[PATCH] xfs: Use refcount_t instead of atomic_t for xmi_refcount

[PATCH] xfs: Use refcount_t instead of atomic_t for xmi_refcount

[Pei Xiao]

Use an API that resembles more the actual use of xmi_refcount.

Found by cocci:
    fs/xfs/xfs_exchmaps_item.c:57:5-24: WARNING: atomic_dec_and_test
variation before object free at line 58.

Fixes: 6c08f434bd33 ("xfs: introduce a file mapping exchange log intent item")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202412260634.uSDUNyYS-lkp@intel.com/
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
---
 fs/xfs/xfs_exchmaps_item.c | 6 +++---
 fs/xfs/xfs_exchmaps_item.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_exchmaps_item.c b/fs/xfs/xfs_exchmaps_item.c
index 264a121c5e16..5975a16c54e3 100644
--- a/fs/xfs/xfs_exchmaps_item.c
+++ b/fs/xfs/xfs_exchmaps_item.c
@@ -57,8 +57,8 @@ STATIC void
 xfs_xmi_release(
 	struct xfs_xmi_log_item	*xmi_lip)
 {
-	ASSERT(atomic_read(&xmi_lip->xmi_refcount) > 0);
-	if (atomic_dec_and_test(&xmi_lip->xmi_refcount)) {
+	ASSERT(refcount_read(&xmi_lip->xmi_refcount) > 0);
+	if (refcount_dec_and_test(&xmi_lip->xmi_refcount)) {
 		xfs_trans_ail_delete(&xmi_lip->xmi_item, 0);
 		xfs_xmi_item_free(xmi_lip);
 	}
@@ -138,7 +138,7 @@ xfs_xmi_init(
 
 	xfs_log_item_init(mp, &xmi_lip->xmi_item, XFS_LI_XMI, &xfs_xmi_item_ops);
 	xmi_lip->xmi_format.xmi_id = (uintptr_t)(void *)xmi_lip;
-	atomic_set(&xmi_lip->xmi_refcount, 2);
+	refcount_set(&xmi_lip->xmi_refcount, 2);
 
 	return xmi_lip;
 }
diff --git a/fs/xfs/xfs_exchmaps_item.h b/fs/xfs/xfs_exchmaps_item.h
index efa368d25d09..b8be3bca3155 100644
--- a/fs/xfs/xfs_exchmaps_item.h
+++ b/fs/xfs/xfs_exchmaps_item.h
@@ -38,7 +38,7 @@ struct kmem_cache;
  */
 struct xfs_xmi_log_item {
 	struct xfs_log_item		xmi_item;
-	atomic_t			xmi_refcount;
+	refcount_t			xmi_refcount;
 	struct xfs_xmi_log_format	xmi_format;
 };
 
-- 
2.25.1

Re: [PATCH] xfs: Use refcount_t instead of atomic_t for xmi_refcount

[Darrick J. Wong]

On Mon, Dec 30, 2024 at 03:18:16PM +0800, Pei Xiao wrote:
> Use an API that resembles more the actual use of xmi_refcount.
> 
> Found by cocci:
>     fs/xfs/xfs_exchmaps_item.c:57:5-24: WARNING: atomic_dec_and_test
> variation before object free at line 58.
> 
> Fixes: 6c08f434bd33 ("xfs: introduce a file mapping exchange log intent item")
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202412260634.uSDUNyYS-lkp@intel.com/
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>

What has changed since
https://lore.kernel.org/linux-xfs/1508497678-10508-1-git-send-email-elena.reshetova@intel.com/
and if something has, why wouldn't you apply atomic_t -> refcount_t for
/all/ the log intent item types?

--D

> ---
>  fs/xfs/xfs_exchmaps_item.c | 6 +++---
>  fs/xfs/xfs_exchmaps_item.h | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/xfs/xfs_exchmaps_item.c b/fs/xfs/xfs_exchmaps_item.c
> index 264a121c5e16..5975a16c54e3 100644
> --- a/fs/xfs/xfs_exchmaps_item.c
> +++ b/fs/xfs/xfs_exchmaps_item.c
> @@ -57,8 +57,8 @@ STATIC void
>  xfs_xmi_release(
>  	struct xfs_xmi_log_item	*xmi_lip)
>  {
> -	ASSERT(atomic_read(&xmi_lip->xmi_refcount) > 0);
> -	if (atomic_dec_and_test(&xmi_lip->xmi_refcount)) {
> +	ASSERT(refcount_read(&xmi_lip->xmi_refcount) > 0);
> +	if (refcount_dec_and_test(&xmi_lip->xmi_refcount)) {
>  		xfs_trans_ail_delete(&xmi_lip->xmi_item, 0);
>  		xfs_xmi_item_free(xmi_lip);
>  	}
> @@ -138,7 +138,7 @@ xfs_xmi_init(
>  
>  	xfs_log_item_init(mp, &xmi_lip->xmi_item, XFS_LI_XMI, &xfs_xmi_item_ops);
>  	xmi_lip->xmi_format.xmi_id = (uintptr_t)(void *)xmi_lip;
> -	atomic_set(&xmi_lip->xmi_refcount, 2);
> +	refcount_set(&xmi_lip->xmi_refcount, 2);
>  
>  	return xmi_lip;
>  }
> diff --git a/fs/xfs/xfs_exchmaps_item.h b/fs/xfs/xfs_exchmaps_item.h
> index efa368d25d09..b8be3bca3155 100644
> --- a/fs/xfs/xfs_exchmaps_item.h
> +++ b/fs/xfs/xfs_exchmaps_item.h
> @@ -38,7 +38,7 @@ struct kmem_cache;
>   */
>  struct xfs_xmi_log_item {
>  	struct xfs_log_item		xmi_item;
> -	atomic_t			xmi_refcount;
> +	refcount_t			xmi_refcount;
>  	struct xfs_xmi_log_format	xmi_format;
>  };
>  
> -- 
> 2.25.1
> 
>