btrfs: check for commit error at btrfs_attach_transaction_barrier()

btrfs_attach_transaction_barrier() is used to get a handle pointing to the
current running transaction if the transaction has not started its commit
yet (its state is < TRANS_STATE_COMMIT_START). If the transaction commit
has started, then we wait for the transaction to commit and finish before
returning - however we completely ignore if the transaction was aborted
due to some error during its commit, we simply return ERR_PT(-ENOENT),
which makes the caller assume everything is fine and no errors happened.

This could make an fsync return success (0) to user space when in fact we
had a transaction abort and the target inode changes were therefore not
persisted.

Fix this by checking for the return value from btrfs_wait_for_commit(),
and if it returned an error, return it back to the caller.

Fixes: d4edf39bd5db ("Btrfs: fix uncompleted transaction")
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index f11d803..91b6c2f 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -826,8 +826,13 @@ btrfs_attach_transaction_barrier(struct btrfs_root *root)
 
        trans = start_transaction(root, 0, TRANS_ATTACH,
                                  BTRFS_RESERVE_NO_FLUSH, true);
-       if (trans == ERR_PTR(-ENOENT))
-               btrfs_wait_for_commit(root->fs_info, 0);
+       if (trans == ERR_PTR(-ENOENT)) {
+               int ret;
+
+               ret = btrfs_wait_for_commit(root->fs_info, 0);
+               if (ret)
+                       return ERR_PTR(ret);
+       }
 
        return trans;
 }