mm: frontswap: split out __frontswap_unuse_pages

An attempt at making frontswap_shrink shorter and more readable. This patch
splits out walking through the swap list to find an entry with enough
pages to unuse.

Also, assert that the internal __frontswap_unuse_pages is called under swap
lock, since that part of code was previously directly happen inside the lock.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/mm/frontswap.c b/mm/frontswap.c
index 5faf840f872614d6d33e2391bd0795a5a6333685..faa43b7eea6faec163234defc5d7318290a94d6a 100644 (file)
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -230,6 +230,41 @@ static unsigned long __frontswap_curr_pages(void)
        return totalpages;
 }
 
+static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
+                                       int *swapid)
+{
+       int ret = -EINVAL;
+       struct swap_info_struct *si = NULL;
+       int si_frontswap_pages;
+       unsigned long total_pages_to_unuse = total;
+       unsigned long pages = 0, pages_to_unuse = 0;
+       int type;
+
+       assert_spin_locked(&swap_lock);
+       for (type = swap_list.head; type >= 0; type = si->next) {
+               si = swap_info[type];
+               si_frontswap_pages = atomic_read(&si->frontswap_pages);
+               if (total_pages_to_unuse < si_frontswap_pages) {
+                       pages = pages_to_unuse = total_pages_to_unuse;
+               } else {
+                       pages = si_frontswap_pages;
+                       pages_to_unuse = 0; /* unuse all */
+               }
+               /* ensure there is enough RAM to fetch pages from frontswap */
+               if (security_vm_enough_memory_mm(current->mm, pages)) {
+                       ret = -ENOMEM;
+                       continue;
+               }
+               vm_unacct_memory(pages);
+               *unused = pages_to_unuse;
+               *swapid = type;
+               ret = 0;
+               break;
+       }
+
+       return ret;
+}
+
 /*
  * Frontswap, like a true swap device, may unnecessarily retain pages
  * under certain circumstances; "shrink" frontswap is essentially a
@@ -240,11 +275,9 @@ static unsigned long __frontswap_curr_pages(void)
  */
 void frontswap_shrink(unsigned long target_pages)
 {
-       struct swap_info_struct *si = NULL;
-       int si_frontswap_pages;
        unsigned long total_pages = 0, total_pages_to_unuse;
-       unsigned long pages = 0, pages_to_unuse = 0;
-       int type;
+       unsigned long pages_to_unuse = 0;
+       int type, ret;
        bool locked = false;
 
        /*
@@ -258,22 +291,8 @@ void frontswap_shrink(unsigned long target_pages)
        if (total_pages <= target_pages)
                goto out;
        total_pages_to_unuse = total_pages - target_pages;
-       for (type = swap_list.head; type >= 0; type = si->next) {
-               si = swap_info[type];
-               si_frontswap_pages = atomic_read(&si->frontswap_pages);
-               if (total_pages_to_unuse < si_frontswap_pages) {
-                       pages = pages_to_unuse = total_pages_to_unuse;
-               } else {
-                       pages = si_frontswap_pages;
-                       pages_to_unuse = 0; /* unuse all */
-               }
-               /* ensure there is enough RAM to fetch pages from frontswap */
-               if (security_vm_enough_memory_mm(current->mm, pages))
-                       continue;
-               vm_unacct_memory(pages);
-               break;
-       }
-       if (type < 0)
+       ret = __frontswap_unuse_pages(total_pages_to_unuse, &pages_to_unuse, &type);
+       if (ret < 0)
                goto out;
        locked = false;
        spin_unlock(&swap_lock);