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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <3088327.1628774588@warthog.procyon.org.uk> References: <3088327.1628774588@warthog.procyon.org.uk> <162876946134.3068428.15475611190876694695.stgit@warthog.procyon.org.uk> <162876947840.3068428.12591293664586646085.stgit@warthog.procyon.org.uk> To: Matthew Wilcox Cc: dhowells@redhat.com, trond.myklebust@primarydata.com, darrick.wong@oracle.com, hch@lst.de, jlayton@kernel.org, sfrench@samba.org, torvalds@linux-foundation.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mm: Make swap_readpage() for SWP_FS_OPS use ->direct_IO() not ->readpage() MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3088957.1628775479.1@warthog.procyon.org.uk> Date: Thu, 12 Aug 2021 14:37:59 +0100 Message-ID: <3088958.1628775479@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=MIJVBZ0j; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf13.hostedemail.com: domain of dhowells@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=dhowells@redhat.com X-Stat-Signature: tbzbkkkgqiso7ts4fx4qnt6h8mz1qbkc X-Rspamd-Queue-Id: 42C3E100C755 X-Rspamd-Server: rspam05 X-HE-Tag: 1628775486-472384 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: David Howells wrote: > Matthew Wilcox wrote: > > > After submitting the IO here ... > > > > > + if (ret != -EIOCBQUEUED) > > > + swapfile_read_complete(&ki->iocb, ret, 0); > > > > We only touch the 'ki' here ... if the caller didn't call read_complete > > > > > + swapfile_put_kiocb(ki); > > > > Except for here, which is only touched in order to put the refcount. > > > > So why can't swapfile_read_complete() do the work of freeing the ki? > > When I was doing something similar for cachefiles, I couldn't get it to work > like that. I'll have another look at that. Ah, yes. generic_file_direct_write() accesses in the kiocb *after* calling ->direct_IO(), so the kiocb *must not* go away until after generic_file_direct_write() has returned. David