[PATCH 4/5] fs: make FSCONFIG_CMD_RECONFIGURE killable on s_umount

[Josef Bacik]

fsconfig(2) with FSCONFIG_CMD_RECONFIGURE is the remount of the new mount
API, and like mount(2) with MS_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().  A wait which is cut short is treated like any
other failure to reconfigure, the context ends up in FS_CONTEXT_FAILED.

Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
 fs/fsopen.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/fsopen.c b/fs/fsopen.c
index 70024870fefa..c139cec2f1fe 100644
--- a/fs/fsopen.c
+++ b/fs/fsopen.c
@@ -267,9 +267,11 @@ static int vfs_cmd_reconfigure(struct fs_context *fc)
 		return -EPERM;
 	}
 
-	down_write(&sb->s_umount);
-	ret = reconfigure_super(fc);
-	up_write(&sb->s_umount);
+	ret = down_write_killable(&sb->s_umount);
+	if (!ret) {
+		ret = reconfigure_super(fc);
+		up_write(&sb->s_umount);
+	}
 	if (ret) {
 		fc->phase = FS_CONTEXT_FAILED;
 		return ret;

-- 
2.55.0