From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Subject: [PATCH V7 3/4] mm: frontswap: add swap hooks and extend try_to_unuse
This third patch of four in the frontswap series adds hooks in the swap
subsystem and extends try_to_unuse so that frontswap_shrink can do a
"partial swapoff". Also, declarations for the extern-ified swap variables
in the first patch are declared.
Note that failed frontswap_map allocation is safe... failure is noted
by lack of "FS" in the subsequent printk.
[v7: rebase to 3.0-rc3]
[v7: JBeulich@xxxxxxxxxx: use new static inlines, no-ops if not config'd]
[v6: rebase to 3.1-rc1]
[v6: lliubbo@xxxxxxxxx: use vzalloc]
[v5: accidentally posted stale code for v4 that failed to compile :-(]
[v4: rebase to 2.6.39]
Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Reviewed-by: Konrad Wilk <konrad.wilk@xxxxxxxxxx>
Acked-by: Jan Beulich <JBeulich@xxxxxxxxxx>
Acked-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
Cc: Matthew Wilcox <matthew@xxxxxx>
Cc: Chris Mason <chris.mason@xxxxxxxxxx>
Cc: Rik Riel <riel@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
--- linux/mm/swapfile.c 2011-08-08 08:19:26.336684746 -0600
+++ frontswap/mm/swapfile.c 2011-08-23 08:21:15.301998803 -0600
@@ -32,6 +32,8 @@
#include <linux/memcontrol.h>
#include <linux/poll.h>
#include <linux/oom.h>
+#include <linux/frontswap.h>
+#include <linux/swapfile.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
@@ -43,7 +45,7 @@ static bool swap_count_continued(struct
static void free_swap_count_continuations(struct swap_info_struct *);
static sector_t map_swap_entry(swp_entry_t, struct block_device**);
-static DEFINE_SPINLOCK(swap_lock);
+DEFINE_SPINLOCK(swap_lock);
static unsigned int nr_swapfiles;
long nr_swap_pages;
long total_swap_pages;
@@ -54,9 +56,9 @@ static const char Unused_file[] = "Unuse
static const char Bad_offset[] = "Bad swap offset entry ";
static const char Unused_offset[] = "Unused swap offset entry ";
-static struct swap_list_t swap_list = {-1, -1};
+struct swap_list_t swap_list = {-1, -1};
-static struct swap_info_struct *swap_info[MAX_SWAPFILES];
+struct swap_info_struct *swap_info[MAX_SWAPFILES];
static DEFINE_MUTEX(swapon_mutex);
@@ -557,6 +559,7 @@ static unsigned char swap_entry_free(str
swap_list.next = p->type;
nr_swap_pages++;
p->inuse_pages--;
+ frontswap_flush_page(p->type, offset);
if ((p->flags & SWP_BLKDEV) &&
disk->fops->swap_slot_free_notify)
disk->fops->swap_slot_free_notify(p->bdev, offset);
@@ -1022,7 +1025,7 @@ static int unuse_mm(struct mm_struct *mm
* Recycle to start on reaching the end, returning 0 when empty.
*/
static unsigned int find_next_to_unuse(struct swap_info_struct *si,
- unsigned int prev)
+ unsigned int prev, bool frontswap)
{
unsigned int max = si->max;
unsigned int i = prev;
@@ -1048,6 +1051,12 @@ static unsigned int find_next_to_unuse(s
prev = 0;
i = 1;
}
+ if (frontswap) {
+ if (frontswap_test(si, i))
+ break;
+ else
+ continue;
+ }
count = si->swap_map[i];
if (count && swap_count(count) != SWAP_MAP_BAD)
break;
@@ -1059,8 +1068,12 @@ static unsigned int find_next_to_unuse(s
* We completely avoid races by reading each swap page in advance,
* and then search for the process using it. All the necessary
* page table adjustments can then be made atomically.
+ *
+ * if the boolean frontswap is true, only unuse pages_to_unuse pages;
+ * pages_to_unuse==0 means all pages; ignored if frontswap is false
*/
-static int try_to_unuse(unsigned int type)
+int try_to_unuse(unsigned int type, bool frontswap,
+ unsigned long pages_to_unuse)
{
struct swap_info_struct *si = swap_info[type];
struct mm_struct *start_mm;
@@ -1093,7 +1106,7 @@ static int try_to_unuse(unsigned int typ
* one pass through swap_map is enough, but not necessarily:
* there are races when an instance of an entry might be missed.
*/
- while ((i = find_next_to_unuse(si, i)) != 0) {
+ while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
if (signal_pending(current)) {
retval = -EINTR;
break;
@@ -1260,6 +1273,10 @@ static int try_to_unuse(unsigned int typ
* interactive performance.
*/
cond_resched();
+ if (frontswap && pages_to_unuse > 0) {
+ if (!--pages_to_unuse)
+ break;
+ }
}
mmput(start_mm);
@@ -1519,7 +1536,8 @@ bad_bmap:
}
static void enable_swap_info(struct swap_info_struct *p, int prio,
- unsigned char *swap_map)
+ unsigned char *swap_map,
+ unsigned long *frontswap_map)
{
int i, prev;
@@ -1529,6 +1547,7 @@ static void enable_swap_info(struct swap
else
p->prio = --least_priority;
p->swap_map = swap_map;
+ frontswap_map_set(p, frontswap_map);
p->flags |= SWP_WRITEOK;
nr_swap_pages += p->pages;
total_swap_pages += p->pages;
@@ -1545,6 +1564,7 @@ static void enable_swap_info(struct swap
swap_list.head = swap_list.next = p->type;
else
swap_info[prev]->next = p->type;
+ frontswap_init(p->type);
spin_unlock(&swap_lock);
}
@@ -1616,7 +1636,7 @@ SYSCALL_DEFINE1(swapoff, const char __us
spin_unlock(&swap_lock);
oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
- err = try_to_unuse(type);
+ err = try_to_unuse(type, false, 0); /* force all pages to be unused */
test_set_oom_score_adj(oom_score_adj);
if (err) {
@@ -1627,7 +1647,7 @@ SYSCALL_DEFINE1(swapoff, const char __us
* 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);
+ enable_swap_info(p, p->prio, p->swap_map, frontswap_map_get(p));
goto out_dput;
}
@@ -1653,9 +1673,11 @@ SYSCALL_DEFINE1(swapoff, const char __us
swap_map = p->swap_map;
p->swap_map = NULL;
p->flags = 0;
+ frontswap_flush_area(type);
spin_unlock(&swap_lock);
mutex_unlock(&swapon_mutex);
vfree(swap_map);
+ vfree(frontswap_map_get(p));
/* Destroy swap account informatin */
swap_cgroup_swapoff(type);
@@ -2019,6 +2041,7 @@ SYSCALL_DEFINE2(swapon, const char __use
sector_t span;
unsigned long maxpages;
unsigned char *swap_map = NULL;
+ unsigned long *frontswap_map = NULL;
struct page *page = NULL;
struct inode *inode = NULL;
@@ -2099,6 +2122,9 @@ SYSCALL_DEFINE2(swapon, const char __use
error = nr_extents;
goto bad_swap;
}
+ /* frontswap enabled? set up bit-per-page map for frontswap */
+ if (frontswap_enabled)
+ frontswap_map = vzalloc(maxpages / sizeof(long));
if (p->bdev) {
if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
@@ -2114,14 +2140,15 @@ SYSCALL_DEFINE2(swapon, const char __use
if (swap_flags & SWAP_FLAG_PREFER)
prio =
(swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
- enable_swap_info(p, prio, swap_map);
+ enable_swap_info(p, prio, swap_map, frontswap_map);
printk(KERN_INFO "Adding %uk swap on %s. "
- "Priority:%d extents:%d across:%lluk %s%s\n",
+ "Priority:%d extents:%d across:%lluk %s%s%s\n",
p->pages<<(PAGE_SHIFT-10), name, p->prio,
nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
- (p->flags & SWP_DISCARDABLE) ? "D" : "");
+ (p->flags & SWP_DISCARDABLE) ? "D" : "",
+ (frontswap_map) ? "FS" : "");
mutex_unlock(&swapon_mutex);
atomic_inc(&proc_poll_event);
@@ -2312,6 +2339,10 @@ int valid_swaphandles(swp_entry_t entry,
base++;
spin_lock(&swap_lock);
+ if (frontswap_test(si, target)) {
+ spin_unlock(&swap_lock);
+ return 0;
+ }
if (end > si->max) /* don't go beyond end of map */
end = si->max;
@@ -2322,6 +2353,9 @@ int valid_swaphandles(swp_entry_t entry,
break;
if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
break;
+ /* Don't read in frontswap pages */
+ if (frontswap_test(si, toff))
+ break;
}
/* Count contiguous allocated slots below our target */
for (toff = target; --toff >= base; nr_pages++) {
@@ -2330,6 +2364,9 @@ int valid_swaphandles(swp_entry_t entry,
break;
if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
break;
+ /* Don't read in frontswap pages */
+ if (frontswap_test(si, toff))
+ break;
}
spin_unlock(&swap_lock);
--- linux/mm/page_io.c 2011-07-20 14:50:42.395999221 -0600
+++ frontswap/mm/page_io.c 2011-08-23 08:20:09.778810690 -0600
@@ -18,6 +18,7 @@
#include <linux/bio.h>
#include <linux/swapops.h>
#include <linux/writeback.h>
+#include <linux/frontswap.h>
#include <asm/pgtable.h>
static struct bio *get_swap_bio(gfp_t gfp_flags,
@@ -98,6 +99,12 @@ int swap_writepage(struct page *page, st
unlock_page(page);
goto out;
}
+ if (frontswap_put_page(page) == 0) {
+ set_page_writeback(page);
+ unlock_page(page);
+ end_page_writeback(page);
+ goto out;
+ }
bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
if (bio == NULL) {
set_page_dirty(page);
@@ -122,6 +129,11 @@ int swap_readpage(struct page *page)
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(PageUptodate(page));
+ if (frontswap_get_page(page) == 0) {
+ SetPageUptodate(page);
+ unlock_page(page);
+ goto out;
+ }
bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
if (bio == NULL) {
unlock_page(page);
--
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