Re: [PATCH 1/4] mm: page_alloc: __GFP_FS lockdep annotation for direct compaction

["Vlastimil Babka (SUSE)" <vbabka@kernel.org>]

On 6/26/26 20:21, Johannes Weiner wrote:
> A subsequent patch will have some order-0 allocations participate in
> compaction under defrag_mode, to stave off extfrag events.
> 
> Since this is a sprawling expansion of entry points, and compaction
> can enter filesystem paths, add lockdep annotations that catches
> __GFP_FS passing errors.
> 
> Direct reclaim has had this annotation for a while, and since reclaim
> and compaction are usually used in conjunction, this is unlikely to
> unearth old bugs. It's more about future proofing and peace of mind.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

> ---
>  mm/page_alloc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ee902a468c2f..cb422505c6ef 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4152,12 +4152,14 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
>  
>  	psi_memstall_enter(&pflags);
>  	delayacct_compact_start();
> +	fs_reclaim_acquire(gfp_mask);
>  	noreclaim_flag = memalloc_noreclaim_save();
>  
>  	*compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
>  								prio, &page);
>  
>  	memalloc_noreclaim_restore(noreclaim_flag);
> +	fs_reclaim_release(gfp_mask);
>  	psi_memstall_leave(&pflags);
>  	delayacct_compact_end();
>