diff options
| author | Emanuele Giuseppe Esposito <eesposit@redhat.com> | 2023-01-13 21:42:04 +0100 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2023-02-01 16:52:32 +0100 |
| commit | c86422c5549c0983b4b4525b8f56a1c69dd67aa1 (patch) | |
| tree | 9791a300734a7dda8422e6a531b2d0f592a10768 /block/null.c | |
| parent | c057960c4e33becb22d4741156203a4b0d4a3088 (diff) | |
| download | qemu-c86422c5549c0983b4b4525b8f56a1c69dd67aa1.zip qemu-c86422c5549c0983b4b4525b8f56a1c69dd67aa1.tar.gz qemu-c86422c5549c0983b4b4525b8f56a1c69dd67aa1.tar.bz2 | |
block: Convert bdrv_refresh_total_sectors() to co_wrapper_mixed
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>
Diffstat (limited to 'block/null.c')
| -rw-r--r-- | block/null.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/block/null.c b/block/null.c index 306e605..bc4d0c1 100644 --- a/block/null.c +++ b/block/null.c @@ -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, |