On Tue, Aug 20, 2013 at 9:42 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > On Tue, Aug 20, 2013 at 9:00 AM, Jan Kara <jack@xxxxxxx> 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@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
