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Thu, 27 Aug 2026 00:49:21 -0700 (PDT) Date: Thu, 27 Aug 2026 07:49:21 +0000 From: Wei Yang To: "Vlastimil Babka (SUSE)" Cc: Wei Yang , akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Baokun Li Subject: Re: [PATCH] mm: remove out-dated document of __GFP_NOFAIL Message-ID: <20260827074921.mracnqv2m2cugasb@master> Reply-To: Wei Yang References: <20260827030548.16631-1-richard.weiyang@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2310E100002 X-Stat-Signature: dxczmabpfz7w1fwcy1kymqtjbt15h4ho X-Rspam-User: X-HE-Tag: 1787816964-867116 X-HE-Meta: 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 7gUbmW59 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 27, 2026 at 09:35:26AM +0200, Vlastimil Babka (SUSE) wrote: >On 8/27/26 5:05 AM, Wei Yang wrote: >> Commit ee040cbd6e48 ("mm/page_alloc: don't warn about large allocations >> with __GFP_NOFAIL") remove a warning on allocating large folio with >> __GFP_NOFAIL, which is adjusted by commit 903edea6c53f ("mm: warn about >> illegal __GFP_NOFAIL usage in a more appropriate location and manner"). > >"which is adjusted by commit" sounds as 903edea6c53f came later than >ee040cbd6e48, but it's the opposite. Maybe say "which was placed there"? > Got it. >> While in that commit, it also documented this behavior which is >> out-dated now. >> >> Adjust the document to align to current code, and adjust the comment >> while at it. >> >> Signed-off-by: Wei Yang >> Cc: Baokun Li >> --- >> include/linux/gfp_types.h | 2 -- >> mm/page_alloc.c | 2 +- >> 2 files changed, 1 insertion(+), 3 deletions(-) >> >> diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h >> index 190191411009..24fde8eb73df 100644 >> --- a/include/linux/gfp_types.h >> +++ b/include/linux/gfp_types.h >> @@ -243,8 +243,6 @@ enum { >> * used only when there is no reasonable failure policy) but it is >> * definitely preferable to use the flag rather than opencode endless >> * loop around allocator. >> - * Allocating pages from the buddy with __GFP_NOFAIL and order > 1 is >> - * not supported. Please consider using kvmalloc() instead. > >I'm not sure if we want to simply remove the lines, or rather say it's >discouraged (instead of not supported) and still suggest kvmalloc() if >possible. > Reasonable. As mentioned in [1], kvmalloc() maybe not suitable for some cases, I would suggest below change. * Allocating pages from the buddy with __GFP_NOFAIL and order > 1 is * discouraged. Please consider using kvmalloc() instead if possible. Or, you prefer only s/supported/discouraged/ ? [1]: https://lore.kernel.org/all/aQTHMI3t5mNXp0M1@casper.infradead.org >> */ >> #define __GFP_IO ((__force gfp_t)___GFP_IO) >> #define __GFP_FS ((__force gfp_t)___GFP_FS) >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index ab385bc252cc..146f7e0a9462 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -4804,7 +4804,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, >> >> if (unlikely(nofail)) { >> /* >> - * Also we don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM, >> + * We don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM, >> * otherwise, we may result in lockup. >> */ >> WARN_ON_ONCE(!can_direct_reclaim); -- Wei Yang Help you, Help me