The list_lock was moved outside the for loop by commit
e8dfc30582995ae12454cda517b17d6294175b07 ("writeback: elevate queue_io()
into wb_writeback())", however, the commit log says "No behavior change", so
it sounds safe to have the list_lock acquired inside the for loop as it did
before.
Leave tracepoints outside the critical area since tracepoints already have
preempt disabled.
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxx>
---
Tested with ltp on 8 cores Cortex-A57 machine.
fs/fs-writeback.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 1f76d89..9b7b5f6 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1623,7 +1623,6 @@ static long wb_writeback(struct bdi_writeback *wb,
work->older_than_this = &oldest_jif;
blk_start_plug(&plug);
- spin_lock(&wb->list_lock);
for (;;) {
/*
* Stop writeback when nr_pages has been consumed
@@ -1661,15 +1660,19 @@ static long wb_writeback(struct bdi_writeback *wb,
oldest_jif = jiffies;
trace_writeback_start(wb, work);
+
+ spin_lock(&wb->list_lock);
if (list_empty(&wb->b_io))
queue_io(wb, work);
if (work->sb)
progress = writeback_sb_inodes(work->sb, wb, work);
else
progress = __writeback_inodes_wb(wb, work);
- trace_writeback_written(wb, work);
wb_update_bandwidth(wb, wb_start);
+ spin_unlock(&wb->list_lock);
+
+ trace_writeback_written(wb, work);
/*
* Did we write something? Try for more
@@ -1693,15 +1696,14 @@ static long wb_writeback(struct bdi_writeback *wb,
*/
if (!list_empty(&wb->b_more_io)) {
trace_writeback_wait(wb, work);
+ spin_lock(&wb->list_lock);
inode = wb_inode(wb->b_more_io.prev);
- spin_lock(&inode->i_lock);
spin_unlock(&wb->list_lock);
+ spin_lock(&inode->i_lock);
/* This function drops i_lock... */
inode_sleep_on_writeback(inode);
- spin_lock(&wb->list_lock);
}
}
- spin_unlock(&wb->list_lock);
blk_finish_plug(&plug);
return nr_pages - work->nr_pages;
--
2.0.2
--
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