lkml.org 
[lkml]   [2020]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/2] kernfs: remove mutex in kernfs_dop_revalidate
On Wed, Dec 02, 2020 at 10:58:37PM +0800, Fox Chen wrote:
> There is a big mutex in kernfs_dop_revalidate which slows down the
> concurrent performance of kernfs.
>
> Since kernfs_dop_revalidate only does some checks, the lock is
> largely unnecessary. Also, according to kernel filesystem locking
> document:
> https://www.kernel.org/doc/html/latest/filesystems/locking.html
> locking is not in the protocal for d_revalidate operation.
>
> This patch remove this mutex from
> kernfs_dop_revalidate, so kernfs_dop_revalidate
> can run concurrently.
>
> Signed-off-by: Fox Chen <foxhlchen@gmail.com>
> ---
> fs/kernfs/dir.c | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> index 9aec80b9d7c6..c2267c93f546 100644
> --- a/fs/kernfs/dir.c
> +++ b/fs/kernfs/dir.c
> @@ -26,7 +26,6 @@ static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
>
> static bool kernfs_active(struct kernfs_node *kn)
> {
> - lockdep_assert_held(&kernfs_mutex);
> return atomic_read(&kn->active) >= 0;
> }
>
> @@ -557,10 +556,9 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
>
> /* Always perform fresh lookup for negatives */
> if (d_really_is_negative(dentry))
> - goto out_bad_unlocked;
> + goto out_bad;
>
> kn = kernfs_dentry_node(dentry);
> - mutex_lock(&kernfs_mutex);
>
> /* The kernfs node has been deactivated */
> if (!kernfs_active(kn))
> @@ -579,11 +577,8 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
> kernfs_info(dentry->d_sb)->ns != kn->ns)
> goto out_bad;
>
> - mutex_unlock(&kernfs_mutex);
> return 1;
> out_bad:
> - mutex_unlock(&kernfs_mutex);
> -out_bad_unlocked:
> return 0;
> }
>
> @@ -650,6 +645,8 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
> kn->mode = mode;
> kn->flags = flags;
>
> + rwlock_init(&kn->iattr_rwlock);

Ah, now you initialize this, it should go into patch 1, right? :)

greg k-h

\
 
 \ /
  Last update: 2020-12-02 19:27    [W:0.367 / U:0.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site