* [Qemu-devel] [PATCH v5] blockdev: acquire aio_context for bitmap add/remove
@ 2019-02-18 23:31 John Snow
2019-02-19 14:59 ` Eric Blake
0 siblings, 1 reply; 3+ messages in thread
From: John Snow @ 2019-02-18 23:31 UTC (permalink / raw)
To: qemu-devel, qemu-block
Cc: Max Reitz, Kevin Wolf, Markus Armbruster, pbonzini, vsementsov,
eblake, 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>
---
v5: I'm having a really bad day. This version actually has the semicolon.
---
blockdev.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)
diff --git a/blockdev.c b/blockdev.c
index fb18e9c975..8714ad2702 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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [Qemu-devel] [PATCH v5] blockdev: acquire aio_context for bitmap add/remove
2019-02-18 23:31 [Qemu-devel] [PATCH v5] blockdev: acquire aio_context for bitmap add/remove John Snow
@ 2019-02-19 14:59 ` Eric Blake
2019-02-19 19:56 ` John Snow
0 siblings, 1 reply; 3+ messages in thread
From: Eric Blake @ 2019-02-19 14:59 UTC (permalink / raw)
To: John Snow, qemu-devel, qemu-block
Cc: Max Reitz, Kevin Wolf, Markus Armbruster, pbonzini, vsementsov
On 2/18/19 5:31 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>
> ---
> v5: I'm having a really bad day. This version actually has the semicolon.
> ---
> blockdev.c | 26 ++++++++++++++++++++------
> 1 file changed, 20 insertions(+), 6 deletions(-)
Reviewed-by: Eric Blake <eblake@redhat.com>
and yes, this time it builds.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Qemu-devel] [PATCH v5] blockdev: acquire aio_context for bitmap add/remove
2019-02-19 14:59 ` Eric Blake
@ 2019-02-19 19:56 ` John Snow
0 siblings, 0 replies; 3+ messages in thread
From: John Snow @ 2019-02-19 19:56 UTC (permalink / raw)
To: Eric Blake, qemu-devel, qemu-block
Cc: Kevin Wolf, pbonzini, vsementsov, Markus Armbruster, Max Reitz
On 2/19/19 9:59 AM, Eric Blake wrote:
> On 2/18/19 5:31 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>
>> ---
>> v5: I'm having a really bad day. This version actually has the semicolon.
>> ---
>> blockdev.c | 26 ++++++++++++++++++++------
>> 1 file changed, 20 insertions(+), 6 deletions(-)
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
>
> and yes, this time it builds.
>
I am really very sorry for the noise on this simple series. Thank you
for the review and your patience.
--John
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-02-19 19:56 UTC | newest]
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2019-02-18 23:31 [Qemu-devel] [PATCH v5] blockdev: acquire aio_context for bitmap add/remove John Snow
2019-02-19 14:59 ` Eric Blake
2019-02-19 19:56 ` John Snow
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