This function, in addition to be called by a generated_co_wrapper, is also called elsewhere else. The strategy is to always take the lock at the function called when the coroutine is created, to avoid recursive locking.
By protecting brdv_co_pread, we also automatically protect the following other generated_co_wrappers: blk_co_pread blk_co_preadv blk_co_preadv_part Protecting bdrv_driver_preadv() implies that the following BlockDriver callbacks always called with graph rdlock taken: - bdrv_co_preadv_part - bdrv_co_preadv - bdrv_aio_preadv - bdrv_co_readv Signed-off-by: Emanuele Giuseppe Esposito <eespo...@redhat.com> --- block/block-backend.c | 1 + block/io.c | 1 + block/mirror.c | 6 ++++-- include/block/block_int-common.h | 5 +++++ include/block/block_int-io.h | 1 + tests/unit/test-bdrv-drain.c | 2 ++ 6 files changed, 14 insertions(+), 2 deletions(-) diff --git a/block/block-backend.c b/block/block-backend.c index d48ec3a2ac..083ed6009e 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -1289,6 +1289,7 @@ blk_co_do_preadv_part(BlockBackend *blk, int64_t offset, int64_t bytes, IO_CODE(); blk_wait_while_drained(blk); + GRAPH_RDLOCK_GUARD(); /* Call blk_bs() only after waiting, the graph may have changed */ bs = blk_bs(blk); diff --git a/block/io.c b/block/io.c index 92c74648fb..cfc201ef91 100644 --- a/block/io.c +++ b/block/io.c @@ -942,6 +942,7 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs, unsigned int nb_sectors; QEMUIOVector local_qiov; int ret; + assert_bdrv_graph_readable(); bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort); assert(!(flags & ~bs->supported_read_flags)); diff --git a/block/mirror.c b/block/mirror.c index 251adc5ae0..f509cc1cb1 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -389,8 +389,10 @@ static void coroutine_fn mirror_co_read(void *opaque) op->is_in_flight = true; trace_mirror_one_iteration(s, op->offset, op->bytes); - ret = bdrv_co_preadv(s->mirror_top_bs->backing, op->offset, op->bytes, - &op->qiov, 0); + WITH_GRAPH_RDLOCK_GUARD() { + ret = bdrv_co_preadv(s->mirror_top_bs->backing, op->offset, op->bytes, + &op->qiov, 0); + } mirror_read_complete(op, ret); } diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h index e8d2e4b6c7..64c5bb64de 100644 --- a/include/block/block_int-common.h +++ b/include/block/block_int-common.h @@ -476,6 +476,7 @@ struct BlockDriver { Error **errp); /* aio */ + /* Called with graph rdlock held. */ BlockAIOCB *(*bdrv_aio_preadv)(BlockDriverState *bs, int64_t offset, int64_t bytes, QEMUIOVector *qiov, BdrvRequestFlags flags, BlockCompletionFunc *cb, void *opaque); @@ -489,6 +490,7 @@ struct BlockDriver { int64_t offset, int bytes, BlockCompletionFunc *cb, void *opaque); + /* Called with graph rdlock held. */ int coroutine_fn (*bdrv_co_readv)(BlockDriverState *bs, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov); @@ -506,11 +508,14 @@ struct BlockDriver { * no larger than 'max_transfer'. * * The buffer in @qiov may point directly to guest memory. + * + * Called with graph rdlock held. */ int coroutine_fn (*bdrv_co_preadv)(BlockDriverState *bs, int64_t offset, int64_t bytes, QEMUIOVector *qiov, BdrvRequestFlags flags); + /* Called with graph rdlock held. */ int coroutine_fn (*bdrv_co_preadv_part)(BlockDriverState *bs, int64_t offset, int64_t bytes, QEMUIOVector *qiov, size_t qiov_offset, diff --git a/include/block/block_int-io.h b/include/block/block_int-io.h index ae88507d6a..ac6ad3b3ff 100644 --- a/include/block/block_int-io.h +++ b/include/block/block_int-io.h @@ -60,6 +60,7 @@ static inline int coroutine_fn bdrv_co_pread(BdrvChild *child, { QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes); IO_CODE(); + assert_bdrv_graph_readable(); return bdrv_co_preadv(child, offset, bytes, &qiov, flags); } diff --git a/tests/unit/test-bdrv-drain.c b/tests/unit/test-bdrv-drain.c index 2686a8acee..90edc2f5bf 100644 --- a/tests/unit/test-bdrv-drain.c +++ b/tests/unit/test-bdrv-drain.c @@ -967,6 +967,8 @@ static void coroutine_fn test_co_delete_by_drain(void *opaque) void *buffer = g_malloc(65536); QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buffer, 65536); + GRAPH_RDLOCK_GUARD(); + /* Pretend some internal write operation from parent to child. * Important: We have to read from the child, not from the parent! * Draining works by first propagating it all up the tree to the -- 2.31.1