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Date: Wed, 29 Jul 2009 07:11:10 -0700
From: Martin Bligh <mbligh@...gle.com>
To: Wu Fengguang <fengguang.wu@...el.com>
Cc: Chad Talbott <ctalbott@...gle.com>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, Michael Rubin <mrubin@...gle.com>,
Andrew Morton <akpm@...gle.com>, sandeen@...hat.com,
Michael Davidson <md@...gle.com>
Subject: Re: Bug in kernel 2.6.31, Slow wb_kupdate writeout
> --- mm.orig/fs/fs-writeback.c
> +++ mm/fs/fs-writeback.c
> @@ -325,7 +325,8 @@ __sync_single_inode(struct inode *inode,
> * soon as the queue becomes uncongested.
> */
> inode->i_state |= I_DIRTY_PAGES;
> - if (wbc->nr_to_write <= 0) {
> + if (wbc->nr_to_write <= 0 ||
> + wbc->encountered_congestion) {
> /*
> * slice used up: queue for next turn
> */
>
That's not sufficient - it only the problem in the wb_kupdate path. If you want
to be more conservative, how about we do this?
--- linux-2.6.30/fs/fs-writeback.c.old 2009-07-29 00:08:29.000000000 -0700
+++ linux-2.6.30/fs/fs-writeback.c 2009-07-29 07:08:48.000000000 -0700
@@ -323,43 +323,14 @@ __sync_single_inode(struct inode *inode,
* We didn't write back all the pages. nfs_writepages(
)
* sometimes bales out without doing anything. Redirty
* the inode; Move it from s_io onto s_more_io/s_dirty.
+ * It may well have just encountered congestion
*/
- /*
- * akpm: if the caller was the kupdate function we put
- * this inode at the head of s_dirty so it gets first
- * consideration. Otherwise, move it to the tail, for
- * the reasons described there. I'm not really sure
- * how much sense this makes. Presumably I had a good
- * reasons for doing it this way, and I'd rather not
- * muck with it at present.
- */
- if (wbc->for_kupdate) {
- /*
- * For the kupdate function we move the inode
- * to s_more_io so it will get more writeout as
- * soon as the queue becomes uncongested.
- */
- inode->i_state |= I_DIRTY_PAGES;
- if (wbc->nr_to_write <= 0) {
- /*
- * slice used up: queue for next turn
- */
- requeue_io(inode);
- } else {
- /*
- * somehow blocked: retry later
- */
- redirty_tail(inode);
- }
- } else {
- /*
- * Otherwise fully redirty the inode so that
- * other inodes on this superblock will get som
e
- * writeout. Otherwise heavy writing to one
- * file would indefinitely suspend writeout of
- * all the other files.
- */
- inode->i_state |= I_DIRTY_PAGES;
+ inode->i_state |= I_DIRTY_PAGES;
+ if (wbc->nr_to_write <= 0 || /* sliced used up */
+ wbc->encountered_congestion)
+ requeue_io(inode);
+ else {
+ /* somehow blocked: retry later */
redirty_tail(inode);
}
} else if (inode->i_state & I_DIRTY) {
--
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