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From: Kent Overstreet To: Matthew Wilcox Cc: NeilBrown , Dave Chinner , 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: 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-Rspamd-Queue-Id: B3B91140005 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: qko5hxqano1btxf8wobi1di9u7ga97mg X-HE-Tag: 1709517944-669049 X-HE-Meta: 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 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 Mon, Mar 04, 2024 at 12:35:05AM +0000, Matthew Wilcox wrote: > On Mon, Mar 04, 2024 at 09:45:48AM +1100, NeilBrown wrote: > > I have in mind a more explicit statement of how much waiting is > > acceptable. > > > > GFP_NOFAIL - wait indefinitely > > GFP_KILLABLE - wait indefinitely unless fatal signal is pending. > > GFP_RETRY - may retry but deadlock, though unlikely, is possible. So > > don't wait indefinitely. May abort more quickly if fatal > > signal is pending. > > GFP_NO_RETRY - only try things once. This may sleep, but will give up > > fairly quickly. Either deadlock is a significant > > possibility, or alternate strategy is fairly cheap. > > GFP_ATOMIC - don't sleep - same as current. > > I don't think these should be GFP flags. Rather, these should be > context flags (and indeed, they're mutually exclusive, so this is a > small integer to represent where we are on the spectrum). That is > we want code to do Why? Context flags are for /context/, i.e. the scope where you take a lock that's GFP_FS unsafe. These really are callsite specific - "how bad is it if we have to deal with an allocation failure here?"