sys_swapon: separate swap_info allocation

Move the swap_info allocation to its own 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: Pekka Enberg <penberg@kernel.org>
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>

mm/swapfile.c

@@ -1844,33 +1844,15 @@ static int __init max_swapfiles_check(void)
 late_initcall(max_swapfiles_check);
 #endif
 
-SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
+static struct swap_info_struct *alloc_swap_info(void)
 {
 	struct swap_info_struct *p;
-	char *name = NULL;
-	struct block_device *bdev = NULL;
-	struct file *swap_file = NULL;
-	struct address_space *mapping;
 	unsigned int type;
-	int i, prev;
 	int error;
-	union swap_header *swap_header;
-	unsigned int nr_good_pages;
-	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;
-	int did_down = 0;
-
-	if (!capable(CAP_SYS_ADMIN))
-		return -EPERM;
 
 	p = kzalloc(sizeof(*p), GFP_KERNEL);
 	if (!p)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
 	spin_lock(&swap_lock);
 	for (type = 0; type < nr_swapfiles; type++) {
@@ -1906,6 +1888,41 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	p->next = -1;
 	spin_unlock(&swap_lock);
 
+	return p;
+
+out:
+	return ERR_PTR(error);
+}
+
+SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
+{
+	struct swap_info_struct *p;
+	char *name = NULL;
+	struct block_device *bdev = NULL;
+	struct file *swap_file = NULL;
+	struct address_space *mapping;
+	int i, prev;
+	int error;
+	union swap_header *swap_header;
+	unsigned int nr_good_pages;
+	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;
+	int did_down = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	p = alloc_swap_info();
+	if (IS_ERR(p)) {
+		error = PTR_ERR(p);
+		goto out;
+	}
+
 	name = getname(specialfile);
 	error = PTR_ERR(name);
 	if (IS_ERR(name)) {