f2fs: Fix deadlock in shutdown ioctl

f2fs_ioc_shutdown() ioctl gets stuck in the below path
when issued with F2FS_GOING_DOWN_FULLSYNC option.

__switch_to+0x90/0xc4
percpu_down_write+0x8c/0xc0
freeze_super+0xec/0x1e4
freeze_bdev+0xc4/0xcc
f2fs_ioctl+0xc0c/0x1ce0
f2fs_compat_ioctl+0x98/0x1f0

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 18ceb38340e0b6479e64eaa5502996ccbd96eb75..9ea8bca1866609ecb15eb5f13031f9f1a88a001c 100644 (file)
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1857,9 +1857,11 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
        if (get_user(in, (__u32 __user *)arg))
                return -EFAULT;
 
-       ret = mnt_want_write_file(filp);
-       if (ret)
-               return ret;
+       if (in != F2FS_GOING_DOWN_FULLSYNC) {
+               ret = mnt_want_write_file(filp);
+               if (ret)
+                       return ret;
+       }
 
        switch (in) {
        case F2FS_GOING_DOWN_FULLSYNC:
@@ -1900,7 +1902,8 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
 
        f2fs_update_time(sbi, REQ_TIME);
 out:
-       mnt_drop_write_file(filp);
+       if (in != F2FS_GOING_DOWN_FULLSYNC)
+               mnt_drop_write_file(filp);
        return ret;
 }