Patch "libfs: Add simple_offset_empty()" has been added to the 6.6-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    libfs: Add simple_offset_empty()

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     libfs-add-simple_offset_empty.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-110403-greg=kroah.com@vger.kernel.org Fri Jan 24 20:20:42 2025
From: cel@kernel.org
Date: Fri, 24 Jan 2025 14:19:38 -0500
Subject: libfs: Add simple_offset_empty()
To: Hugh Dickins <hughd@google.com>, Andrew Morten <akpm@linux-foundation.org>, Christian Brauner <brauner@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Sasha Levin <sashal@kernel.org>
Cc: <linux-fsdevel@vger.kernel.org>, <stable@vger.kernel.org>, <linux-mm@kvack.org>, yukuai3@huawei.com, yangerkun@huawei.com, Chuck Lever <chuck.lever@oracle.com>, Jan Kara <jack@suse.cz>
Message-ID: <20250124191946.22308-4-cel@kernel.org>

From: Chuck Lever <chuck.lever@oracle.com>

[ Upstream commit ecba88a3b32d733d41e27973e25b2bc580f64281 ]

For simple filesystems that use directory offset mapping, rely
strictly on the directory offset map to tell when a directory has
no children.

After this patch is applied, the emptiness test holds only the RCU
read lock when the directory being tested has no children.

In addition, this adds another layer of confirmation that
simple_offset_add/remove() are working as expected.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://lore.kernel.org/r/170820143463.6328.7872919188371286951.stgit@91.116.238.104.host.secureserver.net
Signed-off-by: Christian Brauner <brauner@kernel.org>
Stable-dep-of: 5a1a25be995e ("libfs: Add simple_offset_rename() API")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/libfs.c         |   32 ++++++++++++++++++++++++++++++++
 include/linux/fs.h |    1 +
 mm/shmem.c         |    4 ++--
 3 files changed, 35 insertions(+), 2 deletions(-)

--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -313,6 +313,38 @@ void simple_offset_remove(struct offset_
 }
 
 /**
+ * simple_offset_empty - Check if a dentry can be unlinked
+ * @dentry: dentry to be tested
+ *
+ * Returns 0 if @dentry is a non-empty directory; otherwise returns 1.
+ */
+int simple_offset_empty(struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	struct offset_ctx *octx;
+	struct dentry *child;
+	unsigned long index;
+	int ret = 1;
+
+	if (!inode || !S_ISDIR(inode->i_mode))
+		return ret;
+
+	index = DIR_OFFSET_MIN;
+	octx = inode->i_op->get_offset_ctx(inode);
+	xa_for_each(&octx->xa, index, child) {
+		spin_lock(&child->d_lock);
+		if (simple_positive(child)) {
+			spin_unlock(&child->d_lock);
+			ret = 0;
+			break;
+		}
+		spin_unlock(&child->d_lock);
+	}
+
+	return ret;
+}
+
+/**
  * simple_offset_rename_exchange - exchange rename with directory offsets
  * @old_dir: parent of dentry being moved
  * @old_dentry: dentry being moved
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3197,6 +3197,7 @@ struct offset_ctx {
 void simple_offset_init(struct offset_ctx *octx);
 int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry);
 void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry);
+int simple_offset_empty(struct dentry *dentry);
 int simple_offset_rename_exchange(struct inode *old_dir,
 				  struct dentry *old_dentry,
 				  struct inode *new_dir,
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3368,7 +3368,7 @@ static int shmem_unlink(struct inode *di
 
 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
 {
-	if (!simple_empty(dentry))
+	if (!simple_offset_empty(dentry))
 		return -ENOTEMPTY;
 
 	drop_nlink(d_inode(dentry));
@@ -3425,7 +3425,7 @@ static int shmem_rename2(struct mnt_idma
 		return simple_offset_rename_exchange(old_dir, old_dentry,
 						     new_dir, new_dentry);
 
-	if (!simple_empty(new_dentry))
+	if (!simple_offset_empty(new_dentry))
 		return -ENOTEMPTY;
 
 	if (flags & RENAME_WHITEOUT) {


Patches currently in stable-queue which might be from cel@kernel.org are

queue-6.6/libfs-replace-simple_offset-end-of-directory-detection.patch
queue-6.6/libfs-re-arrange-locking-in-offset_iterate_dir.patch
queue-6.6/libfs-add-simple_offset_empty.patch
queue-6.6/shmem-fix-shmem_rename2.patch
queue-6.6/revert-libfs-add-simple_offset_empty.patch
queue-6.6/libfs-use-d_children-list-to-iterate-simple_offset-directories.patch
queue-6.6/libfs-define-a-minimum-directory-offset.patch
queue-6.6/libfs-return-enospc-when-the-directory-offset-range-is-exhausted.patch
queue-6.6/libfs-fix-simple_offset_rename_exchange.patch
queue-6.6/libfs-add-simple_offset_rename-api.patch