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t=1787817827; bh=cNLnyWjL8DesrYLjnmrDKChGfbafqlwaKvit0A9aYBs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=BrcCTXI+b79Ps7jW4U9P8tYTSax/uesrCiFgIHl0hEXor8vyMSZyt72JUBlNLZY/z tD3QOsg1AWjDXs+xXwqaJNoHjhj24PXvr/DA9HqEWFkTjZEHA5eHsMKJNn8D351Guc OLG6IsqlWXAipfDO3+F9RYea9DR/O7AF3RRADIQtKnP7AsdhwA9Y7NkRjaZxppiFJB 82qzxp4Zz9w3/oZcc9M7zte4so8a+FD2vpWxbPhCwOvAWPoCt/eqYX4LaOvxOpks7Y h4NCeRUVJz4zc534Fj9W/5hMbZcxBNI9bgMPMQsttAe7eAaGi3NC3+WaXqZCaeTbf1 wFqZgMj8O7tvQ== Message-ID: <78561ffa-d075-4570-aaed-60744f11160f@kernel.org> Date: Thu, 27 Aug 2026 10:03:41 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: remove out-dated document of __GFP_NOFAIL To: Wei Yang Cc: 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 References: <20260827030548.16631-1-richard.weiyang@gmail.com> <20260827074921.mracnqv2m2cugasb@master> From: "Vlastimil Babka (SUSE)" Content-Language: en-US In-Reply-To: <20260827074921.mracnqv2m2cugasb@master> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: c35dc3sxpbchuiy6xg7a61cqxgjgndsg X-Rspamd-Queue-Id: F285E40007 X-Rspamd-Server: rspam06 X-HE-Tag: 1787817827-567975 X-HE-Meta: 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 ABxXaKRX 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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 8/27/26 9:49 AM, Wei Yang wrote: > 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. Yeah that's great! Thanks. > 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); >