diff mbox series

[REPOST,v4,1/5] kernfs: move revalidate to be near lookup

Message ID 162218363530.34379.16741129191900256265.stgit@web.messagingengine.com (mailing list archive)
State New
Headers show
Series kernfs: proposed locking and concurrency improvement | expand

Commit Message

Ian Kent May 28, 2021, 6:33 a.m. UTC
While the dentry operation kernfs_dop_revalidate() is grouped with
dentry type functions it also has a strong affinity to the inode
operation ->lookup().

In order to take advantage of the VFS negative dentry caching that
can be used to reduce path lookup overhead on non-existent paths it
will need to call kernfs_find_ns(). So, to avoid a forward declaration,
move it to be near kernfs_iop_lookup().

There's no functional change from this patch.

Signed-off-by: Ian Kent <raven@themaw.net>
---
 fs/kernfs/dir.c |   86 ++++++++++++++++++++++++++++---------------------------
 1 file changed, 43 insertions(+), 43 deletions(-)

Comments

Eric W. Biederman June 3, 2021, 2:50 p.m. UTC | #1
Ian Kent <raven@themaw.net> writes:

> While the dentry operation kernfs_dop_revalidate() is grouped with
> dentry type functions it also has a strong affinity to the inode
> operation ->lookup().
>
> In order to take advantage of the VFS negative dentry caching that
> can be used to reduce path lookup overhead on non-existent paths it
> will need to call kernfs_find_ns(). So, to avoid a forward declaration,
> move it to be near kernfs_iop_lookup().
>
> There's no functional change from this patch.

Does this patch compile independently?

During the code movement  kernfs_active is replaced
by kernfs_active_read which does not exist yet.

Eric

> Signed-off-by: Ian Kent <raven@themaw.net>
> ---
>  fs/kernfs/dir.c |   86 ++++++++++++++++++++++++++++---------------------------
>  1 file changed, 43 insertions(+), 43 deletions(-)
>
> diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> index 7e0e62deab53c..4c69e2af82dac 100644
> --- a/fs/kernfs/dir.c
> +++ b/fs/kernfs/dir.c
> @@ -548,49 +548,6 @@ void kernfs_put(struct kernfs_node *kn)
>  }
>  EXPORT_SYMBOL_GPL(kernfs_put);
>  
> -static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
> -{
> -	struct kernfs_node *kn;
> -
> -	if (flags & LOOKUP_RCU)
> -		return -ECHILD;
> -
> -	/* Always perform fresh lookup for negatives */
> -	if (d_really_is_negative(dentry))
> -		goto out_bad_unlocked;
> -
> -	kn = kernfs_dentry_node(dentry);
> -	mutex_lock(&kernfs_mutex);
> -
> -	/* The kernfs node has been deactivated */
> -	if (!kernfs_active(kn))
> -		goto out_bad;
> -
> -	/* The kernfs node has been moved? */
> -	if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
> -		goto out_bad;
> -
> -	/* The kernfs node has been renamed */
> -	if (strcmp(dentry->d_name.name, kn->name) != 0)
> -		goto out_bad;
> -
> -	/* The kernfs node has been moved to a different namespace */
> -	if (kn->parent && kernfs_ns_enabled(kn->parent) &&
> -	    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;
> -}
> -
> -const struct dentry_operations kernfs_dops = {
> -	.d_revalidate	= kernfs_dop_revalidate,
> -};
> -
>  /**
>   * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
>   * @dentry: the dentry in question
> @@ -1073,6 +1030,49 @@ struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
>  	return ERR_PTR(rc);
>  }
>  
> +static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
> +{
> +	struct kernfs_node *kn;
> +
> +	if (flags & LOOKUP_RCU)
> +		return -ECHILD;
> +
> +	/* Always perform fresh lookup for negatives */
> +	if (d_really_is_negative(dentry))
> +		goto out_bad_unlocked;
> +
> +	kn = kernfs_dentry_node(dentry);
> +	mutex_lock(&kernfs_mutex);
> +
> +	/* The kernfs node has been deactivated */
> +	if (!kernfs_active_read(kn))
> +		goto out_bad;
> +
> +	/* The kernfs node has been moved? */
> +	if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
> +		goto out_bad;
> +
> +	/* The kernfs node has been renamed */
> +	if (strcmp(dentry->d_name.name, kn->name) != 0)
> +		goto out_bad;
> +
> +	/* The kernfs node has been moved to a different namespace */
> +	if (kn->parent && kernfs_ns_enabled(kn->parent) &&
> +	    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;
> +}
> +
> +const struct dentry_operations kernfs_dops = {
> +	.d_revalidate	= kernfs_dop_revalidate,
> +};
> +
>  static struct dentry *kernfs_iop_lookup(struct inode *dir,
>  					struct dentry *dentry,
>  					unsigned int flags)
Ian Kent June 4, 2021, 2:29 a.m. UTC | #2
On Thu, 2021-06-03 at 09:50 -0500, Eric W. Biederman wrote:
> Ian Kent <raven@themaw.net> writes:
> 
> > While the dentry operation kernfs_dop_revalidate() is grouped with
> > dentry type functions it also has a strong affinity to the inode
> > operation ->lookup().
> > 
> > In order to take advantage of the VFS negative dentry caching that
> > can be used to reduce path lookup overhead on non-existent paths it
> > will need to call kernfs_find_ns(). So, to avoid a forward
> > declaration,
> > move it to be near kernfs_iop_lookup().
> > 
> > There's no functional change from this patch.
> 
> Does this patch compile independently?

Doubt it.

> 
> During the code movement  kernfs_active is replaced
> by kernfs_active_read which does not exist yet.

Oops, that was a consequence of reordering the series which I
didn't catch.

I'll fix that when I post a v5 which I'm going to have to do.

Thanks for looking at this Eric,
Ian
> 
> Eric
> 
> > Signed-off-by: Ian Kent <raven@themaw.net>
> > ---
> >  fs/kernfs/dir.c |   86 ++++++++++++++++++++++++++++---------------
> > ------------
> >  1 file changed, 43 insertions(+), 43 deletions(-)
> > 
> > diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> > index 7e0e62deab53c..4c69e2af82dac 100644
> > --- a/fs/kernfs/dir.c
> > +++ b/fs/kernfs/dir.c
> > @@ -548,49 +548,6 @@ void kernfs_put(struct kernfs_node *kn)
> >  }
> >  EXPORT_SYMBOL_GPL(kernfs_put);
> >  
> > -static int kernfs_dop_revalidate(struct dentry *dentry, unsigned
> > int flags)
> > -{
> > -       struct kernfs_node *kn;
> > -
> > -       if (flags & LOOKUP_RCU)
> > -               return -ECHILD;
> > -
> > -       /* Always perform fresh lookup for negatives */
> > -       if (d_really_is_negative(dentry))
> > -               goto out_bad_unlocked;
> > -
> > -       kn = kernfs_dentry_node(dentry);
> > -       mutex_lock(&kernfs_mutex);
> > -
> > -       /* The kernfs node has been deactivated */
> > -       if (!kernfs_active(kn))
> > -               goto out_bad;
> > -
> > -       /* The kernfs node has been moved? */
> > -       if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
> > -               goto out_bad;
> > -
> > -       /* The kernfs node has been renamed */
> > -       if (strcmp(dentry->d_name.name, kn->name) != 0)
> > -               goto out_bad;
> > -
> > -       /* The kernfs node has been moved to a different namespace
> > */
> > -       if (kn->parent && kernfs_ns_enabled(kn->parent) &&
> > -           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;
> > -}
> > -
> > -const struct dentry_operations kernfs_dops = {
> > -       .d_revalidate   = kernfs_dop_revalidate,
> > -};
> > -
> >  /**
> >   * kernfs_node_from_dentry - determine kernfs_node associated with
> > a dentry
> >   * @dentry: the dentry in question
> > @@ -1073,6 +1030,49 @@ struct kernfs_node
> > *kernfs_create_empty_dir(struct kernfs_node *parent,
> >         return ERR_PTR(rc);
> >  }
> >  
> > +static int kernfs_dop_revalidate(struct dentry *dentry, unsigned
> > int flags)
> > +{
> > +       struct kernfs_node *kn;
> > +
> > +       if (flags & LOOKUP_RCU)
> > +               return -ECHILD;
> > +
> > +       /* Always perform fresh lookup for negatives */
> > +       if (d_really_is_negative(dentry))
> > +               goto out_bad_unlocked;
> > +
> > +       kn = kernfs_dentry_node(dentry);
> > +       mutex_lock(&kernfs_mutex);
> > +
> > +       /* The kernfs node has been deactivated */
> > +       if (!kernfs_active_read(kn))
> > +               goto out_bad;
> > +
> > +       /* The kernfs node has been moved? */
> > +       if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
> > +               goto out_bad;
> > +
> > +       /* The kernfs node has been renamed */
> > +       if (strcmp(dentry->d_name.name, kn->name) != 0)
> > +               goto out_bad;
> > +
> > +       /* The kernfs node has been moved to a different namespace
> > */
> > +       if (kn->parent && kernfs_ns_enabled(kn->parent) &&
> > +           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;
> > +}
> > +
> > +const struct dentry_operations kernfs_dops = {
> > +       .d_revalidate   = kernfs_dop_revalidate,
> > +};
> > +
> >  static struct dentry *kernfs_iop_lookup(struct inode *dir,
> >                                         struct dentry *dentry,
> >                                         unsigned int flags)
diff mbox series

Patch

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 7e0e62deab53c..4c69e2af82dac 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -548,49 +548,6 @@  void kernfs_put(struct kernfs_node *kn)
 }
 EXPORT_SYMBOL_GPL(kernfs_put);
 
-static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
-{
-	struct kernfs_node *kn;
-
-	if (flags & LOOKUP_RCU)
-		return -ECHILD;
-
-	/* Always perform fresh lookup for negatives */
-	if (d_really_is_negative(dentry))
-		goto out_bad_unlocked;
-
-	kn = kernfs_dentry_node(dentry);
-	mutex_lock(&kernfs_mutex);
-
-	/* The kernfs node has been deactivated */
-	if (!kernfs_active(kn))
-		goto out_bad;
-
-	/* The kernfs node has been moved? */
-	if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
-		goto out_bad;
-
-	/* The kernfs node has been renamed */
-	if (strcmp(dentry->d_name.name, kn->name) != 0)
-		goto out_bad;
-
-	/* The kernfs node has been moved to a different namespace */
-	if (kn->parent && kernfs_ns_enabled(kn->parent) &&
-	    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;
-}
-
-const struct dentry_operations kernfs_dops = {
-	.d_revalidate	= kernfs_dop_revalidate,
-};
-
 /**
  * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
  * @dentry: the dentry in question
@@ -1073,6 +1030,49 @@  struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
 	return ERR_PTR(rc);
 }
 
+static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	struct kernfs_node *kn;
+
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	/* Always perform fresh lookup for negatives */
+	if (d_really_is_negative(dentry))
+		goto out_bad_unlocked;
+
+	kn = kernfs_dentry_node(dentry);
+	mutex_lock(&kernfs_mutex);
+
+	/* The kernfs node has been deactivated */
+	if (!kernfs_active_read(kn))
+		goto out_bad;
+
+	/* The kernfs node has been moved? */
+	if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
+		goto out_bad;
+
+	/* The kernfs node has been renamed */
+	if (strcmp(dentry->d_name.name, kn->name) != 0)
+		goto out_bad;
+
+	/* The kernfs node has been moved to a different namespace */
+	if (kn->parent && kernfs_ns_enabled(kn->parent) &&
+	    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;
+}
+
+const struct dentry_operations kernfs_dops = {
+	.d_revalidate	= kernfs_dop_revalidate,
+};
+
 static struct dentry *kernfs_iop_lookup(struct inode *dir,
 					struct dentry *dentry,
 					unsigned int flags)