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: Cesar Eduardo Barros <cesarb@cesarb.net> Tested-by: Eric B Munson <emunson@mgebm.net> Acked-by: Eric B Munson <emunson@mgebm.net> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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: Cesar Eduardo Barros <cesarb@cesarb.net> Tested-by: Eric B Munson <emunson@mgebm.net> Acked-by: Eric B Munson <emunson@mgebm.net> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cesar Eduardo Barros · Linus Torvalds
1 parent 5de771e41f
Showing 1 changed file with 78 additions and 62 deletions Side-by-side Diff
mm/swapfile.c
@@ -1918,6 +1918,82 @@
 	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 @@
 	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 @@
 	}
 	swap_header = kmap(page);
  
-	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
-		printk(KERN_ERR "Unable to find swap-space signature\n");
+	maxpages = read_swap_header(p, swap_header, inode);
+	if (unlikely(!maxpages)) {
 		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;
-
-	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);
...	...	@@ -1918,6 +1918,82 @@
1918	1918	return 0;
1919	1919	}
1920	1920
	1921	+static unsigned long read_swap_header(struct swap_info_struct *p,
	1922	+ union swap_header *swap_header,
	1923	+ struct inode *inode)
	1924	+{
	1925	+ int i;
	1926	+ unsigned long maxpages;
	1927	+ unsigned long swapfilepages;
	1928	+
	1929	+ if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
	1930	+ printk(KERN_ERR "Unable to find swap-space signature\n");
	1931	+ goto bad_swap;
	1932	+ }
	1933	+
	1934	+ /* swap partition endianess hack... */
	1935	+ if (swab32(swap_header->info.version) == 1) {
	1936	+ swab32s(&swap_header->info.version);
	1937	+ swab32s(&swap_header->info.last_page);
	1938	+ swab32s(&swap_header->info.nr_badpages);
	1939	+ for (i = 0; i < swap_header->info.nr_badpages; i++)
	1940	+ swab32s(&swap_header->info.badpages[i]);
	1941	+ }
	1942	+ /* Check the swap header's sub-version */
	1943	+ if (swap_header->info.version != 1) {
	1944	+ printk(KERN_WARNING
	1945	+ "Unable to handle swap header version %d\n",
	1946	+ swap_header->info.version);
	1947	+ goto bad_swap;
	1948	+ }
	1949	+
	1950	+ p->lowest_bit = 1;
	1951	+ p->cluster_next = 1;
	1952	+ p->cluster_nr = 0;
	1953	+
	1954	+ /*
	1955	+ * Find out how many pages are allowed for a single swap
	1956	+ * device. There are two limiting factors: 1) the number of
	1957	+ * bits for the swap offset in the swp_entry_t type and
	1958	+ * 2) the number of bits in the a swap pte as defined by
	1959	+ * the different architectures. In order to find the
	1960	+ * largest possible bit mask a swap entry with swap type 0
	1961	+ * and swap offset ~0UL is created, encoded to a swap pte,
	1962	+ * decoded to a swp_entry_t again and finally the swap
	1963	+ * offset is extracted. This will mask all the bits from
	1964	+ * the initial ~0UL mask that can't be encoded in either
	1965	+ * the swp_entry_t or the architecture definition of a
	1966	+ * swap pte.
	1967	+ */
	1968	+ maxpages = swp_offset(pte_to_swp_entry(
	1969	+ swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
	1970	+ if (maxpages > swap_header->info.last_page) {
	1971	+ maxpages = swap_header->info.last_page + 1;
	1972	+ /* p->max is an unsigned int: don't overflow it */
	1973	+ if ((unsigned int)maxpages == 0)
	1974	+ maxpages = UINT_MAX;
	1975	+ }
	1976	+ p->highest_bit = maxpages - 1;
	1977	+
	1978	+ if (!maxpages)
	1979	+ goto bad_swap;
	1980	+ swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
	1981	+ if (swapfilepages && maxpages > swapfilepages) {
	1982	+ printk(KERN_WARNING
	1983	+ "Swap area shorter than signature indicates\n");
	1984	+ goto bad_swap;
	1985	+ }
	1986	+ if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
	1987	+ goto bad_swap;
	1988	+ if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
	1989	+ goto bad_swap;
	1990	+
	1991	+ return maxpages;
	1992	+
	1993	+bad_swap:
	1994	+ return 0;
	1995	+}
	1996	+
1921	1997	SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
1922	1998	{
1923	1999	struct swap_info_struct *p;
...	...	@@ -1931,7 +2007,6 @@
1931	2007	int nr_extents = 0;
1932	2008	sector_t span;
1933	2009	unsigned long maxpages;
1934		- unsigned long swapfilepages;
1935	2010	unsigned char *swap_map = NULL;
1936	2011	struct page *page = NULL;
1937	2012	struct inode *inode = NULL;
1938	2013
...	...	@@ -1989,70 +2064,11 @@
1989	2064	}
1990	2065	swap_header = kmap(page);
1991	2066
1992		- if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1993		- printk(KERN_ERR "Unable to find swap-space signature\n");
	2067	+ maxpages = read_swap_header(p, swap_header, inode);
	2068	+ if (unlikely(!maxpages)) {
1994	2069	error = -EINVAL;
1995	2070	goto bad_swap;
1996	2071	}
1997		-
1998		- /* swap partition endianess hack... */
1999		- if (swab32(swap_header->info.version) == 1) {
2000		- swab32s(&swap_header->info.version);
2001		- swab32s(&swap_header->info.last_page);
2002		- swab32s(&swap_header->info.nr_badpages);
2003		- for (i = 0; i < swap_header->info.nr_badpages; i++)
2004		- swab32s(&swap_header->info.badpages[i]);
2005		- }
2006		- /* Check the swap header's sub-version */
2007		- if (swap_header->info.version != 1) {
2008		- printk(KERN_WARNING
2009		- "Unable to handle swap header version %d\n",
2010		- swap_header->info.version);
2011		- error = -EINVAL;
2012		- goto bad_swap;
2013		- }
2014		-
2015		- p->lowest_bit = 1;
2016		- p->cluster_next = 1;
2017		- p->cluster_nr = 0;
2018		-
2019		- /*
2020		- * Find out how many pages are allowed for a single swap
2021		- * device. There are two limiting factors: 1) the number of
2022		- * bits for the swap offset in the swp_entry_t type and
2023		- * 2) the number of bits in the a swap pte as defined by
2024		- * the different architectures. In order to find the
2025		- * largest possible bit mask a swap entry with swap type 0
2026		- * and swap offset ~0UL is created, encoded to a swap pte,
2027		- * decoded to a swp_entry_t again and finally the swap
2028		- * offset is extracted. This will mask all the bits from
2029		- * the initial ~0UL mask that can't be encoded in either
2030		- * the swp_entry_t or the architecture definition of a
2031		- * swap pte.
2032		- */
2033		- maxpages = swp_offset(pte_to_swp_entry(
2034		- swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
2035		- if (maxpages > swap_header->info.last_page) {
2036		- maxpages = swap_header->info.last_page + 1;
2037		- /* p->max is an unsigned int: don't overflow it */
2038		- if ((unsigned int)maxpages == 0)
2039		- maxpages = UINT_MAX;
2040		- }
2041		- p->highest_bit = maxpages - 1;
2042		-
2043		- error = -EINVAL;
2044		- if (!maxpages)
2045		- goto bad_swap;
2046		- swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
2047		- if (swapfilepages && maxpages > swapfilepages) {
2048		- printk(KERN_WARNING
2049		- "Swap area shorter than signature indicates\n");
2050		- goto bad_swap;
2051		- }
2052		- if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
2053		- goto bad_swap;
2054		- if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
2055		- goto bad_swap;
2056	2072
2057	2073	/* OK, set up the swap map and apply the bad block list */
2058	2074	swap_map = vzalloc(maxpages);