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From: Kent Overstreet To: Dan Carpenter Cc: Vlastimil Babka , NeilBrown , Dave Chinner , Matthew Wilcox , Amir Goldstein , paulmck@kernel.org, lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-fsdevel , Jan Kara Subject: Re: [Lsf-pc] [LSF/MM/BPF TOPIC] Reclamation interactions with RCU Message-ID: <5vwztnuwnu4tdcopfxgdqiv2qkgdsvdskvrs6sdpadj4fcgti7@v4otdcsc6uxr> References: <170925937840.24797.2167230750547152404@noble.neil.brown.name> <170933687972.24797.18406852925615624495@noble.neil.brown.name> <170950594802.24797.17587526251920021411@noble.neil.brown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 2C70614001A X-Stat-Signature: anbkpdbnqptsbzwcy5tbodeft3qz98jd X-HE-Tag: 1710961762-905833 X-HE-Meta: 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 kZDMMbiy 112sEwDihwN/zn7fbRy74HdFZPcXG0WdY2TgAlItlfdPm/m8D3oTMK3dIZcYyRgdLVvp+d/cEMTWmNy4= 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 Wed, Mar 20, 2024 at 09:32:52PM +0300, Dan Carpenter wrote: > On Tue, Mar 12, 2024 at 03:46:32PM +0100, Vlastimil Babka wrote: > > But if we change it to effectively mean GFP_NOFAIL (for non-costly > > allocations), there should be a manageable number of places to change to a > > variant that allows failure. > > What does that even mean if GFP_NOFAIL can fail for "costly" allocations? > I thought GFP_NOFAIL couldn't fail at all... > > Unfortunately, it's common that when we can't decide on a sane limit for > something people just say "let the user decide based on how much memory > they have". I have added some integer overflow checks which allow the > user to allocate up to UINT_MAX bytes so I know this code is out > there. We can't just s/GFP_KERNEL/GFP_NOFAIL/. > > From a static analysis perspective it would be nice if the callers > explicitly marked which allocations can fail and which can't. GFP_NOFAIL throws a warning if the allocation size is > 2 pages, which is a separate issue from whether the allocation becomes fallible - someone would have to - oh, I don't know, read the code to answer that question. I think we can ditch the 2 page limit on GFP_NOFAIL, though.