Re: [PATCH v2] mm: remove redundant __GFP_NOWARN

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Tue, Aug 12, 2025 at 09:52:25PM +0800, Qianfeng Rong wrote:
> Commit 16f5dfbc851b ("gfp: include __GFP_NOWARN in GFP_NOWAIT") made
> GFP_NOWAIT implicitly include __GFP_NOWARN.
>
> Therefore, explicit __GFP_NOWARN combined with GFP_NOWAIT (e.g.,
> `GFP_NOWAIT | __GFP_NOWARN`) is now redundant.  Let's clean up these
> redundant flags across subsystems.
>
> No functional changes.
>
> Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
> Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>

LGTM, I wonder if there are other such redundancies in the kernel?

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

> ---
> v1->v2:
> - Added a modification to remove redundant __GFP_NOWARN in
>   mm/damon/ops-common.c
> ---
>  mm/damon/ops-common.c | 2 +-
>  mm/filemap.c          | 2 +-
>  mm/mmu_gather.c       | 4 ++--
>  mm/rmap.c             | 2 +-
>  mm/vmalloc.c          | 2 +-
>  5 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
> index 99321ff5cb92..b43595730f08 100644
> --- a/mm/damon/ops-common.c
> +++ b/mm/damon/ops-common.c
> @@ -303,7 +303,7 @@ static unsigned int __damon_migrate_folio_list(
>  		 * instead of migrated.
>  		 */
>  		.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) |
> -			__GFP_NOWARN | __GFP_NOMEMALLOC | GFP_NOWAIT,
> +			__GFP_NOMEMALLOC | GFP_NOWAIT,
>  		.nid = target_nid,
>  	};
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 4e5c9544fee4..c21e98657e0b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1961,7 +1961,7 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
>  			gfp &= ~__GFP_FS;
>  		if (fgp_flags & FGP_NOWAIT) {
>  			gfp &= ~GFP_KERNEL;
> -			gfp |= GFP_NOWAIT | __GFP_NOWARN;
> +			gfp |= GFP_NOWAIT;
>  		}
>  		if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
>  			fgp_flags |= FGP_LOCK;
> diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c
> index b49cc6385f1f..374aa6f021c6 100644
> --- a/mm/mmu_gather.c
> +++ b/mm/mmu_gather.c
> @@ -32,7 +32,7 @@ static bool tlb_next_batch(struct mmu_gather *tlb)
>  	if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
>  		return false;
>
> -	batch = (void *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
> +	batch = (void *)__get_free_page(GFP_NOWAIT);
>  	if (!batch)
>  		return false;
>
> @@ -364,7 +364,7 @@ void tlb_remove_table(struct mmu_gather *tlb, void *table)
>  	struct mmu_table_batch **batch = &tlb->batch;
>
>  	if (*batch == NULL) {
> -		*batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
> +		*batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT);
>  		if (*batch == NULL) {
>  			tlb_table_invalidate(tlb);
>  			tlb_remove_table_one(table);
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 568198e9efc2..7baa7385e1ce 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -285,7 +285,7 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
>  	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
>  		struct anon_vma *anon_vma;
>
> -		avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
> +		avc = anon_vma_chain_alloc(GFP_NOWAIT);
>  		if (unlikely(!avc)) {
>  			unlock_anon_vma_root(root);
>  			root = NULL;
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 6dbcdceecae1..90c3de1a0417 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -5177,7 +5177,7 @@ static void vmap_init_nodes(void)
>  	int n = clamp_t(unsigned int, num_possible_cpus(), 1, 128);
>
>  	if (n > 1) {
> -		vn = kmalloc_array(n, sizeof(*vn), GFP_NOWAIT | __GFP_NOWARN);
> +		vn = kmalloc_array(n, sizeof(*vn), GFP_NOWAIT);
>  		if (vn) {
>  			/* Node partition is 16 pages. */
>  			vmap_zone_size = (1 << 4) * PAGE_SIZE;
> --
> 2.34.1
>