lkml.org 
[lkml]   [2007]   [Feb]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: dirty balancing deadlock
From
Date
How about this?

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;
+
if (!dirty_exceeded)
dirty_exceeded = 1;

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2007-02-19 18:15    [W:0.136 / U:0.208 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site