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swap_info: include first_swap_extent
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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>
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Hugh Dickins authored and Linus Torvalds committed Dec 15, 2009
1 parent efa90a9 commit 9625a5f
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Showing 2 changed files with 37 additions and 35 deletions.
2 changes: 1 addition & 1 deletion include/linux/swap.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down
70 changes: 36 additions & 34 deletions mm/swapfile.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand Down Expand Up @@ -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);
}
}
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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 */
Expand Down Expand Up @@ -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);
Expand All @@ -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) {
Expand All @@ -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;
}

Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -1508,15 +1513,12 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
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)
Expand Down Expand Up @@ -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;
Expand All @@ -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);
Expand Down

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