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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20221021010310.29521-2-stephen.s.brennan@oracle.com>
Date:   Thu, 20 Oct 2022 18:03:08 -0700
From:   Stephen Brennan <stephen.s.brennan@...cle.com>
To:     Jan Kara <jack@...e.cz>, Alexander Viro <viro@...iv.linux.org.uk>
Cc:     linux-fsdevel@...r.kernel.org, Amir Goldstein <amir73il@...il.com>,
        linux-kernel@...r.kernel.org,
        Stephen Brennan <stephen.s.brennan@...cle.com>
Subject: [PATCH v2 1/3] fsnotify: Use d_find_any_alias to get dentry associated with inode

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@...cle.com>
---
 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) */
+	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);
 }
 
 /* Are inode/sb/mount interested in parent and name info with this event? */
-- 
2.34.1