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Thu, 29 Aug 2024 21:45:31 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id a82iMfvr0Ga6TQAAD6G6ig (envelope-from ); Thu, 29 Aug 2024 21:45:31 +0000 Message-ID: Date: Thu, 29 Aug 2024 23:45:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] mm: drop PF_MEMALLOC_NORECLAIM Content-Language: en-US To: Michal Hocko , Matthew Wilcox Cc: Andrew Morton , Christoph Hellwig , Yafang Shao , Kent Overstreet , jack@suse.cz, Christian Brauner , Alexander Viro , Paul Moore , James Morris , "Serge E. Hallyn" , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-bcachefs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240826085347.1152675-1-mhocko@kernel.org> <20240826085347.1152675-3-mhocko@kernel.org> From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C8B8D8000B X-Stat-Signature: jc6jcr6cu7shspfyjewdgbfcxrshohfi X-Rspam-User: X-HE-Tag: 1724967934-788645 X-HE-Meta: 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 y9GqsE1W WiELJX9ycz4zgdEOKSE7nw5FvUk1IZsX+fpT1uPpmVaIQiTViqITVikpVL+Tcejyp2jKLTZcJVnzXqmubyTxE2SJEJwkch27fq7714aWoLafUk9flB1DVZyxPPhkjNxYqlVbP2vHdHh72+5HgRSujr90YJxBRnN7ORnGjfzn2GB5+G8e1minH+L8S1S4jUQenMa2iQnirNfp1RloAUW2ZpvT162HmXsomiTBg246chJJdvMPxzZyBKaa7+Hy//CJ1AzOitD3iAtAFRhBj6B/32osk6Ll9XT+2Tim6ug8Gnq1p0rWhWyiOE0PIhHqPZW5TllXMgYv3VDb/riJKCWto5A5+nbsHskxrZN29tWXmmWzVWDa2NUkEHnyaNtJukwqFxoRgiffacGK/iWn4R/fQQvx0CyBlxUFIDjgNbZ4spRAHGU9ef77KmVRTjmeMJsAkU5SEun813QqLb0fvQ9zvlq8qUCO5vciKY7vx0jXl+Qdnq2g= 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 8/26/24 21:18, Michal Hocko wrote: > On Mon 26-08-24 18:49:23, Matthew Wilcox wrote: >> On Mon, Aug 26, 2024 at 06:51:55PM +0200, Michal Hocko wrote: > [...] >> > If a plan revert is preferably, I will go with it. >> >> There aren't any other users of PF_MEMALLOC_NOWARN and it definitely >> seems like something you want at a callsite rather than blanket for every >> allocation below this point. We don't seem to have many PF_ flags left, >> so let's not keep it around if there's no immediate plans for it. > > Good point. What about this? > --- > From 923cd429d4b1a3520c93bcf46611ae74a3158865 Mon Sep 17 00:00:00 2001 > From: Michal Hocko > Date: Mon, 26 Aug 2024 21:15:02 +0200 > Subject: [PATCH] Revert "mm: introduce PF_MEMALLOC_NORECLAIM, > PF_MEMALLOC_NOWARN" > > This reverts commit eab0af905bfc3e9c05da2ca163d76a1513159aa4. > > There is no existing user of those flags. PF_MEMALLOC_NOWARN is > dangerous because a nested allocation context can use GFP_NOFAIL which > could cause unexpected failure. Such a code would be hard to maintain > because it could be deeper in the call chain. > > PF_MEMALLOC_NORECLAIM has been added even when it was pointed out [1] > that such a allocation contex is inherently unsafe if the context > doesn't fully control all allocations called from this context. > > While PF_MEMALLOC_NOWARN is not dangerous the way PF_MEMALLOC_NORECLAIM > is it doesn't have any user and as Matthew has pointed out we are > running out of those flags so better reclaim it without any real users. > > [1] https://lore.kernel.org/all/ZcM0xtlKbAOFjv5n@tiehlicka/ > > Signed-off-by: Michal Hocko Reviewed-by: Vlastimil Babka > --- > include/linux/sched.h | 4 ++-- > include/linux/sched/mm.h | 17 ++++------------- > 2 files changed, 6 insertions(+), 15 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index f8d150343d42..731ff1078c9e 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1657,8 +1657,8 @@ extern struct pid *cad_pid; > * I am cleaning dirty pages from some other bdi. */ > #define PF_KTHREAD 0x00200000 /* I am a kernel thread */ > #define PF_RANDOMIZE 0x00400000 /* Randomize virtual address space */ > -#define PF_MEMALLOC_NORECLAIM 0x00800000 /* All allocation requests will clear __GFP_DIRECT_RECLAIM */ > -#define PF_MEMALLOC_NOWARN 0x01000000 /* All allocation requests will inherit __GFP_NOWARN */ > +#define PF__HOLE__00800000 0x00800000 > +#define PF__HOLE__01000000 0x01000000 > #define PF__HOLE__02000000 0x02000000 > #define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_mask */ > #define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */ > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h > index 91546493c43d..07c4fde32827 100644 > --- a/include/linux/sched/mm.h > +++ b/include/linux/sched/mm.h > @@ -258,25 +258,16 @@ static inline gfp_t current_gfp_context(gfp_t flags) > { > unsigned int pflags = READ_ONCE(current->flags); > > - if (unlikely(pflags & (PF_MEMALLOC_NOIO | > - PF_MEMALLOC_NOFS | > - PF_MEMALLOC_NORECLAIM | > - PF_MEMALLOC_NOWARN | > - PF_MEMALLOC_PIN))) { > + if (unlikely(pflags & (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS | PF_MEMALLOC_PIN))) { > /* > - * Stronger flags before weaker flags: > - * NORECLAIM implies NOIO, which in turn implies NOFS > + * NOIO implies both NOIO and NOFS and it is a weaker context > + * so always make sure it makes precedence > */ > - if (pflags & PF_MEMALLOC_NORECLAIM) > - flags &= ~__GFP_DIRECT_RECLAIM; > - else if (pflags & PF_MEMALLOC_NOIO) > + if (pflags & PF_MEMALLOC_NOIO) > flags &= ~(__GFP_IO | __GFP_FS); > else if (pflags & PF_MEMALLOC_NOFS) > flags &= ~__GFP_FS; > > - if (pflags & PF_MEMALLOC_NOWARN) > - flags |= __GFP_NOWARN; > - > if (pflags & PF_MEMALLOC_PIN) > flags &= ~__GFP_MOVABLE; > }