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block: Convert bdrv_refresh_total_sectors() to co_wrapper_mixed

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BlockDriver->bdrv_getlength is categorized as IO callback, and it
currently doesn't run in a coroutine. We should let it take a graph
rdlock since the callback traverses the block nodes graph, which however
is only possible in a coroutine.

Therefore turn it into a co_wrapper to move the actual function into a
coroutine where the lock can be taken.

Because now this function creates a new coroutine and polls, we need to
take the AioContext lock where it is missing, for the only reason that
internally co_wrapper calls AIO_WAIT_WHILE and it expects to release the
AioContext lock.

This is especially messy when a co_wrapper creates a coroutine and polls
in bdrv_open_driver, because this function has so many callers in so
many context that it can easily lead to deadlocks. Therefore the new
rule for bdrv_open_driver is that the caller must always hold the
AioContext lock of the given bs (except if it is a coroutine), because
the function calls bdrv_refresh_total_sectors() which is now a
co_wrapper.

Once the rwlock is ultimated and placed in every place it needs to be,
we will poll using AIO_WAIT_WHILE_UNLOCKED and remove the AioContext
lock.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230113204212.359076-7-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Emanuele Giuseppe Esposito 2023-01-13 21:42:04 +01:00 • committed by Kevin Wolf
parent c057960c4e
commit c86422c554
35 changed files with 161 additions and 121 deletions
Download patch file Download diff file Expand all files Collapse all files

6
block/null.c
View file

@ -100,7 +100,7 @@ static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
return ret;
}
static int64_t null_getlength(BlockDriverState *bs)
static int64_t coroutine_fn null_co_getlength(BlockDriverState *bs)
{
BDRVNullState *s = bs->opaque;
return s->length;
@ -284,7 +284,7 @@ static BlockDriver bdrv_null_co = {
.bdrv_file_open = null_file_open,
.bdrv_parse_filename = null_co_parse_filename,
.bdrv_getlength = null_getlength,
.bdrv_co_getlength = null_co_getlength,
.bdrv_get_allocated_file_size = null_allocated_file_size,
.bdrv_co_preadv = null_co_preadv,
@ -305,7 +305,7 @@ static BlockDriver bdrv_null_aio = {
.bdrv_file_open = null_file_open,
.bdrv_parse_filename = null_aio_parse_filename,
.bdrv_getlength = null_getlength,
.bdrv_co_getlength = null_co_getlength,
.bdrv_get_allocated_file_size = null_allocated_file_size,
.bdrv_aio_preadv = null_aio_preadv,