kernel/drivers/md/persistent-data/dm-block-manager.h, branch linux-6.9.y

dm thin metadata: Fix ABBA deadlock by resetting dm_bufio_client

2023-06-16T22:24:13Z

As described in commit 8111964f1b85 ("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 8111964f1b85 ("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: 8111964f1b85 ("dm thin: Fix ABBA deadlock between shrink_slab and dm_pool_abort_metadata") Cc: stable@vger.kernel.org Signed-off-by: Li Lingfeng Signed-off-by: Mike Snitzer

dm: change "unsigned" to "unsigned int"

2023-02-14T19:23:06Z

Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm: add missing SPDX-License-Indentifiers

2023-02-14T19:23:06Z

'GPL-2.0-only' is used instead of 'GPL-2.0' because SPDX has deprecated its use. Suggested-by: John Wiele Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm block manager: remove an unused argument from dm_block_manager_create()

2017-04-27T21:08:41Z

The 'cache_size' argument of dm_block_manager_create() has never been used. Remove it along with the definitions of the constants passed as the 'cache_size' argument. Signed-off-by: Bart Van Assche Reviewed-by: Hannes Reinecke Signed-off-by: Mike Snitzer

dm persistent data: eliminate unnecessary return values

2015-10-31T23:06:02Z

dm_bm_unlock and dm_tm_unlock return an integer value but the returned value is always 0. The calling code sometimes checks the return value and sometimes doesn't. Eliminate these unnecessary return values and also the checks for them. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm thin metadata: remove in-core 'read_only' flag

2015-05-29T18:18:59Z

Leverage the block manager's read_only flag instead of duplicating it; access with new dm_bm_is_read_only() method. Signed-off-by: Mike Snitzer

dm transaction manager: fix corruption due to non-atomic transaction commit

2014-03-27T20:56:23Z

The persistent-data library used by dm-thin, dm-cache, etc is transactional. If anything goes wrong, such as an io error when writing new metadata or a power failure, then we roll back to the last transaction. Atomicity when committing a transaction is achieved by: a) Never overwriting data from the previous transaction. b) Writing the superblock last, after all other metadata has hit the disk. This commit and the following commit ("dm: take care to copy the space map roots before locking the superblock") fix a bug associated with (b). When committing it was possible for the superblock to still be written in spite of an io error occurring during the preceeding metadata flush. With these commits we're careful not to take the write lock out on the superblock until after the metadata flush has completed. Change the transaction manager's semantics for dm_tm_commit() to assume all data has been flushed _before_ the single superblock that is passed in. As a prerequisite, split the block manager's block unlocking and flushing by simplifying dm_bm_flush_and_unlock() to dm_bm_flush(). Now the unlocking must be done separately. This issue was discovered by forcing io errors at the crucial time using dm-flakey. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org

dm thin: allow pool in read-only mode to transition to read-write mode

2013-12-10T21:35:13Z

A thin-pool may be in read-only mode because the pool's data or metadata space was exhausted. To allow for recovery, by adding more space to the pool, we must allow a pool to transition from PM_READ_ONLY to PM_WRITE mode. Otherwise, running out of space will render the pool permanently read-only. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org

dm btree: prefetch child nodes when walking tree for a dm_btree_del

2013-08-23T13:02:14Z

dm-btree now takes advantage of dm-bufio's ability to prefetch data via dm_bm_prefetch(). Prior to this change many btree node visits were causing a synchronous read. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon

dm persistent data: introduce dm_bm_set_read_only

2012-07-27T14:08:15Z

Introduce dm_bm_set_read_only to switch the block manager into a read-only mode. To be used when dm-thin degrades due to io errors on the metadata device. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon