mm/swap: enable swap slots cache usage

Initialize swap slots cache and enable it on swap on.  Drain all swap
slots on swap off.

Link: http://lkml.kernel.org/r/07cbc94882fa95d4ac3cfc50b8dce0b1ec231b93.1484082593.git.tim.c.chen@linux.intel.com
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net> escreveu:
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 30a90fd140b7..2cac12cc9abe 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2190,6 +2190,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
         spin_unlock(&p->lock);
         spin_unlock(&swap_lock);
 
+        disable_swap_slots_cache_lock();
+
         set_current_oom_origin();
         err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
         clear_current_oom_origin();
@@ -2197,9 +2199,12 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
         if (err) {
                 /* re-insert swap space back into swap_list */
                 reinsert_swap_info(p);
+                reenable_swap_slots_cache_unlock();
                 goto out_dput;
         }
 
+        reenable_swap_slots_cache_unlock();
+
         flush_work(&p->discard_work);
 
         destroy_swap_extents(p);
@@ -2886,6 +2891,8 @@ out:
                 putname(name);
         if (inode && S_ISREG(inode->i_mode))
                 inode_unlock(inode);
+        if (!error)
+                enable_swap_slots_cache();
         return error;
 }