On Sat, 2007-09-29 at 19:04 +0800, Fengguang Wu wrote: > On Thu, Sep 27, 2007 at 11:32:36PM -0700, Chakri n wrote: > > Hi, > > > > In my testing, a unresponsive file system can hang all I/O in the system. > > This is not seen in 2.4. > > > > I started 20 threads doing I/O on a NFS share. They are just doing 4K > > writes in a loop. > > > > Now I stop NFS server hosting the NFS share and start a > > "dd" process to write a file on local EXT3 file system. > > > > # dd if=/dev/zero of=/tmp/x count=1000 > > > > This process never progresses. > > Peter, do you think this patch will help?
In another sub-thread: > It's works on .23-rc8-mm2 with out any problems. > > "dd" process does not hang any more. > > Thanks for all the help. > > Cheers > --Chakri So the per-bdi dirty patches that are in -mm already fix the problem. > === > writeback: avoid possible balance_dirty_pages() lockup on light-load bdi > > On a busy-writing system, a writer could be hold up infinitely on a > light-load device. It will be trying to sync more than enough dirty data. > > The problem case: > > 0. sda/nr_dirty >= dirty_limit; > sdb/nr_dirty == 0 > 1. dd writes 32 pages on sdb > 2. balance_dirty_pages() blocks dd, and tries to write 6MB. > 3. it never gets there: there's only 128KB dirty data. > 4. dd may be blocked for a loooong time as long as sda is overloaded > > Fix it by returning on 'zero dirty inodes' in the current bdi. > (In fact there are slight differences between 'dirty inodes' and 'dirty > pages'. > But there is no available counters for 'dirty pages'.) > > Cc: Peter Zijlstra <[EMAIL PROTECTED]> > Signed-off-by: Fengguang Wu <[EMAIL PROTECTED]> > --- > mm/page-writeback.c | 3 +++ > 1 file changed, 3 insertions(+) > > --- linux-2.6.22.orig/mm/page-writeback.c > +++ linux-2.6.22/mm/page-writeback.c > @@ -227,6 +227,9 @@ static void balance_dirty_pages(struct a > if (nr_reclaimable + global_page_state(NR_WRITEBACK) <= > dirty_thresh) > break; > + if (list_empty(&mapping->host->i_sb->s_dirty) && > + list_empty(&mapping->host->i_sb->s_io)) > + break; > > if (!dirty_exceeded) > dirty_exceeded = 1; > On the patch itself, not sure if it would have been enough. As soon as there is a single dirty inode on the list one would get caught in the same problem as before. That is, if NFS_dirty+NFS_unstable+NFS_writeback > dirty_limit this break won't fix it. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
