dm thin metadata: Fix ABBA deadlock by resetting dm_bufio_client
As described in commit 8111964f ("dm thin: Fix ABBA deadlock between shrink_slab and dm_pool_abort_metadata"), ABBA deadlocks will be triggered because shrinker_rwsem currently needs to held by dm_pool_abort_metadata() as a side-effect of thin-pool metadata operation failure. The following three problem scenarios have been noticed: 1) Described by commit 8111964f ("dm thin: Fix ABBA deadlock between shrink_slab and dm_pool_abort_metadata") 2) shrinker_rwsem and throttle->lock P1(drop cache) P2(kworker) drop_caches_sysctl_handler drop_slab shrink_slab down_read(&shrinker_rwsem) - LOCK A do_shrink_slab super_cache_scan prune_icache_sb dispose_list evict ext4_evict_inode ext4_clear_inode ext4_discard_preallocations ext4_mb_load_buddy_gfp ext4_mb_init_cache ext4_wait_block_bitmap __ext4_error ext4_handle_error ext4_commit_super ... dm_submit_bio do_worker throttle_work_update down_write(&t->lock) -- LOCK B process_deferred_bios commit metadata_operation_failed dm_pool_abort_metadata dm_block_manager_create dm_bufio_client_create register_shrinker down_write(&shrinker_rwsem) -- LOCK A thin_map thin_bio_map thin_defer_bio_with_throttle throttle_lock down_read(&t->lock) - LOCK B 3) shrinker_rwsem and wait_on_buffer P1(drop cache) P2(kworker) drop_caches_sysctl_handler drop_slab shrink_slab down_read(&shrinker_rwsem) - LOCK A do_shrink_slab ... ext4_wait_block_bitmap __ext4_error ext4_handle_error jbd2_journal_abort jbd2_journal_update_sb_errno jbd2_write_superblock submit_bh // LOCK B // RELEASE B do_worker throttle_work_update down_write(&t->lock) - LOCK B process_deferred_bios process_bio commit metadata_operation_failed dm_pool_abort_metadata dm_block_manager_create dm_bufio_client_create register_shrinker register_shrinker_prepared down_write(&shrinker_rwsem) - LOCK A bio_endio wait_on_buffer __wait_on_buffer Fix these by resetting dm_bufio_client without holding shrinker_rwsem. Fixes: 8111964f ("dm thin: Fix ABBA deadlock between shrink_slab and dm_pool_abort_metadata") Cc: stable@vger.kernel.org Signed-off-by:Li Lingfeng <lilingfeng3@huawei.com> Signed-off-by:
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