[RFC PATCH v6.6 05/10] libfs: Add simple_offset_rename() API

cel
2025-01-24T19:20:08Z

[ Upstream commit 5a1a25be995e1014abd01600479915683e356f5c ]

I'm about to fix a tmpfs rename bug that requires the use of
internal simple_offset helpers that are not available in mm/shmem.c

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://lore.kernel.org/r/20240415152057.4605-3-cel@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/libfs.c | 21 +++++++++++++++++++++
include/linux/fs.h | 2 ++
mm/shmem.c | 3 +--
3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/fs/libfs.c b/fs/libfs.c
index 2029cb6a0e15..15d8c3300dae 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -356,6 +356,27 @@ int simple_offset_empty(struct dentry *dentry)
return ret;
}

+/**
+ * simple_offset_rename - handle directory offsets for rename
+ * @old_dir: parent directory of source entry
+ * @old_dentry: dentry of source entry
+ * @new_dir: parent_directory of destination entry
+ * @new_dentry: dentry of destination
+ *
+ * Caller provides appropriate serialization.
+ *
+ * Returns zero on success, a negative errno value on failure.
+ */
+int simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry,
+ struct inode *new_dir, struct dentry *new_dentry)
+{
+ struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir);
+ struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir);
+
+ simple_offset_remove(old_ctx, old_dentry);
+ return simple_offset_add(new_ctx, old_dentry);
+}
+
/**
* simple_offset_rename_exchange - exchange rename with directory offsets
* @old_dir: parent of dentry being moved
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5104405ce3e6..e4d139fcaad0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3198,6 +3198,8 @@ 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(struct inode *old_dir, struct dentry *old_dentry,
+ struct inode *new_dir, struct dentry *new_dentry);
int simple_offset_rename_exchange(struct inode *old_dir,
struct dentry *old_dentry,
struct inode *new_dir,
diff --git a/mm/shmem.c b/mm/shmem.c
index aaf679976f3b..ab2b0e87b051 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3434,8 +3434,7 @@ static int shmem_rename2(struct mnt_idmap *idmap,
return error;
}

- simple_offset_remove(shmem_get_offset_ctx(old_dir), old_dentry);
- error = simple_offset_add(shmem_get_offset_ctx(new_dir), old_dentry);
+ error = simple_offset_rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
return error;

--
2.47.0