diff mbox series

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

Message ID 20221111220614.991928-3-stephen.s.brennan@oracle.com
State New
Headers
Series fsnotify: fix softlockups iterating over d_subdirs |

Commit Message

Stephen Brennan Nov. 11, 2022, 10:06 p.m. UTC 
  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(-)

Comments

Amir Goldstein Nov. 12, 2022, 8:53 a.m. UTC | #1 
On Sat, Nov 12, 2022 at 12:06 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>
> ---
>
> 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)

nit: this comment can probably fit in two nicer lines

> +        */
> +       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
>
diff mbox series

Patch

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);
 }
 
 /*