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Commit ca8bd38b authored by Cesar Eduardo Barros's avatar Cesar Eduardo Barros Committed by Linus Torvalds
Browse files

sys_swapon: separate parsing of swapfile header 



Move the code which parses and checks the swapfile header (except for
the bad block list) to a separate function. Only code movement, no
functional changes.

Signed-off-by: default avatarCesar Eduardo Barros <cesarb@cesarb.net>
Tested-by: default avatarEric B Munson <emunson@mgebm.net>
Acked-by: default avatarEric B Munson <emunson@mgebm.net>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5de771e4

mm/swapfile.c

+78 −62
Original line number Diff line number Diff line
@@ -1918,6 +1918,82 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) 
	return 0;

}



static unsigned long read_swap_header(struct swap_info_struct *p,

					union swap_header *swap_header,

					struct inode *inode)

{

	int i;

	unsigned long maxpages;

	unsigned long swapfilepages;



	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {

		printk(KERN_ERR "Unable to find swap-space signature\n");

		goto bad_swap;

	}



	/* swap partition endianess hack... */

	if (swab32(swap_header->info.version) == 1) {

		swab32s(&swap_header->info.version);

		swab32s(&swap_header->info.last_page);

		swab32s(&swap_header->info.nr_badpages);

		for (i = 0; i < swap_header->info.nr_badpages; i++)

			swab32s(&swap_header->info.badpages[i]);

	}

	/* Check the swap header's sub-version */

	if (swap_header->info.version != 1) {

		printk(KERN_WARNING

		       "Unable to handle swap header version %d\n",

		       swap_header->info.version);

		goto bad_swap;

	}



	p->lowest_bit  = 1;

	p->cluster_next = 1;

	p->cluster_nr = 0;



	/*

	 * Find out how many pages are allowed for a single swap

	 * device. There are two limiting factors: 1) the number of

	 * bits for the swap offset in the swp_entry_t type and

	 * 2) the number of bits in the a swap pte as defined by

	 * the different architectures. In order to find the

	 * largest possible bit mask a swap entry with swap type 0

	 * and swap offset ~0UL is created, encoded to a swap pte,

	 * decoded to a swp_entry_t again and finally the swap

	 * offset is extracted. This will mask all the bits from

	 * the initial ~0UL mask that can't be encoded in either

	 * the swp_entry_t or the architecture definition of a

	 * swap pte.

	 */

	maxpages = swp_offset(pte_to_swp_entry(

			swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;

	if (maxpages > swap_header->info.last_page) {

		maxpages = swap_header->info.last_page + 1;

		/* p->max is an unsigned int: don't overflow it */

		if ((unsigned int)maxpages == 0)

			maxpages = UINT_MAX;

	}

	p->highest_bit = maxpages - 1;



	if (!maxpages)

		goto bad_swap;

	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;

	if (swapfilepages && maxpages > swapfilepages) {

		printk(KERN_WARNING

		       "Swap area shorter than signature indicates\n");

		goto bad_swap;

	}

	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))

		goto bad_swap;

	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)

		goto bad_swap;



	return maxpages;



bad_swap:

	return 0;

}



SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)

{

	struct swap_info_struct *p;
@@ -1931,7 +2007,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
	int nr_extents = 0;

	sector_t span;

	unsigned long maxpages;

	unsigned long swapfilepages;

	unsigned char *swap_map = NULL;

	struct page *page = NULL;

	struct inode *inode = NULL;
@@ -1989,70 +2064,11 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
	}

	swap_header = kmap(page);



	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {

		printk(KERN_ERR "Unable to find swap-space signature\n");

		error = -EINVAL;

		goto bad_swap;

	}



	/* swap partition endianess hack... */

	if (swab32(swap_header->info.version) == 1) {

		swab32s(&swap_header->info.version);

		swab32s(&swap_header->info.last_page);

		swab32s(&swap_header->info.nr_badpages);

		for (i = 0; i < swap_header->info.nr_badpages; i++)

			swab32s(&swap_header->info.badpages[i]);

	}

	/* Check the swap header's sub-version */

	if (swap_header->info.version != 1) {

		printk(KERN_WARNING

		       "Unable to handle swap header version %d\n",

		       swap_header->info.version);

		error = -EINVAL;

		goto bad_swap;

	}



	p->lowest_bit  = 1;

	p->cluster_next = 1;

	p->cluster_nr = 0;



	/*

	 * Find out how many pages are allowed for a single swap

	 * device. There are two limiting factors: 1) the number of

	 * bits for the swap offset in the swp_entry_t type and

	 * 2) the number of bits in the a swap pte as defined by

	 * the different architectures. In order to find the

	 * largest possible bit mask a swap entry with swap type 0

	 * and swap offset ~0UL is created, encoded to a swap pte,

	 * decoded to a swp_entry_t again and finally the swap

	 * offset is extracted. This will mask all the bits from

	 * the initial ~0UL mask that can't be encoded in either

	 * the swp_entry_t or the architecture definition of a

	 * swap pte.

	 */

	maxpages = swp_offset(pte_to_swp_entry(

			swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;

	if (maxpages > swap_header->info.last_page) {

		maxpages = swap_header->info.last_page + 1;

		/* p->max is an unsigned int: don't overflow it */

		if ((unsigned int)maxpages == 0)

			maxpages = UINT_MAX;

	}

	p->highest_bit = maxpages - 1;



	maxpages = read_swap_header(p, swap_header, inode);

	if (unlikely(!maxpages)) {

		error = -EINVAL;

	if (!maxpages)

		goto bad_swap;

	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;

	if (swapfilepages && maxpages > swapfilepages) {

		printk(KERN_WARNING

		       "Swap area shorter than signature indicates\n");

		goto bad_swap;

	}

	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))

		goto bad_swap;

	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)

		goto bad_swap;



	/* OK, set up the swap map and apply the bad block list */

	swap_map = vzalloc(maxpages);