[Qemu-devel] [PATCH 0/6] block: Enable byte granularity I/O

[Qemu-devel] [PATCH 0/6] block: Enable byte granularity I/O

[Kevin Wolf]

Previous series have already converted some block drivers to byte-based rather
than sector-based interfaces. However, the common I/O path as well as raw-posix
still enforced a minimum alignment of 512 bytes because some sector-based logic
was involved.

This patch series removes these limitations and a sub-sector request actually
ends up as a sub-sector syscall now.

Kevin Wolf (6):
  block: Byte-based bdrv_co_do_copy_on_readv()
  block: Prepare bdrv_aligned_preadv() for byte-aligned requests
  block: Prepare bdrv_aligned_pwritev() for byte-aligned requests
  raw-posix: Switch to bdrv_co_* interfaces
  raw-posix: Implement .bdrv_co_preadv/pwritev
  block: Don't enforce 512 byte minimum alignment

 block.c               |   2 +-
 block/io.c            | 125 +++++++++++++++++++++++++-------------------------
 block/linux-aio.c     |  83 ++++++++++++++++++++++++---------
 block/mirror.c        |  10 ++--
 block/raw-aio.h       |   2 +
 block/raw-posix.c     |  61 ++++++++++++------------
 include/block/block.h |  10 ++--
 7 files changed, 169 insertions(+), 124 deletions(-)

-- 
1.8.3.1

[Qemu-devel] [PATCH 1/6] block: Byte-based bdrv_co_do_copy_on_readv()

[Kevin Wolf]

In a first step to convert the common I/O path to work on bytes rather
than sectors, this converts the copy-on-read logic that is used by
bdrv_aligned_preadv().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/io.c            | 63 +++++++++++++++++++++++++++++++--------------------
 block/mirror.c        | 10 ++++----
 include/block/block.h | 10 +++++---
 3 files changed, 51 insertions(+), 32 deletions(-)

diff --git a/block/io.c b/block/io.c
index fb99a71..3b34f20 100644
--- a/block/io.c
+++ b/block/io.c
@@ -404,12 +404,12 @@ static void mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
 }
 
 /**
- * Round a region to cluster boundaries
+ * Round a region to cluster boundaries (sector-based)
  */
-void bdrv_round_to_clusters(BlockDriverState *bs,
-                            int64_t sector_num, int nb_sectors,
-                            int64_t *cluster_sector_num,
-                            int *cluster_nb_sectors)
+void bdrv_round_sectors_to_clusters(BlockDriverState *bs,
+                                    int64_t sector_num, int nb_sectors,
+                                    int64_t *cluster_sector_num,
+                                    int *cluster_nb_sectors)
 {
     BlockDriverInfo bdi;
 
@@ -424,6 +424,26 @@ void bdrv_round_to_clusters(BlockDriverState *bs,
     }
 }
 
+/**
+ * Round a region to cluster boundaries
+ */
+void bdrv_round_to_clusters(BlockDriverState *bs,
+                            int64_t offset, unsigned int bytes,
+                            int64_t *cluster_offset,
+                            unsigned int *cluster_bytes)
+{
+    BlockDriverInfo bdi;
+
+    if (bdrv_get_info(bs, &bdi) < 0 || bdi.cluster_size == 0) {
+        *cluster_offset = offset;
+        *cluster_bytes = bytes;
+    } else {
+        int64_t c = bdi.cluster_size;
+        *cluster_offset = QEMU_ALIGN_DOWN(offset, c);
+        *cluster_bytes = QEMU_ALIGN_UP(offset - *cluster_offset + bytes, c);
+    }
+}
+
 static int bdrv_get_cluster_size(BlockDriverState *bs)
 {
     BlockDriverInfo bdi;
@@ -861,7 +881,7 @@ emulate_flags:
 }
 
 static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
+        int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
 {
     /* Perform I/O through a temporary buffer so that users who scribble over
      * their read buffer while the operation is in progress do not end up
@@ -873,21 +893,20 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
     BlockDriver *drv = bs->drv;
     struct iovec iov;
     QEMUIOVector bounce_qiov;
-    int64_t cluster_sector_num;
-    int cluster_nb_sectors;
+    int64_t cluster_offset;
+    unsigned int cluster_bytes;
     size_t skip_bytes;
     int ret;
 
     /* Cover entire cluster so no additional backing file I/O is required when
      * allocating cluster in the image file.
      */
-    bdrv_round_to_clusters(bs, sector_num, nb_sectors,
-                           &cluster_sector_num, &cluster_nb_sectors);
+    bdrv_round_to_clusters(bs, offset, bytes, &cluster_offset, &cluster_bytes);
 
-    trace_bdrv_co_do_copy_on_readv(bs, sector_num, nb_sectors,
-                                   cluster_sector_num, cluster_nb_sectors);
+    trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
+                                   cluster_offset, cluster_bytes);
 
-    iov.iov_len = cluster_nb_sectors * BDRV_SECTOR_SIZE;
+    iov.iov_len = cluster_bytes;
     iov.iov_base = bounce_buffer = qemu_try_blockalign(bs, iov.iov_len);
     if (bounce_buffer == NULL) {
         ret = -ENOMEM;
@@ -896,8 +915,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
 
     qemu_iovec_init_external(&bounce_qiov, &iov, 1);
 
-    ret = bdrv_driver_preadv(bs, cluster_sector_num * BDRV_SECTOR_SIZE,
-                             cluster_nb_sectors * BDRV_SECTOR_SIZE,
+    ret = bdrv_driver_preadv(bs, cluster_offset, cluster_bytes,
                              &bounce_qiov, 0);
     if (ret < 0) {
         goto err;
@@ -905,16 +923,12 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
 
     if (drv->bdrv_co_pwrite_zeroes &&
         buffer_is_zero(bounce_buffer, iov.iov_len)) {
-        ret = bdrv_co_do_pwrite_zeroes(bs,
-                                       cluster_sector_num * BDRV_SECTOR_SIZE,
-                                       cluster_nb_sectors * BDRV_SECTOR_SIZE,
-                                       0);
+        ret = bdrv_co_do_pwrite_zeroes(bs, cluster_offset, cluster_bytes, 0);
     } else {
         /* This does not change the data on the disk, it is not necessary
          * to flush even in cache=writethrough mode.
          */
-        ret = bdrv_driver_pwritev(bs, cluster_sector_num * BDRV_SECTOR_SIZE,
-                                  cluster_nb_sectors * BDRV_SECTOR_SIZE,
+        ret = bdrv_driver_pwritev(bs, cluster_offset, cluster_bytes,
                                   &bounce_qiov, 0);
     }
 
@@ -926,9 +940,8 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
         goto err;
     }
 
-    skip_bytes = (sector_num - cluster_sector_num) * BDRV_SECTOR_SIZE;
-    qemu_iovec_from_buf(qiov, 0, bounce_buffer + skip_bytes,
-                        nb_sectors * BDRV_SECTOR_SIZE);
+    skip_bytes = offset - cluster_offset;
+    qemu_iovec_from_buf(qiov, 0, bounce_buffer + skip_bytes, bytes);
 
 err:
     qemu_vfree(bounce_buffer);
@@ -977,7 +990,7 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
         }
 
         if (!ret || pnum != nb_sectors) {
-            ret = bdrv_co_do_copy_on_readv(bs, sector_num, nb_sectors, qiov);
+            ret = bdrv_co_do_copy_on_readv(bs, offset, bytes, qiov);
             goto out;
         }
     }
diff --git a/block/mirror.c b/block/mirror.c
index 80fd3c7..fbbc496 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -186,8 +186,9 @@ static int mirror_cow_align(MirrorBlockJob *s,
     need_cow |= !test_bit((*sector_num + *nb_sectors - 1) / chunk_sectors,
                           s->cow_bitmap);
     if (need_cow) {
-        bdrv_round_to_clusters(blk_bs(s->target), *sector_num, *nb_sectors,
-                               &align_sector_num, &align_nb_sectors);
+        bdrv_round_sectors_to_clusters(blk_bs(s->target), *sector_num,
+                                       *nb_sectors, &align_sector_num,
+                                       &align_nb_sectors);
     }
 
     if (align_nb_sectors > max_sectors) {
@@ -386,8 +387,9 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
         } else if (ret >= 0 && !(ret & BDRV_BLOCK_DATA)) {
             int64_t target_sector_num;
             int target_nb_sectors;
-            bdrv_round_to_clusters(blk_bs(s->target), sector_num, io_sectors,
-                                   &target_sector_num, &target_nb_sectors);
+            bdrv_round_sectors_to_clusters(blk_bs(s->target), sector_num,
+                                           io_sectors,  &target_sector_num,
+                                           &target_nb_sectors);
             if (target_sector_num == sector_num &&
                 target_nb_sectors == io_sectors) {
                 mirror_method = ret & BDRV_BLOCK_ZERO ?
diff --git a/include/block/block.h b/include/block/block.h
index 54cca28..fb0078f 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -401,10 +401,14 @@ int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
                           const uint8_t *buf, int nb_sectors);
 int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi);
 ImageInfoSpecific *bdrv_get_specific_info(BlockDriverState *bs);
+void bdrv_round_sectors_to_clusters(BlockDriverState *bs,
+                                    int64_t sector_num, int nb_sectors,
+                                    int64_t *cluster_sector_num,
+                                    int *cluster_nb_sectors);
 void bdrv_round_to_clusters(BlockDriverState *bs,
-                            int64_t sector_num, int nb_sectors,
-                            int64_t *cluster_sector_num,
-                            int *cluster_nb_sectors);
+                            int64_t offset, unsigned int bytes,
+                            int64_t *cluster_offset,
+                            unsigned int *cluster_bytes);
 
 const char *bdrv_get_encrypted_filename(BlockDriverState *bs);
 void bdrv_get_backing_filename(BlockDriverState *bs,
-- 
1.8.3.1

[Qemu-devel] [PATCH 2/6] block: Prepare bdrv_aligned_preadv() for byte-aligned requests

[Kevin Wolf]

This patch makes bdrv_aligned_preadv() ready to accept byte-aligned
requests. Note that this doesn't mean that such requests are actually
made. The caller still ensures that all requests are aligned to at least
512 bytes.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/io.c | 41 +++++++++++++++++------------------------
 1 file changed, 17 insertions(+), 24 deletions(-)

diff --git a/block/io.c b/block/io.c
index 3b34f20..2fd88cb 100644
--- a/block/io.c
+++ b/block/io.c
@@ -959,11 +959,6 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
 {
     int ret;
 
-    int64_t sector_num = offset >> BDRV_SECTOR_BITS;
-    unsigned int nb_sectors = bytes >> BDRV_SECTOR_BITS;
-
-    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
-    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
     assert(!qiov || bytes == qiov->size);
     assert((bs->open_flags & BDRV_O_NO_IO) == 0);
 
@@ -982,9 +977,12 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
     }
 
     if (flags & BDRV_REQ_COPY_ON_READ) {
+        int64_t start_sector = offset >> BDRV_SECTOR_BITS;
+        int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
+        unsigned int nb_sectors = end_sector - start_sector;
         int pnum;
 
-        ret = bdrv_is_allocated(bs, sector_num, nb_sectors, &pnum);
+        ret = bdrv_is_allocated(bs, start_sector, nb_sectors, &pnum);
         if (ret < 0) {
             goto out;
         }
@@ -1000,28 +998,24 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
         ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0);
     } else {
         /* Read zeros after EOF */
-        int64_t total_sectors, max_nb_sectors;
+        int64_t total_bytes, max_bytes;
 
-        total_sectors = bdrv_nb_sectors(bs);
-        if (total_sectors < 0) {
-            ret = total_sectors;
+        total_bytes = bdrv_getlength(bs);
+        if (total_bytes < 0) {
+            ret = total_bytes;
             goto out;
         }
 
-        max_nb_sectors = ROUND_UP(MAX(0, total_sectors - sector_num),
-                                  align >> BDRV_SECTOR_BITS);
-        if (nb_sectors < max_nb_sectors) {
+        max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
+        if (bytes < max_bytes) {
             ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0);
-        } else if (max_nb_sectors > 0) {
+        } else if (max_bytes > 0) {
             QEMUIOVector local_qiov;
 
             qemu_iovec_init(&local_qiov, qiov->niov);
-            qemu_iovec_concat(&local_qiov, qiov, 0,
-                              max_nb_sectors * BDRV_SECTOR_SIZE);
+            qemu_iovec_concat(&local_qiov, qiov, 0, max_bytes);
 
-            ret = bdrv_driver_preadv(bs, offset,
-                                     max_nb_sectors * BDRV_SECTOR_SIZE,
-                                     &local_qiov, 0);
+            ret = bdrv_driver_preadv(bs, offset, max_bytes, &local_qiov, 0);
 
             qemu_iovec_destroy(&local_qiov);
         } else {
@@ -1029,11 +1023,10 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
         }
 
         /* Reading beyond end of file is supposed to produce zeroes */
-        if (ret == 0 && total_sectors < sector_num + nb_sectors) {
-            uint64_t offset = MAX(0, total_sectors - sector_num);
-            uint64_t bytes = (sector_num + nb_sectors - offset) *
-                              BDRV_SECTOR_SIZE;
-            qemu_iovec_memset(qiov, offset * BDRV_SECTOR_SIZE, 0, bytes);
+        if (ret == 0 && total_bytes < offset + bytes) {
+            uint64_t zero_offset = MAX(0, total_bytes - offset);
+            uint64_t zero_bytes = offset + bytes - zero_offset;
+            qemu_iovec_memset(qiov, zero_offset, 0, zero_bytes);
         }
     }
 
-- 
1.8.3.1

[Qemu-devel] [PATCH 3/6] block: Prepare bdrv_aligned_pwritev() for byte-aligned requests

[Kevin Wolf]

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/io.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/block/io.c b/block/io.c
index 2fd88cb..4af9c59 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1241,11 +1241,9 @@ static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs,
     bool waited;
     int ret;
 
-    int64_t sector_num = offset >> BDRV_SECTOR_BITS;
-    unsigned int nb_sectors = bytes >> BDRV_SECTOR_BITS;
+    int64_t start_sector = offset >> BDRV_SECTOR_BITS;
+    int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
 
-    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
-    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
     assert(!qiov || bytes == qiov->size);
     assert((bs->open_flags & BDRV_O_NO_IO) == 0);
 
@@ -1269,22 +1267,21 @@ static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs,
         /* Do nothing, write notifier decided to fail this request */
     } else if (flags & BDRV_REQ_ZERO_WRITE) {
         bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO);
-        ret = bdrv_co_do_pwrite_zeroes(bs, sector_num << BDRV_SECTOR_BITS,
-                                       nb_sectors << BDRV_SECTOR_BITS, flags);
+        ret = bdrv_co_do_pwrite_zeroes(bs, offset, bytes, flags);
     } else {
         bdrv_debug_event(bs, BLKDBG_PWRITEV);
         ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, flags);
     }
     bdrv_debug_event(bs, BLKDBG_PWRITEV_DONE);
 
-    bdrv_set_dirty(bs, sector_num, nb_sectors);
+    bdrv_set_dirty(bs, start_sector, end_sector - start_sector);
 
     if (bs->wr_highest_offset < offset + bytes) {
         bs->wr_highest_offset = offset + bytes;
     }
 
     if (ret >= 0) {
-        bs->total_sectors = MAX(bs->total_sectors, sector_num + nb_sectors);
+        bs->total_sectors = MAX(bs->total_sectors, end_sector);
     }
 
     return ret;
-- 
1.8.3.1

[Qemu-devel] [PATCH 4/6] raw-posix: Switch to bdrv_co_* interfaces

[Kevin Wolf]

In order to use the modern byte-based .bdrv_co_preadv/pwritev()
interface, this patch switches raw-posix to coroutine-based interfaces
as a first step. In terms of semantics and performance, it doesn't make
a difference with the existing code whether we go from a coroutine to a
callback-based interface already in block/io.c or only in linux-aio.c

As there have been concerns in the past that this change may be a step
in the wrong direction with respect to a possible AIO fast path, the
old callback-based interface for linux-aio is left around and can be
reactivated when a fast path (e.g. directly from virtio-blk dataplane,
bypassing the whole block layer) is implemented.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/linux-aio.c | 85 +++++++++++++++++++++++++++++++++++++++++--------------
 block/raw-aio.h   |  2 ++
 block/raw-posix.c | 59 ++++++++++++++++++--------------------
 3 files changed, 92 insertions(+), 54 deletions(-)

diff --git a/block/linux-aio.c b/block/linux-aio.c
index 294b2bf..1a56543 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -13,6 +13,7 @@
 #include "qemu/queue.h"
 #include "block/raw-aio.h"
 #include "qemu/event_notifier.h"
+#include "qemu/coroutine.h"
 
 #include <libaio.h>
 
@@ -30,6 +31,7 @@
 
 struct qemu_laiocb {
     BlockAIOCB common;
+    Coroutine *co;
     LinuxAioState *ctx;
     struct iocb iocb;
     ssize_t ret;
@@ -88,9 +90,14 @@ static void qemu_laio_process_completion(struct qemu_laiocb *laiocb)
             }
         }
     }
-    laiocb->common.cb(laiocb->common.opaque, ret);
 
-    qemu_aio_unref(laiocb);
+    laiocb->ret = ret;
+    if (laiocb->co) {
+        qemu_coroutine_enter(laiocb->co, NULL);
+    } else {
+        laiocb->common.cb(laiocb->common.opaque, ret);
+        qemu_aio_unref(laiocb);
+    }
 }
 
 /* The completion BH fetches completed I/O requests and invokes their
@@ -232,22 +239,12 @@ void laio_io_unplug(BlockDriverState *bs, LinuxAioState *s)
     }
 }
 
-BlockAIOCB *laio_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
-        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
-        BlockCompletionFunc *cb, void *opaque, int type)
+static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset,
+                          int type)
 {
-    struct qemu_laiocb *laiocb;
-    struct iocb *iocbs;
-    off_t offset = sector_num * 512;
-
-    laiocb = qemu_aio_get(&laio_aiocb_info, bs, cb, opaque);
-    laiocb->nbytes = nb_sectors * 512;
-    laiocb->ctx = s;
-    laiocb->ret = -EINPROGRESS;
-    laiocb->is_read = (type == QEMU_AIO_READ);
-    laiocb->qiov = qiov;
-
-    iocbs = &laiocb->iocb;
+    LinuxAioState *s = laiocb->ctx;
+    struct iocb *iocbs = &laiocb->iocb;
+    QEMUIOVector *qiov = laiocb->qiov;
 
     switch (type) {
     case QEMU_AIO_WRITE:
@@ -260,7 +257,7 @@ BlockAIOCB *laio_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
     default:
         fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
                         __func__, type);
-        goto out_free_aiocb;
+        return -EIO;
     }
     io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e));
 
@@ -270,11 +267,55 @@ BlockAIOCB *laio_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
         (!s->io_q.plugged || s->io_q.n >= MAX_QUEUED_IO)) {
         ioq_submit(s);
     }
-    return &laiocb->common;
 
-out_free_aiocb:
-    qemu_aio_unref(laiocb);
-    return NULL;
+    return 0;
+}
+
+int laio_submit_co(BlockDriverState *bs, LinuxAioState *s, int fd,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, int type)
+{
+    off_t offset = sector_num * 512;
+    int ret;
+
+    struct qemu_laiocb laiocb = {
+        .co         = qemu_coroutine_self(),
+        .nbytes     = nb_sectors * 512,
+        .ctx        = s,
+        .is_read    = (type == QEMU_AIO_READ),
+        .qiov       = qiov,
+    };
+
+    ret = laio_do_submit(fd, &laiocb, offset, type);
+    if (ret < 0) {
+        return ret;
+    }
+
+    qemu_coroutine_yield();
+    return laiocb.ret;
+}
+
+BlockAIOCB *laio_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockCompletionFunc *cb, void *opaque, int type)
+{
+    struct qemu_laiocb *laiocb;
+    off_t offset = sector_num * 512;
+    int ret;
+
+    laiocb = qemu_aio_get(&laio_aiocb_info, bs, cb, opaque);
+    laiocb->nbytes = nb_sectors * 512;
+    laiocb->ctx = s;
+    laiocb->ret = -EINPROGRESS;
+    laiocb->is_read = (type == QEMU_AIO_READ);
+    laiocb->qiov = qiov;
+
+    ret = laio_do_submit(fd, laiocb, offset, type);
+    if (ret < 0) {
+        qemu_aio_unref(laiocb);
+        return NULL;
+    }
+
+    return &laiocb->common;
 }
 
 void laio_detach_aio_context(LinuxAioState *s, AioContext *old_context)
diff --git a/block/raw-aio.h b/block/raw-aio.h
index 714714e..1037502 100644
--- a/block/raw-aio.h
+++ b/block/raw-aio.h
@@ -38,6 +38,8 @@
 typedef struct LinuxAioState LinuxAioState;
 LinuxAioState *laio_init(void);
 void laio_cleanup(LinuxAioState *s);
+int laio_submit_co(BlockDriverState *bs, LinuxAioState *s, int fd,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, int type);
 BlockAIOCB *laio_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
         BlockCompletionFunc *cb, void *opaque, int type);
diff --git a/block/raw-posix.c b/block/raw-posix.c
index ce2e20f..af7f69f 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -1325,14 +1325,13 @@ static BlockAIOCB *paio_submit(BlockDriverState *bs, int fd,
     return thread_pool_submit_aio(pool, aio_worker, acb, cb, opaque);
 }
 
-static BlockAIOCB *raw_aio_submit(BlockDriverState *bs,
-        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
-        BlockCompletionFunc *cb, void *opaque, int type)
+static int coroutine_fn raw_co_rw(BlockDriverState *bs, int64_t sector_num,
+                                  int nb_sectors, QEMUIOVector *qiov, int type)
 {
     BDRVRawState *s = bs->opaque;
 
     if (fd_open(bs) < 0)
-        return NULL;
+        return -EIO;
 
     /*
      * Check if the underlying device requires requests to be aligned,
@@ -1345,14 +1344,26 @@ static BlockAIOCB *raw_aio_submit(BlockDriverState *bs,
             type |= QEMU_AIO_MISALIGNED;
 #ifdef CONFIG_LINUX_AIO
         } else if (s->use_aio) {
-            return laio_submit(bs, s->aio_ctx, s->fd, sector_num, qiov,
-                               nb_sectors, cb, opaque, type);
+            return laio_submit_co(bs, s->aio_ctx, s->fd, sector_num, qiov,
+                               nb_sectors, type);
 #endif
         }
     }
 
-    return paio_submit(bs, s->fd, sector_num, qiov, nb_sectors,
-                       cb, opaque, type);
+    return paio_submit_co(bs, s->fd, sector_num * BDRV_SECTOR_SIZE, qiov,
+                          nb_sectors * BDRV_SECTOR_SIZE, type);
+}
+
+static int coroutine_fn raw_co_readv(BlockDriverState *bs, int64_t sector_num,
+                                     int nb_sectors, QEMUIOVector *qiov)
+{
+    return raw_co_rw(bs, sector_num, nb_sectors, qiov, QEMU_AIO_READ);
+}
+
+static int coroutine_fn raw_co_writev(BlockDriverState *bs, int64_t sector_num,
+                                      int nb_sectors, QEMUIOVector *qiov)
+{
+    return raw_co_rw(bs, sector_num, nb_sectors, qiov, QEMU_AIO_WRITE);
 }
 
 static void raw_aio_plug(BlockDriverState *bs)
@@ -1375,22 +1386,6 @@ static void raw_aio_unplug(BlockDriverState *bs)
 #endif
 }
 
-static BlockAIOCB *raw_aio_readv(BlockDriverState *bs,
-        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
-        BlockCompletionFunc *cb, void *opaque)
-{
-    return raw_aio_submit(bs, sector_num, qiov, nb_sectors,
-                          cb, opaque, QEMU_AIO_READ);
-}
-
-static BlockAIOCB *raw_aio_writev(BlockDriverState *bs,
-        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
-        BlockCompletionFunc *cb, void *opaque)
-{
-    return raw_aio_submit(bs, sector_num, qiov, nb_sectors,
-                          cb, opaque, QEMU_AIO_WRITE);
-}
-
 static BlockAIOCB *raw_aio_flush(BlockDriverState *bs,
         BlockCompletionFunc *cb, void *opaque)
 {
@@ -1957,8 +1952,8 @@ BlockDriver bdrv_file = {
     .bdrv_co_get_block_status = raw_co_get_block_status,
     .bdrv_co_pwrite_zeroes = raw_co_pwrite_zeroes,
 
-    .bdrv_aio_readv = raw_aio_readv,
-    .bdrv_aio_writev = raw_aio_writev,
+    .bdrv_co_readv          = raw_co_readv,
+    .bdrv_co_writev         = raw_co_writev,
     .bdrv_aio_flush = raw_aio_flush,
     .bdrv_aio_discard = raw_aio_discard,
     .bdrv_refresh_limits = raw_refresh_limits,
@@ -2405,8 +2400,8 @@ static BlockDriver bdrv_host_device = {
     .create_opts         = &raw_create_opts,
     .bdrv_co_pwrite_zeroes = hdev_co_pwrite_zeroes,
 
-    .bdrv_aio_readv	= raw_aio_readv,
-    .bdrv_aio_writev	= raw_aio_writev,
+    .bdrv_co_readv          = raw_co_readv,
+    .bdrv_co_writev         = raw_co_writev,
     .bdrv_aio_flush	= raw_aio_flush,
     .bdrv_aio_discard   = hdev_aio_discard,
     .bdrv_refresh_limits = raw_refresh_limits,
@@ -2535,8 +2530,8 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_create         = hdev_create,
     .create_opts         = &raw_create_opts,
 
-    .bdrv_aio_readv     = raw_aio_readv,
-    .bdrv_aio_writev    = raw_aio_writev,
+    .bdrv_co_readv          = raw_co_readv,
+    .bdrv_co_writev         = raw_co_writev,
     .bdrv_aio_flush	= raw_aio_flush,
     .bdrv_refresh_limits = raw_refresh_limits,
     .bdrv_io_plug = raw_aio_plug,
@@ -2670,8 +2665,8 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_create        = hdev_create,
     .create_opts        = &raw_create_opts,
 
-    .bdrv_aio_readv     = raw_aio_readv,
-    .bdrv_aio_writev    = raw_aio_writev,
+    .bdrv_co_readv          = raw_co_readv,
+    .bdrv_co_writev         = raw_co_writev,
     .bdrv_aio_flush	= raw_aio_flush,
     .bdrv_refresh_limits = raw_refresh_limits,
     .bdrv_io_plug = raw_aio_plug,
-- 
1.8.3.1

[Qemu-devel] [PATCH 5/6] raw-posix: Implement .bdrv_co_preadv/pwritev

[Kevin Wolf]

The raw-posix block driver actually supports byte-aligned requests now
on non-O_DIRECT images, like it already (and previously incorrectly)
claimed in bs->request_alignment.

For some block drivers this means that a RMW cycle can be avoided when
they write sub-sector metadata e.g. for cluster allocation.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/linux-aio.c |  6 ++----
 block/raw-aio.h   |  2 +-
 block/raw-posix.c | 42 ++++++++++++++++++++++--------------------
 3 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/block/linux-aio.c b/block/linux-aio.c
index 1a56543..8dc34db 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -272,14 +272,12 @@ static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset,
 }
 
 int laio_submit_co(BlockDriverState *bs, LinuxAioState *s, int fd,
-        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, int type)
+                   uint64_t offset, QEMUIOVector *qiov, int type)
 {
-    off_t offset = sector_num * 512;
     int ret;
-
     struct qemu_laiocb laiocb = {
         .co         = qemu_coroutine_self(),
-        .nbytes     = nb_sectors * 512,
+        .nbytes     = qiov->size,
         .ctx        = s,
         .is_read    = (type == QEMU_AIO_READ),
         .qiov       = qiov,
diff --git a/block/raw-aio.h b/block/raw-aio.h
index 1037502..3f5b8bb 100644
--- a/block/raw-aio.h
+++ b/block/raw-aio.h
@@ -39,7 +39,7 @@ typedef struct LinuxAioState LinuxAioState;
 LinuxAioState *laio_init(void);
 void laio_cleanup(LinuxAioState *s);
 int laio_submit_co(BlockDriverState *bs, LinuxAioState *s, int fd,
-        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, int type);
+                   uint64_t offset, QEMUIOVector *qiov, int type);
 BlockAIOCB *laio_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
         BlockCompletionFunc *cb, void *opaque, int type);
diff --git a/block/raw-posix.c b/block/raw-posix.c
index af7f69f..0db7876 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -1325,8 +1325,8 @@ static BlockAIOCB *paio_submit(BlockDriverState *bs, int fd,
     return thread_pool_submit_aio(pool, aio_worker, acb, cb, opaque);
 }
 
-static int coroutine_fn raw_co_rw(BlockDriverState *bs, int64_t sector_num,
-                                  int nb_sectors, QEMUIOVector *qiov, int type)
+static int coroutine_fn raw_co_prw(BlockDriverState *bs, uint64_t offset,
+                                   uint64_t bytes, QEMUIOVector *qiov, int type)
 {
     BDRVRawState *s = bs->opaque;
 
@@ -1344,26 +1344,27 @@ static int coroutine_fn raw_co_rw(BlockDriverState *bs, int64_t sector_num,
             type |= QEMU_AIO_MISALIGNED;
 #ifdef CONFIG_LINUX_AIO
         } else if (s->use_aio) {
-            return laio_submit_co(bs, s->aio_ctx, s->fd, sector_num, qiov,
-                               nb_sectors, type);
+            assert(qiov->size == bytes);
+            return laio_submit_co(bs, s->aio_ctx, s->fd, offset, qiov, type);
 #endif
         }
     }
 
-    return paio_submit_co(bs, s->fd, sector_num * BDRV_SECTOR_SIZE, qiov,
-                          nb_sectors * BDRV_SECTOR_SIZE, type);
+    return paio_submit_co(bs, s->fd, offset, qiov, bytes, type);
 }
 
-static int coroutine_fn raw_co_readv(BlockDriverState *bs, int64_t sector_num,
-                                     int nb_sectors, QEMUIOVector *qiov)
+static int coroutine_fn raw_co_preadv(BlockDriverState *bs, uint64_t offset,
+                                      uint64_t bytes, QEMUIOVector *qiov,
+                                      int flags)
 {
-    return raw_co_rw(bs, sector_num, nb_sectors, qiov, QEMU_AIO_READ);
+    return raw_co_prw(bs, offset, bytes, qiov, QEMU_AIO_READ);
 }
 
-static int coroutine_fn raw_co_writev(BlockDriverState *bs, int64_t sector_num,
-                                      int nb_sectors, QEMUIOVector *qiov)
+static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, uint64_t offset,
+                                       uint64_t bytes, QEMUIOVector *qiov,
+                                       int flags)
 {
-    return raw_co_rw(bs, sector_num, nb_sectors, qiov, QEMU_AIO_WRITE);
+    return raw_co_prw(bs, offset, bytes, qiov, QEMU_AIO_WRITE);
 }
 
 static void raw_aio_plug(BlockDriverState *bs)
@@ -1952,8 +1953,8 @@ BlockDriver bdrv_file = {
     .bdrv_co_get_block_status = raw_co_get_block_status,
     .bdrv_co_pwrite_zeroes = raw_co_pwrite_zeroes,
 
-    .bdrv_co_readv          = raw_co_readv,
-    .bdrv_co_writev         = raw_co_writev,
+    .bdrv_co_preadv         = raw_co_preadv,
+    .bdrv_co_pwritev        = raw_co_pwritev,
     .bdrv_aio_flush = raw_aio_flush,
     .bdrv_aio_discard = raw_aio_discard,
     .bdrv_refresh_limits = raw_refresh_limits,
@@ -2400,8 +2401,8 @@ static BlockDriver bdrv_host_device = {
     .create_opts         = &raw_create_opts,
     .bdrv_co_pwrite_zeroes = hdev_co_pwrite_zeroes,
 
-    .bdrv_co_readv          = raw_co_readv,
-    .bdrv_co_writev         = raw_co_writev,
+    .bdrv_co_preadv         = raw_co_preadv,
+    .bdrv_co_pwritev        = raw_co_pwritev,
     .bdrv_aio_flush	= raw_aio_flush,
     .bdrv_aio_discard   = hdev_aio_discard,
     .bdrv_refresh_limits = raw_refresh_limits,
@@ -2530,8 +2531,9 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_create         = hdev_create,
     .create_opts         = &raw_create_opts,
 
-    .bdrv_co_readv          = raw_co_readv,
-    .bdrv_co_writev         = raw_co_writev,
+
+    .bdrv_co_preadv         = raw_co_preadv,
+    .bdrv_co_pwritev        = raw_co_pwritev,
     .bdrv_aio_flush	= raw_aio_flush,
     .bdrv_refresh_limits = raw_refresh_limits,
     .bdrv_io_plug = raw_aio_plug,
@@ -2665,8 +2667,8 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_create        = hdev_create,
     .create_opts        = &raw_create_opts,
 
-    .bdrv_co_readv          = raw_co_readv,
-    .bdrv_co_writev         = raw_co_writev,
+    .bdrv_co_preadv         = raw_co_preadv,
+    .bdrv_co_pwritev        = raw_co_pwritev,
     .bdrv_aio_flush	= raw_aio_flush,
     .bdrv_refresh_limits = raw_refresh_limits,
     .bdrv_io_plug = raw_aio_plug,
-- 
1.8.3.1

[Qemu-devel] [PATCH 6/6] block: Don't enforce 512 byte minimum alignment

[Kevin Wolf]

If block drivers say that they can do an alignment < 512 bytes, let's
just suppose they mean it. raw-posix used to be an offender with respect
to this, but it can actually deal with byte-aligned requests now.

The default is still 512 bytes for any drivers that only implement
sector-based interfaces, but it is 1 now for drivers that implement
.bdrv_co_preadv.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c    | 2 +-
 block/io.c | 8 +++-----
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/block.c b/block.c
index f54bc25..3d850a2 100644
--- a/block.c
+++ b/block.c
@@ -937,7 +937,7 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
         goto fail_opts;
     }
 
-    bs->request_alignment = 512;
+    bs->request_alignment = drv->bdrv_co_preadv ? 1 : 512;
     bs->zero_beyond_eof = true;
     bs->read_only = !(bs->open_flags & BDRV_O_RDWR);
 
diff --git a/block/io.c b/block/io.c
index 4af9c59..b3d6228 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1044,8 +1044,7 @@ int coroutine_fn bdrv_co_preadv(BlockDriverState *bs,
     BlockDriver *drv = bs->drv;
     BdrvTrackedRequest req;
 
-    /* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */
-    uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
+    uint64_t align = bs->request_alignment;
     uint8_t *head_buf = NULL;
     uint8_t *tail_buf = NULL;
     QEMUIOVector local_qiov;
@@ -1296,7 +1295,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BlockDriverState *bs,
     uint8_t *buf = NULL;
     QEMUIOVector local_qiov;
     struct iovec iov;
-    uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
+    uint64_t align = bs->request_alignment;
     unsigned int head_padding_bytes, tail_padding_bytes;
     int ret = 0;
 
@@ -1383,8 +1382,7 @@ int coroutine_fn bdrv_co_pwritev(BlockDriverState *bs,
     BdrvRequestFlags flags)
 {
     BdrvTrackedRequest req;
-    /* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */
-    uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
+    uint64_t align = bs->request_alignment;
     uint8_t *head_buf = NULL;
     uint8_t *tail_buf = NULL;
     QEMUIOVector local_qiov;
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH 1/6] block: Byte-based bdrv_co_do_copy_on_readv()

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1752 bytes --]

On 06/08/2016 08:10 AM, Kevin Wolf wrote:
> In a first step to convert the common I/O path to work on bytes rather
> than sectors, this converts the copy-on-read logic that is used by
> bdrv_aligned_preadv().
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/io.c            | 63 +++++++++++++++++++++++++++++++--------------------
>  block/mirror.c        | 10 ++++----
>  include/block/block.h | 10 +++++---
>  3 files changed, 51 insertions(+), 32 deletions(-)
> 

> @@ -873,21 +893,20 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
>      BlockDriver *drv = bs->drv;
>      struct iovec iov;
>      QEMUIOVector bounce_qiov;
> -    int64_t cluster_sector_num;
> -    int cluster_nb_sectors;
> +    int64_t cluster_offset;
> +    unsigned int cluster_bytes;
>      size_t skip_bytes;
>      int ret;
>  
>      /* Cover entire cluster so no additional backing file I/O is required when
>       * allocating cluster in the image file.
>       */
> -    bdrv_round_to_clusters(bs, sector_num, nb_sectors,
> -                           &cluster_sector_num, &cluster_nb_sectors);
> +    bdrv_round_to_clusters(bs, offset, bytes, &cluster_offset, &cluster_bytes);
>  
> -    trace_bdrv_co_do_copy_on_readv(bs, sector_num, nb_sectors,
> -                                   cluster_sector_num, cluster_nb_sectors);
> +    trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
> +                                   cluster_offset, cluster_bytes);

Missing patch to trace-events to advertise new semantics.

With that fixed,
Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH 2/6] block: Prepare bdrv_aligned_preadv() for byte-aligned requests

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1871 bytes --]

On 06/08/2016 08:10 AM, Kevin Wolf wrote:
> This patch makes bdrv_aligned_preadv() ready to accept byte-aligned
> requests. Note that this doesn't mean that such requests are actually
> made. The caller still ensures that all requests are aligned to at least
> 512 bytes.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/io.c | 41 +++++++++++++++++------------------------
>  1 file changed, 17 insertions(+), 24 deletions(-)
> 
> diff --git a/block/io.c b/block/io.c
> index 3b34f20..2fd88cb 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -959,11 +959,6 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
>  {
>      int ret;
>  
> -    int64_t sector_num = offset >> BDRV_SECTOR_BITS;
> -    unsigned int nb_sectors = bytes >> BDRV_SECTOR_BITS;
> -
> -    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);

My recent patch proposal conflicts here; I can drop (or rebase) mine,
but I think you want to keep the asserts, after modifying them to:

assert((offset & (align - 1)) == 0);
assert((bytes & (align - 1)) == 0);

and maybe add 'assert(is_power_of_2(align)); for good measure.


>  
> -        max_nb_sectors = ROUND_UP(MAX(0, total_sectors - sector_num),
> -                                  align >> BDRV_SECTOR_BITS);
> -        if (nb_sectors < max_nb_sectors) {
> +        max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
> +        if (bytes < max_bytes) {

Another one of my posted patches switches this to <= to avoid a harmless
off-by-one, also something I can rebase.

Whether you add the assertions, or leave it for me to (re-)add them in
my rebase,

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH 3/6] block: Prepare bdrv_aligned_pwritev() for byte-aligned requests

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1665 bytes --]

On 06/08/2016 08:10 AM, Kevin Wolf wrote:
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/io.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/block/io.c b/block/io.c
> index 2fd88cb..4af9c59 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -1241,11 +1241,9 @@ static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs,
>      bool waited;
>      int ret;
>  
> -    int64_t sector_num = offset >> BDRV_SECTOR_BITS;
> -    unsigned int nb_sectors = bytes >> BDRV_SECTOR_BITS;
> +    int64_t start_sector = offset >> BDRV_SECTOR_BITS;
> +    int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
>  
> -    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);

I wonder if we should add an 'unsigned int align' parameter to this
function, to mirror bdrv_aligned_preadv() - that way, we can assert that
any divisions we do based on 'align' are indeed aligned. If we do that,
then just as in the previous patch, I think we would want to keep
'assert((offset & (align - 1)) == 0)'.  But at the moment, I don't see
any divisions based on align, so I think you are okay.


>      if (ret >= 0) {
> -        bs->total_sectors = MAX(bs->total_sectors, sector_num + nb_sectors);
> +        bs->total_sectors = MAX(bs->total_sectors, end_sector);

Someday, we may want bs->total_bytes instead of total_sectors, but
unrelated to this patch.

Looks clean:
Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH 4/6] raw-posix: Switch to bdrv_co_* interfaces

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 3123 bytes --]

On 06/08/2016 08:10 AM, Kevin Wolf wrote:
> In order to use the modern byte-based .bdrv_co_preadv/pwritev()
> interface, this patch switches raw-posix to coroutine-based interfaces
> as a first step. In terms of semantics and performance, it doesn't make
> a difference with the existing code whether we go from a coroutine to a
> callback-based interface already in block/io.c or only in linux-aio.c
> 
> As there have been concerns in the past that this change may be a step
> in the wrong direction with respect to a possible AIO fast path, the
> old callback-based interface for linux-aio is left around and can be
> reactivated when a fast path (e.g. directly from virtio-blk dataplane,
> bypassing the whole block layer) is implemented.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/linux-aio.c | 85 +++++++++++++++++++++++++++++++++++++++++--------------
>  block/raw-aio.h   |  2 ++
>  block/raw-posix.c | 59 ++++++++++++++++++--------------------
>  3 files changed, 92 insertions(+), 54 deletions(-)
> 

> +
> +int laio_submit_co(BlockDriverState *bs, LinuxAioState *s, int fd,
> +        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, int type)
> +{
> +    off_t offset = sector_num * 512;

BDRV_SECTOR_SIZE instead of a magic number?

> +    int ret;
> +
> +    struct qemu_laiocb laiocb = {
> +        .co         = qemu_coroutine_self(),
> +        .nbytes     = nb_sectors * 512,

and again


> +
> +BlockAIOCB *laio_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
> +        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
> +        BlockCompletionFunc *cb, void *opaque, int type)
> +{
> +    struct qemu_laiocb *laiocb;
> +    off_t offset = sector_num * 512;
> +    int ret;
> +
> +    laiocb = qemu_aio_get(&laio_aiocb_info, bs, cb, opaque);
> +    laiocb->nbytes = nb_sectors * 512;

and again


> @@ -1345,14 +1344,26 @@ static BlockAIOCB *raw_aio_submit(BlockDriverState *bs,
>              type |= QEMU_AIO_MISALIGNED;
>  #ifdef CONFIG_LINUX_AIO
>          } else if (s->use_aio) {
> -            return laio_submit(bs, s->aio_ctx, s->fd, sector_num, qiov,
> -                               nb_sectors, cb, opaque, type);
> +            return laio_submit_co(bs, s->aio_ctx, s->fd, sector_num, qiov,
> +                               nb_sectors, type);

Indentation is now off


> @@ -1957,8 +1952,8 @@ BlockDriver bdrv_file = {
>      .bdrv_co_get_block_status = raw_co_get_block_status,
>      .bdrv_co_pwrite_zeroes = raw_co_pwrite_zeroes,
>  
> -    .bdrv_aio_readv = raw_aio_readv,
> -    .bdrv_aio_writev = raw_aio_writev,
> +    .bdrv_co_readv          = raw_co_readv,
> +    .bdrv_co_writev         = raw_co_writev,
>      .bdrv_aio_flush = raw_aio_flush,

Why bother with indented alignment of '=' when none of the neighbors do?

Findings are minor enough, so up to you whether to fix them or just mark
this:

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH 5/6] raw-posix: Implement .bdrv_co_preadv/pwritev

[Eric Blake]

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On 06/08/2016 08:10 AM, Kevin Wolf wrote:
> The raw-posix block driver actually supports byte-aligned requests now
> on non-O_DIRECT images, like it already (and previously incorrectly)
> claimed in bs->request_alignment.
> 
> For some block drivers this means that a RMW cycle can be avoided when
> they write sub-sector metadata e.g. for cluster allocation.

[well, there's still probably a RMW going on, but it's being done by the
kernel, rather than qemu - and choice of caching may let the kernel
optimize things... not worth cluttering the commit message with this,
though]

> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---

> +++ b/block/linux-aio.c
> @@ -272,14 +272,12 @@ static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset,
>  }
>  
>  int laio_submit_co(BlockDriverState *bs, LinuxAioState *s, int fd,
> -        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, int type)
> +                   uint64_t offset, QEMUIOVector *qiov, int type)
>  {
> -    off_t offset = sector_num * 512;
>      int ret;
> -
>      struct qemu_laiocb laiocb = {
>          .co         = qemu_coroutine_self(),
> -        .nbytes     = nb_sectors * 512,
> +        .nbytes     = qiov->size,

So for this interface, we require non-NULL qiov and no duplicated
length; I guess it isn't used for write_zeroes.  We may still want to do
some consistency sweep to decide what level of NULL-ness we want for
representing write_zeroes, rather than ad hoc decisions at each layer of
the call stack, but that's a task for another day.

> @@ -1344,26 +1344,27 @@ static int coroutine_fn raw_co_rw(BlockDriverState *bs, int64_t sector_num,
>              type |= QEMU_AIO_MISALIGNED;
>  #ifdef CONFIG_LINUX_AIO
>          } else if (s->use_aio) {
> -            return laio_submit_co(bs, s->aio_ctx, s->fd, sector_num, qiov,
> -                               nb_sectors, type);
> +            assert(qiov->size == bytes);

Worth hoisting the assertion outside of the #ifdef?...

> +            return laio_submit_co(bs, s->aio_ctx, s->fd, offset, qiov, type);
>  #endif
>          }
>      }
>  
> -    return paio_submit_co(bs, s->fd, sector_num * BDRV_SECTOR_SIZE, qiov,
> -                          nb_sectors * BDRV_SECTOR_SIZE, type);
> +    return paio_submit_co(bs, s->fd, offset, qiov, bytes, type);

...then again, paio_submit_co() also does the assert - and this is more
evidence of our inconsistency on whether we duplicate a separate bytes
parameter or reuse qiov->size.

>  
> -static int coroutine_fn raw_co_readv(BlockDriverState *bs, int64_t sector_num,
> -                                     int nb_sectors, QEMUIOVector *qiov)
> +static int coroutine_fn raw_co_preadv(BlockDriverState *bs, uint64_t offset,
> +                                      uint64_t bytes, QEMUIOVector *qiov,
> +                                      int flags)
>  {
> -    return raw_co_rw(bs, sector_num, nb_sectors, qiov, QEMU_AIO_READ);
> +    return raw_co_prw(bs, offset, bytes, qiov, QEMU_AIO_READ);

We ignore flags, but that's not a change in semantics.  (Maybe someday
we need .supported_read_flags)

>  }
>  
> -static int coroutine_fn raw_co_writev(BlockDriverState *bs, int64_t sector_num,
> -                                      int nb_sectors, QEMUIOVector *qiov)
> +static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, uint64_t offset,
> +                                       uint64_t bytes, QEMUIOVector *qiov,
> +                                       int flags)
>  {
> -    return raw_co_rw(bs, sector_num, nb_sectors, qiov, QEMU_AIO_WRITE);
> +    return raw_co_prw(bs, offset, bytes, qiov, QEMU_AIO_WRITE);

And here, we could assert(!flags) (since we intentionally don't set
.supported_write_flags) - but I won't insist.

None of my comments require a code change, other than a possible added
assertion, so:

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH 6/6] block: Don't enforce 512 byte minimum alignment

[Eric Blake]

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On 06/08/2016 08:10 AM, Kevin Wolf wrote:
> If block drivers say that they can do an alignment < 512 bytes, let's
> just suppose they mean it. raw-posix used to be an offender with respect
> to this, but it can actually deal with byte-aligned requests now.
> 
> The default is still 512 bytes for any drivers that only implement
> sector-based interfaces, but it is 1 now for drivers that implement
> .bdrv_co_preadv.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c    | 2 +-
>  block/io.c | 8 +++-----
>  2 files changed, 4 insertions(+), 6 deletions(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH 0/6] block: Enable byte granularity I/O

[Stefan Hajnoczi]

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On Wed, Jun 08, 2016 at 04:10:05PM +0200, Kevin Wolf wrote:
> Previous series have already converted some block drivers to byte-based rather
> than sector-based interfaces. However, the common I/O path as well as raw-posix
> still enforced a minimum alignment of 512 bytes because some sector-based logic
> was involved.
> 
> This patch series removes these limitations and a sub-sector request actually
> ends up as a sub-sector syscall now.
> 
> Kevin Wolf (6):
>   block: Byte-based bdrv_co_do_copy_on_readv()
>   block: Prepare bdrv_aligned_preadv() for byte-aligned requests
>   block: Prepare bdrv_aligned_pwritev() for byte-aligned requests
>   raw-posix: Switch to bdrv_co_* interfaces
>   raw-posix: Implement .bdrv_co_preadv/pwritev
>   block: Don't enforce 512 byte minimum alignment
> 
>  block.c               |   2 +-
>  block/io.c            | 125 +++++++++++++++++++++++++-------------------------
>  block/linux-aio.c     |  83 ++++++++++++++++++++++++---------
>  block/mirror.c        |  10 ++--
>  block/raw-aio.h       |   2 +
>  block/raw-posix.c     |  61 ++++++++++++------------
>  include/block/block.h |  10 ++--
>  7 files changed, 169 insertions(+), 124 deletions(-)

I've taken an initial look and it looks good.  Will review next revision
in depth so it can be merged after Eric's comments have been addressed.

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Re: [Qemu-devel] [PATCH 0/6] block: Enable byte granularity I/O

[Kevin Wolf]

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Am 13.06.2016 um 15:27 hat Stefan Hajnoczi geschrieben:
> On Wed, Jun 08, 2016 at 04:10:05PM +0200, Kevin Wolf wrote:
> > Previous series have already converted some block drivers to byte-based rather
> > than sector-based interfaces. However, the common I/O path as well as raw-posix
> > still enforced a minimum alignment of 512 bytes because some sector-based logic
> > was involved.
> > 
> > This patch series removes these limitations and a sub-sector request actually
> > ends up as a sub-sector syscall now.
> > 
> > Kevin Wolf (6):
> >   block: Byte-based bdrv_co_do_copy_on_readv()
> >   block: Prepare bdrv_aligned_preadv() for byte-aligned requests
> >   block: Prepare bdrv_aligned_pwritev() for byte-aligned requests
> >   raw-posix: Switch to bdrv_co_* interfaces
> >   raw-posix: Implement .bdrv_co_preadv/pwritev
> >   block: Don't enforce 512 byte minimum alignment
> > 
> >  block.c               |   2 +-
> >  block/io.c            | 125 +++++++++++++++++++++++++-------------------------
> >  block/linux-aio.c     |  83 ++++++++++++++++++++++++---------
> >  block/mirror.c        |  10 ++--
> >  block/raw-aio.h       |   2 +
> >  block/raw-posix.c     |  61 ++++++++++++------------
> >  include/block/block.h |  10 ++--
> >  7 files changed, 169 insertions(+), 124 deletions(-)
> 
> I've taken an initial look and it looks good.  Will review next revision
> in depth so it can be merged after Eric's comments have been addressed.

Eric commented a lot, but only requested very few minor changes that
wouldn't strictly require resending the series. If you think it's
worthwhile to send a v2 for them, I can do that, but it shouldn't make a
big difference for your review.

Kevin

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Re: [Qemu-devel] [PATCH 0/6] block: Enable byte granularity I/O

[Stefan Hajnoczi]

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On Mon, Jun 13, 2016 at 03:43:06PM +0200, Kevin Wolf wrote:
> Am 13.06.2016 um 15:27 hat Stefan Hajnoczi geschrieben:
> > On Wed, Jun 08, 2016 at 04:10:05PM +0200, Kevin Wolf wrote:
> > > Previous series have already converted some block drivers to byte-based rather
> > > than sector-based interfaces. However, the common I/O path as well as raw-posix
> > > still enforced a minimum alignment of 512 bytes because some sector-based logic
> > > was involved.
> > > 
> > > This patch series removes these limitations and a sub-sector request actually
> > > ends up as a sub-sector syscall now.
> > > 
> > > Kevin Wolf (6):
> > >   block: Byte-based bdrv_co_do_copy_on_readv()
> > >   block: Prepare bdrv_aligned_preadv() for byte-aligned requests
> > >   block: Prepare bdrv_aligned_pwritev() for byte-aligned requests
> > >   raw-posix: Switch to bdrv_co_* interfaces
> > >   raw-posix: Implement .bdrv_co_preadv/pwritev
> > >   block: Don't enforce 512 byte minimum alignment
> > > 
> > >  block.c               |   2 +-
> > >  block/io.c            | 125 +++++++++++++++++++++++++-------------------------
> > >  block/linux-aio.c     |  83 ++++++++++++++++++++++++---------
> > >  block/mirror.c        |  10 ++--
> > >  block/raw-aio.h       |   2 +
> > >  block/raw-posix.c     |  61 ++++++++++++------------
> > >  include/block/block.h |  10 ++--
> > >  7 files changed, 169 insertions(+), 124 deletions(-)
> > 
> > I've taken an initial look and it looks good.  Will review next revision
> > in depth so it can be merged after Eric's comments have been addressed.
> 
> Eric commented a lot, but only requested very few minor changes that
> wouldn't strictly require resending the series. If you think it's
> worthwhile to send a v2 for them, I can do that, but it shouldn't make a
> big difference for your review.

Okay, I'll review v1.

Stefan

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Re: [Qemu-devel] [PATCH 4/6] raw-posix: Switch to bdrv_co_* interfaces

[Stefan Hajnoczi]

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On Wed, Jun 08, 2016 at 04:10:09PM +0200, Kevin Wolf wrote:
> diff --git a/block/raw-aio.h b/block/raw-aio.h
> index 714714e..1037502 100644
> --- a/block/raw-aio.h
> +++ b/block/raw-aio.h
> @@ -38,6 +38,8 @@
>  typedef struct LinuxAioState LinuxAioState;
>  LinuxAioState *laio_init(void);
>  void laio_cleanup(LinuxAioState *s);
> +int laio_submit_co(BlockDriverState *bs, LinuxAioState *s, int fd,
> +        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, int type);

Please add coroutine_fn.

Please rename to laio_co_submit(), the naming convention is
bdrv_co_foo() instead of bdrv_foo_co().

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Re: [Qemu-devel] [PATCH 6/6] block: Don't enforce 512 byte minimum alignment

[Stefan Hajnoczi]

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On Wed, Jun 08, 2016 at 04:10:11PM +0200, Kevin Wolf wrote:
> diff --git a/block.c b/block.c
> index f54bc25..3d850a2 100644
> --- a/block.c
> +++ b/block.c
> @@ -937,7 +937,7 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
>          goto fail_opts;
>      }
>  
> -    bs->request_alignment = 512;
> +    bs->request_alignment = drv->bdrv_co_preadv ? 1 : 512;

What happens in the raw-posix.c AIO case?  There we should still use
512.

Stefan

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Re: [Qemu-devel] [PATCH 1/6] block: Byte-based bdrv_co_do_copy_on_readv()

[Stefan Hajnoczi]

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On Wed, Jun 08, 2016 at 04:10:06PM +0200, Kevin Wolf wrote:
> In a first step to convert the common I/O path to work on bytes rather
> than sectors, this converts the copy-on-read logic that is used by
> bdrv_aligned_preadv().
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/io.c            | 63 +++++++++++++++++++++++++++++++--------------------
>  block/mirror.c        | 10 ++++----
>  include/block/block.h | 10 +++++---
>  3 files changed, 51 insertions(+), 32 deletions(-)

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

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Re: [Qemu-devel] [PATCH 2/6] block: Prepare bdrv_aligned_preadv() for byte-aligned requests

[Stefan Hajnoczi]

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On Wed, Jun 08, 2016 at 04:10:07PM +0200, Kevin Wolf wrote:
> This patch makes bdrv_aligned_preadv() ready to accept byte-aligned
> requests. Note that this doesn't mean that such requests are actually
> made. The caller still ensures that all requests are aligned to at least
> 512 bytes.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/io.c | 41 +++++++++++++++++------------------------
>  1 file changed, 17 insertions(+), 24 deletions(-)

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

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Re: [Qemu-devel] [PATCH 3/6] block: Prepare bdrv_aligned_pwritev() for byte-aligned requests

[Stefan Hajnoczi]

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On Wed, Jun 08, 2016 at 04:10:08PM +0200, Kevin Wolf wrote:
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/io.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)

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

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Re: [Qemu-devel] [PATCH 5/6] raw-posix: Implement .bdrv_co_preadv/pwritev

[Stefan Hajnoczi]

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On Wed, Jun 08, 2016 at 04:10:10PM +0200, Kevin Wolf wrote:
> The raw-posix block driver actually supports byte-aligned requests now
> on non-O_DIRECT images, like it already (and previously incorrectly)
> claimed in bs->request_alignment.
> 
> For some block drivers this means that a RMW cycle can be avoided when
> they write sub-sector metadata e.g. for cluster allocation.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/linux-aio.c |  6 ++----
>  block/raw-aio.h   |  2 +-
>  block/raw-posix.c | 42 ++++++++++++++++++++++--------------------
>  3 files changed, 25 insertions(+), 25 deletions(-)

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

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Re: [Qemu-devel] [PATCH 0/6] block: Enable byte granularity I/O

[Stefan Hajnoczi]

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On Mon, Jun 13, 2016 at 03:43:06PM +0200, Kevin Wolf wrote:
> Am 13.06.2016 um 15:27 hat Stefan Hajnoczi geschrieben:
> > On Wed, Jun 08, 2016 at 04:10:05PM +0200, Kevin Wolf wrote:
> > > Previous series have already converted some block drivers to byte-based rather
> > > than sector-based interfaces. However, the common I/O path as well as raw-posix
> > > still enforced a minimum alignment of 512 bytes because some sector-based logic
> > > was involved.
> > > 
> > > This patch series removes these limitations and a sub-sector request actually
> > > ends up as a sub-sector syscall now.
> > > 
> > > Kevin Wolf (6):
> > >   block: Byte-based bdrv_co_do_copy_on_readv()
> > >   block: Prepare bdrv_aligned_preadv() for byte-aligned requests
> > >   block: Prepare bdrv_aligned_pwritev() for byte-aligned requests
> > >   raw-posix: Switch to bdrv_co_* interfaces
> > >   raw-posix: Implement .bdrv_co_preadv/pwritev
> > >   block: Don't enforce 512 byte minimum alignment
> > > 
> > >  block.c               |   2 +-
> > >  block/io.c            | 125 +++++++++++++++++++++++++-------------------------
> > >  block/linux-aio.c     |  83 ++++++++++++++++++++++++---------
> > >  block/mirror.c        |  10 ++--
> > >  block/raw-aio.h       |   2 +
> > >  block/raw-posix.c     |  61 ++++++++++++------------
> > >  include/block/block.h |  10 ++--
> > >  7 files changed, 169 insertions(+), 124 deletions(-)
> > 
> > I've taken an initial look and it looks good.  Will review next revision
> > in depth so it can be merged after Eric's comments have been addressed.
> 
> Eric commented a lot, but only requested very few minor changes that
> wouldn't strictly require resending the series. If you think it's
> worthwhile to send a v2 for them, I can do that, but it shouldn't make a
> big difference for your review.

Done.  Looks very close.

Stefan

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Re: [Qemu-devel] [PATCH 6/6] block: Don't enforce 512 byte minimum alignment

[Kevin Wolf]

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Am 14.06.2016 um 14:09 hat Stefan Hajnoczi geschrieben:
> On Wed, Jun 08, 2016 at 04:10:11PM +0200, Kevin Wolf wrote:
> > diff --git a/block.c b/block.c
> > index f54bc25..3d850a2 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -937,7 +937,7 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
> >          goto fail_opts;
> >      }
> >  
> > -    bs->request_alignment = 512;
> > +    bs->request_alignment = drv->bdrv_co_preadv ? 1 : 512;
> 
> What happens in the raw-posix.c AIO case?  There we should still use
> 512.

I'm only changing the default value here. raw-posix already overrides
bs->request_alignment as needed, see raw_probe_alignment().

Kevin

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