swap_info: include first_swap_extent

Make better use of the space by folding first swap_extent into its
swap_info_struct, instead of just the list_head: swap partitions need
only that one, and for others it's used as a circular list anyway.

[jirislaby@gmail.com: fix crash on double swapon]
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/swap.h b/include/linux/swap.h
index f1c248796fb8cec28734a1d4d9745a9dd8ce34fb..109dfe7942377928327078fd3b11406e78d04889 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -165,7 +165,7 @@ struct swap_info_struct {
        signed char     next;           /* next type on the swap list */
        struct file *swap_file;
        struct block_device *bdev;
-       struct list_head extent_list;
+       struct swap_extent first_swap_extent;
        struct swap_extent *curr_swap_extent;
        unsigned short *swap_map;
        unsigned int lowest_bit;

diff --git a/mm/swapfile.c b/mm/swapfile.c
index dc88a7e4257ec529a9a4944b2cb06620276d1e2f..16de84b56644bc46364dfb628bf67ed0186c2add 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -145,23 +145,28 @@ void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
 static int discard_swap(struct swap_info_struct *si)
 {
        struct swap_extent *se;
+       sector_t start_block;
+       sector_t nr_blocks;
        int err = 0;
 
-       list_for_each_entry(se, &si->extent_list, list) {
-               sector_t start_block = se->start_block << (PAGE_SHIFT - 9);
-               sector_t nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
+       /* Do not discard the swap header page! */
+       se = &si->first_swap_extent;
+       start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
+       nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
+       if (nr_blocks) {
+               err = blkdev_issue_discard(si->bdev, start_block,
+                               nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER);
+               if (err)
+                       return err;
+               cond_resched();
+       }
 
-               if (se->start_page == 0) {
-                       /* Do not discard the swap header page! */
-                       start_block += 1 << (PAGE_SHIFT - 9);
-                       nr_blocks -= 1 << (PAGE_SHIFT - 9);
-                       if (!nr_blocks)
-                               continue;
-               }
+       list_for_each_entry(se, &si->first_swap_extent.list, list) {
+               start_block = se->start_block << (PAGE_SHIFT - 9);
+               nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
 
                err = blkdev_issue_discard(si->bdev, start_block,
-                                               nr_blocks, GFP_KERNEL,
-                                               DISCARD_FL_BARRIER);
+                               nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER);
                if (err)
                        break;
 
@@ -200,14 +205,11 @@ static void discard_swap_cluster(struct swap_info_struct *si,
                        start_block <<= PAGE_SHIFT - 9;
                        nr_blocks <<= PAGE_SHIFT - 9;
                        if (blkdev_issue_discard(si->bdev, start_block,
-                                                       nr_blocks, GFP_NOIO,
-                                                       DISCARD_FL_BARRIER))
+                                   nr_blocks, GFP_NOIO, DISCARD_FL_BARRIER))
                                break;
                }
 
                lh = se->list.next;
-               if (lh == &si->extent_list)
-                       lh = lh->next;
                se = list_entry(lh, struct swap_extent, list);
        }
 }
@@ -761,10 +763,8 @@ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
                        return type;
                }
                if (bdev == sis->bdev) {
-                       struct swap_extent *se;
+                       struct swap_extent *se = &sis->first_swap_extent;
 
-                       se = list_entry(sis->extent_list.next,
-                                       struct swap_extent, list);
                        if (se->start_block == offset) {
                                if (bdev_p)
                                        *bdev_p = bdgrab(sis->bdev);
@@ -1310,8 +1310,6 @@ sector_t map_swap_page(swp_entry_t entry, struct block_device **bdev)
                        return se->start_block + (offset - se->start_page);
                }
                lh = se->list.next;
-               if (lh == &sis->extent_list)
-                       lh = lh->next;
                se = list_entry(lh, struct swap_extent, list);
                sis->curr_swap_extent = se;
                BUG_ON(se == start_se);         /* It *must* be present */
@@ -1340,10 +1338,10 @@ sector_t swapdev_block(int type, pgoff_t offset)
  */
 static void destroy_swap_extents(struct swap_info_struct *sis)
 {
-       while (!list_empty(&sis->extent_list)) {
+       while (!list_empty(&sis->first_swap_extent.list)) {
                struct swap_extent *se;
 
-               se = list_entry(sis->extent_list.next,
+               se = list_entry(sis->first_swap_extent.list.next,
                                struct swap_extent, list);
                list_del(&se->list);
                kfree(se);
@@ -1364,8 +1362,15 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
        struct swap_extent *new_se;
        struct list_head *lh;
 
-       lh = sis->extent_list.prev;     /* The highest page extent */
-       if (lh != &sis->extent_list) {
+       if (start_page == 0) {
+               se = &sis->first_swap_extent;
+               sis->curr_swap_extent = se;
+               se->start_page = 0;
+               se->nr_pages = nr_pages;
+               se->start_block = start_block;
+               return 1;
+       } else {
+               lh = sis->first_swap_extent.list.prev;  /* Highest extent */
                se = list_entry(lh, struct swap_extent, list);
                BUG_ON(se->start_page + se->nr_pages != start_page);
                if (se->start_block + se->nr_pages == start_block) {
@@ -1385,7 +1390,7 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
        new_se->nr_pages = nr_pages;
        new_se->start_block = start_block;
 
-       list_add_tail(&new_se->list, &sis->extent_list);
+       list_add_tail(&new_se->list, &sis->first_swap_extent.list);
        return 1;
 }
 
@@ -1437,7 +1442,7 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
        if (S_ISBLK(inode->i_mode)) {
                ret = add_swap_extent(sis, 0, sis->max, 0);
                *span = sis->pages;
-               goto done;
+               goto out;
        }
 
        blkbits = inode->i_blkbits;
@@ -1508,15 +1513,12 @@ reprobe:
        sis->max = page_no;
        sis->pages = page_no - 1;
        sis->highest_bit = page_no - 1;
-done:
-       sis->curr_swap_extent = list_entry(sis->extent_list.prev,
-                                       struct swap_extent, list);
-       goto out;
+out:
+       return ret;
 bad_bmap:
        printk(KERN_ERR "swapon: swapfile has holes\n");
        ret = -EINVAL;
-out:
-       return ret;
+       goto out;
 }
 
 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
@@ -1815,7 +1817,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
                kfree(p);
                goto out;
        }
-       INIT_LIST_HEAD(&p->extent_list);
        if (type >= nr_swapfiles) {
                p->type = type;
                swap_info[type] = p;
@@ -1834,6 +1835,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
                 * would be relying on p->type to remain valid.
                 */
        }
+       INIT_LIST_HEAD(&p->first_swap_extent.list);
        p->flags = SWP_USED;
        p->next = -1;
        spin_unlock(&swap_lock);