cachefiles: change cachefiles_bury_object to use start_renaming_dentry()

Rather then using lock_rename() and lookup_one() etc we can use
the new start_renaming_dentry().  This is part of centralising dir
locking and lookup so that locking rules can be changed.

Some error check are removed as not necessary.  Checks for rep being a
non-dir or IS_DEADDIR and the check that ->graveyard is still a
directory only provide slightly more informative errors and have been
dropped.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20260224222542.3458677-11-neilb@ownmail.net
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 32 insertions, 61 deletions

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index e5ec90dccc27..c464c72a51cb 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -270,7 +270,8 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
 			   struct dentry *rep,
 			   enum fscache_why_object_killed why)
 {
-	struct dentry *grave, *trap;
+	struct dentry *grave;
+	struct renamedata rd = {};
 	struct path path, path_to_graveyard;
 	char nbuffer[8 + 8 + 1];
 	int ret;
@@ -302,77 +303,55 @@ try_again:
 		(uint32_t) ktime_get_real_seconds(),
 		(uint32_t) atomic_inc_return(&cache->gravecounter));
 
-	/* do the multiway lock magic */
-	trap = lock_rename(cache->graveyard, dir);
-	if (IS_ERR(trap))
-		return PTR_ERR(trap);
-
-	/* do some checks before getting the grave dentry */
-	if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
-		/* the entry was probably culled when we dropped the parent dir
-		 * lock */
-		unlock_rename(cache->graveyard, dir);
-		_leave(" = 0 [culled?]");
-		return 0;
-	}
-
-	if (!d_can_lookup(cache->graveyard)) {
-		unlock_rename(cache->graveyard, dir);
-		cachefiles_io_error(cache, "Graveyard no longer a directory");
-		return -EIO;
-	}
+	rd.mnt_idmap = &nop_mnt_idmap;
+	rd.old_parent = dir;
+	rd.new_parent = cache->graveyard;
+	rd.flags = 0;
+	ret = start_renaming_dentry(&rd, 0, rep, &QSTR(nbuffer));
+	if (ret) {
+		/* Some errors aren't fatal */
+		if (ret == -EXDEV)
+			/* double-lock failed */
+			return ret;
+		if (d_unhashed(rep) || rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
+			/* the entry was probably culled when we dropped the parent dir
+			 * lock */
+			_leave(" = 0 [culled?]");
+			return 0;
+		}
+		if (ret == -EINVAL || ret == -ENOTEMPTY) {
+			cachefiles_io_error(cache, "May not make directory loop");
+			return -EIO;
+		}
+		if (ret == -ENOMEM) {
+			_leave(" = -ENOMEM");
+			return -ENOMEM;
+		}
 
-	if (trap == rep) {
-		unlock_rename(cache->graveyard, dir);
-		cachefiles_io_error(cache, "May not make directory loop");
+		cachefiles_io_error(cache, "Lookup error %d", ret);
 		return -EIO;
 	}
 
 	if (d_mountpoint(rep)) {
-		unlock_rename(cache->graveyard, dir);
+		end_renaming(&rd);
 		cachefiles_io_error(cache, "Mountpoint in cache");
 		return -EIO;
 	}
 
-	grave = lookup_one(&nop_mnt_idmap, &QSTR(nbuffer), cache->graveyard);
-	if (IS_ERR(grave)) {
-		unlock_rename(cache->graveyard, dir);
-		trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
-					   PTR_ERR(grave),
-					   cachefiles_trace_lookup_error);
-
-		if (PTR_ERR(grave) == -ENOMEM) {
-			_leave(" = -ENOMEM");
-			return -ENOMEM;
-		}
-
-		cachefiles_io_error(cache, "Lookup error %ld", PTR_ERR(grave));
-		return -EIO;
-	}
-
+	grave = rd.new_dentry;
 	if (d_is_positive(grave)) {
-		unlock_rename(cache->graveyard, dir);
-		dput(grave);
+		end_renaming(&rd);
 		grave = NULL;
 		cond_resched();
 		goto try_again;
 	}
 
 	if (d_mountpoint(grave)) {
-		unlock_rename(cache->graveyard, dir);
-		dput(grave);
+		end_renaming(&rd);
 		cachefiles_io_error(cache, "Mountpoint in graveyard");
 		return -EIO;
 	}
 
-	/* target should not be an ancestor of source */
-	if (trap == grave) {
-		unlock_rename(cache->graveyard, dir);
-		dput(grave);
-		cachefiles_io_error(cache, "May not make directory loop");
-		return -EIO;
-	}
-
 	/* attempt the rename */
 	path.mnt = cache->mnt;
 	path.dentry = dir;
@@ -382,13 +361,6 @@ try_again:
 	if (ret < 0) {
 		cachefiles_io_error(cache, "Rename security error %d", ret);
 	} else {
-		struct renamedata rd = {
-			.mnt_idmap	= &nop_mnt_idmap,
-			.old_parent	= dir,
-			.old_dentry	= rep,
-			.new_parent	= cache->graveyard,
-			.new_dentry	= grave,
-		};
 		trace_cachefiles_rename(object, d_inode(rep)->i_ino, why);
 		ret = cachefiles_inject_read_error();
 		if (ret == 0)
@@ -402,8 +374,7 @@ try_again:
 	}
 
 	__cachefiles_unmark_inode_in_use(object, d_inode(rep));
-	unlock_rename(cache->graveyard, dir);
-	dput(grave);
+	end_renaming(&rd);
 	_leave(" = 0");
 	return 0;
 }