From: Ian Kent <raven@themaw.net>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Tejun Heo <tj@kernel.org>
Cc: Eric Sandeen <sandeen@sandeen.net>,
Fox Chen <foxhlchen@gmail.com>,
Brice Goglin <brice.goglin@gmail.com>,
Al Viro <viro@ZenIV.linux.org.uk>,
Rick Lindsley <ricklind@linux.vnet.ibm.com>,
David Howells <dhowells@redhat.com>,
Miklos Szeredi <miklos@szeredi.hu>,
Marcelo Tosatti <mtosatti@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Carlos Maiolino <cmaiolino@redhat.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [PATCH v7 2/6] kernfs: add a revision to identify directory node changes
Date: Tue, 15 Jun 2021 18:26:07 +0800 [thread overview]
Message-ID: <162375276735.232295.14056277248741694521.stgit@web.messagingengine.com> (raw)
In-Reply-To: <162375263398.232295.14755578426619198534.stgit@web.messagingengine.com>
Add a revision counter to kernfs directory nodes so it can be used
to detect if a directory node has changed during negative dentry
revalidation.
There's an assumption that sizeof(unsigned long) <= sizeof(pointer)
on all architectures and as far as I know that assumption holds.
So adding a revision counter to the struct kernfs_elem_dir variant of
the kernfs_node type union won't increase the size of the kernfs_node
struct. This is because struct kernfs_elem_dir is at least
sizeof(pointer) smaller than the largest union variant. It's tempting
to make the revision counter a u64 but that would increase the size of
kernfs_node on archs where sizeof(pointer) is smaller than the revision
counter.
Signed-off-by: Ian Kent <raven@themaw.net>
---
fs/kernfs/dir.c | 3 +++
fs/kernfs/kernfs-internal.h | 19 +++++++++++++++++++
include/linux/kernfs.h | 5 +++++
3 files changed, 27 insertions(+)
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 33166ec90a112..48704c5b6a072 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -372,6 +372,7 @@ 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;
}
@@ -394,6 +395,7 @@ 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);
@@ -1573,6 +1575,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
*/
kernfs_unlink_sibling(kn);
kernfs_get(new_parent);
+ kernfs_inc_rev(new_parent);
/* rename_lock protects ->parent and ->name accessors */
spin_lock_irq(&kernfs_rename_lock);
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index ccc3b44f6306f..6a38897b4d02c 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -81,6 +81,25 @@ static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry)
return d_inode(dentry)->i_private;
}
+static inline void kernfs_set_rev(struct kernfs_node *parent,
+ struct dentry *dentry)
+{
+ dentry->d_time = parent->dir.rev;
+}
+
+static inline void kernfs_inc_rev(struct kernfs_node *parent)
+{
+ parent->dir.rev++;
+}
+
+static inline bool kernfs_dir_changed(struct kernfs_node *parent,
+ struct dentry *dentry)
+{
+ if (parent->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 9e8ca8743c268..d68b4ad095737 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 negative dentry revalidation.
+ */
+ unsigned long rev;
};
struct kernfs_elem_symlink {
next prev parent reply other threads:[~2021-06-15 10:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-15 10:25 [PATCH v7 0/6] kernfs: proposed locking and concurrency improvement Ian Kent
2021-06-15 10:25 ` [PATCH v7 1/6] kernfs: move revalidate to be near lookup Ian Kent
2021-06-15 15:06 ` Greg Kroah-Hartman
2021-06-15 10:26 ` Ian Kent [this message]
2021-06-16 9:11 ` [PATCH v7 2/6] kernfs: add a revision to identify directory node changes Miklos Szeredi
2021-06-15 10:26 ` [PATCH v7 3/6] kernfs: use VFS negative dentry caching Ian Kent
2021-06-16 9:12 ` Miklos Szeredi
2021-06-15 10:26 ` [PATCH v7 4/6] kernfs: switch kernfs to use an rwsem Ian Kent
2021-06-15 10:26 ` [PATCH v7 5/6] kernfs: use i_lock to protect concurrent inode updates Ian Kent
2021-06-15 10:27 ` [PATCH v7 6/6] kernfs: dont call d_splice_alias() under kernfs node lock Ian Kent
2021-06-15 10:39 ` [PATCH v7 0/6] kernfs: proposed locking and concurrency improvement Ian Kent
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