Re: [PATCH v2 1/3] fsnotify: Use d_find_any_alias to get dentry associated with inode

Amir Goldstein
2022-10-21T09:26:26Z

On Fri, Oct 21, 2022 at 4:03 AM Stephen Brennan
<stephen.s.brennan@oracle.com> wrote:
>
> 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>

one nit below

> ---
> fs/notify/fsnotify.c | 41 ++++++++++++++++++-----------------------
> 1 file changed, 18 insertions(+), 23 deletions(-)
>
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index 7974e91ffe13..6c338322f0c3 100644
> --- a/fs/notify/fsnotify.c
> +++ b/fs/notify/fsnotify.c
> @@ -105,7 +105,7 @@ void fsnotify_sb_delete(struct super_block *sb)
> */
> void __fsnotify_update_child_dentry_flags(struct inode *inode)
> {
> - struct dentry *alias;
> + struct dentry *alias, *child;
> int watched;
>
> if (!S_ISDIR(inode->i_mode))
> @@ -114,30 +114,25 @@ void __fsnotify_update_child_dentry_flags(struct inode *inode)
> /* determine if the children should tell inode about their events */
> watched = fsnotify_inode_watches_children(inode);
>
> - 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);
>
> - 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) */

Please add new lines at the beginning and end of this multi line comment.

Thanks,
Amir.