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. Which btw made me realize that even your scheme doesn't completely make sure timestamp is updated after mmap write - if you have pages 0 and 1, you write to both of them - CMTIME flag gets set. Then fsync_range(fd, 0, 4096) is called. We write the page 0, writeprotect it, update timestamps. But page 1 is still writeable so writes to it won't set CMTIME flag, neither update the timestamp... Not that I think this can be reasonably solved but it is a food for thought. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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
