}
}
- result->refcnt = 1;
+ atomic_set(&result->refcnt, 1);
/* The empty path is special. */
if (unlikely(!len)) {
if (empty)
memcpy((char *)result->name, filename, len);
result->uptr = NULL;
result->aname = NULL;
- result->refcnt = 1;
+ atomic_set(&result->refcnt, 1);
audit_getname(result);
return result;
if (IS_ERR(name))
return;
- BUG_ON(name->refcnt <= 0);
+ if (WARN_ON_ONCE(!atomic_read(&name->refcnt)))
+ return;
- if (--name->refcnt > 0)
+ if (!atomic_dec_and_test(&name->refcnt))
return;
if (name->name != name->iname) {
p = d_ancestor(p2, p1);
if (p) {
inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
- inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
+ inode_lock_nested(p1->d_inode, I_MUTEX_PARENT2);
return p;
}
p = d_ancestor(p1, p2);
- if (p) {
- inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
- inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
- return p;
- }
-
- lock_two_inodes(p1->d_inode, p2->d_inode,
- I_MUTEX_PARENT, I_MUTEX_PARENT2);
- return NULL;
+ inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
+ inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
+ return p;
}
/*
*
* a) we can get into loop creation.
* b) race potential - two innocent renames can create a loop together.
- * That's where 4.4 screws up. Current fix: serialization on
+ * That's where 4.4BSD screws up. Current fix: serialization on
* sb->s_vfs_rename_mutex. We might be more accurate, but that's another
* story.
- * c) we have to lock _four_ objects - parents and victim (if it exists),
- * and source.
+ * c) we may have to lock up to _four_ objects - parents and victim (if it exists),
+ * and source (if it's a non-directory or a subdirectory that moves to
+ * different parent).
* And that - after we got ->i_mutex on parents (until then we don't know
* whether the target exists). Solution: try to be smart with locking
* order for inodes. We rely on the fact that tree topology may change
bool new_is_dir = false;
unsigned max_links = new_dir->i_sb->s_max_links;
struct name_snapshot old_name;
+ bool lock_old_subdir, lock_new_subdir;
if (source == target)
return 0;
take_dentry_name_snapshot(&old_name, old_dentry);
dget(new_dentry);
/*
- * Lock all moved children. Moved directories may need to change parent
- * pointer so they need the lock to prevent against concurrent
- * directory changes moving parent pointer. For regular files we've
- * historically always done this. The lockdep locking subclasses are
- * somewhat arbitrary but RENAME_EXCHANGE in particular can swap
- * regular files and directories so it's difficult to tell which
- * subclasses to use.
+ * Lock children.
+ * The source subdirectory needs to be locked on cross-directory
+ * rename or cross-directory exchange since its parent changes.
+ * The target subdirectory needs to be locked on cross-directory
+ * exchange due to parent change and on any rename due to becoming
+ * a victim.
+ * Non-directories need locking in all cases (for NFS reasons);
+ * they get locked after any subdirectories (in inode address order).
+ *
+ * NOTE: WE ONLY LOCK UNRELATED DIRECTORIES IN CROSS-DIRECTORY CASE.
+ * NEVER, EVER DO THAT WITHOUT ->s_vfs_rename_mutex.
*/
- lock_two_inodes(source, target, I_MUTEX_NORMAL, I_MUTEX_NONDIR2);
+ lock_old_subdir = new_dir != old_dir;
+ lock_new_subdir = new_dir != old_dir || !(flags & RENAME_EXCHANGE);
+ if (is_dir) {
+ if (lock_old_subdir)
+ inode_lock_nested(source, I_MUTEX_CHILD);
+ if (target && (!new_is_dir || lock_new_subdir))
+ inode_lock(target);
+ } else if (new_is_dir) {
+ if (lock_new_subdir)
+ inode_lock_nested(target, I_MUTEX_CHILD);
+ inode_lock(source);
+ } else {
+ lock_two_nondirectories(source, target);
+ }
error = -EPERM;
if (IS_SWAPFILE(source) || (target && IS_SWAPFILE(target)))
d_exchange(old_dentry, new_dentry);
}
out:
- inode_unlock(source);
- if (target)
+ if (!is_dir || lock_old_subdir)
+ inode_unlock(source);
+ if (target && (!new_is_dir || lock_new_subdir))
inode_unlock(target);
dput(new_dentry);
if (!error) {