[PATCH 4/8] cachefiles: Use lookup_one() rather than lookup_one_len()

[NeilBrown <neil@brown.name>]

lookup_one_len() does not support idmapped mounts and does permission
checking on the non-mapped uids.  This means that cachefiles cannot
correctly use idmapped mounts as a backing store.

This patch changes to use lookup_one() and lookup_one_positive_unlocked(),
passing the relevant vfsmount so idmapping can be honoured.

This requires passing the name in a qstr.  This is easily done with
QSTR() as the name is always nul terminated, and often strlen is used
anyway.  ->d_name_len is removed as no longer useful.

Note that there are still many places where cachefiles uses
nop_mnt_idmap so more work is needed to properly support idmapped
mounts.

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/cachefiles/internal.h |  1 -
 fs/cachefiles/key.c      |  1 -
 fs/cachefiles/namei.c    | 14 +++++++-------
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 38c236e38cef..b62cd3e9a18e 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -71,7 +71,6 @@ struct cachefiles_object {
 	int				debug_id;
 	spinlock_t			lock;
 	refcount_t			ref;
-	u8				d_name_len;	/* Length of filename */
 	enum cachefiles_content		content_info:8;	/* Info about content presence */
 	unsigned long			flags;
 #define CACHEFILES_OBJECT_USING_TMPFILE	0		/* Have an unlinked tmpfile */
diff --git a/fs/cachefiles/key.c b/fs/cachefiles/key.c
index bf935e25bdbe..4927b533b9ae 100644
--- a/fs/cachefiles/key.c
+++ b/fs/cachefiles/key.c
@@ -132,7 +132,6 @@ bool cachefiles_cook_key(struct cachefiles_object *object)
 success:
 	name[len] = 0;
 	object->d_name = name;
-	object->d_name_len = len;
 	_leave(" = %s", object->d_name);
 	return true;
 }
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 83a60126de0f..a440a2ff5d41 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -98,7 +98,7 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
 retry:
 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
-		subdir = lookup_one_len(dirname, dir, strlen(dirname));
+		subdir = lookup_one(cache->mnt, QSTR(dirname), dir);
 	else
 		subdir = ERR_PTR(ret);
 	trace_cachefiles_lookup(NULL, dir, subdir);
@@ -337,7 +337,7 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
 		return -EIO;
 	}
 
-	grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
+	grave = lookup_one(cache->mnt, QSTR(nbuffer), cache->graveyard);
 	if (IS_ERR(grave)) {
 		unlock_rename(cache->graveyard, dir);
 		trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
@@ -629,8 +629,8 @@ bool cachefiles_look_up_object(struct cachefiles_object *object)
 	/* Look up path "cache/vol/fanout/file". */
 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
-		dentry = lookup_positive_unlocked(object->d_name, fan,
-						  object->d_name_len);
+		dentry = lookup_one_positive_unlocked(volume->cache->mnt,
+						      QSTR(object->d_name), fan);
 	else
 		dentry = ERR_PTR(ret);
 	trace_cachefiles_lookup(object, fan, dentry);
@@ -682,7 +682,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
 	inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
-		dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
+		dentry = lookup_one(cache->mnt, QSTR(object->d_name), fan);
 	else
 		dentry = ERR_PTR(ret);
 	if (IS_ERR(dentry)) {
@@ -701,7 +701,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
 		dput(dentry);
 		ret = cachefiles_inject_read_error();
 		if (ret == 0)
-			dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
+			dentry = lookup_one(cache->mnt, QSTR(object->d_name), fan);
 		else
 			dentry = ERR_PTR(ret);
 		if (IS_ERR(dentry)) {
@@ -750,7 +750,7 @@ static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache,
 
 	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
 
-	victim = lookup_one_len(filename, dir, strlen(filename));
+	victim = lookup_one(cache->mnt, QSTR(filename), dir);
 	if (IS_ERR(victim))
 		goto lookup_error;
 	if (d_is_negative(victim))
-- 
2.48.1