[PATCH for-5.0? 0/9] block/io: safer inc/dec in_flight sections

[PATCH for-5.0? 0/9] block/io: safer inc/dec in_flight sections

[Vladimir Sementsov-Ogievskiy]

Hi all!

This is inspired by Kevin's
"block: Fix blk->in_flight during blk_wait_while_drained()" series.

So, like it's now done for block-backends, let's expand
in_flight-protected sections for bdrv_ interfaces, including
coroutine_enter and BDRV_POLL_WHILE loop into these sections.

Vladimir Sementsov-Ogievskiy (9):
  block/io: refactor bdrv_is_allocated_above to run only one coroutine
  block/io: refactor bdrv_co_ioctl: move aio stuff to corresponding
    block
  block/io: move flush and pdiscard stuff down
  block/io: move bdrv_rw_co_entry and friends down
  block/io: expand in_flight inc/dec section: simple cases
  block/io: expand in_flight inc/dec section: block-status
  block/io: add bdrv_do_pwrite_zeroes
  block/io: move bdrv_make_zero under block-status
  block/io: expand in_flight inc/dec section: bdrv_make_zero

 block/io.c | 780 +++++++++++++++++++++++++++++++++++------------------
 1 file changed, 516 insertions(+), 264 deletions(-)

-- 
2.21.0

[PATCH 1/9] block/io: refactor bdrv_is_allocated_above to run only one coroutine

[Vladimir Sementsov-Ogievskiy]

bdrv_is_allocated_above creates new coroutine on each iteration if
called from non-coroutine context. To simplify expansion of in_flight
inc/dec sections in further patch let's refactor it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 72 insertions(+), 5 deletions(-)

diff --git a/block/io.c b/block/io.c
index aba67f66b9..a9f1a3e93e 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2482,6 +2482,22 @@ static int coroutine_fn bdrv_co_block_status_above(BlockDriverState *bs,
     return ret;
 }
 
+static int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs,
+                                             int64_t offset, int64_t bytes,
+                                             int64_t *pnum)
+{
+    int ret;
+    int64_t dummy;
+
+    ret = bdrv_co_block_status_above(bs, backing_bs(bs), false, offset,
+                                     bytes, pnum ? pnum : &dummy, NULL,
+                                     NULL);
+    if (ret < 0) {
+        return ret;
+    }
+    return !!(ret & BDRV_BLOCK_ALLOCATED);
+}
+
 /* Coroutine wrapper for bdrv_block_status_above() */
 static void coroutine_fn bdrv_block_status_above_co_entry(void *opaque)
 {
@@ -2578,10 +2594,10 @@ int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,
  * but 'pnum' will only be 0 when end of file is reached.
  *
  */
-int bdrv_is_allocated_above(BlockDriverState *top,
-                            BlockDriverState *base,
-                            bool include_base, int64_t offset,
-                            int64_t bytes, int64_t *pnum)
+static int coroutine_fn
+bdrv_co_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
+                           bool include_base, int64_t offset, int64_t bytes,
+                           int64_t *pnum)
 {
     BlockDriverState *intermediate;
     int ret;
@@ -2595,7 +2611,7 @@ int bdrv_is_allocated_above(BlockDriverState *top,
         int64_t size_inter;
 
         assert(intermediate);
-        ret = bdrv_is_allocated(intermediate, offset, bytes, &pnum_inter);
+        ret = bdrv_co_is_allocated(intermediate, offset, bytes, &pnum_inter);
         if (ret < 0) {
             return ret;
         }
@@ -2624,6 +2640,57 @@ int bdrv_is_allocated_above(BlockDriverState *top,
     return 0;
 }
 
+typedef struct BdrvCoIsAllocatedAboveData {
+    BlockDriverState *top;
+    BlockDriverState *base;
+    bool include_base;
+    int64_t offset;
+    int64_t bytes;
+    int64_t *pnum;
+    int ret;
+    bool done;
+} BdrvCoIsAllocatedAboveData;
+
+static void coroutine_fn bdrv_is_allocated_above_co_entry(void *opaque)
+{
+    BdrvCoIsAllocatedAboveData *data = opaque;
+
+    data->ret = bdrv_co_is_allocated_above(data->top, data->base,
+                                           data->include_base,
+                                           data->offset, data->bytes,
+                                           data->pnum);
+    data->done = true;
+    aio_wait_kick();
+}
+
+int coroutine_fn
+bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
+                        bool include_base, int64_t offset, int64_t bytes,
+                        int64_t *pnum)
+{
+    Coroutine *co;
+    BdrvCoIsAllocatedAboveData data = {
+        .top = top,
+        .base = base,
+        .include_base = include_base,
+        .offset = offset,
+        .bytes = bytes,
+        .pnum = pnum,
+        .done = false,
+    };
+
+    if (qemu_in_coroutine()) {
+        /* Fast-path if already in coroutine context */
+        bdrv_is_allocated_above_co_entry(&data);
+    } else {
+        co = qemu_coroutine_create(bdrv_is_allocated_above_co_entry, &data);
+        bdrv_coroutine_enter(top, co);
+        BDRV_POLL_WHILE(top, !data.done);
+    }
+
+    return data.ret;
+}
+
 typedef struct BdrvVmstateCo {
     BlockDriverState    *bs;
     QEMUIOVector        *qiov;
-- 
2.21.0

[PATCH 2/9] block/io: refactor bdrv_co_ioctl: move aio stuff to corresponding block

[Vladimir Sementsov-Ogievskiy]

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/block/io.c b/block/io.c
index a9f1a3e93e..29e53271b6 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3126,31 +3126,38 @@ int bdrv_pdiscard(BdrvChild *child, int64_t offset, int64_t bytes)
 
 int bdrv_co_ioctl(BlockDriverState *bs, int req, void *buf)
 {
+    int ret;
     BlockDriver *drv = bs->drv;
-    CoroutineIOCompletion co = {
-        .coroutine = qemu_coroutine_self(),
-    };
-    BlockAIOCB *acb;
 
     bdrv_inc_in_flight(bs);
+
     if (!drv || (!drv->bdrv_aio_ioctl && !drv->bdrv_co_ioctl)) {
-        co.ret = -ENOTSUP;
+        ret = -ENOTSUP;
         goto out;
     }
 
     if (drv->bdrv_co_ioctl) {
-        co.ret = drv->bdrv_co_ioctl(bs, req, buf);
+        ret = drv->bdrv_co_ioctl(bs, req, buf);
     } else {
+        CoroutineIOCompletion co = {
+            .coroutine = qemu_coroutine_self(),
+        };
+        BlockAIOCB *acb;
+
         acb = drv->bdrv_aio_ioctl(bs, req, buf, bdrv_co_io_em_complete, &co);
         if (!acb) {
-            co.ret = -ENOTSUP;
+            ret = -ENOTSUP;
             goto out;
         }
+
         qemu_coroutine_yield();
+        ret = co.ret;
     }
+
 out:
     bdrv_dec_in_flight(bs);
-    return co.ret;
+
+    return ret;
 }
 
 void *qemu_blockalign(BlockDriverState *bs, size_t size)
-- 
2.21.0

[PATCH 3/9] block/io: move flush and pdiscard stuff down

[Vladimir Sementsov-Ogievskiy]

bdrv_co_flush and bdrv_co_pdiscard will become static in further patch,
move their usage down.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 56 +++++++++++++++++++++++++++---------------------------
 1 file changed, 28 insertions(+), 28 deletions(-)

diff --git a/block/io.c b/block/io.c
index 29e53271b6..379e86eeb5 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2828,20 +2828,6 @@ void bdrv_aio_cancel_async(BlockAIOCB *acb)
 /**************************************************************/
 /* Coroutine block device emulation */
 
-typedef struct FlushCo {
-    BlockDriverState *bs;
-    int ret;
-} FlushCo;
-
-
-static void coroutine_fn bdrv_flush_co_entry(void *opaque)
-{
-    FlushCo *rwco = opaque;
-
-    rwco->ret = bdrv_co_flush(rwco->bs);
-    aio_wait_kick();
-}
-
 int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
 {
     int current_gen;
@@ -2954,6 +2940,19 @@ early_exit:
     return ret;
 }
 
+typedef struct FlushCo {
+    BlockDriverState *bs;
+    int ret;
+} FlushCo;
+
+static void coroutine_fn bdrv_flush_co_entry(void *opaque)
+{
+    FlushCo *rwco = opaque;
+
+    rwco->ret = bdrv_co_flush(rwco->bs);
+    aio_wait_kick();
+}
+
 int bdrv_flush(BlockDriverState *bs)
 {
     Coroutine *co;
@@ -2974,20 +2973,6 @@ int bdrv_flush(BlockDriverState *bs)
     return flush_co.ret;
 }
 
-typedef struct DiscardCo {
-    BdrvChild *child;
-    int64_t offset;
-    int64_t bytes;
-    int ret;
-} DiscardCo;
-static void coroutine_fn bdrv_pdiscard_co_entry(void *opaque)
-{
-    DiscardCo *rwco = opaque;
-
-    rwco->ret = bdrv_co_pdiscard(rwco->child, rwco->offset, rwco->bytes);
-    aio_wait_kick();
-}
-
 int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset,
                                   int64_t bytes)
 {
@@ -3102,6 +3087,21 @@ out:
     return ret;
 }
 
+typedef struct DiscardCo {
+    BdrvChild *child;
+    int64_t offset;
+    int64_t bytes;
+    int ret;
+} DiscardCo;
+
+static void coroutine_fn bdrv_pdiscard_co_entry(void *opaque)
+{
+    DiscardCo *rwco = opaque;
+
+    rwco->ret = bdrv_co_pdiscard(rwco->child, rwco->offset, rwco->bytes);
+    aio_wait_kick();
+}
+
 int bdrv_pdiscard(BdrvChild *child, int64_t offset, int64_t bytes)
 {
     Coroutine *co;
-- 
2.21.0

[PATCH 4/9] block/io: move bdrv_rw_co_entry and friends down

[Vladimir Sementsov-Ogievskiy]

We are going to use bdrv_co_pwritev_part and bdrv_co_preadv_part in
bdrv_rw_co_entry, so move it down.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 361 +++++++++++++++++++++++++++--------------------------
 1 file changed, 181 insertions(+), 180 deletions(-)

diff --git a/block/io.c b/block/io.c
index 379e86eeb5..dfbe68f428 100644
--- a/block/io.c
+++ b/block/io.c
@@ -891,186 +891,6 @@ static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset,
     return 0;
 }
 
-typedef struct RwCo {
-    BdrvChild *child;
-    int64_t offset;
-    QEMUIOVector *qiov;
-    bool is_write;
-    int ret;
-    BdrvRequestFlags flags;
-} RwCo;
-
-static void coroutine_fn bdrv_rw_co_entry(void *opaque)
-{
-    RwCo *rwco = opaque;
-
-    if (!rwco->is_write) {
-        rwco->ret = bdrv_co_preadv(rwco->child, rwco->offset,
-                                   rwco->qiov->size, rwco->qiov,
-                                   rwco->flags);
-    } else {
-        rwco->ret = bdrv_co_pwritev(rwco->child, rwco->offset,
-                                    rwco->qiov->size, rwco->qiov,
-                                    rwco->flags);
-    }
-    aio_wait_kick();
-}
-
-/*
- * Process a vectored synchronous request using coroutines
- */
-static int bdrv_prwv_co(BdrvChild *child, int64_t offset,
-                        QEMUIOVector *qiov, bool is_write,
-                        BdrvRequestFlags flags)
-{
-    Coroutine *co;
-    RwCo rwco = {
-        .child = child,
-        .offset = offset,
-        .qiov = qiov,
-        .is_write = is_write,
-        .ret = NOT_DONE,
-        .flags = flags,
-    };
-
-    if (qemu_in_coroutine()) {
-        /* Fast-path if already in coroutine context */
-        bdrv_rw_co_entry(&rwco);
-    } else {
-        co = qemu_coroutine_create(bdrv_rw_co_entry, &rwco);
-        bdrv_coroutine_enter(child->bs, co);
-        BDRV_POLL_WHILE(child->bs, rwco.ret == NOT_DONE);
-    }
-    return rwco.ret;
-}
-
-int bdrv_pwrite_zeroes(BdrvChild *child, int64_t offset,
-                       int bytes, BdrvRequestFlags flags)
-{
-    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, NULL, bytes);
-
-    return bdrv_prwv_co(child, offset, &qiov, true,
-                        BDRV_REQ_ZERO_WRITE | flags);
-}
-
-/*
- * Completely zero out a block device with the help of bdrv_pwrite_zeroes.
- * The operation is sped up by checking the block status and only writing
- * zeroes to the device if they currently do not return zeroes. Optional
- * flags are passed through to bdrv_pwrite_zeroes (e.g. BDRV_REQ_MAY_UNMAP,
- * BDRV_REQ_FUA).
- *
- * Returns < 0 on error, 0 on success. For error codes see bdrv_write().
- */
-int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
-{
-    int ret;
-    int64_t target_size, bytes, offset = 0;
-    BlockDriverState *bs = child->bs;
-
-    target_size = bdrv_getlength(bs);
-    if (target_size < 0) {
-        return target_size;
-    }
-
-    for (;;) {
-        bytes = MIN(target_size - offset, BDRV_REQUEST_MAX_BYTES);
-        if (bytes <= 0) {
-            return 0;
-        }
-        ret = bdrv_block_status(bs, offset, bytes, &bytes, NULL, NULL);
-        if (ret < 0) {
-            return ret;
-        }
-        if (ret & BDRV_BLOCK_ZERO) {
-            offset += bytes;
-            continue;
-        }
-        ret = bdrv_pwrite_zeroes(child, offset, bytes, flags);
-        if (ret < 0) {
-            return ret;
-        }
-        offset += bytes;
-    }
-}
-
-int bdrv_preadv(BdrvChild *child, int64_t offset, QEMUIOVector *qiov)
-{
-    int ret;
-
-    ret = bdrv_prwv_co(child, offset, qiov, false, 0);
-    if (ret < 0) {
-        return ret;
-    }
-
-    return qiov->size;
-}
-
-/* See bdrv_pwrite() for the return codes */
-int bdrv_pread(BdrvChild *child, int64_t offset, void *buf, int bytes)
-{
-    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
-
-    if (bytes < 0) {
-        return -EINVAL;
-    }
-
-    return bdrv_preadv(child, offset, &qiov);
-}
-
-int bdrv_pwritev(BdrvChild *child, int64_t offset, QEMUIOVector *qiov)
-{
-    int ret;
-
-    ret = bdrv_prwv_co(child, offset, qiov, true, 0);
-    if (ret < 0) {
-        return ret;
-    }
-
-    return qiov->size;
-}
-
-/* Return no. of bytes on success or < 0 on error. Important errors are:
-  -EIO         generic I/O error (may happen for all errors)
-  -ENOMEDIUM   No media inserted.
-  -EINVAL      Invalid offset or number of bytes
-  -EACCES      Trying to write a read-only device
-*/
-int bdrv_pwrite(BdrvChild *child, int64_t offset, const void *buf, int bytes)
-{
-    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
-
-    if (bytes < 0) {
-        return -EINVAL;
-    }
-
-    return bdrv_pwritev(child, offset, &qiov);
-}
-
-/*
- * Writes to the file and ensures that no writes are reordered across this
- * request (acts as a barrier)
- *
- * Returns 0 on success, -errno in error cases.
- */
-int bdrv_pwrite_sync(BdrvChild *child, int64_t offset,
-                     const void *buf, int count)
-{
-    int ret;
-
-    ret = bdrv_pwrite(child, offset, buf, count);
-    if (ret < 0) {
-        return ret;
-    }
-
-    ret = bdrv_flush(child->bs);
-    if (ret < 0) {
-        return ret;
-    }
-
-    return 0;
-}
-
 typedef struct CoroutineIOCompletion {
     Coroutine *coroutine;
     int ret;
@@ -2185,6 +2005,187 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
                            BDRV_REQ_ZERO_WRITE | flags);
 }
 
+typedef struct RwCo {
+    BdrvChild *child;
+    int64_t offset;
+    QEMUIOVector *qiov;
+    bool is_write;
+    int ret;
+    BdrvRequestFlags flags;
+} RwCo;
+
+static void coroutine_fn bdrv_rw_co_entry(void *opaque)
+{
+    RwCo *rwco = opaque;
+
+    if (!rwco->is_write) {
+        rwco->ret = bdrv_co_preadv(rwco->child, rwco->offset,
+                                   rwco->qiov->size, rwco->qiov,
+                                   rwco->flags);
+    } else {
+        rwco->ret = bdrv_co_pwritev(rwco->child, rwco->offset,
+                                    rwco->qiov->size, rwco->qiov,
+                                    rwco->flags);
+    }
+    aio_wait_kick();
+}
+
+/*
+ * Process a vectored synchronous request using coroutines
+ */
+static int bdrv_prwv_co(BdrvChild *child, int64_t offset,
+                        QEMUIOVector *qiov, bool is_write,
+                        BdrvRequestFlags flags)
+{
+    Coroutine *co;
+    RwCo rwco = {
+        .child = child,
+        .offset = offset,
+        .qiov = qiov,
+        .is_write = is_write,
+        .ret = NOT_DONE,
+        .flags = flags,
+    };
+
+    if (qemu_in_coroutine()) {
+        /* Fast-path if already in coroutine context */
+        bdrv_rw_co_entry(&rwco);
+    } else {
+        co = qemu_coroutine_create(bdrv_rw_co_entry, &rwco);
+        bdrv_coroutine_enter(child->bs, co);
+        BDRV_POLL_WHILE(child->bs, rwco.ret == NOT_DONE);
+    }
+    return rwco.ret;
+}
+
+int bdrv_pwrite_zeroes(BdrvChild *child, int64_t offset,
+                       int bytes, BdrvRequestFlags flags)
+{
+    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, NULL, bytes);
+
+    return bdrv_prwv_co(child, offset, &qiov, true,
+                        BDRV_REQ_ZERO_WRITE | flags);
+}
+
+/* See bdrv_pwrite() for the return codes */
+int bdrv_pread(BdrvChild *child, int64_t offset, void *buf, int bytes)
+{
+    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
+
+    if (bytes < 0) {
+        return -EINVAL;
+    }
+
+    return bdrv_preadv(child, offset, &qiov);
+}
+
+int bdrv_pwritev(BdrvChild *child, int64_t offset, QEMUIOVector *qiov)
+{
+    int ret;
+
+    ret = bdrv_prwv_co(child, offset, qiov, true, 0);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return qiov->size;
+}
+
+/*
+ * Return no. of bytes on success or < 0 on error. Important errors are:
+ * -EIO         generic I/O error (may happen for all errors)
+ * -ENOMEDIUM   No media inserted.
+ * -EINVAL      Invalid offset or number of bytes
+ * -EACCES      Trying to write a read-only device
+ */
+int bdrv_pwrite(BdrvChild *child, int64_t offset, const void *buf, int bytes)
+{
+    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
+
+    if (bytes < 0) {
+        return -EINVAL;
+    }
+
+    return bdrv_pwritev(child, offset, &qiov);
+}
+
+/*
+ * Writes to the file and ensures that no writes are reordered across this
+ * request (acts as a barrier)
+ *
+ * Returns 0 on success, -errno in error cases.
+ */
+int bdrv_pwrite_sync(BdrvChild *child, int64_t offset,
+                     const void *buf, int count)
+{
+    int ret;
+
+    ret = bdrv_pwrite(child, offset, buf, count);
+    if (ret < 0) {
+        return ret;
+    }
+
+    ret = bdrv_flush(child->bs);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return 0;
+}
+
+/*
+ * Completely zero out a block device with the help of bdrv_pwrite_zeroes.
+ * The operation is sped up by checking the block status and only writing
+ * zeroes to the device if they currently do not return zeroes. Optional
+ * flags are passed through to bdrv_pwrite_zeroes (e.g. BDRV_REQ_MAY_UNMAP,
+ * BDRV_REQ_FUA).
+ *
+ * Returns < 0 on error, 0 on success. For error codes see bdrv_write().
+ */
+int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
+{
+    int ret;
+    int64_t target_size, bytes, offset = 0;
+    BlockDriverState *bs = child->bs;
+
+    target_size = bdrv_getlength(bs);
+    if (target_size < 0) {
+        return target_size;
+    }
+
+    for (;;) {
+        bytes = MIN(target_size - offset, BDRV_REQUEST_MAX_BYTES);
+        if (bytes <= 0) {
+            return 0;
+        }
+        ret = bdrv_block_status(bs, offset, bytes, &bytes, NULL, NULL);
+        if (ret < 0) {
+            return ret;
+        }
+        if (ret & BDRV_BLOCK_ZERO) {
+            offset += bytes;
+            continue;
+        }
+        ret = bdrv_pwrite_zeroes(child, offset, bytes, flags);
+        if (ret < 0) {
+            return ret;
+        }
+        offset += bytes;
+    }
+}
+
+int bdrv_preadv(BdrvChild *child, int64_t offset, QEMUIOVector *qiov)
+{
+    int ret;
+
+    ret = bdrv_prwv_co(child, offset, qiov, false, 0);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return qiov->size;
+}
+
 /*
  * Flush ALL BDSes regardless of if they are reachable via a BlkBackend or not.
  */
-- 
2.21.0

[PATCH 5/9] block/io: expand in_flight inc/dec section: simple cases

[Vladimir Sementsov-Ogievskiy]

It's safer to expand in_flight request to start before enter to
coroutine in synchronous wrappers and end after BDRV_POLL_WHILE loop.
Note that qemu_coroutine_enter may only schedule the coroutine in some
circumstances.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 155 ++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 119 insertions(+), 36 deletions(-)

diff --git a/block/io.c b/block/io.c
index dfbe68f428..9b57c7e422 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1511,7 +1511,8 @@ int coroutine_fn bdrv_co_preadv(BdrvChild *child,
     return bdrv_co_preadv_part(child, offset, bytes, qiov, 0, flags);
 }
 
-int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
+/* To be called between exactly one pair of bdrv_inc/dec_in_flight() */
+static int coroutine_fn bdrv_do_preadv_part(BdrvChild *child,
     int64_t offset, unsigned int bytes,
     QEMUIOVector *qiov, size_t qiov_offset,
     BdrvRequestFlags flags)
@@ -1540,8 +1541,6 @@ int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
         return 0;
     }
 
-    bdrv_inc_in_flight(bs);
-
     /* Don't do copy-on-read if we read data before write operation */
     if (atomic_read(&bs->copy_on_read)) {
         flags |= BDRV_REQ_COPY_ON_READ;
@@ -1554,13 +1553,26 @@ int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
                               bs->bl.request_alignment,
                               qiov, qiov_offset, flags);
     tracked_request_end(&req);
-    bdrv_dec_in_flight(bs);
 
     bdrv_padding_destroy(&pad);
 
     return ret;
 }
 
+int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
+    int64_t offset, unsigned int bytes,
+    QEMUIOVector *qiov, size_t qiov_offset,
+    BdrvRequestFlags flags)
+{
+    int ret;
+
+    bdrv_inc_in_flight(child->bs);
+    ret = bdrv_do_preadv_part(child, offset, bytes, qiov, qiov_offset, flags);
+    bdrv_dec_in_flight(child->bs);
+
+    return ret;
+}
+
 static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
     int64_t offset, int bytes, BdrvRequestFlags flags)
 {
@@ -1922,7 +1934,8 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
     return bdrv_co_pwritev_part(child, offset, bytes, qiov, 0, flags);
 }
 
-int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
+/* To be called between exactly one pair of bdrv_inc/dec_in_flight() */
+static int coroutine_fn bdrv_do_pwritev_part(BdrvChild *child,
     int64_t offset, unsigned int bytes, QEMUIOVector *qiov, size_t qiov_offset,
     BdrvRequestFlags flags)
 {
@@ -1962,7 +1975,6 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
         return 0;
     }
 
-    bdrv_inc_in_flight(bs);
     /*
      * Align write if necessary by performing a read-modify-write cycle.
      * Pad qiov with the read parts and be sure to have a tracked request not
@@ -1987,7 +1999,19 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
 
 out:
     tracked_request_end(&req);
-    bdrv_dec_in_flight(bs);
+
+    return ret;
+}
+
+int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
+    int64_t offset, unsigned int bytes, QEMUIOVector *qiov, size_t qiov_offset,
+    BdrvRequestFlags flags)
+{
+    int ret;
+
+    bdrv_inc_in_flight(child->bs);
+    ret = bdrv_do_pwritev_part(child, offset, bytes, qiov, qiov_offset, flags);
+    bdrv_dec_in_flight(child->bs);
 
     return ret;
 }
@@ -2019,12 +2043,12 @@ static void coroutine_fn bdrv_rw_co_entry(void *opaque)
     RwCo *rwco = opaque;
 
     if (!rwco->is_write) {
-        rwco->ret = bdrv_co_preadv(rwco->child, rwco->offset,
-                                   rwco->qiov->size, rwco->qiov,
+        rwco->ret = bdrv_do_preadv_part(rwco->child, rwco->offset,
+                                   rwco->qiov->size, rwco->qiov, 0,
                                    rwco->flags);
     } else {
-        rwco->ret = bdrv_co_pwritev(rwco->child, rwco->offset,
-                                    rwco->qiov->size, rwco->qiov,
+        rwco->ret = bdrv_do_pwritev_part(rwco->child, rwco->offset,
+                                    rwco->qiov->size, rwco->qiov, 0,
                                     rwco->flags);
     }
     aio_wait_kick();
@@ -2047,6 +2071,8 @@ static int bdrv_prwv_co(BdrvChild *child, int64_t offset,
         .flags = flags,
     };
 
+    bdrv_inc_in_flight(child->bs);
+
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
         bdrv_rw_co_entry(&rwco);
@@ -2055,6 +2081,9 @@ static int bdrv_prwv_co(BdrvChild *child, int64_t offset,
         bdrv_coroutine_enter(child->bs, co);
         BDRV_POLL_WHILE(child->bs, rwco.ret == NOT_DONE);
     }
+
+    bdrv_dec_in_flight(child->bs);
+
     return rwco.ret;
 }
 
@@ -2700,15 +2729,14 @@ typedef struct BdrvVmstateCo {
     int                 ret;
 } BdrvVmstateCo;
 
+/* To be called between exactly one pair of bdrv_inc/dec_in_flight() */
 static int coroutine_fn
-bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
+bdrv_do_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
                    bool is_read)
 {
     BlockDriver *drv = bs->drv;
     int ret = -ENOTSUP;
 
-    bdrv_inc_in_flight(bs);
-
     if (!drv) {
         ret = -ENOMEDIUM;
     } else if (drv->bdrv_load_vmstate) {
@@ -2718,17 +2746,18 @@ bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
             ret = drv->bdrv_save_vmstate(bs, qiov, pos);
         }
     } else if (bs->file) {
-        ret = bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
+        bdrv_inc_in_flight(bs->file->bs);
+        ret = bdrv_do_rw_vmstate(bs->file->bs, qiov, pos, is_read);
+        bdrv_dec_in_flight(bs->file->bs);
     }
 
-    bdrv_dec_in_flight(bs);
     return ret;
 }
 
 static void coroutine_fn bdrv_co_rw_vmstate_entry(void *opaque)
 {
     BdrvVmstateCo *co = opaque;
-    co->ret = bdrv_co_rw_vmstate(co->bs, co->qiov, co->pos, co->is_read);
+    co->ret = bdrv_do_rw_vmstate(co->bs, co->qiov, co->pos, co->is_read);
     aio_wait_kick();
 }
 
@@ -2736,8 +2765,12 @@ static inline int
 bdrv_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
                 bool is_read)
 {
+    int ret;
+
+    bdrv_inc_in_flight(bs);
+
     if (qemu_in_coroutine()) {
-        return bdrv_co_rw_vmstate(bs, qiov, pos, is_read);
+        ret = bdrv_do_rw_vmstate(bs, qiov, pos, is_read);
     } else {
         BdrvVmstateCo data = {
             .bs         = bs,
@@ -2750,8 +2783,12 @@ bdrv_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
 
         bdrv_coroutine_enter(bs, co);
         BDRV_POLL_WHILE(bs, data.ret == -EINPROGRESS);
-        return data.ret;
+        ret = data.ret;
     }
+
+    bdrv_dec_in_flight(bs);
+
+    return ret;
 }
 
 int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
@@ -2829,16 +2866,14 @@ void bdrv_aio_cancel_async(BlockAIOCB *acb)
 /**************************************************************/
 /* Coroutine block device emulation */
 
-int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
+/* To be called between exactly one pair of bdrv_inc/dec_in_flight() */
+static int coroutine_fn bdrv_do_flush(BlockDriverState *bs)
 {
     int current_gen;
-    int ret = 0;
-
-    bdrv_inc_in_flight(bs);
+    int ret;
 
-    if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs) ||
-        bdrv_is_sg(bs)) {
-        goto early_exit;
+    if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs) || bdrv_is_sg(bs)) {
+        return 0;
     }
 
     qemu_co_mutex_lock(&bs->reqs_lock);
@@ -2936,8 +2971,17 @@ out:
     qemu_co_queue_next(&bs->flush_queue);
     qemu_co_mutex_unlock(&bs->reqs_lock);
 
-early_exit:
+    return ret;
+}
+
+int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
+{
+    int ret;
+
+    bdrv_inc_in_flight(bs);
+    ret = bdrv_do_flush(bs);
     bdrv_dec_in_flight(bs);
+
     return ret;
 }
 
@@ -2950,7 +2994,7 @@ static void coroutine_fn bdrv_flush_co_entry(void *opaque)
 {
     FlushCo *rwco = opaque;
 
-    rwco->ret = bdrv_co_flush(rwco->bs);
+    rwco->ret = bdrv_do_flush(rwco->bs);
     aio_wait_kick();
 }
 
@@ -2962,6 +3006,8 @@ int bdrv_flush(BlockDriverState *bs)
         .ret = NOT_DONE,
     };
 
+    bdrv_inc_in_flight(bs);
+
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
         bdrv_flush_co_entry(&flush_co);
@@ -2971,11 +3017,14 @@ int bdrv_flush(BlockDriverState *bs)
         BDRV_POLL_WHILE(bs, flush_co.ret == NOT_DONE);
     }
 
+    bdrv_dec_in_flight(bs);
+
     return flush_co.ret;
 }
 
-int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset,
-                                  int64_t bytes)
+/* To be called between exactly one pair of bdrv_inc/dec_in_flight() */
+static int coroutine_fn bdrv_do_pdiscahd(BdrvChild *child, int64_t offset,
+                                         int64_t bytes)
 {
     BdrvTrackedRequest req;
     int max_pdiscard, ret;
@@ -3013,7 +3062,6 @@ int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset,
     head = offset % align;
     tail = (offset + bytes) % align;
 
-    bdrv_inc_in_flight(bs);
     tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_DISCARD);
 
     ret = bdrv_co_write_req_prepare(child, offset, bytes, &req, 0);
@@ -3084,7 +3132,19 @@ int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset,
 out:
     bdrv_co_write_req_finish(child, req.offset, req.bytes, &req, ret);
     tracked_request_end(&req);
-    bdrv_dec_in_flight(bs);
+    return ret;
+}
+
+int coroutine_fn bdrv_co_pdiscard(BdrvChild *child,
+                                  int64_t offset, int64_t bytes)
+{
+    int ret;
+    BlockDriverState *bs = child->bs;
+
+    bdrv_inc_in_flight(child->bs);
+    ret = bdrv_do_pdiscahd(child, offset, bytes);
+    bdrv_dec_in_flight(child->bs);
+
     return ret;
 }
 
@@ -3113,6 +3173,8 @@ int bdrv_pdiscard(BdrvChild *child, int64_t offset, int64_t bytes)
         .ret = NOT_DONE,
     };
 
+    bdrv_inc_in_flight(child->bs);
+
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
         bdrv_pdiscard_co_entry(&rwco);
@@ -3122,6 +3184,8 @@ int bdrv_pdiscard(BdrvChild *child, int64_t offset, int64_t bytes)
         BDRV_POLL_WHILE(child->bs, rwco.ret == NOT_DONE);
     }
 
+    bdrv_dec_in_flight(child->bs);
+
     return rwco.ret;
 }
 
@@ -3412,9 +3476,12 @@ static void bdrv_parent_cb_resize(BlockDriverState *bs)
  * If 'exact' is true, the file must be resized to exactly the given
  * 'offset'.  Otherwise, it is sufficient for the node to be at least
  * 'offset' bytes in length.
+ *
+ * To be called between exactly one pair of bdrv_inc/dec_in_flight()
  */
-int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
-                                  PreallocMode prealloc, Error **errp)
+static int coroutine_fn bdrv_do_truncate(BdrvChild *child,
+                                         int64_t offset, bool exact,
+                                         PreallocMode prealloc, Error **errp)
 {
     BlockDriverState *bs = child->bs;
     BlockDriver *drv = bs->drv;
@@ -3445,7 +3512,6 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
         new_bytes = 0;
     }
 
-    bdrv_inc_in_flight(bs);
     tracked_request_begin(&req, bs, offset - new_bytes, new_bytes,
                           BDRV_TRACKED_TRUNCATE);
 
@@ -3494,6 +3560,19 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
 
 out:
     tracked_request_end(&req);
+
+    return ret;
+}
+
+int coroutine_fn bdrv_co_truncate(BdrvChild *child,
+                                  int64_t offset, bool exact,
+                                  PreallocMode prealloc, Error **errp)
+{
+    int ret;
+    BlockDriverState *bs = child->bs;
+
+    bdrv_inc_in_flight(bs);
+    ret = bdrv_do_truncate(child, offset, exact, prealloc, errp);
     bdrv_dec_in_flight(bs);
 
     return ret;
@@ -3511,7 +3590,7 @@ typedef struct TruncateCo {
 static void coroutine_fn bdrv_truncate_co_entry(void *opaque)
 {
     TruncateCo *tco = opaque;
-    tco->ret = bdrv_co_truncate(tco->child, tco->offset, tco->exact,
+    tco->ret = bdrv_do_truncate(tco->child, tco->offset, tco->exact,
                                 tco->prealloc, tco->errp);
     aio_wait_kick();
 }
@@ -3529,6 +3608,8 @@ int bdrv_truncate(BdrvChild *child, int64_t offset, bool exact,
         .ret        = NOT_DONE,
     };
 
+    bdrv_inc_in_flight(child->bs);
+
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
         bdrv_truncate_co_entry(&tco);
@@ -3538,5 +3619,7 @@ int bdrv_truncate(BdrvChild *child, int64_t offset, bool exact,
         BDRV_POLL_WHILE(child->bs, tco.ret == NOT_DONE);
     }
 
+    bdrv_dec_in_flight(child->bs);
+
     return tco.ret;
 }
-- 
2.21.0

[PATCH 6/9] block/io: expand in_flight inc/dec section: block-status

[Vladimir Sementsov-Ogievskiy]

It's safer to expand in_flight request to start before enter to
coroutine in synchronous wrappers and end after BDRV_POLL_WHILE loop.
Note that qemu_coroutine_enter may only schedule the coroutine in some
circumstances.

block-status requests are complex, they involve querying different
block driver states across backing chain. Let's expand only in_flight
section for the top bs, keeping other sections as is.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 60 +++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 46 insertions(+), 14 deletions(-)

diff --git a/block/io.c b/block/io.c
index 9b57c7e422..760170731f 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2302,6 +2302,10 @@ int coroutine_fn bdrv_co_block_status_from_backing(BlockDriverState *bs,
  * _ZERO where possible; otherwise, the result favors larger 'pnum',
  * with a focus on accurate BDRV_BLOCK_ALLOCATED.
  *
+ * If 'inc_in_flight' is true, in_flight counter will be increased for bs during
+ * the operation. All nested block_status calls will increase the counter for
+ * corresponding bs anyway.
+ *
  * If 'offset' is beyond the end of the disk image the return value is
  * BDRV_BLOCK_EOF and 'pnum' is set to 0.
  *
@@ -2320,7 +2324,7 @@ int coroutine_fn bdrv_co_block_status_from_backing(BlockDriverState *bs,
  * set to the host mapping and BDS corresponding to the guest offset.
  */
 static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
-                                             bool want_zero,
+                                             bool want_zero, bool inc_in_flight,
                                              int64_t offset, int64_t bytes,
                                              int64_t *pnum, int64_t *map,
                                              BlockDriverState **file)
@@ -2371,7 +2375,9 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
         goto early_out;
     }
 
-    bdrv_inc_in_flight(bs);
+    if (inc_in_flight) {
+        bdrv_inc_in_flight(bs);
+    }
 
     /* Round out to request_alignment boundaries */
     align = bs->bl.request_alignment;
@@ -2408,7 +2414,7 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
 
     if (ret & BDRV_BLOCK_RAW) {
         assert(ret & BDRV_BLOCK_OFFSET_VALID && local_file);
-        ret = bdrv_co_block_status(local_file, want_zero, local_map,
+        ret = bdrv_co_block_status(local_file, want_zero, true, local_map,
                                    *pnum, pnum, &local_map, &local_file);
         goto out;
     }
@@ -2435,7 +2441,7 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
         int64_t file_pnum;
         int ret2;
 
-        ret2 = bdrv_co_block_status(local_file, want_zero, local_map,
+        ret2 = bdrv_co_block_status(local_file, want_zero, true, local_map,
                                     *pnum, &file_pnum, NULL, NULL);
         if (ret2 >= 0) {
             /* Ignore errors.  This is just providing extra information, it
@@ -2458,7 +2464,9 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
     }
 
 out:
-    bdrv_dec_in_flight(bs);
+    if (inc_in_flight) {
+        bdrv_dec_in_flight(bs);
+    }
     if (ret >= 0 && offset + *pnum == total_size) {
         ret |= BDRV_BLOCK_EOF;
     }
@@ -2472,9 +2480,15 @@ early_out:
     return ret;
 }
 
+/*
+ * If 'inc_in_flight' is true, in_flight counter will be increased for bs during
+ * the operation. All block_status calls to the backing chain of bs will
+ * increase the counter for corresponding bs anyway.
+ */
 static int coroutine_fn bdrv_co_block_status_above(BlockDriverState *bs,
                                                    BlockDriverState *base,
                                                    bool want_zero,
+                                                   bool inc_in_flight,
                                                    int64_t offset,
                                                    int64_t bytes,
                                                    int64_t *pnum,
@@ -2487,11 +2501,13 @@ static int coroutine_fn bdrv_co_block_status_above(BlockDriverState *bs,
 
     assert(bs != base);
     for (p = bs; p != base; p = backing_bs(p)) {
-        ret = bdrv_co_block_status(p, want_zero, offset, bytes, pnum, map,
-                                   file);
+        ret = bdrv_co_block_status(p, want_zero, inc_in_flight,
+                                   offset, bytes, pnum, map, file);
         if (ret < 0) {
             break;
         }
+        inc_in_flight = true;
+
         if (ret & BDRV_BLOCK_ZERO && ret & BDRV_BLOCK_EOF && !first) {
             /*
              * Reading beyond the end of the file continues to read
@@ -2513,15 +2529,16 @@ static int coroutine_fn bdrv_co_block_status_above(BlockDriverState *bs,
 }
 
 static int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs,
+                                             bool inc_in_flight,
                                              int64_t offset, int64_t bytes,
                                              int64_t *pnum)
 {
     int ret;
     int64_t dummy;
 
-    ret = bdrv_co_block_status_above(bs, backing_bs(bs), false, offset,
-                                     bytes, pnum ? pnum : &dummy, NULL,
-                                     NULL);
+    ret = bdrv_co_block_status_above(bs, backing_bs(bs), false, inc_in_flight,
+                                     offset, bytes, pnum ? pnum : &dummy,
+                                     NULL, NULL);
     if (ret < 0) {
         return ret;
     }
@@ -2534,7 +2551,7 @@ static void coroutine_fn bdrv_block_status_above_co_entry(void *opaque)
     BdrvCoBlockStatusData *data = opaque;
 
     data->ret = bdrv_co_block_status_above(data->bs, data->base,
-                                           data->want_zero,
+                                           data->want_zero, false,
                                            data->offset, data->bytes,
                                            data->pnum, data->map, data->file);
     data->done = true;
@@ -2566,6 +2583,8 @@ static int bdrv_common_block_status_above(BlockDriverState *bs,
         .done = false,
     };
 
+    bdrv_inc_in_flight(bs);
+
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
         bdrv_block_status_above_co_entry(&data);
@@ -2574,6 +2593,9 @@ static int bdrv_common_block_status_above(BlockDriverState *bs,
         bdrv_coroutine_enter(bs, co);
         BDRV_POLL_WHILE(bs, !data.done);
     }
+
+    bdrv_dec_in_flight(bs);
+
     return data.ret;
 }
 
@@ -2623,15 +2645,19 @@ int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,
  * words, the result is not necessarily the maximum possible range);
  * but 'pnum' will only be 0 when end of file is reached.
  *
+ * To be called between exactly one pair of bdrv_inc/dec_in_flight() for top bs.
+ * bdrv_do_is_allocated_above takes care of increasing in_fligth for other block
+ * driver states from bs backing chain.
  */
 static int coroutine_fn
-bdrv_co_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
+bdrv_do_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
                            bool include_base, int64_t offset, int64_t bytes,
                            int64_t *pnum)
 {
     BlockDriverState *intermediate;
     int ret;
     int64_t n = bytes;
+    bool inc_in_flight = false;
 
     assert(base || !include_base);
 
@@ -2641,10 +2667,12 @@ bdrv_co_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
         int64_t size_inter;
 
         assert(intermediate);
-        ret = bdrv_co_is_allocated(intermediate, offset, bytes, &pnum_inter);
+        ret = bdrv_co_is_allocated(intermediate, inc_in_flight, offset, bytes,
+                                   &pnum_inter);
         if (ret < 0) {
             return ret;
         }
+        inc_in_flight = true;
         if (ret) {
             *pnum = pnum_inter;
             return 1;
@@ -2685,7 +2713,7 @@ static void coroutine_fn bdrv_is_allocated_above_co_entry(void *opaque)
 {
     BdrvCoIsAllocatedAboveData *data = opaque;
 
-    data->ret = bdrv_co_is_allocated_above(data->top, data->base,
+    data->ret = bdrv_do_is_allocated_above(data->top, data->base,
                                            data->include_base,
                                            data->offset, data->bytes,
                                            data->pnum);
@@ -2709,6 +2737,8 @@ bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
         .done = false,
     };
 
+    bdrv_inc_in_flight(top);
+
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
         bdrv_is_allocated_above_co_entry(&data);
@@ -2718,6 +2748,8 @@ bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
         BDRV_POLL_WHILE(top, !data.done);
     }
 
+    bdrv_inc_in_flight(top);
+
     return data.ret;
 }
 
-- 
2.21.0

[PATCH 7/9] block/io: add bdrv_do_pwrite_zeroes

[Vladimir Sementsov-Ogievskiy]

We'll need a bdrv_co_pwrite_zeroes version without inc/dec in_flight to
be used in further implementation of bdrv_make_zero.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/block/io.c b/block/io.c
index 760170731f..b1fc8b2367 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2016,8 +2016,10 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
     return ret;
 }
 
-int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
-                                       int bytes, BdrvRequestFlags flags)
+/* To be called between exactly one pair of bdrv_inc/dec_in_flight() */
+static int coroutine_fn
+bdrv_do_pwrite_zeroes(BdrvChild *child, int64_t offset, int bytes,
+                      BdrvRequestFlags flags)
 {
     trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags);
 
@@ -2025,8 +2027,21 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
         flags &= ~BDRV_REQ_MAY_UNMAP;
     }
 
-    return bdrv_co_pwritev(child, offset, bytes, NULL,
-                           BDRV_REQ_ZERO_WRITE | flags);
+    return bdrv_do_pwritev_part(child, offset, bytes, NULL, 0,
+                                BDRV_REQ_ZERO_WRITE | flags);
+}
+
+int coroutine_fn
+bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset, int bytes,
+                      BdrvRequestFlags flags)
+{
+    int ret;
+
+    bdrv_inc_in_flight(child->bs);
+    ret = bdrv_do_pwrite_zeroes(child, offset, bytes, flags);
+    bdrv_dec_in_flight(child->bs);
+
+    return ret;
 }
 
 typedef struct RwCo {
-- 
2.21.0

[PATCH 8/9] block/io: move bdrv_make_zero under block-status

[Vladimir Sementsov-Ogievskiy]

We are going to use bdrv_co_block_status in bdrv_make_zero, so move it
now down.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 82 +++++++++++++++++++++++++++---------------------------
 1 file changed, 41 insertions(+), 41 deletions(-)

diff --git a/block/io.c b/block/io.c
index b1fc8b2367..d2ac9ac7b5 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2177,47 +2177,6 @@ int bdrv_pwrite_sync(BdrvChild *child, int64_t offset,
     return 0;
 }
 
-/*
- * Completely zero out a block device with the help of bdrv_pwrite_zeroes.
- * The operation is sped up by checking the block status and only writing
- * zeroes to the device if they currently do not return zeroes. Optional
- * flags are passed through to bdrv_pwrite_zeroes (e.g. BDRV_REQ_MAY_UNMAP,
- * BDRV_REQ_FUA).
- *
- * Returns < 0 on error, 0 on success. For error codes see bdrv_write().
- */
-int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
-{
-    int ret;
-    int64_t target_size, bytes, offset = 0;
-    BlockDriverState *bs = child->bs;
-
-    target_size = bdrv_getlength(bs);
-    if (target_size < 0) {
-        return target_size;
-    }
-
-    for (;;) {
-        bytes = MIN(target_size - offset, BDRV_REQUEST_MAX_BYTES);
-        if (bytes <= 0) {
-            return 0;
-        }
-        ret = bdrv_block_status(bs, offset, bytes, &bytes, NULL, NULL);
-        if (ret < 0) {
-            return ret;
-        }
-        if (ret & BDRV_BLOCK_ZERO) {
-            offset += bytes;
-            continue;
-        }
-        ret = bdrv_pwrite_zeroes(child, offset, bytes, flags);
-        if (ret < 0) {
-            return ret;
-        }
-        offset += bytes;
-    }
-}
-
 int bdrv_preadv(BdrvChild *child, int64_t offset, QEMUIOVector *qiov)
 {
     int ret;
@@ -2768,6 +2727,47 @@ bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
     return data.ret;
 }
 
+/*
+ * Completely zero out a block device with the help of bdrv_pwrite_zeroes.
+ * The operation is sped up by checking the block status and only writing
+ * zeroes to the device if they currently do not return zeroes. Optional
+ * flags are passed through to bdrv_pwrite_zeroes (e.g. BDRV_REQ_MAY_UNMAP,
+ * BDRV_REQ_FUA).
+ *
+ * Returns < 0 on error, 0 on success. For error codes see bdrv_write().
+ */
+int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
+{
+    int ret;
+    int64_t target_size, bytes, offset = 0;
+    BlockDriverState *bs = child->bs;
+
+    target_size = bdrv_getlength(bs);
+    if (target_size < 0) {
+        return target_size;
+    }
+
+    for (;;) {
+        bytes = MIN(target_size - offset, BDRV_REQUEST_MAX_BYTES);
+        if (bytes <= 0) {
+            return 0;
+        }
+        ret = bdrv_block_status(bs, offset, bytes, &bytes, NULL, NULL);
+        if (ret < 0) {
+            return ret;
+        }
+        if (ret & BDRV_BLOCK_ZERO) {
+            offset += bytes;
+            continue;
+        }
+        ret = bdrv_pwrite_zeroes(child, offset, bytes, flags);
+        if (ret < 0) {
+            return ret;
+        }
+        offset += bytes;
+    }
+}
+
 typedef struct BdrvVmstateCo {
     BlockDriverState    *bs;
     QEMUIOVector        *qiov;
-- 
2.21.0

[PATCH 9/9] block/io: expand in_flight inc/dec section: bdrv_make_zero

[Vladimir Sementsov-Ogievskiy]

It's safer to expand in_flight request to start before enter to
coroutine in synchronous wrappers and end after BDRV_POLL_WHILE loop.
Note that qemu_coroutine_enter may only schedule the coroutine in some
circumstances.

bdrv_make_zero update includes refactoring: move the whole loop into
coroutine, which has additional benefit of not create/enter new
coroutine on each iteration.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 50 insertions(+), 3 deletions(-)

diff --git a/block/io.c b/block/io.c
index d2ac9ac7b5..220b5c04d7 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2735,8 +2735,11 @@ bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
  * BDRV_REQ_FUA).
  *
  * Returns < 0 on error, 0 on success. For error codes see bdrv_write().
+ *
+ * To be called between exactly one pair of bdrv_inc/dec_in_flight()
  */
-int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
+static int coroutine_fn
+bdrv_do_make_zero(BdrvChild *child, BdrvRequestFlags flags)
 {
     int ret;
     int64_t target_size, bytes, offset = 0;
@@ -2752,7 +2755,8 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
         if (bytes <= 0) {
             return 0;
         }
-        ret = bdrv_block_status(bs, offset, bytes, &bytes, NULL, NULL);
+        ret = bdrv_co_block_status(bs, true, false,
+                                   offset, bytes, &bytes, NULL, NULL);
         if (ret < 0) {
             return ret;
         }
@@ -2760,7 +2764,7 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
             offset += bytes;
             continue;
         }
-        ret = bdrv_pwrite_zeroes(child, offset, bytes, flags);
+        ret = bdrv_do_pwrite_zeroes(child, offset, bytes, flags);
         if (ret < 0) {
             return ret;
         }
@@ -2768,6 +2772,49 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
     }
 }
 
+typedef struct BdrvDoMakeZeroData {
+    BdrvChild *child;
+    BdrvRequestFlags flags;
+    int ret;
+    bool done;
+} BdrvDoMakeZeroData;
+
+static void coroutine_fn bdrv_make_zero_co_entry(void *opaque)
+{
+    BdrvDoMakeZeroData *data = opaque;
+
+    data->ret = bdrv_do_make_zero(data->child, data->flags);
+    data->done = true;
+    aio_wait_kick();
+}
+
+int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
+{
+    int ret;
+
+    bdrv_inc_in_flight(child->bs);
+
+    if (qemu_in_coroutine()) {
+        /* Fast-path if already in coroutine context */
+        ret = bdrv_do_make_zero(child, flags);
+    } else {
+        BdrvDoMakeZeroData data = {
+            .child = child,
+            .flags = flags,
+            .done = false,
+        };
+        Coroutine *co = qemu_coroutine_create(bdrv_make_zero_co_entry, &data);
+
+        bdrv_coroutine_enter(child->bs, co);
+        BDRV_POLL_WHILE(child->bs, !data.done);
+        ret = data.ret;
+    }
+
+    bdrv_dec_in_flight(child->bs);
+
+    return ret;
+}
+
 typedef struct BdrvVmstateCo {
     BlockDriverState    *bs;
     QEMUIOVector        *qiov;
-- 
2.21.0

Re: [PATCH for-5.0? 0/9] block/io: safer inc/dec in_flight sections

[no-reply]

Patchew URL: https://patchew.org/QEMU/20200408093051.9893-1-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
export ARCH=x86_64
make docker-image-fedora V=1 NETWORK=1
time make docker-test-debug@fedora TARGET_LIST=x86_64-softmmu J=14 NETWORK=1
=== TEST SCRIPT END ===

  CC      qemu-storage-daemon.o
  CC      chardev/char.o
  CC      chardev/char-fd.o
/tmp/qemu-test/src/block/io.c:3236:23: error: unused variable 'bs' [-Werror,-Wunused-variable]
    BlockDriverState *bs = child->bs;
                      ^
1 error generated.
make: *** [/tmp/qemu-test/src/rules.mak:69: block/io.o] Error 1
make: *** Waiting for unfinished jobs....
Traceback (most recent call last):
  File "./tests/docker/docker.py", line 664, in <module>
---
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['sudo', '-n', 'docker', 'run', '--label', 'com.qemu.instance.uuid=fe09506e16304737ad88a479330eedd0', '-u', '1001', '--security-opt', 'seccomp=unconfined', '--rm', '-e', 'TARGET_LIST=x86_64-softmmu', '-e', 'EXTRA_CONFIGURE_OPTS=', '-e', 'V=', '-e', 'J=14', '-e', 'DEBUG=', '-e', 'SHOW_ENV=', '-e', 'CCACHE_DIR=/var/tmp/ccache', '-v', '/home/patchew/.cache/qemu-docker-ccache:/var/tmp/ccache:z', '-v', '/var/tmp/patchew-tester-tmp-p88wn5d0/src/docker-src.2020-04-08-06.11.00.19577:/var/tmp/qemu:z,ro', 'qemu:fedora', '/var/tmp/qemu/run', 'test-debug']' returned non-zero exit status 2.
filter=--filter=label=com.qemu.instance.uuid=fe09506e16304737ad88a479330eedd0
make[1]: *** [docker-run] Error 1
make[1]: Leaving directory `/var/tmp/patchew-tester-tmp-p88wn5d0/src'
make: *** [docker-run-test-debug@fedora] Error 2

real    3m59.109s
user    0m8.928s


The full log is available at
http://patchew.org/logs/20200408093051.9893-1-vsementsov@virtuozzo.com/testing.asan/?type=message.
---
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Please send your feedback to patchew-devel@redhat.com

Re: [PATCH for-5.0? 0/9] block/io: safer inc/dec in_flight sections

[no-reply]

Patchew URL: https://patchew.org/QEMU/20200408093051.9893-1-vsementsov@virtuozzo.com/



Hi,

This series failed the docker-quick@centos7 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
make docker-image-centos7 V=1 NETWORK=1
time make docker-test-quick@centos7 SHOW_ENV=1 J=14 NETWORK=1
=== TEST SCRIPT END ===

  CC      crypto/tlssession.o
  CC      crypto/secret.o
/tmp/qemu-test/src/block/io.c: In function 'bdrv_co_pdiscard':
/tmp/qemu-test/src/block/io.c:3236:23: error: unused variable 'bs' [-Werror=unused-variable]
     BlockDriverState *bs = child->bs;
                       ^
cc1: all warnings being treated as errors
make: *** [block/io.o] Error 1
make: *** Waiting for unfinished jobs....
Traceback (most recent call last):
  File "./tests/docker/docker.py", line 664, in <module>
---
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['sudo', '-n', 'docker', 'run', '--label', 'com.qemu.instance.uuid=a0f1e41cc0a74bd7a341e17a6e374b91', '-u', '1003', '--security-opt', 'seccomp=unconfined', '--rm', '-e', 'TARGET_LIST=', '-e', 'EXTRA_CONFIGURE_OPTS=', '-e', 'V=', '-e', 'J=14', '-e', 'DEBUG=', '-e', 'SHOW_ENV=1', '-e', 'CCACHE_DIR=/var/tmp/ccache', '-v', '/home/patchew2/.cache/qemu-docker-ccache:/var/tmp/ccache:z', '-v', '/var/tmp/patchew-tester-tmp-jzfd32f9/src/docker-src.2020-04-08-06.20.30.5705:/var/tmp/qemu:z,ro', 'qemu:centos7', '/var/tmp/qemu/run', 'test-quick']' returned non-zero exit status 2.
filter=--filter=label=com.qemu.instance.uuid=a0f1e41cc0a74bd7a341e17a6e374b91
make[1]: *** [docker-run] Error 1
make[1]: Leaving directory `/var/tmp/patchew-tester-tmp-jzfd32f9/src'
make: *** [docker-run-test-quick@centos7] Error 2

real    2m13.993s
user    0m8.229s


The full log is available at
http://patchew.org/logs/20200408093051.9893-1-vsementsov@virtuozzo.com/testing.docker-quick@centos7/?type=message.
---
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Please send your feedback to patchew-devel@redhat.com

Re: [PATCH for-5.0? 0/9] block/io: safer inc/dec in_flight sections

[no-reply]

Patchew URL: https://patchew.org/QEMU/20200408093051.9893-1-vsementsov@virtuozzo.com/



Hi,

This series failed the docker-mingw@fedora 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
export ARCH=x86_64
make docker-image-fedora V=1 NETWORK=1
time make docker-test-mingw@fedora J=14 NETWORK=1
=== TEST SCRIPT END ===

  CC      hw/acpi/cpu_hotplug.o
  CC      hw/acpi/memory_hotplug.o
/tmp/qemu-test/src/block/io.c: In function 'bdrv_co_pdiscard':
/tmp/qemu-test/src/block/io.c:3236:23: error: unused variable 'bs' [-Werror=unused-variable]
     BlockDriverState *bs = child->bs;
                       ^~
cc1: all warnings being treated as errors
make: *** [/tmp/qemu-test/src/rules.mak:69: block/io.o] Error 1
make: *** Waiting for unfinished jobs....
Traceback (most recent call last):
  File "./tests/docker/docker.py", line 664, in <module>
---
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['sudo', '-n', 'docker', 'run', '--label', 'com.qemu.instance.uuid=0a3c46e828f54c7eacc85733f086e093', '-u', '1003', '--security-opt', 'seccomp=unconfined', '--rm', '-e', 'TARGET_LIST=', '-e', 'EXTRA_CONFIGURE_OPTS=', '-e', 'V=', '-e', 'J=14', '-e', 'DEBUG=', '-e', 'SHOW_ENV=', '-e', 'CCACHE_DIR=/var/tmp/ccache', '-v', '/home/patchew2/.cache/qemu-docker-ccache:/var/tmp/ccache:z', '-v', '/var/tmp/patchew-tester-tmp-9znq69ii/src/docker-src.2020-04-08-06.23.18.12334:/var/tmp/qemu:z,ro', 'qemu:fedora', '/var/tmp/qemu/run', 'test-mingw']' returned non-zero exit status 2.
filter=--filter=label=com.qemu.instance.uuid=0a3c46e828f54c7eacc85733f086e093
make[1]: *** [docker-run] Error 1
make[1]: Leaving directory `/var/tmp/patchew-tester-tmp-9znq69ii/src'
make: *** [docker-run-test-mingw@fedora] Error 2

real    2m12.399s
user    0m8.326s


The full log is available at
http://patchew.org/logs/20200408093051.9893-1-vsementsov@virtuozzo.com/testing.docker-mingw@fedora/?type=message.
---
Email generated automatically by Patchew [https://patchew.org/].
Please send your feedback to patchew-devel@redhat.com

Re: [PATCH for-5.0? 0/9] block/io: safer inc/dec in_flight sections

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 621 bytes --]

On Wed, Apr 08, 2020 at 12:30:42PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
> 
> This is inspired by Kevin's
> "block: Fix blk->in_flight during blk_wait_while_drained()" series.
> 
> So, like it's now done for block-backends, let's expand
> in_flight-protected sections for bdrv_ interfaces, including
> coroutine_enter and BDRV_POLL_WHILE loop into these sections.

This looks like a code improvement but let's leave it for the next
release since QEMU 5.0 is in freeze and this patch series does not fix a
specific user-visible bug.

I will review this in depth next week.  Thanks!

Stefan

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Re: [PATCH for-5.0? 0/9] block/io: safer inc/dec in_flight sections

[Vladimir Sementsov-Ogievskiy]

09.04.2020 20:00, Stefan Hajnoczi wrote:
> On Wed, Apr 08, 2020 at 12:30:42PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> This is inspired by Kevin's
>> "block: Fix blk->in_flight during blk_wait_while_drained()" series.
>>
>> So, like it's now done for block-backends, let's expand
>> in_flight-protected sections for bdrv_ interfaces, including
>> coroutine_enter and BDRV_POLL_WHILE loop into these sections.
> 
> This looks like a code improvement but let's leave it for the next
> release since QEMU 5.0 is in freeze and this patch series does not fix a
> specific user-visible bug.
> 
> I will review this in depth next week.  Thanks!
> 

Hmm, it possibly fixes some bugs, but at least I didn't see them :) Anyway, it shouldn't be a degradation.

-- 
Best regards,
Vladimir

Re: [PATCH 1/9] block/io: refactor bdrv_is_allocated_above to run only one coroutine

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 473 bytes --]

On Wed, Apr 08, 2020 at 12:30:43PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> +int coroutine_fn
> +bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
> +                        bool include_base, int64_t offset, int64_t bytes,
> +                        int64_t *pnum)

s/coroutine_fn//

Only functions that must be called from coroutine context should be
marked as coroutine_fn.  Since this function supports both contexts, so
it doesn't apply here.

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Re: [PATCH 2/9] block/io: refactor bdrv_co_ioctl: move aio stuff to corresponding block

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 304 bytes --]

On Wed, Apr 08, 2020 at 12:30:44PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/io.c | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)

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

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Re: [PATCH 3/9] block/io: move flush and pdiscard stuff down

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 448 bytes --]

On Wed, Apr 08, 2020 at 12:30:45PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> bdrv_co_flush and bdrv_co_pdiscard will become static in further patch,
> move their usage down.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/io.c | 56 +++++++++++++++++++++++++++---------------------------
>  1 file changed, 28 insertions(+), 28 deletions(-)

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

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Re: [PATCH 4/9] block/io: move bdrv_rw_co_entry and friends down

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 613 bytes --]

On Wed, Apr 08, 2020 at 12:30:46PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> We are going to use bdrv_co_pwritev_part and bdrv_co_preadv_part in
> bdrv_rw_co_entry, so move it down.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/io.c | 361 +++++++++++++++++++++++++++--------------------------
>  1 file changed, 181 insertions(+), 180 deletions(-)

Note to other reviewers: Comment formatting was changed to conform to
coding style and function order was changed.  Otherwise the code is
unmodified.

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

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Re: [PATCH 5/9] block/io: expand in_flight inc/dec section: simple cases

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 1710 bytes --]

On Wed, Apr 08, 2020 at 12:30:47PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> It's safer to expand in_flight request to start before enter to

Please explain what exeactly "safer" means.  If I understand correctly
this is just a refactoring and does not fix bugs that have been hit in
the real world.

Is this just a generate attempt to avoid accidentally performing
operations that need to happen as part of the request after the dec
call?

> @@ -2718,17 +2746,18 @@ bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
>              ret = drv->bdrv_save_vmstate(bs, qiov, pos);
>          }
>      } else if (bs->file) {
> -        ret = bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
> +        bdrv_inc_in_flight(bs->file->bs);
> +        ret = bdrv_do_rw_vmstate(bs->file->bs, qiov, pos, is_read);
> +        bdrv_dec_in_flight(bs->file->bs);

Here we inc/dec...

>      }
>  
> -    bdrv_dec_in_flight(bs);
>      return ret;
>  }
>  
>  static void coroutine_fn bdrv_co_rw_vmstate_entry(void *opaque)
>  {
>      BdrvVmstateCo *co = opaque;
> -    co->ret = bdrv_co_rw_vmstate(co->bs, co->qiov, co->pos, co->is_read);
> +    co->ret = bdrv_do_rw_vmstate(co->bs, co->qiov, co->pos, co->is_read);

...here we don't.  The code is correct, but bdrv_co_rw_vmstate_entry()
should also document that its caller must inc/dec.

> @@ -2950,7 +2994,7 @@ static void coroutine_fn bdrv_flush_co_entry(void *opaque)
>  {
>      FlushCo *rwco = opaque;
>  
> -    rwco->ret = bdrv_co_flush(rwco->bs);
> +    rwco->ret = bdrv_do_flush(rwco->bs);
>      aio_wait_kick();
>  }

This function should also document that the caller must inc/dec.

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Re: [PATCH 7/9] block/io: add bdrv_do_pwrite_zeroes

[Stefan Hajnoczi]

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On Wed, Apr 08, 2020 at 12:30:49PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> We'll need a bdrv_co_pwrite_zeroes version without inc/dec in_flight to
> be used in further implementation of bdrv_make_zero.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/io.c | 23 +++++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)

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

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Re: [PATCH 8/9] block/io: move bdrv_make_zero under block-status

[Stefan Hajnoczi]

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On Wed, Apr 08, 2020 at 12:30:50PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> We are going to use bdrv_co_block_status in bdrv_make_zero, so move it
> now down.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/io.c | 82 +++++++++++++++++++++++++++---------------------------
>  1 file changed, 41 insertions(+), 41 deletions(-)

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

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Re: [PATCH 9/9] block/io: expand in_flight inc/dec section: bdrv_make_zero

[Stefan Hajnoczi]

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On Wed, Apr 08, 2020 at 12:30:51PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> @@ -2768,6 +2772,49 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
>      }
>  }
>  
> +typedef struct BdrvDoMakeZeroData {
> +    BdrvChild *child;
> +    BdrvRequestFlags flags;
> +    int ret;
> +    bool done;
> +} BdrvDoMakeZeroData;
> +
> +static void coroutine_fn bdrv_make_zero_co_entry(void *opaque)

Please document that the caller must inc/dec.

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Re: [PATCH 6/9] block/io: expand in_flight inc/dec section: block-status

[Stefan Hajnoczi]

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On Wed, Apr 08, 2020 at 12:30:48PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> It's safer to expand in_flight request to start before enter to
> coroutine in synchronous wrappers and end after BDRV_POLL_WHILE loop.
> Note that qemu_coroutine_enter may only schedule the coroutine in some
> circumstances.
> 
> block-status requests are complex, they involve querying different
> block driver states across backing chain. Let's expand only in_flight
> section for the top bs, keeping other sections as is.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/io.c | 60 +++++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 46 insertions(+), 14 deletions(-)

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

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Re: [PATCH 5/9] block/io: expand in_flight inc/dec section: simple cases

[Vladimir Sementsov-Ogievskiy]

20.04.2020 19:22, Stefan Hajnoczi wrote:
> On Wed, Apr 08, 2020 at 12:30:47PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> It's safer to expand in_flight request to start before enter to
> 
> Please explain what exeactly "safer" means.  If I understand correctly
> this is just a refactoring and does not fix bugs that have been hit in
> the real world.
> 
> Is this just a generate attempt to avoid accidentally performing
> operations that need to happen as part of the request after the dec
> call?

Consider write.

It's possible, that qemu_coroutine_enter only schedules execution, assume such case.
Then we may possibly have the following:

1. Somehow check that we are not in drained section in outer code

2. call bdrv_pwritev(), assuming that it will increse in_flight, which will protect us from starting drained section

3. it calls bdrv_prwv_co -> bdrv_coroutine_enter (not yet increased in_flight)

4. assume coroutine not yet actually entered, only scheduled, and we go to some code, which starts drained section (as in_flight is zero)

5. scheduled coroutine starts, and blindly increases in_flight, and we are in drained section with in_flight request.

The series does the same thing for block/io.c like Kevin's "block: Fix blk->in_flight during blk_wait_while_drained()" for blk layer.

> 
>> @@ -2718,17 +2746,18 @@ bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
>>               ret = drv->bdrv_save_vmstate(bs, qiov, pos);
>>           }
>>       } else if (bs->file) {
>> -        ret = bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
>> +        bdrv_inc_in_flight(bs->file->bs);
>> +        ret = bdrv_do_rw_vmstate(bs->file->bs, qiov, pos, is_read);
>> +        bdrv_dec_in_flight(bs->file->bs);
> 
> Here we inc/dec...
> 
>>       }
>>   
>> -    bdrv_dec_in_flight(bs);
>>       return ret;
>>   }
>>   
>>   static void coroutine_fn bdrv_co_rw_vmstate_entry(void *opaque)
>>   {
>>       BdrvVmstateCo *co = opaque;
>> -    co->ret = bdrv_co_rw_vmstate(co->bs, co->qiov, co->pos, co->is_read);
>> +    co->ret = bdrv_do_rw_vmstate(co->bs, co->qiov, co->pos, co->is_read);
> 
> ...here we don't.  The code is correct, but bdrv_co_rw_vmstate_entry()
> should also document that its caller must inc/dec.
> 
>> @@ -2950,7 +2994,7 @@ static void coroutine_fn bdrv_flush_co_entry(void *opaque)
>>   {
>>       FlushCo *rwco = opaque;
>>   
>> -    rwco->ret = bdrv_co_flush(rwco->bs);
>> +    rwco->ret = bdrv_do_flush(rwco->bs);
>>       aio_wait_kick();
>>   }
> 
> This function should also document that the caller must inc/dec.
> 


-- 
Best regards,
Vladimir

Re: [PATCH 5/9] block/io: expand in_flight inc/dec section: simple cases

[Stefan Hajnoczi]

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On Wed, Apr 22, 2020 at 04:47:07PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> 20.04.2020 19:22, Stefan Hajnoczi wrote:
> > On Wed, Apr 08, 2020 at 12:30:47PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> > > It's safer to expand in_flight request to start before enter to
> > 
> > Please explain what exeactly "safer" means.  If I understand correctly
> > this is just a refactoring and does not fix bugs that have been hit in
> > the real world.
> > 
> > Is this just a generate attempt to avoid accidentally performing
> > operations that need to happen as part of the request after the dec
> > call?
> 
> Consider write.
> 
> It's possible, that qemu_coroutine_enter only schedules execution, assume such case.
> Then we may possibly have the following:
> 
> 1. Somehow check that we are not in drained section in outer code
> 
> 2. call bdrv_pwritev(), assuming that it will increse in_flight, which will protect us from starting drained section
> 
> 3. it calls bdrv_prwv_co -> bdrv_coroutine_enter (not yet increased in_flight)
> 
> 4. assume coroutine not yet actually entered, only scheduled, and we go to some code, which starts drained section (as in_flight is zero)
> 
> 5. scheduled coroutine starts, and blindly increases in_flight, and we are in drained section with in_flight request.
> 
> The series does the same thing for block/io.c like Kevin's "block: Fix blk->in_flight during blk_wait_while_drained()" for blk layer.

Please include this in the commit description.  Thanks!

Stefan

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Re: [PATCH 4/9] block/io: move bdrv_rw_co_entry and friends down

[Vladimir Sementsov-Ogievskiy]

20.04.2020 19:04, Stefan Hajnoczi wrote:
> On Wed, Apr 08, 2020 at 12:30:46PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> We are going to use bdrv_co_pwritev_part and bdrv_co_preadv_part in
>> bdrv_rw_co_entry, so move it down.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>   block/io.c | 361 +++++++++++++++++++++++++++--------------------------
>>   1 file changed, 181 insertions(+), 180 deletions(-)
> 
> Note to other reviewers: Comment formatting was changed to conform to
> coding style and function order was changed.  Otherwise the code is
> unmodified.

I think, I'll put it directly to commit message, hope you don't mind.

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


-- 
Best regards,
Vladimir