swap_info: swap_map of chars not shorts

Halve the vmalloc'ed swap_map array from unsigned shorts to unsigned chars: it's still very unusual to reach a swap count of 126, and the next patch allows it to be extended indefinitely. Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

swap_info: swap_map of chars not shorts
Halve the vmalloc'ed swap_map array from unsigned shorts to unsigned chars: it's still very unusual to reach a swap count of 126, and the next patch allows it to be extended indefinitely. Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Hugh Dickins · Linus Torvalds
1 parent 253d553ba7
Showing 2 changed files with 27 additions and 21 deletions Side-by-side Diff
include/linux/swap.h
mm/swapfile.c
@@ -151,9 +151,9 @@
  
 #define SWAP_CLUSTER_MAX 32
  
-#define SWAP_MAP_MAX	0x7ffe
-#define SWAP_MAP_BAD	0x7fff
-#define SWAP_HAS_CACHE  0x8000		/* There is a swap cache of entry. */
+#define SWAP_MAP_MAX	0x7e
+#define SWAP_MAP_BAD	0x7f
+#define SWAP_HAS_CACHE	0x80		/* There is a swap cache of entry. */
  
 /*
  * The in-memory structure used to track swap areas.
@@ -167,7 +167,7 @@
 	struct block_device *bdev;
 	struct swap_extent first_swap_extent;
 	struct swap_extent *curr_swap_extent;
-	unsigned short *swap_map;
+	unsigned char *swap_map;
 	unsigned int lowest_bit;
 	unsigned int highest_bit;
 	unsigned int lowest_alloc;	/* while preparing discard cluster */
@@ -53,7 +53,7 @@
  
 static DEFINE_MUTEX(swapon_mutex);
  
-static inline int swap_count(unsigned short ent)
+static inline unsigned char swap_count(unsigned char ent)
 {
 	return ent & ~SWAP_HAS_CACHE;
 }
@@ -203,7 +203,7 @@
 #define LATENCY_LIMIT		256
  
 static inline unsigned long scan_swap_map(struct swap_info_struct *si,
-					  unsigned short usage)
+					  unsigned char usage)
 {
 	unsigned long offset;
 	unsigned long scan_base;
  
@@ -531,12 +531,12 @@
 	return NULL;
 }
  
-static unsigned short swap_entry_free(struct swap_info_struct *p,
-			   swp_entry_t entry, unsigned short usage)
+static unsigned char swap_entry_free(struct swap_info_struct *p,
+				     swp_entry_t entry, unsigned char usage)
 {
 	unsigned long offset = swp_offset(entry);
-	unsigned short count;
-	unsigned short has_cache;
+	unsigned char count;
+	unsigned char has_cache;
  
 	count = p->swap_map[offset];
 	has_cache = count & SWAP_HAS_CACHE;
@@ -591,7 +591,7 @@
 void swapcache_free(swp_entry_t entry, struct page *page)
 {
 	struct swap_info_struct *p;
-	unsigned short count;
+	unsigned char count;
  
 	p = swap_info_get(entry);
 	if (p) {
@@ -975,7 +975,7 @@
 {
 	unsigned int max = si->max;
 	unsigned int i = prev;
-	int count;
+	unsigned char count;
  
 	/*
 	 * No need for swap_lock here: we're just looking
@@ -1013,8 +1013,8 @@
 {
 	struct swap_info_struct *si = swap_info[type];
 	struct mm_struct *start_mm;
-	unsigned short *swap_map;
-	unsigned short swcount;
+	unsigned char *swap_map;
+	unsigned char swcount;
 	struct page *page;
 	swp_entry_t entry;
 	unsigned int i = 0;
@@ -1174,6 +1174,12 @@
 		 * If that's wrong, then we should worry more about
 		 * exit_mmap() and do_munmap() cases described above:
 		 * we might be resetting SWAP_MAP_MAX too early here.
+		 *
+		 * Yes, that's wrong: though very unlikely, swap count 0x7ffe
+		 * could surely occur if pid_max raised from PID_MAX_DEFAULT;
+		 * and we are now lowering SWAP_MAP_MAX to 0x7e, making it
+		 * much easier to reach.  But the next patch will fix that.
+		 *
 		 * We know "Undead"s can happen, they're okay, so don't
 		 * report them; but do report if we reset SWAP_MAP_MAX.
 		 */
@@ -1492,7 +1498,7 @@
 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 {
 	struct swap_info_struct *p = NULL;
-	unsigned short *swap_map;
+	unsigned char *swap_map;
 	struct file *swap_file, *victim;
 	struct address_space *mapping;
 	struct inode *inode;
@@ -1762,7 +1768,7 @@
 	sector_t span;
 	unsigned long maxpages = 1;
 	unsigned long swapfilepages;
-	unsigned short *swap_map = NULL;
+	unsigned char *swap_map = NULL;
 	struct page *page = NULL;
 	struct inode *inode = NULL;
 	int did_down = 0;
  
@@ -1938,13 +1944,13 @@
 		goto bad_swap;
  
 	/* OK, set up the swap map and apply the bad block list */
-	swap_map = vmalloc(maxpages * sizeof(short));
+	swap_map = vmalloc(maxpages);
 	if (!swap_map) {
 		error = -ENOMEM;
 		goto bad_swap;
 	}
  
-	memset(swap_map, 0, maxpages * sizeof(short));
+	memset(swap_map, 0, maxpages);
 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
 		int page_nr = swap_header->info.badpages[i];
 		if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
  
@@ -2082,12 +2088,12 @@
  * - swap-cache reference is requested but there is already one. -> EEXIST
  * - swap-cache reference is requested but the entry is not used. -> ENOENT
  */
-static int __swap_duplicate(swp_entry_t entry, unsigned short usage)
+static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
 {
 	struct swap_info_struct *p;
 	unsigned long offset, type;
-	unsigned short count;
-	unsigned short has_cache;
+	unsigned char count;
+	unsigned char has_cache;
 	int err = -EINVAL;
  
 	if (non_swap_entry(entry))
...	...	@@ -151,9 +151,9 @@
151	151
152	152	#define SWAP_CLUSTER_MAX 32
153	153
154		-#define SWAP_MAP_MAX 0x7ffe
155		-#define SWAP_MAP_BAD 0x7fff
156		-#define SWAP_HAS_CACHE 0x8000 /* There is a swap cache of entry. */
	154	+#define SWAP_MAP_MAX 0x7e
	155	+#define SWAP_MAP_BAD 0x7f
	156	+#define SWAP_HAS_CACHE 0x80 /* There is a swap cache of entry. */
157	157
158	158	/*
159	159	* The in-memory structure used to track swap areas.
...	...	@@ -167,7 +167,7 @@
167	167	struct block_device *bdev;
168	168	struct swap_extent first_swap_extent;
169	169	struct swap_extent *curr_swap_extent;
170		- unsigned short *swap_map;
	170	+ unsigned char *swap_map;
171	171	unsigned int lowest_bit;
172	172	unsigned int highest_bit;
173	173	unsigned int lowest_alloc; /* while preparing discard cluster */
...	...	@@ -53,7 +53,7 @@
53	53
54	54	static DEFINE_MUTEX(swapon_mutex);
55	55
56		-static inline int swap_count(unsigned short ent)
	56	+static inline unsigned char swap_count(unsigned char ent)
57	57	{
58	58	return ent & ~SWAP_HAS_CACHE;
59	59	}
...	...	@@ -203,7 +203,7 @@
203	203	#define LATENCY_LIMIT 256
204	204
205	205	static inline unsigned long scan_swap_map(struct swap_info_struct *si,
206		- unsigned short usage)
	206	+ unsigned char usage)
207	207	{
208	208	unsigned long offset;
209	209	unsigned long scan_base;
210	210
...	...	@@ -531,12 +531,12 @@
531	531	return NULL;
532	532	}
533	533
534		-static unsigned short swap_entry_free(struct swap_info_struct *p,
535		- swp_entry_t entry, unsigned short usage)
	534	+static unsigned char swap_entry_free(struct swap_info_struct *p,
	535	+ swp_entry_t entry, unsigned char usage)
536	536	{
537	537	unsigned long offset = swp_offset(entry);
538		- unsigned short count;
539		- unsigned short has_cache;
	538	+ unsigned char count;
	539	+ unsigned char has_cache;
540	540
541	541	count = p->swap_map[offset];
542	542	has_cache = count & SWAP_HAS_CACHE;
...	...	@@ -591,7 +591,7 @@
591	591	void swapcache_free(swp_entry_t entry, struct page *page)
592	592	{
593	593	struct swap_info_struct *p;
594		- unsigned short count;
	594	+ unsigned char count;
595	595
596	596	p = swap_info_get(entry);
597	597	if (p) {
...	...	@@ -975,7 +975,7 @@
975	975	{
976	976	unsigned int max = si->max;
977	977	unsigned int i = prev;
978		- int count;
	978	+ unsigned char count;
979	979
980	980	/*
981	981	* No need for swap_lock here: we're just looking
...	...	@@ -1013,8 +1013,8 @@
1013	1013	{
1014	1014	struct swap_info_struct *si = swap_info[type];
1015	1015	struct mm_struct *start_mm;
1016		- unsigned short *swap_map;
1017		- unsigned short swcount;
	1016	+ unsigned char *swap_map;
	1017	+ unsigned char swcount;
1018	1018	struct page *page;
1019	1019	swp_entry_t entry;
1020	1020	unsigned int i = 0;
...	...	@@ -1174,6 +1174,12 @@
1174	1174	* If that's wrong, then we should worry more about
1175	1175	* exit_mmap() and do_munmap() cases described above:
1176	1176	* we might be resetting SWAP_MAP_MAX too early here.
	1177	+ *
	1178	+ * Yes, that's wrong: though very unlikely, swap count 0x7ffe
	1179	+ * could surely occur if pid_max raised from PID_MAX_DEFAULT;
	1180	+ * and we are now lowering SWAP_MAP_MAX to 0x7e, making it
	1181	+ * much easier to reach. But the next patch will fix that.
	1182	+ *
1177	1183	* We know "Undead"s can happen, they're okay, so don't
1178	1184	* report them; but do report if we reset SWAP_MAP_MAX.
1179	1185	*/
...	...	@@ -1492,7 +1498,7 @@
1492	1498	SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
1493	1499	{
1494	1500	struct swap_info_struct *p = NULL;
1495		- unsigned short *swap_map;
	1501	+ unsigned char *swap_map;
1496	1502	struct file swap_file, victim;
1497	1503	struct address_space *mapping;
1498	1504	struct inode *inode;
...	...	@@ -1762,7 +1768,7 @@
1762	1768	sector_t span;
1763	1769	unsigned long maxpages = 1;
1764	1770	unsigned long swapfilepages;
1765		- unsigned short *swap_map = NULL;
	1771	+ unsigned char *swap_map = NULL;
1766	1772	struct page *page = NULL;
1767	1773	struct inode *inode = NULL;
1768	1774	int did_down = 0;
1769	1775
...	...	@@ -1938,13 +1944,13 @@
1938	1944	goto bad_swap;
1939	1945
1940	1946	/* OK, set up the swap map and apply the bad block list */
1941		- swap_map = vmalloc(maxpages * sizeof(short));
	1947	+ swap_map = vmalloc(maxpages);
1942	1948	if (!swap_map) {
1943	1949	error = -ENOMEM;
1944	1950	goto bad_swap;
1945	1951	}
1946	1952
1947		- memset(swap_map, 0, maxpages * sizeof(short));
	1953	+ memset(swap_map, 0, maxpages);
1948	1954	for (i = 0; i < swap_header->info.nr_badpages; i++) {
1949	1955	int page_nr = swap_header->info.badpages[i];
1950	1956	if (page_nr <= 0 \|\| page_nr >= swap_header->info.last_page) {
1951	1957
...	...	@@ -2082,12 +2088,12 @@
2082	2088	* - swap-cache reference is requested but there is already one. -> EEXIST
2083	2089	* - swap-cache reference is requested but the entry is not used. -> ENOENT
2084	2090	*/
2085		-static int __swap_duplicate(swp_entry_t entry, unsigned short usage)
	2091	+static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
2086	2092	{
2087	2093	struct swap_info_struct *p;
2088	2094	unsigned long offset, type;
2089		- unsigned short count;
2090		- unsigned short has_cache;
	2095	+ unsigned char count;
	2096	+ unsigned char has_cache;
2091	2097	int err = -EINVAL;
2092	2098
2093	2099	if (non_swap_entry(entry))