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authorCesar Eduardo Barros <cesarb@cesarb.net>2012-12-11 16:01:13 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-11 17:22:24 -0800
commitcf0cac0a09341549dedabcfc2a66dcbc2eaaf2b9 (patch)
tree09afb47fc1da246c65b061d09831e3bbe544d612 /mm/swapfile.c
parente9868505987a03a26a3979f27b82911ccc003752 (diff)
downloadlinux-cf0cac0a09341549dedabcfc2a66dcbc2eaaf2b9.tar.gz
mm: refactor reinsert of swap_info in sys_swapoff()
The block within sys_swapoff() which re-inserts the swap_info into the swap_list in case of failure of try_to_unuse() reads a few values outside the swap_lock. While this is safe at that point, it is subtle code. Simplify the code by moving the reading of these values to a separate function, refactoring it a bit so they are read from within the swap_lock. This is easier to understand, and matches better the way it worked before I unified the insertion of the swap_info from both sys_swapon and sys_swapoff. This change should make no functional difference. The only real change is moving the read of two or three structure fields to within the lock (frontswap_map_get() is nothing more than a read of p->frontswap_map). Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Dan Magenheimer <dan.magenheimer@oracle.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c26
1 files changed, 17 insertions, 9 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f91a25547ff..27a52b73157 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1443,13 +1443,12 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
return generic_swapfile_activate(sis, swap_file, span);
}
-static void enable_swap_info(struct swap_info_struct *p, int prio,
+static void _enable_swap_info(struct swap_info_struct *p, int prio,
unsigned char *swap_map,
unsigned long *frontswap_map)
{
int i, prev;
- spin_lock(&swap_lock);
if (prio >= 0)
p->prio = prio;
else
@@ -1473,6 +1472,21 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
else
swap_info[prev]->next = p->type;
frontswap_init(p->type);
+}
+
+static void enable_swap_info(struct swap_info_struct *p, int prio,
+ unsigned char *swap_map,
+ unsigned long *frontswap_map)
+{
+ spin_lock(&swap_lock);
+ _enable_swap_info(p, prio, swap_map, frontswap_map);
+ spin_unlock(&swap_lock);
+}
+
+static void reinsert_swap_info(struct swap_info_struct *p)
+{
+ spin_lock(&swap_lock);
+ _enable_swap_info(p, p->prio, p->swap_map, frontswap_map_get(p));
spin_unlock(&swap_lock);
}
@@ -1548,14 +1562,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj);
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 */
- enable_swap_info(p, p->prio, p->swap_map, frontswap_map_get(p));
+ reinsert_swap_info(p);
goto out_dput;
}