| Message ID | 2af066124843c9a7e2b831c57dc9f57c0603254b.1451574005.git.zhaolei@cn.fujitsu.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c index c65b42f..fb21bf0 100644 --- a/fs/btrfs/reada.c +++ b/fs/btrfs/reada.c @@ -713,7 +713,7 @@ static int reada_start_machine_dev(struct btrfs_fs_info *fs_info, logical = re->logical; spin_lock(&re->lock); - if (re->scheduled_for == NULL) { + if (!re->scheduled_for && !list_empty(&re->extctl)) { re->scheduled_for = dev; need_kick = 1; }
We can see following loop(10000 times) in trace_log: [ 75.416137] ZL_DEBUG: reada_start_machine_dev:730: pid=771 comm=kworker/u2:3 re->ref_cnt ffff88003741e0c0 1 -> 2 [ 75.417413] ZL_DEBUG: reada_extent_put:524: pid=771 comm=kworker/u2:3 re = ffff88003741e0c0, refcnt = 2 -> 1 [ 75.418611] ZL_DEBUG: __readahead_hook:129: pid=771 comm=kworker/u2:3 re->ref_cnt ffff88003741e0c0 1 -> 2 [ 75.419793] ZL_DEBUG: reada_extent_put:524: pid=771 comm=kworker/u2:3 re = ffff88003741e0c0, refcnt = 2 -> 1 [ 75.421016] ZL_DEBUG: reada_start_machine_dev:730: pid=771 comm=kworker/u2:3 re->ref_cnt ffff88003741e0c0 1 -> 2 [ 75.422324] ZL_DEBUG: reada_extent_put:524: pid=771 comm=kworker/u2:3 re = ffff88003741e0c0, refcnt = 2 -> 1 [ 75.423661] ZL_DEBUG: __readahead_hook:129: pid=771 comm=kworker/u2:3 re->ref_cnt ffff88003741e0c0 1 -> 2 [ 75.424882] ZL_DEBUG: reada_extent_put:524: pid=771 comm=kworker/u2:3 re = ffff88003741e0c0, refcnt = 2 -> 1 ...(10000 times) [ 124.101672] ZL_DEBUG: reada_start_machine_dev:730: pid=771 comm=kworker/u2:3 re->ref_cnt ffff88003741e0c0 1 -> 2 [ 124.102850] ZL_DEBUG: reada_extent_put:524: pid=771 comm=kworker/u2:3 re = ffff88003741e0c0, refcnt = 2 -> 1 [ 124.104008] ZL_DEBUG: __readahead_hook:129: pid=771 comm=kworker/u2:3 re->ref_cnt ffff88003741e0c0 1 -> 2 [ 124.105121] ZL_DEBUG: reada_extent_put:524: pid=771 comm=kworker/u2:3 re = ffff88003741e0c0, refcnt = 2 -> 1 Reason: If more than one user trigger reada in same extent, the first task finished setting of reada data struct and call reada_start_machine() to start, and the second task only add a ref_count but have not add reada_extctl struct completely, the reada_extent can not finished all jobs, and will be selected in __reada_start_machine() for 10000 times(total times in __reada_start_machine()). Fix: For a reada_extent without job, we don't need to run it, just return 0 to let caller break. Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com> --- fs/btrfs/reada.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)