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block: acquire AioContext in qmp_query_blockstats()

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Make query-blockstats safe for dataplane by acquiring the
BlockDriverState's AioContext.  This ensures that the dataplane IOThread
and the main loop's monitor code do not race.

Note the assumption that acquiring the drive's BDS AioContext also
protects ->file and ->backing_hd.  This assumption is made by other
aio_context_acquire() callers too.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Tested-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2014-06-17 14:32:05 +08:00 committed by Kevin Wolf
parent ac46821f2c
commit 13344f3a17
1 changed files with 4 additions and 0 deletions
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4
block/qapi.c
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@ -360,7 +360,11 @@ BlockStatsList *qmp_query_blockstats(Error **errp)
while ((bs = bdrv_next(bs))) {
BlockStatsList *info = g_malloc0(sizeof(*info));
AioContext *ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
info->value = bdrv_query_stats(bs);
aio_context_release(ctx);
*p_next = info;
p_next = &info->next;