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

[David Laight <david.laight.linux@gmail.com>]

On Tue, 24 Feb 2026 15:07:10 +1030
Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:

> 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@kernel.org>
> > Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
> > ---
> >   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.

The global change really ought to have used u64 to add the type-check.
Otherwise it will have added 'very hard to find' bugs in the very code
it is trying to make better.

Using *buf for the type might be a reasonable pattern for new code.

	David