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mm: frontswap: core swap subsystem hooks and headers
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:
parent
c3ba969815
commit
38b5faf4b1
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@ -197,6 +197,10 @@ struct swap_info_struct {
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struct block_device *bdev; /* swap device or bdev of swap file */
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struct file *swap_file; /* seldom referenced */
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unsigned int old_block_size; /* seldom referenced */
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#ifdef CONFIG_FRONTSWAP
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unsigned long *frontswap_map; /* frontswap in-use, one bit per page */
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atomic_t frontswap_pages; /* frontswap pages in-use counter */
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#endif
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};
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struct swap_list_t {
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13
include/linux/swapfile.h
Normal file
13
include/linux/swapfile.h
Normal file
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@ -0,0 +1,13 @@
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#ifndef _LINUX_SWAPFILE_H
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#define _LINUX_SWAPFILE_H
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/*
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* these were static in swapfile.c but frontswap.c needs them and we don't
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* want to expose them to the dozens of source files that include swap.h
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*/
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extern spinlock_t swap_lock;
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extern struct swap_list_t swap_list;
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extern struct swap_info_struct *swap_info[];
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extern int try_to_unuse(unsigned int, bool, unsigned long);
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#endif /* _LINUX_SWAPFILE_H */
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12
mm/page_io.c
12
mm/page_io.c
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@ -18,6 +18,7 @@
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#include <linux/bio.h>
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#include <linux/swapops.h>
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#include <linux/writeback.h>
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#include <linux/frontswap.h>
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#include <asm/pgtable.h>
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static struct bio *get_swap_bio(gfp_t gfp_flags,
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@ -98,6 +99,12 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
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unlock_page(page);
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goto out;
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}
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if (frontswap_put_page(page) == 0) {
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set_page_writeback(page);
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unlock_page(page);
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end_page_writeback(page);
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goto out;
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}
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bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
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if (bio == NULL) {
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set_page_dirty(page);
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@ -122,6 +129,11 @@ int swap_readpage(struct page *page)
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VM_BUG_ON(!PageLocked(page));
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VM_BUG_ON(PageUptodate(page));
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if (frontswap_get_page(page) == 0) {
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SetPageUptodate(page);
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unlock_page(page);
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goto out;
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}
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bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
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if (bio == NULL) {
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unlock_page(page);
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@ -31,6 +31,8 @@
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#include <linux/memcontrol.h>
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#include <linux/poll.h>
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#include <linux/oom.h>
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#include <linux/frontswap.h>
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#include <linux/swapfile.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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@ -42,7 +44,7 @@ static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
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static void free_swap_count_continuations(struct swap_info_struct *);
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static sector_t map_swap_entry(swp_entry_t, struct block_device**);
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static DEFINE_SPINLOCK(swap_lock);
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DEFINE_SPINLOCK(swap_lock);
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static unsigned int nr_swapfiles;
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long nr_swap_pages;
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long total_swap_pages;
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@ -53,9 +55,9 @@ static const char Unused_file[] = "Unused swap file entry ";
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static const char Bad_offset[] = "Bad swap offset entry ";
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static const char Unused_offset[] = "Unused swap offset entry ";
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static struct swap_list_t swap_list = {-1, -1};
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struct swap_list_t swap_list = {-1, -1};
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static struct swap_info_struct *swap_info[MAX_SWAPFILES];
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struct swap_info_struct *swap_info[MAX_SWAPFILES];
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static DEFINE_MUTEX(swapon_mutex);
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@ -556,6 +558,7 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
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swap_list.next = p->type;
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nr_swap_pages++;
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p->inuse_pages--;
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frontswap_invalidate_page(p->type, offset);
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if ((p->flags & SWP_BLKDEV) &&
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disk->fops->swap_slot_free_notify)
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disk->fops->swap_slot_free_notify(p->bdev, offset);
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@ -1016,11 +1019,12 @@ static int unuse_mm(struct mm_struct *mm,
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}
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/*
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* Scan swap_map from current position to next entry still in use.
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* Scan swap_map (or frontswap_map if frontswap parameter is true)
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* from current position to next entry still in use.
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* Recycle to start on reaching the end, returning 0 when empty.
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*/
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static unsigned int find_next_to_unuse(struct swap_info_struct *si,
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unsigned int prev)
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unsigned int prev, bool frontswap)
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{
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unsigned int max = si->max;
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unsigned int i = prev;
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@ -1046,6 +1050,12 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si,
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prev = 0;
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i = 1;
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}
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if (frontswap) {
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if (frontswap_test(si, i))
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break;
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else
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continue;
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}
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count = si->swap_map[i];
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if (count && swap_count(count) != SWAP_MAP_BAD)
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break;
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@ -1057,8 +1067,12 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si,
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* We completely avoid races by reading each swap page in advance,
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* and then search for the process using it. All the necessary
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* page table adjustments can then be made atomically.
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*
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* if the boolean frontswap is true, only unuse pages_to_unuse pages;
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* pages_to_unuse==0 means all pages; ignored if frontswap is false
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*/
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static int try_to_unuse(unsigned int type)
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int try_to_unuse(unsigned int type, bool frontswap,
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unsigned long pages_to_unuse)
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{
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struct swap_info_struct *si = swap_info[type];
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struct mm_struct *start_mm;
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@ -1091,7 +1105,7 @@ static int try_to_unuse(unsigned int type)
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* one pass through swap_map is enough, but not necessarily:
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* there are races when an instance of an entry might be missed.
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*/
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while ((i = find_next_to_unuse(si, i)) != 0) {
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while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
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if (signal_pending(current)) {
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retval = -EINTR;
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break;
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@ -1258,6 +1272,10 @@ static int try_to_unuse(unsigned int type)
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* interactive performance.
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*/
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cond_resched();
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if (frontswap && pages_to_unuse > 0) {
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if (!--pages_to_unuse)
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break;
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}
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}
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mmput(start_mm);
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@ -1517,7 +1535,8 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
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}
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static void enable_swap_info(struct swap_info_struct *p, int prio,
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unsigned char *swap_map)
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unsigned char *swap_map,
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unsigned long *frontswap_map)
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{
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int i, prev;
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@ -1527,6 +1546,7 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
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else
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p->prio = --least_priority;
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p->swap_map = swap_map;
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frontswap_map_set(p, frontswap_map);
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p->flags |= SWP_WRITEOK;
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nr_swap_pages += p->pages;
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total_swap_pages += p->pages;
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@ -1543,6 +1563,7 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
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swap_list.head = swap_list.next = p->type;
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else
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swap_info[prev]->next = p->type;
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frontswap_init(p->type);
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spin_unlock(&swap_lock);
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}
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@ -1616,7 +1637,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
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spin_unlock(&swap_lock);
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oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
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err = try_to_unuse(type);
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err = try_to_unuse(type, false, 0); /* force all pages to be unused */
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compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj);
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if (err) {
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@ -1627,7 +1648,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
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* sys_swapoff for this swap_info_struct at this point.
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*/
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/* re-insert swap space back into swap_list */
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enable_swap_info(p, p->prio, p->swap_map);
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enable_swap_info(p, p->prio, p->swap_map, frontswap_map_get(p));
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goto out_dput;
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}
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@ -1653,9 +1674,11 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
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swap_map = p->swap_map;
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p->swap_map = NULL;
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p->flags = 0;
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frontswap_invalidate_area(type);
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spin_unlock(&swap_lock);
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mutex_unlock(&swapon_mutex);
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vfree(swap_map);
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vfree(frontswap_map_get(p));
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/* Destroy swap account informatin */
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swap_cgroup_swapoff(type);
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@ -2019,6 +2042,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
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sector_t span;
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unsigned long maxpages;
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unsigned char *swap_map = NULL;
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unsigned long *frontswap_map = NULL;
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struct page *page = NULL;
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struct inode *inode = NULL;
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@ -2102,6 +2126,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
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error = nr_extents;
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goto bad_swap;
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}
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/* frontswap enabled? set up bit-per-page map for frontswap */
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if (frontswap_enabled)
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frontswap_map = vzalloc(maxpages / sizeof(long));
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if (p->bdev) {
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if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
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if (swap_flags & SWAP_FLAG_PREFER)
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prio =
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(swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
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enable_swap_info(p, prio, swap_map);
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enable_swap_info(p, prio, swap_map, frontswap_map);
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printk(KERN_INFO "Adding %uk swap on %s. "
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"Priority:%d extents:%d across:%lluk %s%s\n",
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"Priority:%d extents:%d across:%lluk %s%s%s\n",
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p->pages<<(PAGE_SHIFT-10), name, p->prio,
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nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
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(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
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(p->flags & SWP_DISCARDABLE) ? "D" : "");
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(p->flags & SWP_DISCARDABLE) ? "D" : "",
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(frontswap_map) ? "FS" : "");
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mutex_unlock(&swapon_mutex);
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atomic_inc(&proc_poll_event);
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