Convert to requeue_io_wait() for case:
- kupdate cannot write all pages due to some blocking condition;
- during sync, a file is being written to too fast, starving other
files.
In the case of sync, requeue_io_wait() can break the starvation because the
inode requeued into s_more_io_wait will be served _after_ normal inodes, hence
won't stand in the way of other inodes in the next run.
Cc: Michael Rubin <mrubin@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
---
fs/fs-writeback.c | 33 ++++++++-------------------------
1 files changed, 8 insertions(+), 25 deletions(-)
--- linux-mm.orig/fs/fs-writeback.c
+++ linux-mm/fs/fs-writeback.c
@@ -275,37 +275,20 @@ __sync_single_inode(struct inode *inode,
mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
/*
* 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.
+ * sometimes bales out without doing anything.
*/
- /*
- * 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) {
+ inode->i_state |= I_DIRTY_PAGES;
+ if (wbc->for_kupdate && wbc->nr_to_write <= 0)
/*
- * 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.
+ * slice used up: queue for next turn
*/
- inode->i_state |= I_DIRTY_PAGES;
requeue_io(inode);
- } else {
+ else
/*
- * Otherwise fully redirty the inode so that
- * other inodes on this superblock will get some
- * writeout. Otherwise heavy writing to one
- * file would indefinitely suspend writeout of
- * all the other files.
+ * 1) somehow blocked in kupdate: retry later
+ * 2) fast writer during sync: give others a try
*/
- inode->i_state |= I_DIRTY_PAGES;
- redirty_tail(inode);
- }
+ requeue_io_wait(inode);
} else if (inode->i_state & I_DIRTY) {
/*
* Someone redirtied the inode while were writing back
--
-
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