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| author | Kent Overstreet <kent.overstreet@linux.dev> | 2023-03-06 16:58:02 +0300 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@linux.dev> | 2023-10-23 00:09:41 +0300 |
| commit | 2ec254c098da677295c2487ae36e75a26d557222 (patch) | |
| tree | d6c3ffceb92f16978c9e526803a2d8058fa8630b /fs/bcachefs/btree_locking.c | |
| parent | 0d7009d7ca99ad9261a7cffcecd515108377a6ac (diff) | |
| download | linux-2ec254c098da677295c2487ae36e75a26d557222.tar.xz | |
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/bcachefs/btree_locking.c')
| -rw-r--r-- | fs/bcachefs/btree_locking.c | 34 |
1 files changed, 34 insertions, 0 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, |