[PATCH v4 2/5] fsnotify: Use d_find_any_alias to get dentry associated with inode

Stephen Brennan
2022-11-11T22:06:55Z

Rather than iterating over the inode's i_dentry (requiring holding the
i_lock for the entire duration of the function), we know that there
should be only one item in the list. Use d_find_any_alias() and no
longer hold i_lock.

Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
---

Notes:
Changes in v4:
- Bail out if d_find_any_alias() returns NULL
- Rebase on Amir's patch
Changes in v3:
- Add newlines in block comment
- d_find_any_alias() returns a reference, which I was leaking. Add
a dput(alias) at the end.
- Add Amir's R-b

fs/notify/fsnotify.c | 46 ++++++++++++++++++++++----------------------
1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 2c50e9e50d35..409d479cbbc6 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -105,35 +105,35 @@ void fsnotify_sb_delete(struct super_block *sb)
*/
void fsnotify_update_children_dentry_flags(struct inode *inode, bool watched)
{
- struct dentry *alias;
+ struct dentry *alias, *child;

if (!S_ISDIR(inode->i_mode))
return;

- spin_lock(&inode->i_lock);
- /* run all of the dentries associated with this inode. Since this is a
- * directory, there damn well better only be one item on this list */
- hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
- struct dentry *child;
-
- /* run all of the children of the original inode and fix their
- * d_flags to indicate parental interest (their parent is the
- * original inode) */
- spin_lock(&alias->d_lock);
- list_for_each_entry(child, &alias->d_subdirs, d_child) {
- if (!child->d_inode)
- continue;
+ /* Since this is a directory, there damn well better only be one child */
+ alias = d_find_any_alias(inode);
+ if (!alias)
+ return;

- spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
- if (watched)
- child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
- else
- child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
- spin_unlock(&child->d_lock);
- }
- spin_unlock(&alias->d_lock);
+ /*
+ * run all of the children of the original inode and fix their
+ * d_flags to indicate parental interest (their parent is the
+ * original inode)
+ */
+ spin_lock(&alias->d_lock);
+ list_for_each_entry(child, &alias->d_subdirs, d_child) {
+ if (!child->d_inode)
+ continue;
+
+ spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
+ if (watched)
+ child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
+ else
+ child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
+ spin_unlock(&child->d_lock);
}
- spin_unlock(&inode->i_lock);
+ spin_unlock(&alias->d_lock);
+ dput(alias);
}

/*
--
2.34.1