ufs: fix reserved blocks check

a) honour ->s_minfree; don't just go with default (5)
b) don't bother with capability checks until we know we'll need them
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ufs/balloc.c

@@ -400,11 +400,13 @@ u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
 	/*
 	 * There is not enough space for user on the device
 	 */
-	if (!capable(CAP_SYS_RESOURCE) && ufs_freespace(uspi, UFS_MINFREE) <= 0) {
+	if (unlikely(ufs_freespace(uspi, uspi->s_minfree) <= 0)) {
+		if (!capable(CAP_SYS_RESOURCE)) {
 			mutex_unlock(&UFS_SB(sb)->s_lock);
 			UFSD("EXIT (FAILED)\n");
 			return 0;
 		}
+	}
 
 	if (goal >= uspi->s_size) 
 		goal = 0;