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[109.81.94.157]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-427d690152esm19922145e9.13.2024.07.19.03.57.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Jul 2024 03:57:07 -0700 (PDT) Date: Fri, 19 Jul 2024 12:57:06 +0200 From: Michal Hocko To: Barry Song <21cnbao@gmail.com> Cc: akpm@linux-foundation.org, linux-mm@kvack.org, Barry Song , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 18EBD80020 X-Stat-Signature: x6upk1u1qd93bqe9jkwooccs8pj165g4 X-HE-Tag: 1721386628-152678 X-HE-Meta: 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 Xh6auHYC RIwKOcYoASs184D65V2yiTUUpa+J1aT+LdU0KDGH9h2jhXElzkw4s8lzmRGeJtrX8t3zMVokrQ3R9afqmijHZHLgIo6zMO0voUTRSki0srP6hbYDzfjDbplGfpS4HITeYdkBzUidGzCAitlgMLsUvjiKU+z+n1ixDHNvzGUP3dwDr0GXSqcF4VU2Rt7LNJRumHt3F6jnlAMSWGNl1jxBArso2D911RVq3vqluTnNW5Xkq4u5mcSLKV9CdDQiEy9AX93lKn/C/XxLrkH/fM5LQTXHOtGq/3l3leMJ87sE4xNDXH2/iV0Bh0jb1DfNyRZD0n4FECbuegI8UJU+2IwvbYVZm0QAKXuT9Ukvvd+MfUrPPUiDcGya83/AfWZDfT4/OaX2rfcr5OXm4dLSGL+JTT59AlxqHE8fvu0tfXldUv7OLdj1sTOmqzKZSl/kvnNODj4VeI90pSA5J13umpRNlSVUwTPNmrwkbdfM9VJXKSGzR3wM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri 19-07-24 21:58:51, Barry Song wrote: > On Fri, Jul 19, 2024 at 9:45 PM Michal Hocko wrote: > > > > On Fri 19-07-24 21:36:38, Barry Song wrote: > > > And I believe that even most MM experts have no idea when GFP_NOFAIL > > > will fail. This is so bad to keep it as is. > > > > GFP_NOFAIL doesn't fail in any supported scenarios. We are talking how > > to deal with those that are unsupported. I am not sure how much helpful > > it is to document all potential gfp combinations that make no-sense. > > Sorry, I don't see any point from what you are saying. You are simply claiming > this is the fault of those calling "unsupported" APIs while lacking a valid way > to stop this from happening. Bear in mind, Everything which is not forbidden > is allowed. > > I don't think maintainers outside mm know what are supported and what > are not supported. an "unsupported" scenario can find a way to come into > mainline easily. Good luck documenting all of those in a comprehensible way and maintaining the forward. -- Michal Hocko SUSE Labs