sys_swapon: remove did_down variable

Since mutex_lock(&inode->i_mutex) is called just after setting inode,
did_down is always equivalent to (inode && S_ISREG(inode->i_mode)).

Use this fact to remove the did_down variable.
Signed-off-by: NCesar Eduardo Barros <cesarb@cesarb.net>
Tested-by: NEric B Munson <emunson@mgebm.net>
Acked-by: NEric B Munson <emunson@mgebm.net>
Reviewed-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/swapfile.c

@@ -1907,7 +1907,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	unsigned char *swap_map = NULL;
 	struct page *page = NULL;
 	struct inode *inode = NULL;
-	int did_down = 0;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -1962,7 +1961,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	} else if (S_ISREG(inode->i_mode)) {
 		p->bdev = inode->i_sb->s_bdev;
 		mutex_lock(&inode->i_mutex);
-		did_down = 1;
 		if (IS_SWAPFILE(inode)) {
 			error = -EBUSY;
 			goto bad_swap;
@@ -2154,10 +2152,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	spin_unlock(&swap_lock);
 	vfree(swap_map);
 	if (swap_file) {
-		if (did_down) {
+		if (inode && S_ISREG(inode->i_mode))
 			mutex_unlock(&inode->i_mutex);
-			did_down = 0;
-		}
 		filp_close(swap_file, NULL);
 	}
 out:
@@ -2167,7 +2163,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 	if (name)
 		putname(name);
-	if (did_down) {
+	if (inode && S_ISREG(inode->i_mode)) {
 		if (!error)
 			inode->i_flags |= S_SWAPFILE;
 		mutex_unlock(&inode->i_mutex);