Re: [PATCH 5/5] slab: prevent recursive kmalloc() in alloc_empty_sheaf()

[Harry Yoo <harry.yoo@oracle.com>]

On Wed, Nov 05, 2025 at 10:05:33AM +0100, Vlastimil Babka wrote:
> We want to expand usage of sheaves to all non-boot caches, including
> kmalloc caches. Since sheaves themselves are also allocated by
> kmalloc(), we need to prevent excessive or infinite recursion -
> depending on sheaf size, the sheaf can be allocated from smaller, same
> or larger kmalloc size bucket, there's no particular constraint.
> 
> This is similar to allocating the objext arrays so let's just reuse the
> existing mechanisms for those. __GFP_NO_OBJ_EXT in alloc_empty_sheaf()
> will prevent a nested kmalloc() from allocating a sheaf itself - it will
> either have sheaves already, or fallback to a non-sheaf-cached
> allocation (so bootstrap of sheaves in a kmalloc cache that allocates
> sheaves from its own size bucket is possible). Additionally, reuse
> OBJCGS_CLEAR_MASK to clear unwanted gfp flags from the nested
> allocation.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---

Looks good to me,
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>

Maybe the flag can be renamed later!
But I can't come up with a good one right now.

-- 
Cheers,
Harry / Hyeonggon