[PATCH] xfs: removed useless condition in function xfs_attr_node_get

[PATCH] xfs: removed useless condition in function xfs_attr_node_get

[Andrey Strachuk]

At line 1561, variable "state" is being compared
with NULL every loop iteration.

-------------------------------------------------------------------
1561	for (i = 0; state != NULL && i < state->path.active; i++) {
1562		xfs_trans_brelse(args->trans, state->path.blk[i].bp);
1563		state->path.blk[i].bp = NULL;
1564	}
-------------------------------------------------------------------

However, it cannot be NULL.

----------------------------------------
1546	state = xfs_da_state_alloc(args);
----------------------------------------

xfs_da_state_alloc calls kmem_cache_zalloc. kmem_cache_zalloc is
called with __GFP_NOFAIL flag and, therefore, it cannot return NULL.

--------------------------------------------------------------------------
	struct xfs_da_state *
	xfs_da_state_alloc(
	struct xfs_da_args	*args)
	{
		struct xfs_da_state	*state;

		state = kmem_cache_zalloc(xfs_da_state_cache, GFP_NOFS | __GFP_NOFAIL);
		state->args = args;
		state->mp = args->dp->i_mount;
		return state;
	}
--------------------------------------------------------------------------

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Andrey Strachuk <strochuk@ispras.ru>

Fixes: 4d0cdd2bb8f0 ("xfs: clean up xfs_attr_node_hasname")
---
 fs/xfs/libxfs/xfs_attr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index 224649a76cbb..6b8857e53add 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -1558,7 +1558,7 @@ xfs_attr_node_get(
 	 * If not in a transaction, we have to release all the buffers.
 	 */
 out_release:
-	for (i = 0; state != NULL && i < state->path.active; i++) {
+	for (i = 0; i < state->path.active; i++) {
 		xfs_trans_brelse(args->trans, state->path.blk[i].bp);
 		state->path.blk[i].bp = NULL;
 	}
-- 
2.25.1

Re: [PATCH] xfs: removed useless condition in function xfs_attr_node_get

[Darrick J. Wong]

On Wed, Jul 06, 2022 at 04:36:27PM +0300, Andrey Strachuk wrote:
> At line 1561, variable "state" is being compared
> with NULL every loop iteration.
> 
> -------------------------------------------------------------------
> 1561	for (i = 0; state != NULL && i < state->path.active; i++) {
> 1562		xfs_trans_brelse(args->trans, state->path.blk[i].bp);
> 1563		state->path.blk[i].bp = NULL;
> 1564	}
> -------------------------------------------------------------------
> 
> However, it cannot be NULL.
> 
> ----------------------------------------
> 1546	state = xfs_da_state_alloc(args);
> ----------------------------------------
> 
> xfs_da_state_alloc calls kmem_cache_zalloc. kmem_cache_zalloc is
> called with __GFP_NOFAIL flag and, therefore, it cannot return NULL.
> 
> --------------------------------------------------------------------------
> 	struct xfs_da_state *
> 	xfs_da_state_alloc(
> 	struct xfs_da_args	*args)
> 	{
> 		struct xfs_da_state	*state;
> 
> 		state = kmem_cache_zalloc(xfs_da_state_cache, GFP_NOFS | __GFP_NOFAIL);
> 		state->args = args;
> 		state->mp = args->dp->i_mount;
> 		return state;
> 	}
> --------------------------------------------------------------------------
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Andrey Strachuk <strochuk@ispras.ru>
> 
> Fixes: 4d0cdd2bb8f0 ("xfs: clean up xfs_attr_node_hasname")

Nit: usually the tags go at the end with no empty lines between them.

The change looks correct to me, so
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/xfs/libxfs/xfs_attr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 224649a76cbb..6b8857e53add 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -1558,7 +1558,7 @@ xfs_attr_node_get(
>  	 * If not in a transaction, we have to release all the buffers.
>  	 */
>  out_release:
> -	for (i = 0; state != NULL && i < state->path.active; i++) {
> +	for (i = 0; i < state->path.active; i++) {
>  		xfs_trans_brelse(args->trans, state->path.blk[i].bp);
>  		state->path.blk[i].bp = NULL;
>  	}
> -- 
> 2.25.1
>