Re: [PATCH] btrfs: replace kcalloc() calls to kzalloc_objs()

[Qu Wenruo]

在 2026/2/24 10:14, Miquel Sabaté Solà 写道:
> Commit 2932ba8d9c99 ("slab: Introduce kmalloc_obj() and family")
> introduced, among many others, the kzalloc_objs() helper, which has some
> benefits over kcalloc().
>
> Cc: Kees Cook <kees@xxxxxxxxxx>
> Signed-off-by: Miquel Sabaté Solà <mssola@xxxxxxxxxx>
> ---
>   fs/btrfs/block-group.c       | 2 +-
>   fs/btrfs/raid56.c            | 8 ++++----
>   fs/btrfs/tests/zoned-tests.c | 2 +-
>   fs/btrfs/volumes.c           | 6 ++----
>   fs/btrfs/zoned.c             | 5 ++---
>   5 files changed, 10 insertions(+), 13 deletions(-)
>
> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> index 37bea850b3f0..8d85b4707690 100644
> --- a/fs/btrfs/block-group.c
> +++ b/fs/btrfs/block-group.c
> @@ -2239,7 +2239,7 @@ int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
>   	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
>   		io_stripe_size = btrfs_stripe_nr_to_offset(nr_data_stripes(map));
>   
> -	buf = kcalloc(map->num_stripes, sizeof(u64), GFP_NOFS);
> +	buf = kzalloc_objs(*buf, map->num_stripes, GFP_NOFS);

Not sure if we should use *buf for the type.

I still remember we had some bugs related to incorrect type usage.

Another thing is, we may not want to use the kzalloc version.
We don't want to waste CPU time just to zero out the content meanwhile 
we're ensured to re-assign the contents.

Thus kmalloc_objs() maybe better.

Thanks,
Qu


>   	if (!buf) {
>   		ret = -ENOMEM;
>   		goto out;
> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> index 02105d68accb..1ebfed8f0a0a 100644
> --- a/fs/btrfs/raid56.c
> +++ b/fs/btrfs/raid56.c
> @@ -2110,8 +2110,8 @@ static int recover_sectors(struct btrfs_raid_bio *rbio)
>   	 * @unmap_array stores copy of pointers that does not get reordered
>   	 * during reconstruction so that kunmap_local works.
>   	 */
> -	pointers = kcalloc(rbio->real_stripes, sizeof(void *), GFP_NOFS);
> -	unmap_array = kcalloc(rbio->real_stripes, sizeof(void *), GFP_NOFS);
> +	pointers = kzalloc_objs(*pointers, rbio->real_stripes, GFP_NOFS);
> +	unmap_array = kzalloc_objs(*unmap_array, rbio->real_stripes, GFP_NOFS);
>   	if (!pointers || !unmap_array) {
>   		ret = -ENOMEM;
>   		goto out;
> @@ -2844,8 +2844,8 @@ static int recover_scrub_rbio(struct btrfs_raid_bio *rbio)
>   	 * @unmap_array stores copy of pointers that does not get reordered
>   	 * during reconstruction so that kunmap_local works.
>   	 */
> -	pointers = kcalloc(rbio->real_stripes, sizeof(void *), GFP_NOFS);
> -	unmap_array = kcalloc(rbio->real_stripes, sizeof(void *), GFP_NOFS);
> +	pointers = kzalloc_objs(*pointers, rbio->real_stripes, GFP_NOFS);
> +	unmap_array = kzalloc_objs(*unmap_array, rbio->real_stripes, GFP_NOFS);
>   	if (!pointers || !unmap_array) {
>   		ret = -ENOMEM;
>   		goto out;
> diff --git a/fs/btrfs/tests/zoned-tests.c b/fs/btrfs/tests/zoned-tests.c
> index da21c7aea31a..2bc3b14baa41 100644
> --- a/fs/btrfs/tests/zoned-tests.c
> +++ b/fs/btrfs/tests/zoned-tests.c
> @@ -58,7 +58,7 @@ static int test_load_zone_info(struct btrfs_fs_info *fs_info,
>   		return -ENOMEM;
>   	}
>   
> -	zone_info = kcalloc(test->num_stripes, sizeof(*zone_info), GFP_KERNEL);
> +	zone_info = kzalloc_objs(*zone_info, test->num_stripes, GFP_KERNEL);
>   	if (!zone_info) {
>   		test_err("cannot allocate zone info");
>   		return -ENOMEM;
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index e15e138c515b..c0cf8f7c5a8e 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -5499,8 +5499,7 @@ static int calc_one_profile_avail(struct btrfs_fs_info *fs_info,
>   		goto out;
>   	}
>   
> -	devices_info = kcalloc(fs_devices->rw_devices, sizeof(*devices_info),
> -			       GFP_NOFS);
> +	devices_info = kzalloc_objs(*devices_info, fs_devices->rw_devices, GFP_NOFS);
>   	if (!devices_info) {
>   		ret = -ENOMEM;
>   		goto out;
> @@ -6067,8 +6066,7 @@ struct btrfs_block_group *btrfs_create_chunk(struct btrfs_trans_handle *trans,
>   	ctl.space_info = space_info;
>   	init_alloc_chunk_ctl(fs_devices, &ctl);
>   
> -	devices_info = kcalloc(fs_devices->rw_devices, sizeof(*devices_info),
> -			       GFP_NOFS);
> +	devices_info = kzalloc_objs(*devices_info, fs_devices->rw_devices, GFP_NOFS);
>   	if (!devices_info)
>   		return ERR_PTR(-ENOMEM);
>   
> diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
> index ab330ec957bc..851b0de7bed7 100644
> --- a/fs/btrfs/zoned.c
> +++ b/fs/btrfs/zoned.c
> @@ -1697,8 +1697,7 @@ static int btrfs_load_block_group_raid10(struct btrfs_block_group *bg,
>   		return -EINVAL;
>   	}
>   
> -	raid0_allocs = kcalloc(map->num_stripes / map->sub_stripes, sizeof(*raid0_allocs),
> -			       GFP_NOFS);
> +	raid0_allocs = kzalloc_objs(*raid0_allocs, map->num_stripes / map->sub_stripes, GFP_NOFS);
>   	if (!raid0_allocs)
>   		return -ENOMEM;
>   
> @@ -1916,7 +1915,7 @@ int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache, bool new)
>   
>   	cache->physical_map = map;
>   
> -	zone_info = kcalloc(map->num_stripes, sizeof(*zone_info), GFP_NOFS);
> +	zone_info = kzalloc_objs(*zone_info, map->num_stripes, GFP_NOFS);
>   	if (!zone_info) {
>   		ret = -ENOMEM;
>   		goto out;