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 <foxhlc...@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
