diff options
| author | Kent Overstreet <kent.overstreet@linux.dev> | 2023-03-06 08:58:02 -0500 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@linux.dev> | 2023-10-22 17:09:41 -0400 |
| commit | 2ec254c098da677295c2487ae36e75a26d557222 (patch) | |
| tree | d6c3ffceb92f16978c9e526803a2d8058fa8630b /fs | |
| parent | 0d7009d7ca99ad9261a7cffcecd515108377a6ac (diff) | |
bcachefs: Ensure bch2_btree_node_lock_write_nofail() never fails
In order for bch2_btree_node_lock_write_nofail() to never produce a
deadlock, we must ensure we're never holding read locks when using it.
Fortunately, it's only used from code paths where any read locks may be
safely dropped.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/bcachefs/btree_locking.c | 34 | ||||
| -rw-r--r-- | fs/bcachefs/btree_locking.h | 12 |
2 files changed, 38 insertions, 8 deletions
diff --git a/fs/bcachefs/btree_locking.c b/fs/bcachefs/btree_locking.c index 11f83a936dc7..6793d7dd18d7 100644 --- a/fs/bcachefs/btree_locking.c +++ b/fs/bcachefs/btree_locking.c @@ -320,6 +320,40 @@ int __bch2_btree_node_lock_write(struct btree_trans *trans, struct btree_path *p return ret; } +void bch2_btree_node_lock_write_nofail(struct btree_trans *trans, + struct btree_path *path, + struct btree_bkey_cached_common *b) +{ + struct btree_path *linked; + unsigned i; + int ret; + + /* + * XXX BIG FAT NOTICE + * + * Drop all read locks before taking a write lock: + * + * This is a hack, because bch2_btree_node_lock_write_nofail() is a + * hack - but by dropping read locks first, this should never fail, and + * we only use this in code paths where whatever read locks we've + * already taken are no longer needed: + */ + + trans_for_each_path(trans, linked) { + if (!linked->nodes_locked) + continue; + + for (i = 0; i < BTREE_MAX_DEPTH; i++) + if (btree_node_read_locked(linked, i)) { + btree_node_unlock(trans, linked, i); + btree_path_set_dirty(linked, BTREE_ITER_NEED_RELOCK); + } + } + + ret = __btree_node_lock_write(trans, path, b, true); + BUG_ON(ret); +} + /* relock */ static inline bool btree_path_get_locks(struct btree_trans *trans, diff --git a/fs/bcachefs/btree_locking.h b/fs/bcachefs/btree_locking.h index 6d8df25bf076..95089693a420 100644 --- a/fs/bcachefs/btree_locking.h +++ b/fs/bcachefs/btree_locking.h @@ -290,14 +290,6 @@ static inline int __btree_node_lock_write(struct btree_trans *trans, : __bch2_btree_node_lock_write(trans, path, b, lock_may_not_fail); } -static inline void bch2_btree_node_lock_write_nofail(struct btree_trans *trans, - struct btree_path *path, - struct btree_bkey_cached_common *b) -{ - int ret = __btree_node_lock_write(trans, path, b, true); - BUG_ON(ret); -} - static inline int __must_check bch2_btree_node_lock_write(struct btree_trans *trans, struct btree_path *path, @@ -306,6 +298,10 @@ bch2_btree_node_lock_write(struct btree_trans *trans, return __btree_node_lock_write(trans, path, b, false); } +void bch2_btree_node_lock_write_nofail(struct btree_trans *, + struct btree_path *, + struct btree_bkey_cached_common *); + /* relock: */ bool bch2_btree_path_relock_norestart(struct btree_trans *, |