[Qemu-devel] [PATCH v3 0/1] blockdev: acquire aio_context for bitmap add/remove

[Qemu-devel] [PATCH v3 0/1] blockdev: acquire aio_context for bitmap add/remove

[John Snow]

See patch for details.

V3: Add signed-off-by. My script went a bit haywire,
    so this one's for posterity.

John Snow (1):
  blockdev: acquire aio_context for bitmap add/remove

 blockdev.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

-- 
2.17.2

[Qemu-devel] [PATCH v3 1/1] blockdev: acquire aio_context for bitmap add/remove

[John Snow]

When bitmaps are persistent, they may incur a disk read or write when bitmaps
are added or removed. For configurations like virtio-dataplane, failing to
acquire this lock will abort QEMU when disk IO occurs.

We used to acquire aio_context as part of the bitmap lookup, so re-introduce
the lock for just the cases that have an IO penalty. Commit 2119882c removed
these locks, and I failed to notice this when we committed fd5ae4cc, so this
has been broken since persistent bitmaps were introduced.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1672010
Reported-By: Aihua Liang <aliang@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 blockdev.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index fb18e9c975..790b0e0ac8 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2820,6 +2820,7 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
 {
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
+    AioContext *aio_context = NULL;
 
     if (!name || name[0] == '\0') {
         error_setg(errp, "Bitmap name cannot be empty");
@@ -2854,15 +2855,17 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
         disabled = false;
     }
 
-    if (persistent &&
-        !bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp))
-    {
-        return;
+    if (persistent) {
+        aio_context = bdrv_get_aio_context(bs);
+        aio_context_acquire(aio_context);
+        if (!bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp)) {
+            goto out;
+        }
     }
 
     bitmap = bdrv_create_dirty_bitmap(bs, granularity, name, errp);
     if (bitmap == NULL) {
-        return;
+        goto out
     }
 
     if (disabled) {
@@ -2870,6 +2873,10 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
     }
 
     bdrv_dirty_bitmap_set_persistance(bitmap, persistent);
+ out:
+    if (aio_context) {
+        aio_context_release(aio_context);
+    }
 }
 
 void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
@@ -2878,6 +2885,7 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
     Error *local_err = NULL;
+    AioContext *aio_context = NULL;
 
     bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
     if (!bitmap || !bs) {
@@ -2892,14 +2900,20 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
     }
 
     if (bdrv_dirty_bitmap_get_persistance(bitmap)) {
+        aio_context = bdrv_get_aio_context(bs);
+        aio_context_acquire(aio_context);
         bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
         if (local_err != NULL) {
             error_propagate(errp, local_err);
-            return;
+            goto out;
         }
     }
 
     bdrv_release_dirty_bitmap(bs, bitmap);
+ out:
+    if (aio_context) {
+        aio_context_release(aio_context);
+    }
 }
 
 /**
-- 
2.17.2

Re: [Qemu-devel] [PATCH v3 1/1] blockdev: acquire aio_context for bitmap add/remove

[John Snow]

On 2/13/19 2:55 PM, John Snow wrote:
> When bitmaps are persistent, they may incur a disk read or write when bitmaps
> are added or removed. For configurations like virtio-dataplane, failing to
> acquire this lock will abort QEMU when disk IO occurs.
> 
> We used to acquire aio_context as part of the bitmap lookup, so re-introduce
> the lock for just the cases that have an IO penalty. Commit 2119882c removed
> these locks, and I failed to notice this when we committed fd5ae4cc, so this
> has been broken since persistent bitmaps were introduced.
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1672010
> Reported-By: Aihua Liang <aliang@redhat.com>
> Signed-off-by: John Snow <jsnow@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---
>  blockdev.c | 26 ++++++++++++++++++++------
>  1 file changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index fb18e9c975..790b0e0ac8 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -2820,6 +2820,7 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
>  {
>      BlockDriverState *bs;
>      BdrvDirtyBitmap *bitmap;
> +    AioContext *aio_context = NULL;
>  
>      if (!name || name[0] == '\0') {
>          error_setg(errp, "Bitmap name cannot be empty");
> @@ -2854,15 +2855,17 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
>          disabled = false;
>      }
>  
> -    if (persistent &&
> -        !bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp))
> -    {
> -        return;
> +    if (persistent) {
> +        aio_context = bdrv_get_aio_context(bs);
> +        aio_context_acquire(aio_context);
> +        if (!bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp)) {
> +            goto out;
> +        }
>      }
>  
>      bitmap = bdrv_create_dirty_bitmap(bs, granularity, name, errp);
>      if (bitmap == NULL) {
> -        return;
> +        goto out
>      }
>  
>      if (disabled) {
> @@ -2870,6 +2873,10 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
>      }
>  
>      bdrv_dirty_bitmap_set_persistance(bitmap, persistent);
> + out:
> +    if (aio_context) {
> +        aio_context_release(aio_context);
> +    }
>  }
>  
>  void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
> @@ -2878,6 +2885,7 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
>      BlockDriverState *bs;
>      BdrvDirtyBitmap *bitmap;
>      Error *local_err = NULL;
> +    AioContext *aio_context = NULL;
>  
>      bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
>      if (!bitmap || !bs) {
> @@ -2892,14 +2900,20 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
>      }
>  
>      if (bdrv_dirty_bitmap_get_persistance(bitmap)) {
> +        aio_context = bdrv_get_aio_context(bs);
> +        aio_context_acquire(aio_context);
>          bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
>          if (local_err != NULL) {
>              error_propagate(errp, local_err);
> -            return;
> +            goto out;
>          }
>      }
>  
>      bdrv_release_dirty_bitmap(bs, bitmap);
> + out:
> +    if (aio_context) {
> +        aio_context_release(aio_context);
> +    }
>  }
>  
>  /**
> 

Aaaand staged on my bitmaps branch, unless Kevin or Max tell me not to.

Re: [Qemu-devel] [PATCH v3 0/1] blockdev: acquire aio_context for bitmap add/remove

[no-reply]

Patchew URL: https://patchew.org/QEMU/20190213195501.7790-1-jsnow@redhat.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
time make docker-test-mingw@fedora SHOW_ENV=1 J=14
=== TEST SCRIPT END ===

  CC      hw/smbios/smbios_type_38-stub.o
  CC      hw/ssi/pl022.o
/tmp/qemu-test/src/blockdev.c: In function 'qmp_block_dirty_bitmap_add':
/tmp/qemu-test/src/blockdev.c:2868:17: error: expected ';' before '}' token
         goto out
                 ^
                 ;


The full log is available at
http://patchew.org/logs/20190213195501.7790-1-jsnow@redhat.com/testing.docker-mingw@fedora/?type=message.
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