[PATCH] f2fs: stop discard thread in prior during umount

[Chao Yu]

This patch resolves kernel panic for xfstests/081, caused by recent f2fs_bug_on

 f2fs: add f2fs_bug_on in __remove_discard_cmd

For fixing, we will stop discard thread in prior in put_super, in order to
avoid racing in between referrer and releaser.

Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
Signed-off-by: Chao Yu <yuch...@huawei.com>
---
 fs/f2fs/segment.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 9a44aca8d2c5..8e4b70b4174d 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1063,9 +1063,22 @@ void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, 
block_t blkaddr)
                __wait_one_discard_bio(sbi, dc);
 }
 
+static void stop_discard_thread(struct f2fs_sb_info *sbi)
+{
+       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+
+       if (dcc->f2fs_issue_discard) {
+               struct task_struct *discard_thread = dcc->f2fs_issue_discard;
+
+               dcc->f2fs_issue_discard = NULL;
+               kthread_stop(discard_thread);
+       }
+}
+
 /* This comes from f2fs_put_super */
 void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
 {
+       stop_discard_thread(sbi);
        __issue_discard_cmd(sbi, false);
        __wait_discard_cmd(sbi, false);
 }
@@ -1420,12 +1433,7 @@ static void destroy_discard_cmd_control(struct 
f2fs_sb_info *sbi)
        if (!dcc)
                return;
 
-       if (dcc->f2fs_issue_discard) {
-               struct task_struct *discard_thread = dcc->f2fs_issue_discard;
-
-               dcc->f2fs_issue_discard = NULL;
-               kthread_stop(discard_thread);
-       }
+       stop_discard_thread(sbi);
 
        kfree(dcc);
        SM_I(sbi)->dcc_info = NULL;
-- 
2.13.1.388.g69e6b9b4f4a9