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

Ian Kent
2021-05-12T00:39:00Z

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(-)

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)