Writeback of an inode can be stalled by things like internal fs locks being
held. So in case we didn't write anything during a pass through b_io list,
just wait for a moment and try again. When retrying is fruitless for a long
time, or we have some other work to do, we just stop current work to avoid
blocking flusher thread.
CC: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Reviewed-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/fs-writeback.c | 39 +++++++++++++++++++++++++++------------
1 files changed, 27 insertions(+), 12 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 04cf3b9..b619f3a 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -699,8 +699,11 @@ static long wb_writeback(struct bdi_writeback *wb,
unsigned long wb_start = jiffies;
long nr_pages = work->nr_pages;
unsigned long oldest_jif;
- struct inode *inode;
long progress;
+ long pause = 1;
+ long max_pause = dirty_writeback_interval ?
+ msecs_to_jiffies(dirty_writeback_interval * 10) :
+ HZ;
oldest_jif = jiffies;
work->older_than_this = &oldest_jif;
@@ -755,25 +758,37 @@ static long wb_writeback(struct bdi_writeback *wb,
* mean the overall work is done. So we keep looping as long
* as made some progress on cleaning pages or inodes.
*/
- if (progress)
+ if (progress) {
+ pause = 1;
continue;
+ }
/*
* No more inodes for IO, bail
*/
if (list_empty(&wb->b_more_io))
break;
/*
- * Nothing written. Wait for some inode to
- * become available for writeback. Otherwise
- * we'll just busyloop.
+ * Nothing written (some internal fs locks were unavailable or
+ * inode was under writeback from balance_dirty_pages() or
+ * similar conditions).
*/
- if (!list_empty(&wb->b_more_io)) {
- trace_writeback_wait(wb->bdi, work);
- inode = wb_inode(wb->b_more_io.prev);
- spin_lock(&inode->i_lock);
- inode_wait_for_writeback(inode, wb);
- spin_unlock(&inode->i_lock);
- }
+ /* If there's some other work to do, proceed with it... */
+ if (!list_empty(&wb->bdi->work_list) ||
+ (!work->for_background && over_bground_thresh()))
+ break;
+ /*
+ * Wait for a while to avoid busylooping unless we waited for
+ * so long it does not make sense to retry anymore.
+ */
+ if (pause > max_pause)
+ break;
+ trace_writeback_wait(wb->bdi, work);
+ spin_unlock(&wb->list_lock);
+ __set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(pause);
+ if (pause < max_pause)
+ pause <<= 1;
+ spin_lock(&wb->list_lock);
}
spin_unlock(&wb->list_lock);
--
1.7.1
--
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