[REF PATCH] mm/swap: fix swapon failure

[Alex Shi <alex.shi@linux.alibaba.com>]

One of my VM guest has a swapon issue:
root #swapon -v -f /swap1
swapon /swap1
swapon: /swap1: found swap signature: version 1, page-size 4, same byte order
swapon: /swap1: pagesize=4096, swapsize=1607467008, devsize=1607467008
swapon: /swap1: swapon failed: Invalid argument

and bisection report commit 822bca52ee7e "mm/swapfile.c: fix potential
memory leak in sys_swapon" cause the trouble.

Go through the context I found the exit_swap_address_space(p->type)
shouldn't be used in good result path. So just move it to error path.

Fixes: 822bca52ee7e ("mm/swapfile.c: fix potential memory leak in
sys_swapon")
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrew Morton <akpm@linux-foundation.org> 
Cc: "Darrick J. Wong" <darrick.wong@oracle.com> 
Cc: Miaohe Lin <linmiaohe@huawei.com> 
Cc: Hugh Dickins <hughd@google.com>
Cc: linux-mm@kvack.org 
Cc: linux-kernel@vger.kernel.org 
---
 mm/swapfile.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index c8966b8fc6ac..1ac1f737fee3 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3339,7 +3339,8 @@ static bool swap_discardable(struct swap_info_struct *si)
 	error = inode_drain_writes(inode);
 	if (error) {
 		inode->i_flags &= ~S_SWAPFILE;
-		goto free_swap_address_space;
+		exit_swap_address_space(p->type);
+		goto bad_swap_unlock_inode;
 	}
 
 	mutex_lock(&swapon_mutex);
@@ -3364,8 +3365,6 @@ static bool swap_discardable(struct swap_info_struct *si)
 
 	error = 0;
 	goto out;
-free_swap_address_space:
-	exit_swap_address_space(p->type);
 bad_swap_unlock_inode:
 	inode_unlock(inode);
 bad_swap:
-- 
1.8.3.1