sys_swapon: fix inode locking

A conflict between 52c50567d8ab ("mm: swap: unlock swapfile inode mutex
before closing file on bad swapfiles") and 83ef99befc32 ("sys_swapon:
remove did_down variable") caused a double unlock of the inode mutex
(once in bad_swap: before the filp_close, once at the end just before
returning).

The patch which added the extra unlock cleared did_down to avoid
unlocking twice, but the other patch removed the did_down variable.

To fix, set inode to NULL after the first unlock, since it will be used
after that point only for the final unlock.

While checking this patch, I found a path which could unlock without
locking, in case the same inode was added as a swapfile twice. To fix,
move the setting of the inode variable further down, to just before
claim_swapfile, which will lock the inode before doing anything else.

Cc: Mel Gorman <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Eric B Munson <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Andrew Morton <[email protected]>
Signed-off-by: Cesar Eduardo Barros <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions