy allocation
> >>    block/io: bdrv_aligned_preadv: use and support qiov_offset
> >>    block/io: bdrv_aligned_pwritev: use and support qiov_offset
> >>    block/io: introduce bdrv_co_p{read,write}v_part
> >>    block/qcow2: refactor qcow2_co_preadv to use buffer-based io
> >>    block/qcow2: implement .bdrv_co_preadv_part
> >>    block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
> >>
> >>   block/qcow2.h             |   1 +
> >>   include/block/block_int.h |  21 ++
> >>   include/qemu/iov.h        |  10 +-
> >>   block/backup.c            |   2 +-
> >>   block/io.c                | 532 ++++++++++++++++++++++----------------
> >>   block/qcow2-cluster.c     |  14 +-
> >>   block/qcow2.c             | 131 +++++-----
> >>   qemu-img.c                |   4 +-
> >>   util/iov.c                | 153 +++++++++--
> >>   9 files changed, 559 insertions(+), 309 deletions(-)
> >>
> >> -- 
> >> 2.18.0
> > 
> > Thanks, applied to my block tree:
> > https://github.com/stefanha/qemu/commits/block
> > 
> > Stefan
> > 
> 
> Could you please squash this into 01:
> 
> diff --git a/util/iov.c b/util/iov.c
> index 0ed75e764c..5059e10431 100644
> --- a/util/iov.c
> +++ b/util/iov.c
> @@ -422,7 +422,7 @@ void qemu_iovec_init_extended(
>           void *tail_buf, size_t tail_len)
>   {
>       size_t mid_head, mid_tail;
> -    int total_niov, mid_niov;
> +    int total_niov, mid_niov = 0;
>       struct iovec *p, *mid_iov;
> 
>       if (mid_len) {

Done.  Sending the pull request today.

Stefan

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Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 1729 bytes --]

On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
> 
> Here is new parameter qiov_offset for io path, to avoid
> a lot of places with same pattern of creating local_qiov or hd_qiov
> variables.
> 
> These series also includes my
> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
> with some changes [described in 01 and 03 emails]
> 
> Vladimir Sementsov-Ogievskiy (12):
>   util/iov: introduce qemu_iovec_init_extended
>   util/iov: improve qemu_iovec_is_zero
>   block/io: refactor padding
>   block: define .*_part io handlers in BlockDriver
>   block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>   block/io: bdrv_co_do_copy_on_readv: lazy allocation
>   block/io: bdrv_aligned_preadv: use and support qiov_offset
>   block/io: bdrv_aligned_pwritev: use and support qiov_offset
>   block/io: introduce bdrv_co_p{read,write}v_part
>   block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>   block/qcow2: implement .bdrv_co_preadv_part
>   block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
> 
>  block/qcow2.h             |   1 +
>  include/block/block_int.h |  21 ++
>  include/qemu/iov.h        |  10 +-
>  block/backup.c            |   2 +-
>  block/io.c                | 532 ++++++++++++++++++++++----------------
>  block/qcow2-cluster.c     |  14 +-
>  block/qcow2.c             | 131 +++++-----
>  qemu-img.c                |   4 +-
>  util/iov.c                | 153 +++++++++--
>  9 files changed, 559 insertions(+), 309 deletions(-)

qemu-iotests 077 fails after I apply this series (including your
uninitialized variable fix).  I'm afraid I can't include it in the block
pull request, sorry!

Stefan

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Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Vladimir Sementsov-Ogievskiy]

22.08.2019 18:50, Stefan Hajnoczi wrote:
> On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> Here is new parameter qiov_offset for io path, to avoid
>> a lot of places with same pattern of creating local_qiov or hd_qiov
>> variables.
>>
>> These series also includes my
>> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
>> with some changes [described in 01 and 03 emails]
>>
>> Vladimir Sementsov-Ogievskiy (12):
>>    util/iov: introduce qemu_iovec_init_extended
>>    util/iov: improve qemu_iovec_is_zero
>>    block/io: refactor padding
>>    block: define .*_part io handlers in BlockDriver
>>    block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>>    block/io: bdrv_co_do_copy_on_readv: lazy allocation
>>    block/io: bdrv_aligned_preadv: use and support qiov_offset
>>    block/io: bdrv_aligned_pwritev: use and support qiov_offset
>>    block/io: introduce bdrv_co_p{read,write}v_part
>>    block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>>    block/qcow2: implement .bdrv_co_preadv_part
>>    block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
>>
>>   block/qcow2.h             |   1 +
>>   include/block/block_int.h |  21 ++
>>   include/qemu/iov.h        |  10 +-
>>   block/backup.c            |   2 +-
>>   block/io.c                | 532 ++++++++++++++++++++++----------------
>>   block/qcow2-cluster.c     |  14 +-
>>   block/qcow2.c             | 131 +++++-----
>>   qemu-img.c                |   4 +-
>>   util/iov.c                | 153 +++++++++--
>>   9 files changed, 559 insertions(+), 309 deletions(-)
> 
> qemu-iotests 077 fails after I apply this series (including your
> uninitialized variable fix).  I'm afraid I can't include it in the block
> pull request, sorry!
> 
> Stefan
> 

Hmm, 77 don't work on master for me:
077      fail       [20:23:57] [20:23:59]                    output mismatch (see 077.out.bad)
--- /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out     2019-04-22 15:06:56.162045432 +0300
+++ /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out.bad 2019-08-22 20:23:59.124122307 +0300
@@ -1,7 +1,15 @@
  QA output created by 077
+==117186==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
+==117186==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffefc071000; bottom 0x7fad7277b000; size: 0x0051898f6000 (350200225792)
+False positive error reports may follow
+For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
  Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728

  == Some concurrent requests involving RMW ==
+==117197==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
+==117197==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa4fcc000; bottom 0x7fa93a2c1000; size: 0x00566ad0b000 (371159248896)
+False positive error reports may follow
+For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
  wrote XXX/XXX bytes at offset XXX
  XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
  wrote XXX/XXX bytes at offset XXX
@@ -66,6 +74,10 @@
  XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

  == Verify image content ==
+==117219==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
+==117219==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffc722de000; bottom 0x7f0848232000; size: 0x00f42a0ac000 (1048677367808)
+False positive error reports may follow
+For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
  read 512/512 bytes at offset 0
  512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
  read 512/512 bytes at offset 512
@@ -156,5 +168,9 @@
  1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
  read 2048/2048 bytes at offset 71680
  2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+==117229==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
+==117229==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa3342000; bottom 0x7fd85a275000; size: 0x0027490cd000 (168729300992)
+False positive error reports may follow
+For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
  No errors were found on the image.
  *** done
Failures: 077
Failed 1 of 1 tests



-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Vladimir Sementsov-Ogievskiy]

22.08.2019 20:24, Vladimir Sementsov-Ogievskiy wrote:
> 22.08.2019 18:50, Stefan Hajnoczi wrote:
>> On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>>> Hi all!
>>>
>>> Here is new parameter qiov_offset for io path, to avoid
>>> a lot of places with same pattern of creating local_qiov or hd_qiov
>>> variables.
>>>
>>> These series also includes my
>>> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
>>> with some changes [described in 01 and 03 emails]
>>>
>>> Vladimir Sementsov-Ogievskiy (12):
>>>    util/iov: introduce qemu_iovec_init_extended
>>>    util/iov: improve qemu_iovec_is_zero
>>>    block/io: refactor padding
>>>    block: define .*_part io handlers in BlockDriver
>>>    block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>>>    block/io: bdrv_co_do_copy_on_readv: lazy allocation
>>>    block/io: bdrv_aligned_preadv: use and support qiov_offset
>>>    block/io: bdrv_aligned_pwritev: use and support qiov_offset
>>>    block/io: introduce bdrv_co_p{read,write}v_part
>>>    block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>>>    block/qcow2: implement .bdrv_co_preadv_part
>>>    block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
>>>
>>>   block/qcow2.h             |   1 +
>>>   include/block/block_int.h |  21 ++
>>>   include/qemu/iov.h        |  10 +-
>>>   block/backup.c            |   2 +-
>>>   block/io.c                | 532 ++++++++++++++++++++++----------------
>>>   block/qcow2-cluster.c     |  14 +-
>>>   block/qcow2.c             | 131 +++++-----
>>>   qemu-img.c                |   4 +-
>>>   util/iov.c                | 153 +++++++++--
>>>   9 files changed, 559 insertions(+), 309 deletions(-)
>>
>> qemu-iotests 077 fails after I apply this series (including your
>> uninitialized variable fix).  I'm afraid I can't include it in the block
>> pull request, sorry!
>>
>> Stefan
>>
> 
> Hmm, 77 don't work on master for me:
> 077      fail       [20:23:57] [20:23:59]                    output mismatch (see 077.out.bad)
> --- /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out     2019-04-22 15:06:56.162045432 +0300
> +++ /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out.bad 2019-08-22 20:23:59.124122307 +0300
> @@ -1,7 +1,15 @@
>   QA output created by 077
> +==117186==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
> +==117186==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffefc071000; bottom 0x7fad7277b000; size: 0x0051898f6000 (350200225792)
> +False positive error reports may follow
> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>   Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> 
>   == Some concurrent requests involving RMW ==
> +==117197==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
> +==117197==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa4fcc000; bottom 0x7fa93a2c1000; size: 0x00566ad0b000 (371159248896)
> +False positive error reports may follow
> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>   wrote XXX/XXX bytes at offset XXX
>   XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>   wrote XXX/XXX bytes at offset XXX
> @@ -66,6 +74,10 @@
>   XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> 
>   == Verify image content ==
> +==117219==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
> +==117219==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffc722de000; bottom 0x7f0848232000; size: 0x00f42a0ac000 (1048677367808)
> +False positive error reports may follow
> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>   read 512/512 bytes at offset 0
>   512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>   read 512/512 bytes at offset 512
> @@ -156,5 +168,9 @@
>   1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>   read 2048/2048 bytes at offset 71680
>   2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> +==117229==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
> +==117229==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa3342000; bottom 0x7fd85a275000; size: 0x0027490cd000 (168729300992)
> +False positive error reports may follow
> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>   No errors were found on the image.
>   *** done
> Failures: 077
> Failed 1 of 1 tests
> 
> 
> 

But after "block/io: refactor padding" it hangs instead of this fail.. This is not good


-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Vladimir Sementsov-Ogievskiy]

22.08.2019 20:39, Vladimir Sementsov-Ogievskiy wrote:
> 22.08.2019 20:24, Vladimir Sementsov-Ogievskiy wrote:
>> 22.08.2019 18:50, Stefan Hajnoczi wrote:
>>> On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>>>> Hi all!
>>>>
>>>> Here is new parameter qiov_offset for io path, to avoid
>>>> a lot of places with same pattern of creating local_qiov or hd_qiov
>>>> variables.
>>>>
>>>> These series also includes my
>>>> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
>>>> with some changes [described in 01 and 03 emails]
>>>>
>>>> Vladimir Sementsov-Ogievskiy (12):
>>>>    util/iov: introduce qemu_iovec_init_extended
>>>>    util/iov: improve qemu_iovec_is_zero
>>>>    block/io: refactor padding
>>>>    block: define .*_part io handlers in BlockDriver
>>>>    block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>>>>    block/io: bdrv_co_do_copy_on_readv: lazy allocation
>>>>    block/io: bdrv_aligned_preadv: use and support qiov_offset
>>>>    block/io: bdrv_aligned_pwritev: use and support qiov_offset
>>>>    block/io: introduce bdrv_co_p{read,write}v_part
>>>>    block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>>>>    block/qcow2: implement .bdrv_co_preadv_part
>>>>    block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
>>>>
>>>>   block/qcow2.h             |   1 +
>>>>   include/block/block_int.h |  21 ++
>>>>   include/qemu/iov.h        |  10 +-
>>>>   block/backup.c            |   2 +-
>>>>   block/io.c                | 532 ++++++++++++++++++++++----------------
>>>>   block/qcow2-cluster.c     |  14 +-
>>>>   block/qcow2.c             | 131 +++++-----
>>>>   qemu-img.c                |   4 +-
>>>>   util/iov.c                | 153 +++++++++--
>>>>   9 files changed, 559 insertions(+), 309 deletions(-)
>>>
>>> qemu-iotests 077 fails after I apply this series (including your
>>> uninitialized variable fix).  I'm afraid I can't include it in the block
>>> pull request, sorry!
>>>
>>> Stefan
>>>
>>
>> Hmm, 77 don't work on master for me:
>> 077      fail       [20:23:57] [20:23:59]                    output mismatch (see 077.out.bad)
>> --- /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out     2019-04-22 15:06:56.162045432 +0300
>> +++ /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out.bad 2019-08-22 20:23:59.124122307 +0300
>> @@ -1,7 +1,15 @@
>>   QA output created by 077
>> +==117186==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>> +==117186==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffefc071000; bottom 0x7fad7277b000; size: 0x0051898f6000 (350200225792)
>> +False positive error reports may follow
>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>   Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
>>
>>   == Some concurrent requests involving RMW ==
>> +==117197==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>> +==117197==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa4fcc000; bottom 0x7fa93a2c1000; size: 0x00566ad0b000 (371159248896)
>> +False positive error reports may follow
>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>   wrote XXX/XXX bytes at offset XXX
>>   XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>   wrote XXX/XXX bytes at offset XXX
>> @@ -66,6 +74,10 @@
>>   XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>
>>   == Verify image content ==
>> +==117219==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>> +==117219==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffc722de000; bottom 0x7f0848232000; size: 0x00f42a0ac000 (1048677367808)
>> +False positive error reports may follow
>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>   read 512/512 bytes at offset 0
>>   512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>   read 512/512 bytes at offset 512
>> @@ -156,5 +168,9 @@
>>   1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>   read 2048/2048 bytes at offset 71680
>>   2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>> +==117229==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>> +==117229==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa3342000; bottom 0x7fd85a275000; size: 0x0027490cd000 (168729300992)
>> +False positive error reports may follow
>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>   No errors were found on the image.
>>   *** done
>> Failures: 077
>> Failed 1 of 1 tests
>>
>>
>>
> 
> But after "block/io: refactor padding" it hangs instead of this fail.. This is not good
> 
> 

Aha seems it's because 77 has "break pwritev_rmw_after_tail" which may not fire if we have merge_reads = true.

So, for me the following fix for 03 helps (77 fails, but not hangs, so same behavior as on master):

diff --git a/block/io.c b/block/io.c
index 6448f1c503..04e69400d8 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1493,13 +1493,23 @@ static int bdrv_padding_rmw_read(BdrvChild *child,

          qemu_iovec_init_buf(&local_qiov, pad->buf, bytes);

-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
+        if (pad->head) {
+            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
+        }
+        if (pad->merge_reads && pad->tail) {
+            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
+        }
          ret = bdrv_aligned_preadv(child, req, req->overlap_offset, bytes,
                                    align, &local_qiov, 0);
          if (ret < 0) {
              return ret;
          }
-        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
+        if (pad->head) {
+            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
+        }
+        if (pad->merge_reads && pad->tail) {
+            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
+        }


Does it work for you?

-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 6842 bytes --]

On Thu, Aug 22, 2019 at 05:59:43PM +0000, Vladimir Sementsov-Ogievskiy wrote:
> 22.08.2019 20:39, Vladimir Sementsov-Ogievskiy wrote:
> > 22.08.2019 20:24, Vladimir Sementsov-Ogievskiy wrote:
> >> 22.08.2019 18:50, Stefan Hajnoczi wrote:
> >>> On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> >>>> Hi all!
> >>>>
> >>>> Here is new parameter qiov_offset for io path, to avoid
> >>>> a lot of places with same pattern of creating local_qiov or hd_qiov
> >>>> variables.
> >>>>
> >>>> These series also includes my
> >>>> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
> >>>> with some changes [described in 01 and 03 emails]
> >>>>
> >>>> Vladimir Sementsov-Ogievskiy (12):
> >>>>    util/iov: introduce qemu_iovec_init_extended
> >>>>    util/iov: improve qemu_iovec_is_zero
> >>>>    block/io: refactor padding
> >>>>    block: define .*_part io handlers in BlockDriver
> >>>>    block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
> >>>>    block/io: bdrv_co_do_copy_on_readv: lazy allocation
> >>>>    block/io: bdrv_aligned_preadv: use and support qiov_offset
> >>>>    block/io: bdrv_aligned_pwritev: use and support qiov_offset
> >>>>    block/io: introduce bdrv_co_p{read,write}v_part
> >>>>    block/qcow2: refactor qcow2_co_preadv to use buffer-based io
> >>>>    block/qcow2: implement .bdrv_co_preadv_part
> >>>>    block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
> >>>>
> >>>>   block/qcow2.h             |   1 +
> >>>>   include/block/block_int.h |  21 ++
> >>>>   include/qemu/iov.h        |  10 +-
> >>>>   block/backup.c            |   2 +-
> >>>>   block/io.c                | 532 ++++++++++++++++++++++----------------
> >>>>   block/qcow2-cluster.c     |  14 +-
> >>>>   block/qcow2.c             | 131 +++++-----
> >>>>   qemu-img.c                |   4 +-
> >>>>   util/iov.c                | 153 +++++++++--
> >>>>   9 files changed, 559 insertions(+), 309 deletions(-)
> >>>
> >>> qemu-iotests 077 fails after I apply this series (including your
> >>> uninitialized variable fix).  I'm afraid I can't include it in the block
> >>> pull request, sorry!
> >>>
> >>> Stefan
> >>>
> >>
> >> Hmm, 77 don't work on master for me:
> >> 077      fail       [20:23:57] [20:23:59]                    output mismatch (see 077.out.bad)
> >> --- /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out     2019-04-22 15:06:56.162045432 +0300
> >> +++ /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out.bad 2019-08-22 20:23:59.124122307 +0300
> >> @@ -1,7 +1,15 @@
> >>   QA output created by 077
> >> +==117186==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
> >> +==117186==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffefc071000; bottom 0x7fad7277b000; size: 0x0051898f6000 (350200225792)
> >> +False positive error reports may follow
> >> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
> >>   Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> >>
> >>   == Some concurrent requests involving RMW ==
> >> +==117197==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
> >> +==117197==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa4fcc000; bottom 0x7fa93a2c1000; size: 0x00566ad0b000 (371159248896)
> >> +False positive error reports may follow
> >> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
> >>   wrote XXX/XXX bytes at offset XXX
> >>   XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> >>   wrote XXX/XXX bytes at offset XXX
> >> @@ -66,6 +74,10 @@
> >>   XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> >>
> >>   == Verify image content ==
> >> +==117219==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
> >> +==117219==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffc722de000; bottom 0x7f0848232000; size: 0x00f42a0ac000 (1048677367808)
> >> +False positive error reports may follow
> >> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
> >>   read 512/512 bytes at offset 0
> >>   512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> >>   read 512/512 bytes at offset 512
> >> @@ -156,5 +168,9 @@
> >>   1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> >>   read 2048/2048 bytes at offset 71680
> >>   2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> >> +==117229==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
> >> +==117229==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa3342000; bottom 0x7fd85a275000; size: 0x0027490cd000 (168729300992)
> >> +False positive error reports may follow
> >> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
> >>   No errors were found on the image.
> >>   *** done
> >> Failures: 077
> >> Failed 1 of 1 tests
> >>
> >>
> >>
> > 
> > But after "block/io: refactor padding" it hangs instead of this fail.. This is not good
> > 
> > 
> 
> Aha seems it's because 77 has "break pwritev_rmw_after_tail" which may not fire if we have merge_reads = true.
> 
> So, for me the following fix for 03 helps (77 fails, but not hangs, so same behavior as on master):
> 
> diff --git a/block/io.c b/block/io.c
> index 6448f1c503..04e69400d8 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -1493,13 +1493,23 @@ static int bdrv_padding_rmw_read(BdrvChild *child,
> 
>           qemu_iovec_init_buf(&local_qiov, pad->buf, bytes);
> 
> -        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
> +        if (pad->head) {
> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
> +        }
> +        if (pad->merge_reads && pad->tail) {
> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
> +        }
>           ret = bdrv_aligned_preadv(child, req, req->overlap_offset, bytes,
>                                     align, &local_qiov, 0);
>           if (ret < 0) {
>               return ret;
>           }
> -        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
> +        if (pad->head) {
> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
> +        }
> +        if (pad->merge_reads && pad->tail) {
> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
> +        }
> 
> 
> Does it work for you?

Yes, it works as expected now, thanks.  I've squashed in your fix and
will send these patches in the next block pull request.

Stefan

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Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Vladimir Sementsov-Ogievskiy]

23.08.2019 19:21, Stefan Hajnoczi wrote:
> On Thu, Aug 22, 2019 at 05:59:43PM +0000, Vladimir Sementsov-Ogievskiy wrote:
>> 22.08.2019 20:39, Vladimir Sementsov-Ogievskiy wrote:
>>> 22.08.2019 20:24, Vladimir Sementsov-Ogievskiy wrote:
>>>> 22.08.2019 18:50, Stefan Hajnoczi wrote:
>>>>> On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>>>>>> Hi all!
>>>>>>
>>>>>> Here is new parameter qiov_offset for io path, to avoid
>>>>>> a lot of places with same pattern of creating local_qiov or hd_qiov
>>>>>> variables.
>>>>>>
>>>>>> These series also includes my
>>>>>> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
>>>>>> with some changes [described in 01 and 03 emails]
>>>>>>
>>>>>> Vladimir Sementsov-Ogievskiy (12):
>>>>>>     util/iov: introduce qemu_iovec_init_extended
>>>>>>     util/iov: improve qemu_iovec_is_zero
>>>>>>     block/io: refactor padding
>>>>>>     block: define .*_part io handlers in BlockDriver
>>>>>>     block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>>>>>>     block/io: bdrv_co_do_copy_on_readv: lazy allocation
>>>>>>     block/io: bdrv_aligned_preadv: use and support qiov_offset
>>>>>>     block/io: bdrv_aligned_pwritev: use and support qiov_offset
>>>>>>     block/io: introduce bdrv_co_p{read,write}v_part
>>>>>>     block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>>>>>>     block/qcow2: implement .bdrv_co_preadv_part
>>>>>>     block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
>>>>>>
>>>>>>    block/qcow2.h             |   1 +
>>>>>>    include/block/block_int.h |  21 ++
>>>>>>    include/qemu/iov.h        |  10 +-
>>>>>>    block/backup.c            |   2 +-
>>>>>>    block/io.c                | 532 ++++++++++++++++++++++----------------
>>>>>>    block/qcow2-cluster.c     |  14 +-
>>>>>>    block/qcow2.c             | 131 +++++-----
>>>>>>    qemu-img.c                |   4 +-
>>>>>>    util/iov.c                | 153 +++++++++--
>>>>>>    9 files changed, 559 insertions(+), 309 deletions(-)
>>>>>
>>>>> qemu-iotests 077 fails after I apply this series (including your
>>>>> uninitialized variable fix).  I'm afraid I can't include it in the block
>>>>> pull request, sorry!
>>>>>
>>>>> Stefan
>>>>>
>>>>
>>>> Hmm, 77 don't work on master for me:
>>>> 077      fail       [20:23:57] [20:23:59]                    output mismatch (see 077.out.bad)
>>>> --- /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out     2019-04-22 15:06:56.162045432 +0300
>>>> +++ /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out.bad 2019-08-22 20:23:59.124122307 +0300
>>>> @@ -1,7 +1,15 @@
>>>>    QA output created by 077
>>>> +==117186==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>>>> +==117186==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffefc071000; bottom 0x7fad7277b000; size: 0x0051898f6000 (350200225792)
>>>> +False positive error reports may follow
>>>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>>>    Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
>>>>
>>>>    == Some concurrent requests involving RMW ==
>>>> +==117197==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>>>> +==117197==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa4fcc000; bottom 0x7fa93a2c1000; size: 0x00566ad0b000 (371159248896)
>>>> +False positive error reports may follow
>>>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>>>    wrote XXX/XXX bytes at offset XXX
>>>>    XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>>    wrote XXX/XXX bytes at offset XXX
>>>> @@ -66,6 +74,10 @@
>>>>    XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>>
>>>>    == Verify image content ==
>>>> +==117219==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>>>> +==117219==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffc722de000; bottom 0x7f0848232000; size: 0x00f42a0ac000 (1048677367808)
>>>> +False positive error reports may follow
>>>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>>>    read 512/512 bytes at offset 0
>>>>    512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>>    read 512/512 bytes at offset 512
>>>> @@ -156,5 +168,9 @@
>>>>    1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>>    read 2048/2048 bytes at offset 71680
>>>>    2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>> +==117229==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>>>> +==117229==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa3342000; bottom 0x7fd85a275000; size: 0x0027490cd000 (168729300992)
>>>> +False positive error reports may follow
>>>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>>>    No errors were found on the image.
>>>>    *** done
>>>> Failures: 077
>>>> Failed 1 of 1 tests
>>>>
>>>>
>>>>
>>>
>>> But after "block/io: refactor padding" it hangs instead of this fail.. This is not good
>>>
>>>
>>
>> Aha seems it's because 77 has "break pwritev_rmw_after_tail" which may not fire if we have merge_reads = true.
>>
>> So, for me the following fix for 03 helps (77 fails, but not hangs, so same behavior as on master):
>>
>> diff --git a/block/io.c b/block/io.c
>> index 6448f1c503..04e69400d8 100644
>> --- a/block/io.c
>> +++ b/block/io.c
>> @@ -1493,13 +1493,23 @@ static int bdrv_padding_rmw_read(BdrvChild *child,
>>
>>            qemu_iovec_init_buf(&local_qiov, pad->buf, bytes);
>>
>> -        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
>> +        if (pad->head) {
>> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
>> +        }
>> +        if (pad->merge_reads && pad->tail) {
>> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
>> +        }
>>            ret = bdrv_aligned_preadv(child, req, req->overlap_offset, bytes,
>>                                      align, &local_qiov, 0);
>>            if (ret < 0) {
>>                return ret;
>>            }
>> -        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
>> +        if (pad->head) {
>> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
>> +        }
>> +        if (pad->merge_reads && pad->tail) {
>> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
>> +        }
>>
>>
>> Does it work for you?
> 
> Yes, it works as expected now, thanks.  I've squashed in your fix and
> will send these patches in the next block pull request.
> 

Thank you!


-- 
Best regards,
Vladimir