f2fs: wait discard IO completion without cmd_lock held

Wait discard IO completion outside cmd_lock to avoid long latency
of holding cmd_lock in IO busy scenario.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 24a2d5ab6f456379cdabb2e5a58323a3b166517e..a8f4c8146714181dcfdc8ae4a96408fa2a340983 100644 (file)
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -997,17 +997,34 @@ static void __wait_discard_cmd(struct f2fs_sb_info *sbi, bool wait_cond)
        struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
        struct list_head *wait_list = &(dcc->wait_list);
        struct discard_cmd *dc, *tmp;
+       bool need_wait;
+
+next:
+       need_wait = false;
 
        mutex_lock(&dcc->cmd_lock);
        list_for_each_entry_safe(dc, tmp, wait_list, list) {
-               if (!wait_cond || dc->state == D_DONE) {
-                       if (dc->ref)
-                               continue;
+               if (!wait_cond || (dc->state == D_DONE && !dc->ref)) {
                        wait_for_completion_io(&dc->wait);
                        __remove_discard_cmd(sbi, dc);
+               } else {
+                       dc->ref++;
+                       need_wait = true;
+                       break;
                }
        }
        mutex_unlock(&dcc->cmd_lock);
+
+       if (need_wait) {
+               wait_for_completion_io(&dc->wait);
+               mutex_lock(&dcc->cmd_lock);
+               f2fs_bug_on(sbi, dc->state != D_DONE);
+               dc->ref--;
+               if (!dc->ref)
+                       __remove_discard_cmd(sbi, dc);
+               mutex_unlock(&dcc->cmd_lock);
+               goto next;
+       }
 }
 
 /* This should be covered by global mutex, &sit_i->sentry_lock */