diff options
| -rw-r--r-- | fs/ubifs/tnc_commit.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/fs/ubifs/tnc_commit.c b/fs/ubifs/tnc_commit.c index f50c3e5da26..d6fab1a9986 100644 --- a/fs/ubifs/tnc_commit.c +++ b/fs/ubifs/tnc_commit.c @@ -89,6 +89,10 @@ static int make_idx_node(struct ubifs_info *c, struct ubifs_idx_node *idx, ubifs_assert(ubifs_zn_dirty(znode)); ubifs_assert(ubifs_zn_cow(znode)); + /* + * Note, unlike 'write_index()' we do not add memory barriers here + * because this function is called with @c->tnc_mutex locked. + */ __clear_bit(DIRTY_ZNODE, &znode->flags); __clear_bit(COW_ZNODE, &znode->flags); @@ -903,6 +907,28 @@ static int write_index(struct ubifs_info *c) clear_bit(COW_ZNODE, &znode->flags); smp_mb__after_clear_bit(); + /* + * We have marked the znode as clean but have not updated the + * @c->clean_zn_cnt counter. If this znode becomes dirty again + * before 'free_obsolete_znodes()' is called, then + * @c->clean_zn_cnt will be decremented before it gets + * incremented (resulting in 2 decrements for the same znode). + * This means that @c->clean_zn_cnt may become negative for a + * while. + * + * Q: why we cannot increment @c->clean_zn_cnt? + * A: because we do not have the @c->tnc_mutex locked, and the + * following code would be racy and buggy: + * + * if (!ubifs_zn_obsolete(znode)) { + * atomic_long_inc(&c->clean_zn_cnt); + * atomic_long_inc(&ubifs_clean_zn_cnt); + * } + * + * Thus, we just delay the @c->clean_zn_cnt update until we + * have the mutex locked. + */ + /* Do not access znode from this point on */ /* Update buffer positions */ |