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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pPoVP-001QMo-0x; Wed, 08 Feb 2023 17:45:15 +0000 Date: Wed, 8 Feb 2023 17:45:14 +0000 From: Matthew Wilcox To: Luis Chamberlain Cc: hughd@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, p.raghav@samsung.com, dave@stgolabs.net, a.manzanares@samsung.com, linux-kernel@vger.kernel.org Subject: Re: [RFC 2/2] shmem: add support to ignore swap Message-ID: References: <20230207025259.2522793-1-mcgrof@kernel.org> <20230207025259.2522793-3-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: jecxx36ko4z4mrpjk1i7dqddm5mhwz9m X-Rspamd-Queue-Id: C113010001B X-HE-Tag: 1675878324-349657 X-HE-Meta: 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 8uapo8Oo AXMhKaH75i1sEbe77psSXwr089aPUTUU5FT4Ub/angfRESL5im8JxYangfGBlWV8k2RKbnejk9HGlAy6RdA/FgKr20yTtwFuSdF7fNaxFHKIQhIPR0R/k1e0ThfxwqjQbDHNZ+VF22BOfI0C+6aAE2JBXTA== 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: On Wed, Feb 08, 2023 at 08:01:01AM -0800, Luis Chamberlain wrote: > On Tue, Feb 07, 2023 at 04:01:51AM +0000, Matthew Wilcox wrote: > > On Mon, Feb 06, 2023 at 06:52:59PM -0800, Luis Chamberlain wrote: > > > @@ -1334,11 +1336,15 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) > > > struct shmem_inode_info *info; > > > struct address_space *mapping = folio->mapping; > > > struct inode *inode = mapping->host; > > > + struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); > > > swp_entry_t swap; > > > pgoff_t index; > > > > > > BUG_ON(!folio_test_locked(folio)); > > > > > > + if (wbc->for_reclaim && unlikely(sbinfo->noswap)) > > > + return AOP_WRITEPAGE_ACTIVATE; > > > > Not sure this is the best way to handle this. We'll still incur the > > oevrhead of tracking shmem pages on the LRU, only to fail to write them > > out when the VM thinks we should get rid of them. We'd be better off > > not putting them on the LRU in the first place. > > Ah, makes sense, so in effect then if we do that then on reclaim > we should be able to even WARN_ON(sbinfo->noswap) assuming we did > everthing right. > > Hrm, we have invalidate_mapping_pages(mapping, 0, -1) but that seems a bit > too late how about d_mark_dontcache() on shmem_get_inode() instead? I was thinking that the two calls to folio_add_lru() in mm/shmem.c should be conditional on sbinfo->noswap.