Re: [PATCH 3/6] writeback: sync expired inodes first in background writeback

Wu Fengguang
2011-04-21T04:10:17Z

> > Still, given wb_writeback() is the only caller of both
> > __writeback_inodes_sb and writeback_inodes_wb(), I'm wondering if
> > moving the queue_io calls up into wb_writeback() would clean up this
> > logic somewhat. I think Jan mentioned doing something like this as
> > well elsewhere in the thread...
>
> Unfortunately they call queue_io() inside the lock..

OK, let's try moving up the lock too. Do you like this change? :)

Thanks,
Fengguang
---
fs/fs-writeback.c | 22 ++++++----------------
mm/backing-dev.c | 4 ++++
2 files changed, 10 insertions(+), 16 deletions(-)

--- linux-next.orig/fs/fs-writeback.c 2011-04-21 12:04:02.000000000 +0800
+++ linux-next/fs/fs-writeback.c 2011-04-21 12:05:54.000000000 +0800
@@ -591,7 +591,6 @@ void writeback_inodes_wb(struct bdi_writ

if (!wbc->wb_start)
wbc->wb_start = jiffies; /* livelock avoidance */
- spin_lock(&inode_wb_list_lock);

if (list_empty(&wb->b_io))
queue_io(wb, wbc);
@@ -610,22 +609,9 @@ void writeback_inodes_wb(struct bdi_writ
if (ret)
break;
}
- spin_unlock(&inode_wb_list_lock);
/* Leave any unwritten inodes on b_io */
}

-static void __writeback_inodes_sb(struct super_block *sb,
- struct bdi_writeback *wb, struct writeback_control *wbc)
-{
- WARN_ON(!rwsem_is_locked(&sb->s_umount));
-
- spin_lock(&inode_wb_list_lock);
- if (list_empty(&wb->b_io))
- queue_io(wb, wbc);
- writeback_sb_inodes(sb, wb, wbc, true);
- spin_unlock(&inode_wb_list_lock);
-}
-
static inline bool over_bground_thresh(void)
{
unsigned long background_thresh, dirty_thresh;
@@ -652,7 +638,7 @@ static unsigned long writeback_chunk_siz
* The intended call sequence for WB_SYNC_ALL writeback is:
*
* wb_writeback()
- * __writeback_inodes_sb() <== called only once
+ * writeback_sb_inodes() <== called only once
* write_cache_pages() <== called once for each inode
* (quickly) tag currently dirty pages
* (maybe slowly) sync all tagged pages
@@ -742,10 +728,14 @@ static long wb_writeback(struct bdi_writ

retry:
trace_wbc_writeback_start(&wbc, wb->bdi);
+ spin_lock(&inode_wb_list_lock);
+ if (list_empty(&wb->b_io))
+ queue_io(wb, wbc);
if (work->sb)
- __writeback_inodes_sb(work->sb, wb, &wbc);
+ writeback_sb_inodes(work->sb, wb, &wbc, true);
else
writeback_inodes_wb(wb, &wbc);
+ spin_unlock(&inode_wb_list_lock);
trace_wbc_writeback_written(&wbc, wb->bdi);

bdi_update_write_bandwidth(wb->bdi, wbc.wb_start);
--- linux-next.orig/mm/backing-dev.c 2011-04-21 12:06:02.000000000 +0800
+++ linux-next/mm/backing-dev.c 2011-04-21 12:06:31.000000000 +0800
@@ -268,7 +268,11 @@ static void bdi_flush_io(struct backing_
.nr_to_write = 1024,
};

+ spin_lock(&inode_wb_list_lock);
+ if (list_empty(&wb->b_io))
+ queue_io(wb, wbc);
writeback_inodes_wb(&bdi->wb, &wbc);
+ spin_unlock(&inode_wb_list_lock);
}

/*