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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

8
include/block/block-io.h
View file

@ -76,8 +76,12 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
PreallocMode prealloc, BdrvRequestFlags flags,
Error **errp);
int64_t bdrv_nb_sectors(BlockDriverState *bs);
int64_t bdrv_getlength(BlockDriverState *bs);
int64_t coroutine_fn bdrv_co_nb_sectors(BlockDriverState *bs);
int64_t co_wrapper_mixed bdrv_nb_sectors(BlockDriverState *bs);
int64_t coroutine_fn bdrv_co_getlength(BlockDriverState *bs);
int64_t co_wrapper_mixed bdrv_getlength(BlockDriverState *bs);
int64_t bdrv_get_allocated_file_size(BlockDriverState *bs);
BlockMeasureInfo *bdrv_measure(BlockDriver *drv, QemuOpts *opts,
BlockDriverState *in_bs, Error **errp);

2
include/block/block_int-common.h
View file

@ -680,7 +680,7 @@ struct BlockDriver {
int coroutine_fn (*bdrv_co_truncate)(BlockDriverState *bs, int64_t offset,
bool exact, PreallocMode prealloc,
BdrvRequestFlags flags, Error **errp);
int64_t (*bdrv_getlength)(BlockDriverState *bs);
int64_t coroutine_fn (*bdrv_co_getlength)(BlockDriverState *bs);
int64_t (*bdrv_get_allocated_file_size)(BlockDriverState *bs);
BlockMeasureInfo *(*bdrv_measure)(QemuOpts *opts, BlockDriverState *in_bs,
Error **errp);

5
include/block/block_int-io.h
View file

@ -122,7 +122,10 @@ int coroutine_fn bdrv_co_copy_range_to(BdrvChild *src, int64_t src_offset,
BdrvRequestFlags read_flags,
BdrvRequestFlags write_flags);
int bdrv_refresh_total_sectors(BlockDriverState *bs, int64_t hint);
int coroutine_fn bdrv_co_refresh_total_sectors(BlockDriverState *bs,
int64_t hint);
int co_wrapper_mixed
bdrv_refresh_total_sectors(BlockDriverState *bs, int64_t hint);
BdrvChild *bdrv_cow_child(BlockDriverState *bs);
BdrvChild *bdrv_filter_child(BlockDriverState *bs);

10
include/sysemu/block-backend-io.h
View file

@ -61,9 +61,15 @@ bool co_wrapper_mixed blk_is_inserted(BlockBackend *blk);
bool blk_is_available(BlockBackend *blk);
void blk_lock_medium(BlockBackend *blk, bool locked);
void blk_eject(BlockBackend *blk, bool eject_flag);
int64_t blk_getlength(BlockBackend *blk);
int64_t coroutine_fn blk_co_getlength(BlockBackend *blk);
int64_t co_wrapper_mixed blk_getlength(BlockBackend *blk);
void blk_get_geometry(BlockBackend *blk, uint64_t *nb_sectors_ptr);
int64_t blk_nb_sectors(BlockBackend *blk);
int64_t coroutine_fn blk_co_nb_sectors(BlockBackend *blk);
int64_t co_wrapper_mixed blk_nb_sectors(BlockBackend *blk);
void *blk_try_blockalign(BlockBackend *blk, size_t size);
void *blk_blockalign(BlockBackend *blk, size_t size);
bool blk_is_writable(BlockBackend *blk);