linux-kernel - [PATCH 8/8] mm/swap: Enable swap slots cache usage

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Date:   Tue, 27 Sep 2016 10:19:10 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     dave.hansen@...el.com, andi.kleen@...el.com, aaron.lu@...el.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Huang Ying <ying.huang@...el.com>,
        Hugh Dickins <hughd@...gle.com>, Shaohua Li <shli@...nel.org>,
        Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vladimir Davydov <vdavydov@...tuozzo.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>
Subject: [PATCH 8/8] mm/swap: Enable swap slots cache usage

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

Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
---
 mm/swapfile.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index fa6935f..985215b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2132,7 +2132,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	struct address_space *mapping;
 	struct inode *inode;
 	struct filename *pathname;
-	int err, found = 0;
+	int err, found = 0, has_swap = 0;
 	unsigned int old_block_size;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -2144,6 +2144,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	if (IS_ERR(pathname))
 		return PTR_ERR(pathname);
 
+	disable_swap_slots_cache();
 	victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
 	err = PTR_ERR(victim);
 	if (IS_ERR(victim))
@@ -2152,6 +2153,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	mapping = victim->f_mapping;
 	spin_lock(&swap_lock);
 	plist_for_each_entry(p, &swap_active_head, list) {
+		has_swap = 1;
 		if (p->flags & SWP_WRITEOK) {
 			if (p->swap_file->f_mapping == mapping) {
 				found = 1;
@@ -2275,6 +2277,8 @@ out_dput:
 	filp_close(victim, NULL);
 out:
 	putname(pathname);
+	if (has_swap)
+		reenable_swap_slots_cache();
 	return err;
 }
 
@@ -2692,6 +2696,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	init_swap_slot_caches();
 	p = alloc_swap_info();
 	if (IS_ERR(p))
 		return PTR_ERR(p);
-- 
2.5.5