Commit 9bc37e04 authored by Al Viro's avatar Al Viro
Browse files

fs: introduce lock_rename_child() helper 



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: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarNamjae Jeon <linkinjeon@kernel.org>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 211db0ac

fs/namei.c

+57 −11
Original line number Diff line number Diff line
@@ -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);

include/linux/namei.h

+1 −0
Original line number Diff line number Diff line
@@ -83,6 +83,7 @@ extern int follow_down(struct path *path, unsigned int flags); 
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);