From: Stephen Brennan <stephen.s.brennan@oracle.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Amir Goldstein <amir73il@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v3 1/3] fsnotify: Use d_find_any_alias to get dentry associated with inode
Date: Wed, 09 Nov 2022 17:12:58 -0800 [thread overview]
Message-ID: <87pmdvfw85.fsf@oracle.com> (raw)
In-Reply-To: <20221028001016.332663-2-stephen.s.brennan@oracle.com>
Stephen Brennan <stephen.s.brennan@oracle.com> writes:
> 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 since v2:
> - 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 | 44 +++++++++++++++++++++-----------------------
> 1 file changed, 21 insertions(+), 23 deletions(-)
>
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index 7974e91ffe13..7939aa911931 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 +114,28 @@ 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);
Unfortunately, even this patch is not as simple as we would have liked
to believe. Running LTP, fanotify10 test, I reliably panic here because
d_find_any_alias(inode) returns NULL. I've fixed this in my branch
already with a simple if (alias) return watched;
Will continue to work through LTP tests (with lockdep enabled) and work
on the existing dnotify lock ordering issue.
>
> - 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);
> }
>
> /* Are inode/sb/mount interested in parent and name info with this event? */
> --
> 2.34.1
next prev parent reply other threads:[~2022-11-10 1:13 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-13 22:27 [RFC] fsnotify: allow sleepable child dentry flag update Stephen Brennan
2022-10-13 23:51 ` Al Viro
2022-11-01 21:47 ` Stephen Brennan
2022-10-14 8:01 ` Amir Goldstein
2022-10-17 7:59 ` Stephen Brennan
2022-10-17 11:44 ` Amir Goldstein
2022-10-17 16:59 ` Stephen Brennan
2022-10-17 17:42 ` Amir Goldstein
2022-10-17 9:09 ` Jan Kara
2022-10-18 4:12 ` [PATCH 0/2] fsnotify: fix softlockups iterating over d_subdirs Stephen Brennan
2022-10-18 4:12 ` [PATCH 1/2] fsnotify: Protect i_fsnotify_mask and child flags with inode rwsem Stephen Brennan
2022-10-18 7:39 ` Amir Goldstein
2022-10-21 0:33 ` Stephen Brennan
2022-10-21 7:22 ` Amir Goldstein
2022-10-18 4:12 ` [PATCH 2/2] fsnotify: allow sleepable child flag update Stephen Brennan
2022-10-18 5:36 ` Amir Goldstein
2022-10-27 7:50 ` kernel test robot
2022-10-27 8:44 ` Yujie Liu
2022-10-27 22:12 ` Stephen Brennan
2022-10-18 8:07 ` [PATCH 0/2] fsnotify: fix softlockups iterating over d_subdirs Amir Goldstein
2022-10-18 23:52 ` Stephen Brennan
2022-10-19 5:33 ` Amir Goldstein
2022-10-27 22:06 ` Stephen Brennan
2022-10-28 8:58 ` Amir Goldstein
2022-10-21 1:03 ` [PATCH v2 0/3] " Stephen Brennan
2022-10-21 1:03 ` [PATCH v2 1/3] fsnotify: Use d_find_any_alias to get dentry associated with inode Stephen Brennan
2022-10-21 9:25 ` Amir Goldstein
2022-10-21 1:03 ` [PATCH v2 2/3] fsnotify: Protect i_fsnotify_mask and child flags with inode rwsem Stephen Brennan
2022-10-21 4:01 ` kernel test robot
2022-10-21 8:22 ` Amir Goldstein
2022-10-21 9:18 ` Amir Goldstein
2022-10-25 18:02 ` Stephen Brennan
2022-10-26 5:41 ` Amir Goldstein
2022-10-21 9:17 ` Christian Brauner
2022-10-21 9:21 ` Amir Goldstein
2022-10-21 1:03 ` [PATCH v2 3/3] fsnotify: allow sleepable child flag update Stephen Brennan
2022-10-28 0:10 ` [PATCH v3 0/3] fsnotify: fix softlockups iterating over d_subdirs Stephen Brennan
2022-10-28 0:10 ` [PATCH v3 1/3] fsnotify: Use d_find_any_alias to get dentry associated with inode Stephen Brennan
2022-11-10 1:12 ` Stephen Brennan [this message]
2022-10-28 0:10 ` [PATCH v3 2/3] fsnotify: Protect i_fsnotify_mask and child flags with inode rwsem Stephen Brennan
2022-10-28 9:11 ` Amir Goldstein
2022-11-10 0:03 ` kernel test robot
2022-11-10 1:06 ` Stephen Brennan
2022-10-28 0:10 ` [PATCH v3 3/3] fsnotify: allow sleepable child flag update Stephen Brennan
2022-10-28 9:32 ` Amir Goldstein
2022-11-01 21:25 ` Stephen Brennan
2022-11-01 17:51 ` [PATCH v3 0/3] fsnotify: fix softlockups iterating over d_subdirs Jan Kara
2022-11-01 20:48 ` Stephen Brennan
2022-11-02 8:55 ` Amir Goldstein
2022-11-10 20:04 ` Stephen Brennan
2022-11-02 17:52 ` Jan Kara
2022-11-04 23:33 ` Stephen Brennan
2022-11-07 11:56 ` Jan Kara
2022-11-11 22:06 ` [PATCH v4 0/5] " Stephen Brennan
2022-11-11 22:06 ` [PATCH v4 1/5] fsnotify: clear PARENT_WATCHED flags lazily Stephen Brennan
2022-11-11 22:06 ` [PATCH v4 2/5] fsnotify: Use d_find_any_alias to get dentry associated with inode Stephen Brennan
2022-11-12 8:53 ` Amir Goldstein
2022-11-11 22:06 ` [PATCH v4 3/5] dnotify: move fsnotify_recalc_mask() outside spinlock Stephen Brennan
2022-11-12 9:06 ` Amir Goldstein
2022-11-11 22:06 ` [PATCH v4 4/5] fsnotify: allow sleepable child flag update Stephen Brennan
2022-11-12 10:00 ` Amir Goldstein
2022-11-15 7:10 ` kernel test robot
2022-11-11 22:06 ` [PATCH v4 5/5] fsnotify: require inode lock held during " Stephen Brennan
2022-11-12 9:42 ` Amir Goldstein
2022-11-11 22:08 ` [PATCH v4 0/5] fsnotify: fix softlockups iterating over d_subdirs Stephen Brennan
2022-11-22 11:50 ` Jan Kara
2022-11-22 14:03 ` Amir Goldstein
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