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Wed, 21 Aug 2024 00:30:18 -0700 (PDT) Received: from localhost ([193.86.92.181]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5bebc081c59sm7819112a12.85.2024.08.21.00.30.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Aug 2024 00:30:17 -0700 (PDT) Date: Wed, 21 Aug 2024 09:30:17 +0200 From: Michal Hocko To: Christoph Hellwig Cc: Yafang Shao , Andrew Morton , viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, david@fromorbit.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Kent Overstreet Subject: Re: [PATCH] mm: document risk of PF_MEMALLOC_NORECLAIM Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 2EBF316002E X-Stat-Signature: qw9unfpcs66g4uoqxykwux5h81aazd91 X-HE-Tag: 1724225419-319146 X-HE-Meta: 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 kteFiBNd 2CZqKC6oiFd0yrF1QcuqTcR20pZPT1PVTeHkFPG0FULMEbIGJeTW4BW9aSUZBp04/Tw8fKD2Pkuj3B9vHZr30EeAO0g9P3lIONb2O92adpTSjrz4SnGnExPcAFXjxTUQx6rjmE/oeCaA1QCdQUi03pW8IR6M6C3XcZzeF33dODLU206Z/ZEG8XnESomWpAlWSDWjSigtvGj906LbrZUjMXTQBwo4Y31WUZxs+/ksBKCQkFOMdmrwuLeIg0kKn0duYFlu5t+//7fVKFRB0iOyzSAHfnDDfkx3mToOYC5fuBsTNJ114DJUNcgyx61Ja/G4TGWjVTJvnYHxgWnGOzNFaY6w8oAcryGEuKtyBJq71VYgLn2RlGoIQqjL02sZ7zVdBK+fw2h/dejDuR4jRUQyS5+2b5taHV5JpSpaQPc/H8Mx8xmCqnhmkf5KV8MInuZZOuZweMTTVvv+HPIqDkavBAcDryCtJKvNFODwxC5ARftIfDiE= 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 16-08-24 10:54:39, Michal Hocko wrote: > On Fri 16-08-24 01:22:37, Christoph Hellwig wrote: > > On Fri, Aug 16, 2024 at 10:17:54AM +0200, Michal Hocko wrote: > > > Andrew, could you merge the following before PF_MEMALLOC_NORECLAIM can > > > be removed from the tree altogether please? For the full context the > > > email thread starts here: https://lore.kernel.org/all/20240812090525.80299-1-laoar.shao@gmail.com/T/#u > > > > I don't think that's enough. We just need to kill it given that it was > > added without ACKs and despite explicit earlier objections to the API. > > Yes, I think we should kill it before it spreads even more but I would > not like to make the existing user just broken. I have zero visibility > and understanding of the bcachefs code but from a quick look at __bch2_new_inode > it shouldn't be really terribly hard to push GFP_NOWAIT flag there > directly. It would require inode_init_always_gfp variant as well (to not > touch all existing callers that do not have any locking requirements but > I do not see any other nested allocations. > > So a very quick and untested change would look as follows: Anybody managed to give it a more detailed look? I have a fixup for [...] > diff --git a/security/security.c b/security/security.c > index 8cee5b6c6e6d..8634d3bee56f 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -660,14 +660,14 @@ static int lsm_file_alloc(struct file *file) > * > * Returns 0, or -ENOMEM if memory can't be allocated. > */ > -int lsm_inode_alloc(struct inode *inode) > +int lsm_inode_alloc(struct inode *inode, gfp) this > { > if (!lsm_inode_cache) { > inode->i_security = NULL; > return 0; > } > > - inode->i_security = kmem_cache_zalloc(lsm_inode_cache, GFP_NOFS); > + inode->i_security = kmem_cache_zalloc(lsm_inode_cache, gfp); > if (inode->i_security == NULL) > return -ENOMEM; > return 0; -- Michal Hocko SUSE Labs