On Tue 15-09-09 09:08:29, Christoph Hellwig wrote: > On Tue, Sep 15, 2009 at 03:04:19PM +0200, Jens Axboe wrote: > > > > > Let's have a look at the flags in wbc: > > > nonblocking - Currently only set by direct callers of ->writepage() BUT > > > originally wb_kupdate() and background_writeout() also > > > set this flag. Since filesystems and write_cache_pages() > > > use the flag we should set it for equivalent writeouts as > > > well. This should be fixed... > > > > Since this is all handled by the dedicated thread now, dropping the > > nonblocking bit was on purpose. What would the point be, except for > > stopping pdflush being blocked on request allocation? > > Note that this flag just caused utter mess traditionally. btrfs decided > to ignore it completely and ext4 partially. Removing this check in > XFS increases large bufferd write loads massively. > > Just half-removing it is a bad idea, though - if you don't set it > anymore please kill it entirely. The nonblocking flag is still set for writeback done for memory reclaim. OTOH the only real consumer of this flag now seems to be __block_write_full_page() which does trylock_buffer() in case of nonblocking writeback. I'm undecided whether it makes sence or not. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
