sys_swapon: separate final enabling of the swapfile
The block in sys_swapon which does the final adjustments to the
swap_info_struct and to swap_list is the same as the block which
re-inserts it again at sys_swapoff on failure of try_to_unuse(). Move
this code to a separate function, and use it both in sys_swapon and
sys_swapoff.
Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
Tested-by: Eric B Munson <emunson@mgebm.net>
Acked-by: Eric B Munson <emunson@mgebm.net>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 465d972..7243044 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1550,6 +1550,36 @@
goto out;
}
+static void enable_swap_info(struct swap_info_struct *p, int prio,
+ unsigned char *swap_map)
+{
+ int i, prev;
+
+ spin_lock(&swap_lock);
+ if (prio >= 0)
+ p->prio = prio;
+ else
+ p->prio = --least_priority;
+ p->swap_map = swap_map;
+ p->flags |= SWP_WRITEOK;
+ nr_swap_pages += p->pages;
+ total_swap_pages += p->pages;
+
+ /* insert swap space into swap_list: */
+ prev = -1;
+ for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
+ if (p->prio >= swap_info[i]->prio)
+ break;
+ prev = i;
+ }
+ p->next = i;
+ if (prev < 0)
+ swap_list.head = swap_list.next = p->type;
+ else
+ swap_info[prev]->next = p->type;
+ spin_unlock(&swap_lock);
+}
+
SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
{
struct swap_info_struct *p = NULL;
@@ -1621,26 +1651,14 @@
current->flags &= ~PF_OOM_ORIGIN;
if (err) {
+ /*
+ * reading p->prio and p->swap_map outside the lock is
+ * safe here because only sys_swapon and sys_swapoff
+ * change them, and there can be no other sys_swapon or
+ * sys_swapoff for this swap_info_struct at this point.
+ */
/* re-insert swap space back into swap_list */
- spin_lock(&swap_lock);
- if (p->prio < 0)
- p->prio = --least_priority;
- p->flags |= SWP_WRITEOK;
- nr_swap_pages += p->pages;
- total_swap_pages += p->pages;
-
- prev = -1;
- for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
- if (p->prio >= swap_info[i]->prio)
- break;
- prev = i;
- }
- p->next = i;
- if (prev < 0)
- swap_list.head = swap_list.next = type;
- else
- swap_info[prev]->next = type;
- spin_unlock(&swap_lock);
+ enable_swap_info(p, p->prio, p->swap_map);
goto out_dput;
}
@@ -2037,7 +2055,8 @@
char *name;
struct file *swap_file = NULL;
struct address_space *mapping;
- int i, prev;
+ int i;
+ int prio;
int error;
union swap_header *swap_header;
int nr_extents;
@@ -2134,30 +2153,11 @@
}
mutex_lock(&swapon_mutex);
- spin_lock(&swap_lock);
+ prio = -1;
if (swap_flags & SWAP_FLAG_PREFER)
- p->prio =
+ prio =
(swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
- else
- p->prio = --least_priority;
- p->swap_map = swap_map;
- p->flags |= SWP_WRITEOK;
- nr_swap_pages += p->pages;
- total_swap_pages += p->pages;
-
- /* insert swap space into swap_list: */
- prev = -1;
- for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
- if (p->prio >= swap_info[i]->prio)
- break;
- prev = i;
- }
- p->next = i;
- if (prev < 0)
- swap_list.head = swap_list.next = p->type;
- else
- swap_info[prev]->next = p->type;
- spin_unlock(&swap_lock);
+ enable_swap_info(p, prio, swap_map);
printk(KERN_INFO "Adding %uk swap on %s. "
"Priority:%d extents:%d across:%lluk %s%s\n",