GFS2: Size seq_file buffer more carefully

This places a limit on the buffer size for archs with larger
PAGE_SIZE.
Signed-off-by: NSteven Whitehouse <swhiteho@redhat.com>
Reported-by: NEric Dumazet <eric.dumazet@gmail.com>

fs/gfs2/glock.c

@@ -1977,6 +1977,8 @@ static const struct seq_operations gfs2_sbstats_seq_ops = {
 	.show  = gfs2_sbstats_seq_show,
 };
 
+#define GFS2_SEQ_GOODSIZE min(PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER, 65536UL)
+
 static int gfs2_glocks_open(struct inode *inode, struct file *file)
 {
 	int ret = seq_open_private(file, &gfs2_glock_seq_ops,
@@ -1985,9 +1987,9 @@ static int gfs2_glocks_open(struct inode *inode, struct file *file)
 		struct seq_file *seq = file->private_data;
 		struct gfs2_glock_iter *gi = seq->private;
 		gi->sdp = inode->i_private;
-		seq->buf = kmalloc(8*PAGE_SIZE, GFP_KERNEL | __GFP_NOWARN);
+		seq->buf = kmalloc(GFS2_SEQ_GOODSIZE, GFP_KERNEL | __GFP_NOWARN);
 		if (seq->buf)
-			seq->size = 8*PAGE_SIZE;
+			seq->size = GFS2_SEQ_GOODSIZE;
 	}
 	return ret;
 }
@@ -2000,9 +2002,9 @@ static int gfs2_glstats_open(struct inode *inode, struct file *file)
 		struct seq_file *seq = file->private_data;
 		struct gfs2_glock_iter *gi = seq->private;
 		gi->sdp = inode->i_private;
-		seq->buf = kmalloc(8*PAGE_SIZE, GFP_KERNEL | __GFP_NOWARN);
+		seq->buf = kmalloc(GFS2_SEQ_GOODSIZE, GFP_KERNEL | __GFP_NOWARN);
 		if (seq->buf)
-			seq->size = 8*PAGE_SIZE;
+			seq->size = GFS2_SEQ_GOODSIZE;
 	}
 	return ret;
 }