From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Pass the dentry of a source file and the dentry of a destination directory
to lock parent inodes for rename. As soon as this function returns,
->d_parent of the source file dentry is stable and inodes are properly
locked for calling vfs-rename. This helper is needed for ksmbd server.
rename request of SMB protocol has to rename an opened file, no matter
which directory it's in.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
---
fs/namei.c | 68 ++++++++++++++++++++++++++++++++++++-------
include/linux/namei.h | 1 +
2 files changed, 58 insertions(+), 11 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 5855dc6edbd5..984d4f7b47dc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2980,20 +2980,10 @@ static inline int may_create(struct mnt_idmap *idmap,
return inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
}
-/*
- * p1 and p2 should be directories on the same fs.
- */
-struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
+static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
{
struct dentry *p;
- if (p1 == p2) {
- inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
- return NULL;
- }
-
- mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
-
p = d_ancestor(p2, p1);
if (p) {
inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
@@ -3012,8 +3002,64 @@ struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
return NULL;
}
+
+/*
+ * p1 and p2 should be directories on the same fs.
+ */
+struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
+{
+ if (p1 == p2) {
+ inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
+ return NULL;
+ }
+
+ mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
+ return lock_two_directories(p1, p2);
+}
EXPORT_SYMBOL(lock_rename);
+/*
+ * c1 and p2 should be on the same fs.
+ */
+struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
+{
+ if (READ_ONCE(c1->d_parent) == p2) {
+ /*
+ * hopefully won't need to touch ->s_vfs_rename_mutex at all.
+ */
+ inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
+ /*
+ * now that p2 is locked, nobody can move in or out of it,
+ * so the test below is safe.
+ */
+ if (likely(c1->d_parent == p2))
+ return NULL;
+
+ /*
+ * c1 got moved out of p2 while we'd been taking locks;
+ * unlock and fall back to slow case.
+ */
+ inode_unlock(p2->d_inode);
+ }
+
+ mutex_lock(&c1->d_sb->s_vfs_rename_mutex);
+ /*
+ * nobody can move out of any directories on this fs.
+ */
+ if (likely(c1->d_parent != p2))
+ return lock_two_directories(c1->d_parent, p2);
+
+ /*
+ * c1 got moved into p2 while we were taking locks;
+ * we need p2 locked and ->s_vfs_rename_mutex unlocked,
+ * for consistency with lock_rename().
+ */
+ inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
+ mutex_unlock(&c1->d_sb->s_vfs_rename_mutex);
+ return NULL;
+}
+EXPORT_SYMBOL(lock_rename_child);
+
void unlock_rename(struct dentry *p1, struct dentry *p2)
{
inode_unlock(p1->d_inode);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index c2747cfe97ac..4c070fb29a91 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -83,6 +83,7 @@ extern int follow_down(struct path *);
extern int follow_up(struct path *);
extern struct dentry *lock_rename(struct dentry *, struct dentry *);
+extern struct dentry *lock_rename_child(struct dentry *, struct dentry *);
extern void unlock_rename(struct dentry *, struct dentry *);
extern int __must_check nd_jump_link(const struct path *path);
--
2.25.1
