> > How about this? > > I still don't understand this bug. > > > Solves the FUSE deadlock, but not the throttle_vm_writeout() one. > > I'll try to tackle that one as well. > > > > If the per-bdi dirty counter goes below 16, balance_dirty_pages() > > returns. > > > > Does the constant need to tunable? If it's too large, then the global > > threshold is more easily exceeded. If it's too small, then in a tight > > situation progress will be slower. > > > > Thanks, > > Miklos > > > > Index: linux/mm/page-writeback.c > > =================================================================== > > --- linux.orig/mm/page-writeback.c 2007-02-19 17:32:41.000000000 +0100 > > +++ linux/mm/page-writeback.c 2007-02-19 18:05:28.000000000 +0100 > > @@ -198,6 +198,25 @@ static void balance_dirty_pages(struct a > > dirty_thresh) > > break; > > > > + /* > > + * Acquit this producer if there's little or nothing > > + * to write back to this particular queue > > + * > > + * Without this check a deadlock is possible in the > > + * following case: > > + * > > + * - filesystem A writes data through filesystem B > > + * - filesystem A has dirty pages over dirty_thresh > > + * - writeback is started, this triggers a write in B > > + * - balance_dirty_pages() is called synchronously > > + * - the write to B blocks > > + * - the writeback completes, but dirty is still over threshold > > + * - the blocking write prevents futher writes from happening > > + */ > > + if (atomic_long_read(&bdi->nr_dirty) + > > + atomic_long_read(&bdi->nr_writeback) < 16) > > + break; > > + > > The problem seems to that little "- the write to B blocks". > > How come it blocks? I mean, if we cannot retire writes to that filesystem > then we're screwed anyway.
Sorry about the sloppy description. I mean, it's not the lowlevel write that will block, but rather the VFS one (generic_file_aio_write). It will block (or rather loop forever with 0.1 second sleeps) in balance_dirty_pages(). That means, that for this inode, i_mutex is held and no other writer can continue the work. Miklos - 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/
