From: Ian Kent <raven@themaw.net>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Andrew Morton <akpm@linux-foundation.org>,
Al Viro <viro@ZenIV.linux.org.uk>,
Rick Lindsley <ricklind@linux.vnet.ibm.com>,
David Howells <dhowells@redhat.com>,
Miklos Szeredi <miklos@szeredi.hu>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [PATCH v2 4/6] kernfs: use revision to identify directory node changes
Date: Wed, 17 Jun 2020 15:38:03 +0800 [thread overview]
Message-ID: <159237948345.89469.9839924207092477321.stgit@mickey.themaw.net> (raw)
In-Reply-To: <159237905950.89469.6559073274338175600.stgit@mickey.themaw.net>
If a kernfs directory node hasn't changed there's no need to search for
an added (or removed) child dentry.
Add a revision counter to kernfs directory nodes so it can be used
to detect if a directory node has changed.
Signed-off-by: Ian Kent <raven@themaw.net>
---
fs/kernfs/dir.c | 17 +++++++++++++++--
fs/kernfs/kernfs-internal.h | 24 ++++++++++++++++++++++++
include/linux/kernfs.h | 5 +++++
3 files changed, 44 insertions(+), 2 deletions(-)
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index f4943329e578..03f4f179bbc4 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -383,6 +383,7 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
/* successfully added, account subdir number */
if (kernfs_type(kn) == KERNFS_DIR)
kn->parent->dir.subdirs++;
+ kernfs_inc_rev(kn->parent);
return 0;
}
@@ -405,6 +406,7 @@ static bool kernfs_unlink_sibling(struct kernfs_node *kn)
if (kernfs_type(kn) == KERNFS_DIR)
kn->parent->dir.subdirs--;
+ kernfs_inc_rev(kn->parent);
rb_erase(&kn->rb, &kn->parent->dir.children);
RB_CLEAR_NODE(&kn->rb);
@@ -1044,9 +1046,16 @@ struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
{
+ struct kernfs_node *parent;
struct kernfs_node *kn;
if (flags & LOOKUP_RCU) {
+ /* Directory node changed? */
+ parent = kernfs_dentry_node(dentry->d_parent);
+
+ if (!kernfs_dir_changed(parent, dentry))
+ return 1;
+
kn = kernfs_dentry_node(dentry);
if (!kn) {
/* Negative hashed dentry, tell the VFS to switch to
@@ -1093,8 +1102,6 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
kn = kernfs_dentry_node(dentry);
if (!kn) {
- struct kernfs_node *parent;
-
/* If the kernfs node can be found this is a stale negative
* hashed dentry so it must be discarded and the lookup redone.
*/
@@ -1102,6 +1109,10 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
if (parent) {
const void *ns = NULL;
+ /* Directory node changed? */
+ if (kernfs_dir_changed(parent, dentry))
+ goto out_bad;
+
if (kernfs_ns_enabled(parent))
ns = kernfs_info(dentry->d_parent->d_sb)->ns;
kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
@@ -1156,6 +1167,8 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
down_read(&kernfs_rwsem);
+ kernfs_set_rev(dentry, parent);
+
if (kernfs_ns_enabled(parent))
ns = kernfs_info(dir->i_sb)->ns;
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index 097c1a989aa4..a7b0e2074260 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -82,6 +82,30 @@ static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry)
return d_inode(dentry)->i_private;
}
+static inline void kernfs_set_rev(struct dentry *dentry,
+ struct kernfs_node *kn)
+{
+ dentry->d_time = kn->dir.rev;
+}
+
+static inline void kernfs_inc_rev(struct kernfs_node *kn)
+{
+ if (kernfs_type(kn) == KERNFS_DIR) {
+ if (!++kn->dir.rev)
+ kn->dir.rev++;
+ }
+}
+
+static inline bool kernfs_dir_changed(struct kernfs_node *kn,
+ struct dentry *dentry)
+{
+ if (kernfs_type(kn) == KERNFS_DIR) {
+ if (kn->dir.rev != dentry->d_time)
+ return true;
+ }
+ return false;
+}
+
extern const struct super_operations kernfs_sops;
extern struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 89f6a4214a70..74727d98e380 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -98,6 +98,11 @@ struct kernfs_elem_dir {
* better directly in kernfs_node but is here to save space.
*/
struct kernfs_root *root;
+ /*
+ * Monotonic revision counter, used to identify if a directory
+ * node has changed during revalidation.
+ */
+ unsigned long rev;
};
struct kernfs_elem_symlink {
next prev parent reply other threads:[~2020-06-17 7:38 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-17 7:37 [PATCH v2 0/6] kernfs: proposed locking and concurrency improvement Ian Kent
2020-06-17 7:37 ` [PATCH v2 1/6] kernfs: switch kernfs to use an rwsem Ian Kent
2020-06-17 7:37 ` [PATCH v2 2/6] kernfs: move revalidate to be near lookup Ian Kent
2020-06-17 7:37 ` [PATCH v2 3/6] kernfs: improve kernfs path resolution Ian Kent
2020-06-17 7:38 ` Ian Kent [this message]
2020-06-17 7:38 ` [PATCH v2 5/6] kernfs: refactor attr locking Ian Kent
2020-06-17 7:38 ` [PATCH v2 6/6] kernfs: make attr_mutex a local kernfs node lock Ian Kent
2020-06-19 15:38 ` [PATCH v2 0/6] kernfs: proposed locking and concurrency improvement Tejun Heo
2020-06-19 20:41 ` Rick Lindsley
2020-06-19 22:23 ` Tejun Heo
2020-06-20 2:44 ` Rick Lindsley
2020-06-22 17:53 ` Tejun Heo
2020-06-22 21:22 ` Rick Lindsley
2020-06-23 23:13 ` Tejun Heo
2020-06-24 9:04 ` Rick Lindsley
2020-06-24 9:27 ` Greg Kroah-Hartman
2020-06-24 13:19 ` Tejun Heo
2020-06-25 8:15 ` Ian Kent
2020-06-25 9:43 ` Greg Kroah-Hartman
2020-06-26 0:19 ` Ian Kent
2020-06-21 4:55 ` Ian Kent
2020-06-22 17:48 ` Tejun Heo
2020-06-22 18:03 ` Greg Kroah-Hartman
2020-06-22 21:27 ` Rick Lindsley
2020-06-23 5:21 ` Greg Kroah-Hartman
2020-06-23 5:09 ` Ian Kent
2020-06-23 6:02 ` Greg Kroah-Hartman
2020-06-23 8:01 ` Ian Kent
2020-06-23 8:29 ` Ian Kent
2020-06-23 11:49 ` Greg Kroah-Hartman
2020-06-23 9:33 ` Rick Lindsley
2020-06-23 11:45 ` Greg Kroah-Hartman
2020-06-23 22:55 ` Rick Lindsley
2020-06-23 11:51 ` Ian Kent
2020-06-21 3:21 ` Ian Kent
2020-12-10 16:44 ` Fox Chen
2020-12-11 2:01 ` [PATCH " Ian Kent
2020-12-11 2:17 ` Ian Kent
2020-12-13 3:46 ` Ian Kent
2020-12-14 6:14 ` Fox Chen
2020-12-14 13:30 ` Ian Kent
2020-12-15 8:33 ` Fox Chen
2020-12-15 12:59 ` Ian Kent
2020-12-17 4:46 ` Ian Kent
2020-12-17 8:54 ` Fox Chen
2020-12-17 10:09 ` Ian Kent
2020-12-17 11:09 ` Ian Kent
2020-12-17 11:48 ` Ian Kent
2020-12-17 15:14 ` Tejun Heo
2020-12-18 7:36 ` Ian Kent
2020-12-18 8:01 ` Fox Chen
2020-12-18 11:21 ` Ian Kent
2020-12-18 13:20 ` Fox Chen
2020-12-19 0:53 ` Ian Kent
2020-12-19 7:47 ` Fox Chen
2020-12-22 2:17 ` Ian Kent
2020-12-18 14:59 ` Tejun Heo
2020-12-19 7:08 ` Ian Kent
2020-12-19 16:23 ` Tejun Heo
2020-12-19 23:52 ` Ian Kent
2020-12-20 1:37 ` Ian Kent
2020-12-21 9:28 ` Fox Chen
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