z3fold: fix potential race in z3fold_reclaim_page
authorVitaly Wool <vitalywool@gmail.com>
Tue, 3 Oct 2017 23:14:47 +0000 (16:14 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 4 Oct 2017 00:54:24 +0000 (17:54 -0700)
commitd5567c9df1ef001b2a7e6684b3b3498371ee4cae
treeb3ce7486314ee88b61cb34f010947c6b40f8548f
parentd9d73e81fe82fdf4ee65a48c26531edc04108349
z3fold: fix potential race in z3fold_reclaim_page

It is possible that on a (partially) unsuccessful page reclaim,
kref_put() called in z3fold_reclaim_page() does not yield page release,
but the page is released shortly afterwards by another thread.  Then
z3fold_reclaim_page() would try to list_add() that (released) page again
which is obviously a bug.

To avoid that, spin_lock() has to be taken earlier, before the
kref_put() call mentioned earlier.

Link: http://lkml.kernel.org/r/20170913162937.bfff21c7d12b12a5f47639fd@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/z3fold.c