Commit 53092a74 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

[PATCH] swap: show span of swap extents 



The "Adding %dk swap" message shows the number of swap extents, as a guide to
how fragmented the swapfile may be.  But a useful further guide is what total
extent they span across (sometimes scarily large).

And there's no need to keep nr_extents in swap_info: it's unused after the
initial message, so save a little space by keeping it on stack.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 11d31886

include/linux/swap.h

+0 −1
Original line number Diff line number Diff line
@@ -123,7 +123,6 @@ struct swap_info_struct { 
	struct file *swap_file;

	struct block_device *bdev;

	struct list_head extent_list;

	int nr_extents;

	struct swap_extent *curr_swap_extent;

	unsigned old_block_size;

	unsigned short * swap_map;

mm/swapfile.c

+30 −14
Original line number Diff line number Diff line
@@ -854,7 +854,6 @@ static void destroy_swap_extents(struct swap_info_struct *sis) 
		list_del(&se->list);

		kfree(se);

	}

	sis->nr_extents = 0;

}



/*
@@ -893,8 +892,7 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, 
	new_se->start_block = start_block;



	list_add_tail(&new_se->list, &sis->extent_list);

	sis->nr_extents++;

	return 0;

	return 1;

}



/*
@@ -928,7 +926,7 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, 
 * This is extremely effective.  The average number of iterations in

 * map_swap_page() has been measured at about 0.3 per page.  - akpm.

 */

static int setup_swap_extents(struct swap_info_struct *sis)

static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)

{

	struct inode *inode;

	unsigned blocks_per_page;
@@ -936,11 +934,15 @@ static int setup_swap_extents(struct swap_info_struct *sis) 
	unsigned blkbits;

	sector_t probe_block;

	sector_t last_block;

	sector_t lowest_block = -1;

	sector_t highest_block = 0;

	int nr_extents = 0;

	int ret;



	inode = sis->swap_file->f_mapping->host;

	if (S_ISBLK(inode->i_mode)) {

		ret = add_swap_extent(sis, 0, sis->max, 0);

		*span = sis->pages;

		goto done;

	}
@@ -985,19 +987,28 @@ static int setup_swap_extents(struct swap_info_struct *sis) 
			}

		}



		first_block >>= (PAGE_SHIFT - blkbits);

		if (page_no) {	/* exclude the header page */

			if (first_block < lowest_block)

				lowest_block = first_block;

			if (first_block > highest_block)

				highest_block = first_block;

		}



		/*

		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks

		 */

		ret = add_swap_extent(sis, page_no, 1,

				first_block >> (PAGE_SHIFT - blkbits));

		if (ret)

		ret = add_swap_extent(sis, page_no, 1, first_block);

		if (ret < 0)

			goto out;

		nr_extents += ret;

		page_no++;

		probe_block += blocks_per_page;

reprobe:

		continue;

	}

	ret = 0;

	ret = nr_extents;

	*span = 1 + highest_block - lowest_block;

	if (page_no == 0)

		page_no = 1;	/* force Empty message */

	sis->max = page_no;
@@ -1265,6 +1276,8 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags) 
	union swap_header *swap_header = NULL;

	int swap_header_version;

	int nr_good_pages = 0;

	int nr_extents;

	sector_t span;

	unsigned long maxpages = 1;

	int swapfilesize;

	unsigned short *swap_map;
@@ -1300,7 +1313,6 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags) 
		nr_swapfiles = type+1;

	INIT_LIST_HEAD(&p->extent_list);

	p->flags = SWP_USED;

	p->nr_extents = 0;

	p->swap_file = NULL;

	p->old_block_size = 0;

	p->swap_map = NULL;
@@ -1477,9 +1489,11 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags) 
		p->swap_map[0] = SWAP_MAP_BAD;

		p->max = maxpages;

		p->pages = nr_good_pages;

		error = setup_swap_extents(p);

		if (error)

		nr_extents = setup_swap_extents(p, &span);

		if (nr_extents < 0) {

			error = nr_extents;

			goto bad_swap;

		}

		nr_good_pages = p->pages;

	}

	if (!nr_good_pages) {
@@ -1494,9 +1508,11 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags) 
	p->flags = SWP_ACTIVE;

	nr_swap_pages += nr_good_pages;

	total_swap_pages += nr_good_pages;

	printk(KERN_INFO "Adding %dk swap on %s.  Priority:%d extents:%d\n",

		nr_good_pages<<(PAGE_SHIFT-10), name,

		p->prio, p->nr_extents);



	printk(KERN_INFO "Adding %dk swap on %s.  "

			"Priority:%d extents:%d across:%lluk\n",

		nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,

		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));



	/* insert swap space into swap_list: */

	prev = -1;

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