From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Qingfang Deng <dqfext@gmail.com>, Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH 5.10 3/5] kernfs: switch kernfs to use an rwsem
Date: Wed, 21 May 2025 22:03:47 -0400 [thread overview]
Message-ID: <20250521154443-367c6fc07dc3045a@stable.kernel.org> (raw)
In-Reply-To: <20250521015336.3450911-4-dqfext@gmail.com>
[ Sasha's backport helper bot ]
Hi,
✅ All tests passed successfully. No issues detected.
No action required from the submitter.
The upstream commit SHA1 provided is correct: 7ba0273b2f34a55efe967d3c7381fb1da2ca195f
WARNING: Author mismatch between patch and upstream commit:
Backport author: Qingfang Deng<dqfext@gmail.com>
Commit author: Ian Kent<raven@themaw.net>
Status in newer kernel trees:
6.14.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (exact SHA1)
6.1.y | Present (exact SHA1)
5.15.y | Present (exact SHA1)
Note: The patch differs from the upstream commit:
---
1: 7ba0273b2f34a ! 1: a0418b6d194c8 kernfs: switch kernfs to use an rwsem
@@ Metadata
## Commit message ##
kernfs: switch kernfs to use an rwsem
+ Commit 7ba0273b2f34a55efe967d3c7381fb1da2ca195f upstream.
+
The kernfs global lock restricts the ability to perform kernfs node
lookup operations in parallel during path walks.
@@ fs/kernfs/dir.c
-DEFINE_MUTEX(kernfs_mutex);
+DECLARE_RWSEM(kernfs_rwsem);
static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
- static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by rename_lock */
- static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
+ /*
+ * Don't use rename_lock to piggy back on pr_cont_buf. We don't want to
@@ fs/kernfs/dir.c: static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
static bool kernfs_active(struct kernfs_node *kn)
@@ fs/kernfs/dir.c: static void kernfs_drain(struct kernfs_node *kn)
}
/**
+@@ fs/kernfs/dir.c: static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
+ /* If the kernfs parent node has changed discard and
+ * proceed to ->lookup.
+ */
+- mutex_lock(&kernfs_mutex);
++ down_read(&kernfs_rwsem);
+ spin_lock(&dentry->d_lock);
+ parent = kernfs_dentry_node(dentry->d_parent);
+ if (parent) {
+ if (kernfs_dir_changed(parent, dentry)) {
+ spin_unlock(&dentry->d_lock);
+- mutex_unlock(&kernfs_mutex);
++ up_read(&kernfs_rwsem);
+ return 0;
+ }
+ }
+ spin_unlock(&dentry->d_lock);
+- mutex_unlock(&kernfs_mutex);
++ up_read(&kernfs_rwsem);
+
+ /* The kernfs parent node hasn't changed, leave the
+ * dentry negative and return success.
+@@ fs/kernfs/dir.c: static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
+ }
+
+ kn = kernfs_dentry_node(dentry);
+- mutex_lock(&kernfs_mutex);
++ down_read(&kernfs_rwsem);
+
+ /* The kernfs node has been deactivated */
+ if (!kernfs_active(kn))
+@@ fs/kernfs/dir.c: 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);
++ up_read(&kernfs_rwsem);
+ return 1;
+ out_bad:
+- mutex_unlock(&kernfs_mutex);
++ up_read(&kernfs_rwsem);
+ return 0;
+ }
+
@@ fs/kernfs/dir.c: int kernfs_add_one(struct kernfs_node *kn)
bool has_ns;
int ret;
@@ fs/kernfs/dir.c: static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *p
- lockdep_assert_held(&kernfs_mutex);
+ lockdep_assert_held_read(&kernfs_rwsem);
- /* grab kernfs_rename_lock to piggy back on kernfs_pr_cont_buf */
- spin_lock_irq(&kernfs_rename_lock);
+ spin_lock_irq(&kernfs_pr_cont_lock);
+
@@ fs/kernfs/dir.c: struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
{
struct kernfs_node *kn;
@@ fs/kernfs/dir.c: struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *
return kn;
}
-@@ fs/kernfs/dir.c: static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
- /* If the kernfs parent node has changed discard and
- * proceed to ->lookup.
- */
-- mutex_lock(&kernfs_mutex);
-+ down_read(&kernfs_rwsem);
- spin_lock(&dentry->d_lock);
- parent = kernfs_dentry_node(dentry->d_parent);
- if (parent) {
- if (kernfs_dir_changed(parent, dentry)) {
- spin_unlock(&dentry->d_lock);
-- mutex_unlock(&kernfs_mutex);
-+ up_read(&kernfs_rwsem);
- return 0;
- }
- }
- spin_unlock(&dentry->d_lock);
-- mutex_unlock(&kernfs_mutex);
-+ up_read(&kernfs_rwsem);
-
- /* The kernfs parent node hasn't changed, leave the
- * dentry negative and return success.
-@@ fs/kernfs/dir.c: static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
- }
-
- kn = kernfs_dentry_node(dentry);
-- mutex_lock(&kernfs_mutex);
-+ down_read(&kernfs_rwsem);
-
- /* The kernfs node has been deactivated */
- if (!kernfs_active(kn))
-@@ fs/kernfs/dir.c: 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);
-+ up_read(&kernfs_rwsem);
- return 1;
- out_bad:
-- mutex_unlock(&kernfs_mutex);
-+ up_read(&kernfs_rwsem);
- return 0;
- }
-
@@ fs/kernfs/dir.c: static struct dentry *kernfs_iop_lookup(struct inode *dir,
struct inode *inode = NULL;
const void *ns = NULL;
@@ fs/kernfs/dir.c: int kernfs_remove_by_name_ns(struct kernfs_node *parent, const
+ down_write(&kernfs_rwsem);
kn = kernfs_find_ns(parent, name, ns);
- if (kn)
- __kernfs_remove(kn);
+ if (kn) {
+@@ fs/kernfs/dir.c: int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
+ kernfs_put(kn);
+ }
- mutex_unlock(&kernfs_mutex);
+ up_write(&kernfs_rwsem);
@@ fs/kernfs/inode.c: int kernfs_setattr(struct kernfs_node *kn, const struct iattr
return ret;
}
-@@ fs/kernfs/inode.c: int kernfs_iop_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+@@ fs/kernfs/inode.c: int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
if (!kn)
return -EINVAL;
- mutex_lock(&kernfs_mutex);
+ down_write(&kernfs_rwsem);
- error = setattr_prepare(&init_user_ns, dentry, iattr);
+ error = setattr_prepare(dentry, iattr);
if (error)
goto out;
-@@ fs/kernfs/inode.c: int kernfs_iop_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
- setattr_copy(&init_user_ns, inode, iattr);
+@@ fs/kernfs/inode.c: int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
+ setattr_copy(inode, iattr);
out:
- mutex_unlock(&kernfs_mutex);
@@ fs/kernfs/inode.c: int kernfs_iop_setattr(struct user_namespace *mnt_userns, str
return error;
}
-@@ fs/kernfs/inode.c: int kernfs_iop_getattr(struct user_namespace *mnt_userns,
+@@ fs/kernfs/inode.c: int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
struct inode *inode = d_inode(path->dentry);
struct kernfs_node *kn = inode->i_private;
@@ fs/kernfs/inode.c: int kernfs_iop_getattr(struct user_namespace *mnt_userns,
- mutex_unlock(&kernfs_mutex);
+ up_write(&kernfs_rwsem);
- generic_fillattr(&init_user_ns, inode, stat);
+ generic_fillattr(inode, stat);
return 0;
-@@ fs/kernfs/inode.c: int kernfs_iop_permission(struct user_namespace *mnt_userns,
+@@ fs/kernfs/inode.c: int kernfs_iop_permission(struct inode *inode, int mask)
kn = inode->i_private;
@@ fs/kernfs/inode.c: int kernfs_iop_permission(struct user_namespace *mnt_userns,
- mutex_unlock(&kernfs_mutex);
+ up_write(&kernfs_rwsem);
- return generic_permission(&init_user_ns, inode, mask);
+ return generic_permission(inode, mask);
}
## fs/kernfs/kernfs-internal.h ##
---
Results of testing on various branches:
| Branch | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y | Success | Success |
next prev parent reply other threads:[~2025-05-22 2:03 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-21 1:53 [PATCH 5.10 0/5] kernfs: backport locking and concurrency improvement Qingfang Deng
2025-05-21 1:53 ` [PATCH 5.10 1/5] kernfs: add a revision to identify directory node changes Qingfang Deng
2025-05-21 4:16 ` Greg Kroah-Hartman
2025-05-22 2:07 ` Sasha Levin
2025-05-21 1:53 ` [PATCH 5.10 2/5] kernfs: use VFS negative dentry caching Qingfang Deng
2025-05-22 2:05 ` Sasha Levin
2025-05-21 1:53 ` [PATCH 5.10 3/5] kernfs: switch kernfs to use an rwsem Qingfang Deng
2025-05-22 2:03 ` Sasha Levin [this message]
2025-05-21 1:53 ` [PATCH 5.10 4/5] kernfs: use i_lock to protect concurrent inode updates Qingfang Deng
2025-05-22 2:07 ` Sasha Levin
2025-05-21 1:53 ` [PATCH 5.10 5/5] kernfs: dont call d_splice_alias() under kernfs node lock Qingfang Deng
2025-05-22 2:08 ` Sasha Levin
2025-05-21 4:15 ` [PATCH 5.10 0/5] kernfs: backport locking and concurrency improvement Greg Kroah-Hartman
2025-05-21 5:35 ` Ian Kent
2025-05-21 6:09 ` Ian Kent
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