[PATCH v4] btrfs: improve error handling of btrfs_add_link()

[PATCH v4] btrfs: improve error handling of btrfs_add_link()

[Johannes Thumshirn]

err holds the return value of either btrfs_del_root_ref() or
btrfs_del_inode_ref() but it hasn't been checked since it's
introduction with commit fe66a05a0679 (Btrfs: improve error handling
for btrfs_insert_dir_item callers) in 2012.

To quote David:

"If the error handling in the error handling fails, there's not much left to do
and the abort either happened earlier in the callees or is necessary here."

So if one of btrfs_del_root_ref() or btrfs_del_inode_ref() failed, abort the
transaction.

Link: https://lore.kernel.org/linux-btrfs/20181126183759.GJ2842@twin.jikos.cz/
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>

---
Changes to v3:
* abort transaction directly after failed btrfs_del_{inode,root}_ref()
---
 fs/btrfs/inode.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c5c27d5457cc..57c6d17780c4 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6311,6 +6311,7 @@ int btrfs_add_link(struct btrfs_trans_handle *trans,
 	struct btrfs_root *root = parent_inode->root;
 	u64 ino = btrfs_ino(inode);
 	u64 parent_ino = btrfs_ino(parent_inode);
+	int err = 0;
 
 	if (unlikely(ino == BTRFS_FIRST_FREE_OBJECTID)) {
 		memcpy(&key, &inode->root->root_key, sizeof(key));
@@ -6355,18 +6356,22 @@ int btrfs_add_link(struct btrfs_trans_handle *trans,
 fail_dir_item:
 	if (unlikely(ino == BTRFS_FIRST_FREE_OBJECTID)) {
 		u64 local_index;
-		int err;
+
 		err = btrfs_del_root_ref(trans, key.objectid,
 					 root->root_key.objectid, parent_ino,
 					 &local_index, name, name_len);
+		if (err)
+			btrfs_abort_transaction(trans, err);
 
 	} else if (add_backref) {
 		u64 local_index;
-		int err;
 
 		err = btrfs_del_inode_ref(trans, root, name, name_len,
 					  ino, parent_ino, &local_index);
+		if (err)
+			btrfs_abort_transaction(trans, err);
 	}
+
 	return ret;
 }
 
-- 
2.16.4

Re: [PATCH v4] btrfs: improve error handling of btrfs_add_link()

[David Sterba]

On Wed, Dec 12, 2018 at 03:14:17PM +0100, Johannes Thumshirn wrote:
> err holds the return value of either btrfs_del_root_ref() or
> btrfs_del_inode_ref() but it hasn't been checked since it's
> introduction with commit fe66a05a0679 (Btrfs: improve error handling
> for btrfs_insert_dir_item callers) in 2012.
> 
> To quote David:
> 
> "If the error handling in the error handling fails, there's not much left to do
> and the abort either happened earlier in the callees or is necessary here."
> 
> So if one of btrfs_del_root_ref() or btrfs_del_inode_ref() failed, abort the
> transaction.
> 
> Link: https://lore.kernel.org/linux-btrfs/20181126183759.GJ2842@twin.jikos.cz/
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>

Thanks. I've updated the changelog a bit follwing the discussion we had
under the previous iterations.

Reviewed-by: David Sterba <dsterba@suse.com>