linux-kernel - Re: [PATCH v2] mm: remove redundant __GFP

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Message-ID: <aJuDV7OzUZZ4g5lL@pc636>
Date: Tue, 12 Aug 2025 20:09:27 +0200
From: Uladzislau Rezki <urezki@...il.com>
To: Qianfeng Rong <rongqianfeng@...o.com>
Cc: Qianfeng Rong <rongqianfeng@...o.com>, SeongJae Park <sj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Will Deacon <will@...nel.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
	Nick Piggin <npiggin@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	David Hildenbrand <david@...hat.com>,
	Rik van Riel <riel@...riel.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Harry Yoo <harry.yoo@...cle.com>,
	Uladzislau Rezki <urezki@...il.com>, damon@...ts.linux.dev,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH v2] mm: remove redundant __GFP_NOWARN

On Tue, Aug 12, 2025 at 05:46:47PM +0100, Lorenzo Stoakes wrote:
> 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@...cle.com>
> > Signed-off-by: Qianfeng Rong <rongqianfeng@...o.com>
> 
> LGTM, I wonder if there are other such redundancies in the kernel?
> 
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.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
> >
Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@...il.com>

--
Uladzislau Rezki