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Message-ID: <CALCETrXqZ3Fgp9JHRJZCRfW-+qq2T_xw7Y_xyn2i=xK5+pdZoQ@mail.gmail.com> Date: Tue, 20 Aug 2013 12:27:31 -0700 From: Andy Lutomirski <luto@...capital.net> To: Jan Kara <jack@...e.cz> Cc: Dave Chinner <david@...morbit.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>, "Theodore Ts'o" <tytso@....edu>, Dave Hansen <dave.hansen@...ux.intel.com>, xfs@....sgi.com, Tim Chen <tim.c.chen@...ux.intel.com>, Christoph Hellwig <hch@...radead.org> Subject: Re: [PATCH v3 3/5] mm: Notify filesystems when it's time to apply a deferred cmtime update On Tue, Aug 20, 2013 at 9:42 AM, Andy Lutomirski <luto@...capital.net> wrote: > On Tue, Aug 20, 2013 at 9:00 AM, Jan Kara <jack@...e.cz> wrote: >> On Mon 19-08-13 21:14:44, Andy Lutomirski wrote: >>> >> I could require ->writepages *and* ->flush_cmtime to handle the time >>> >> update, but that would complicate non-transactional filesystems. >>> >> Those filesystems should just flush cmtime at the end of writepages. >>> > >>> > do_writepages() is the wrong place to do such updates - we can get >>> > writeback directly through .writepage, so the time updates need to >>> > be in .writepage. That first .writepage call will clear the bit on >>> > the mapping, so it's only done on the first call to .writepage on >>> > the given mapping. >>> >>> Last time I checked, all the paths that actually needed the timestamp >>> update went through .writepages. I'll double-check. >> kswapd can call just .writepage to do the writeout so timestamp update >> should be handled there as well. Otherwise all pages in a mapping can be >> cleaned without timestamp being updated. > > OK, I'll fix that. This is a bit ugly. mpage_writepages and generic_writepages both call ->writepage. If writepage starts checking cmtime, then writepages will do multiple timestamp updates on filesystems that use this code. I can modify vmscan and migrate to flush cmtime -- they seem to be the only callers of ->writepage that aren't themselves called from ->writepages. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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