[PATCH 5/5] fs: make umount(2) of the root killable on s_umount

[Josef Bacik]

Unmounting the root of the caller doesn't unmount anything, it remounts
the filesystem read-only.  So it has the same problem as a remount: it
waits for s_umount in D state, can't be killed, and keeps every later
reader of the lock waiting behind it.

Use down_write_killable() in do_umount_root().

Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
 fs/namespace.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 837f531e494b..b874accabf76 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1897,9 +1897,11 @@ static void shrink_submounts(struct mount *mnt);
 
 static int do_umount_root(struct super_block *sb)
 {
-	int ret = 0;
+	int ret;
 
-	down_write(&sb->s_umount);
+	ret = down_write_killable(&sb->s_umount);
+	if (ret)
+		return ret;
 	if (!sb_rdonly(sb)) {
 		struct fs_context *fc;
 

-- 
2.55.0