[PATCH v2] f2fs: Fix deadlock in shutdown ioctl

[Sahitya Tummala <stummala@codeaurora.org>]

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>
---
v2:
remove lock coverage for only F2FS_GOING_DOWN_FULLSYNC case as suggested by Chao.

 fs/f2fs/file.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 6b94f19..5a132c9 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1857,6 +1857,7 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
 
 	switch (in) {
 	case F2FS_GOING_DOWN_FULLSYNC:
+		mnt_drop_write_file(filp);
 		sb = freeze_bdev(sb->s_bdev);
 		if (IS_ERR(sb)) {
 			ret = PTR_ERR(sb);
@@ -1894,7 +1895,8 @@ 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;
 }
 
-- 
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