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mm: frontswap: core swap subsystem hooks and headers

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This patch, 2of4, contains the changes to the core swap subsystem.
This includes:

(1) makes available core swap data structures (swap_lock, swap_list and
swap_info) that are needed by frontswap.c but we don't need to expose them
to the dozens of files that include swap.h so we create a new swapfile.h
just to extern-ify these and modify their declarations to non-static

(2) adds frontswap-related elements to swap_info_struct.  Frontswap_map
points to vzalloc'ed one-bit-per-swap-page metadata that indicates
whether the swap page is in frontswap or in the device and frontswap_pages
counts how many pages are in frontswap.

(3) adds hooks in the swap subsystem and extends try_to_unuse so that
frontswap_shrink can do a "partial swapoff".

Note that a failed frontswap_map allocation is safe... failure is noted
by lack of "FS" in the subsequent printk.

---

[v14: rebase to 3.4-rc2]
[v10: no change]
[v9: akpm@linux-foundation.org: mark some statics __read_mostly]
[v9: akpm@linux-foundation.org: add clarifying comments]
[v9: akpm@linux-foundation.org: no need to loop repeating try_to_unuse]
[v9: error27@gmail.com: remove superfluous check for NULL]
[v8: rebase to 3.0-rc4]
[v8: kamezawa.hiroyu@jp.fujitsu.com: change counter to atomic_t to avoid races]
[v8: kamezawa.hiroyu@jp.fujitsu.com: comment to clarify informational counters]
[v7: rebase to 3.0-rc3]
[v7: JBeulich@novell.com: add new swap struct elements only if config'd]
[v6: rebase to 3.0-rc1]
[v6: lliubbo@gmail.com: fix null pointer deref if vzalloc fails]
[v6: konrad.wilk@oracl.com: various checks and code clarifications/comments]
[v5: no change from v4]
[v4: rebase to 2.6.39]
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Reviewed-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Jan Beulich <JBeulich@novell.com>
Acked-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Rik Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
[v11: Rebased, fixed mm/swapfile.c context change]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Dan Magenheimer 2012-04-09 17:08:06 -06:00 committed by Konrad Rzeszutek Wilk
parent c3ba969815
commit 38b5faf4b1
4 changed files with 70 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/swap.h
View File

@ -197,6 +197,10 @@ struct swap_info_struct {
struct block_device *bdev; /* swap device or bdev of swap file */
struct file *swap_file; /* seldom referenced */
unsigned int old_block_size; /* seldom referenced */
#ifdef CONFIG_FRONTSWAP
unsigned long *frontswap_map; /* frontswap in-use, one bit per page */
atomic_t frontswap_pages; /* frontswap pages in-use counter */
#endif
};
struct swap_list_t {

13
include/linux/swapfile.h Normal file
View File

@ -0,0 +1,13 @@
#ifndef _LINUX_SWAPFILE_H
#define _LINUX_SWAPFILE_H
/*
* these were static in swapfile.c but frontswap.c needs them and we don't
* want to expose them to the dozens of source files that include swap.h
*/
extern spinlock_t swap_lock;
extern struct swap_list_t swap_list;
extern struct swap_info_struct *swap_info[];
extern int try_to_unuse(unsigned int, bool, unsigned long);
#endif /* _LINUX_SWAPFILE_H */

12
mm/page_io.c
View File

@ -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, struct writeback_control *wbc)
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);

54
mm/swapfile.c
View File

@ -31,6 +31,8 @@
#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>
@ -42,7 +44,7 @@ static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
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;
@ -53,9 +55,9 @@ static const char Unused_file[] = "Unused swap file entry ";
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);
@ -556,6 +558,7 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
swap_list.next = p->type;
nr_swap_pages++;
p->inuse_pages--;
frontswap_invalidate_page(p->type, offset);
if ((p->flags & SWP_BLKDEV) &&
disk->fops->swap_slot_free_notify)
disk->fops->swap_slot_free_notify(p->bdev, offset);
@ -1016,11 +1019,12 @@ static int unuse_mm(struct mm_struct *mm,
}
/*
* Scan swap_map from current position to next entry still in use.
* Scan swap_map (or frontswap_map if frontswap parameter is true)
* from current position to next entry still in use.
* 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;
@ -1046,6 +1050,12 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si,
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;
@ -1057,8 +1067,12 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si,
* 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;
@ -1091,7 +1105,7 @@ static int try_to_unuse(unsigned int type)
* 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;
@ -1258,6 +1272,10 @@ static int try_to_unuse(unsigned int type)
* interactive performance.
*/
cond_resched();
if (frontswap && pages_to_unuse > 0) {
if (!--pages_to_unuse)
break;
}
}
mmput(start_mm);
@ -1517,7 +1535,8 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
}
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;
@ -1527,6 +1546,7 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
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;
@ -1543,6 +1563,7 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
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 +1637,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
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 */
compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj);
if (err) {
@ -1627,7 +1648,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
* 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 +1674,11 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
swap_map = p->swap_map;
p->swap_map = NULL;
p->flags = 0;
frontswap_invalidate_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 +2042,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
sector_t span;
unsigned long maxpages;
unsigned char *swap_map = NULL;
unsigned long *frontswap_map = NULL;
struct page *page = NULL;
struct inode *inode = NULL;
@ -2102,6 +2126,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
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))) {
@ -2117,14 +2144,15 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
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);