From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id n075LS6Q005296 for ; Tue, 6 Jan 2009 23:21:28 -0600 Message-ID: <49643C5A.30608@sgi.com> Date: Wed, 07 Jan 2009 16:23:38 +1100 From: Lachlan McIlroy MIME-Version: 1.0 Subject: Re: [PATCH] fix corruption case for block size < page size References: <49435F35.40109@sandeen.net> <4943FCD7.2010509@sandeen.net> <494735D9.8020809@sgi.com> <49473F5C.3070308@sandeen.net> <49474530.2080809@sgi.com> <4947466D.7000705@sandeen.net> <494748FA.20404@sandeen.net> <49474FE4.2030500@sandeen.net> In-Reply-To: <49474FE4.2030500@sandeen.net> Reply-To: lachlan@sgi.com List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Eric Sandeen Cc: xfs-oss Eric Sandeen wrote: > Eric Sandeen wrote: > >> Gah; or not. what is going on here... Doing just steps 1, 2, 3, 4 >> (ending on the extending truncate): >> >> # xfs_io -c "pwrite -S 0x11 -b 4096 0 4096" -c "mmap -r 0 512" -c "mread >> 0 512" -c "munmap" -c "truncate 256" -c "truncate 514" -t -d -f >> /mnt/scratch/testfile >> >> # xfs_bmap -v /mnt/scratch/testfile >> /mnt/scratch/testfile: >> EXT: FILE-OFFSET BLOCK-RANGE AG AG-OFFSET TOTAL >> 0: [0..0]: 63..63 0 (63..63) 1 >> 1: [1..1]: hole 1 >> >> It looks like what I expect, at this point. But then: >> >> # sync >> # xfs_bmap -v /mnt/scratch/testfile >> /mnt/scratch/testfile: >> EXT: FILE-OFFSET BLOCK-RANGE AG AG-OFFSET TOTAL >> 0: [0..1]: 63..64 0 (63..64) 2 >> >> Um, why'd that last block get mapped in? mmap vs. direct IO I'm >> guessing... w/o the mmap read this does not happen. > > Replying to myself twice? I really need to go to bed. > > So this all does seem to come back to page_state_convert. > > Both the extending write in the original case and the sync above find > their way there; but esp. in the sync test above, why do we have *any* > work to do? Eric, did you find out why sync was allocating that second block? > > With a little instrumentation I see that for the truncate out; sync test > above we get to xfs_vm_writepage() for a page which is *not* dirty, and > yet we call page_state_convert on it and map in that 2nd block... Is > that right!? I guess it is; ->write_cache_pages() clears dirty before > calling writepage. Still why would this page be found dirty on this > path. Bah. Bedtime. > > -Eric _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs