linux-kernel - [PATCH v2 8/8] mm/swap: Enable swap slots cache usage

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Message-Id: <24619a5b1749f6fb62de70d9def6d20d25229a65.1477004978.git.tim.c.chen@linux.intel.com>
Date:   Thu, 20 Oct 2016 16:31:47 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Ying Huang <ying.huang@...el.com>, dave.hansen@...el.com,
        ak@...ux.intel.com, aaron.lu@...el.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, 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.dev@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Hillf Danton <hillf.zj@...baba-inc.com>
Subject: [PATCH v2 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 | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index caf9fe6..e98c725 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))
@@ -2153,10 +2154,13 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	spin_lock(&swap_lock);
 	plist_for_each_entry(p, &swap_active_head, list) {
 		if (p->flags & SWP_WRITEOK) {
-			if (p->swap_file->f_mapping == mapping) {
+			if (p->swap_file->f_mapping == mapping)
 				found = 1;
+			else
+				++has_swap;
+			/* there is another swap device left? */
+			if (found && has_swap)
 				break;
-			}
 		}
 	}
 	if (!found) {
@@ -2275,6 +2279,8 @@ out_dput:
 	filp_close(victim, NULL);
 out:
 	putname(pathname);
+	if (has_swap)
+		reenable_swap_slots_cache();
 	return err;
 }
 
@@ -2692,6 +2698,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	enable_swap_slot_caches();
 	p = alloc_swap_info();
 	if (IS_ERR(p))
 		return PTR_ERR(p);
-- 
2.5.5