Btrfs: fix error check of btrfs_lookup_dentry()

Clean up btrfs_lookup_dentry() to never return NULL, but PTR_ERR(-ENOENT)
instead. This keeps the return value convention consistent.

Callers who use btrfs_lookup_dentry() require a trivial update.

create_snapshot() in particular looks like it can also lose a BUG_ON(!inode)
which is not really needed - there seems less harm in returning ENOENT to
userspace at that point in the stack than there is to crash the machine.

Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

2 files changed, 21 insertions, 7 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e889779c9b37..2bd4f7590c83 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4992,7 +4992,7 @@ struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
                 return ERR_PTR(ret);
 
         if (location.objectid == 0)
-                return NULL;
+                return ERR_PTR(-ENOENT);
 
         if (location.type == BTRFS_INODE_ITEM_KEY) {
                 inode = btrfs_iget(dir->i_sb, &location, root, NULL);
@@ -5056,10 +5056,17 @@ static void btrfs_dentry_release(struct dentry *dentry)
 static struct dentry *btrfs_lookup(struct inode *dir, struct dentry *dentry,
                                    unsigned int flags)
 {
-        struct dentry *ret;
+        struct inode *inode;
 
-        ret = d_splice_alias(btrfs_lookup_dentry(dir, dentry), dentry);
-        return ret;
+        inode = btrfs_lookup_dentry(dir, dentry);
+        if (IS_ERR(inode)) {
+                if (PTR_ERR(inode) == -ENOENT)
+                        inode = NULL;
+                else
+                        return ERR_CAST(inode);
+        }
+
+        return d_splice_alias(inode, dentry);
 }
 
 unsigned char btrfs_filetype_table[] = {
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 60d3d37ef9a2..89c2f6169b92 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -393,6 +393,7 @@ static noinline int create_subvol(struct inode *dir,
         struct btrfs_root *new_root;
         struct btrfs_block_rsv block_rsv;
         struct timespec cur_time = CURRENT_TIME;
+        struct inode *inode;
         int ret;
         int err;
         u64 objectid;
@@ -554,8 +555,14 @@ fail:
         if (err && !ret)
                 ret = err;
 
-        if (!ret)
-                d_instantiate(dentry, btrfs_lookup_dentry(dir, dentry));
+        if (!ret) {
+                inode = btrfs_lookup_dentry(dir, dentry);
+                if (IS_ERR(inode)) {
+                        ret = PTR_ERR(inode);
+                        goto out;
+                }
+                d_instantiate(dentry, inode);
+        }
 out:
         btrfs_subvolume_release_metadata(root, &block_rsv, qgroup_reserved);
         return ret;
@@ -643,7 +650,7 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
                 ret = PTR_ERR(inode);
                 goto fail;
         }
-        BUG_ON(!inode);
+
         d_instantiate(dentry, inode);
         ret = 0;
 fail: