UBIFS: allocate lpt dump buffer on demand

Instead of using pre-allocated 'c->dbg->buf' buffer in
'dump_lpt_leb()', dynamically allocate it when needed. The intend
is to get rid of the pre-allocated 'c->dbg->buf' buffer and save
128KiB of RAM (or more if PEB size is larger). Indeed, currently we
allocate this memory even if the user never enables any self-check,
which is wasteful.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/lpt_commit.c

@@ -1881,25 +1881,31 @@ int dbg_chk_lpt_sz(struct ubifs_info *c, int action, int len)
 static void dump_lpt_leb(const struct ubifs_info *c, int lnum)
 {
 	int err, len = c->leb_size, node_type, node_num, node_len, offs;
-	void *buf = c->dbg->buf;
+	void *buf, *p;
 
 	printk(KERN_DEBUG "(pid %d) start dumping LEB %d\n",
 	       current->pid, lnum);
+	buf = p = __vmalloc(c->leb_size, GFP_KERNEL | GFP_NOFS, PAGE_KERNEL);
+	if (!buf) {
+		ubifs_err("cannot allocate memory to dump LPT");
+		return;
+	}
+
 	err = ubi_read(c->ubi, lnum, buf, 0, c->leb_size);
 	if (err) {
 		ubifs_err("cannot read LEB %d, error %d", lnum, err);
-		return;
+		goto out;
 	}
 	while (1) {
 		offs = c->leb_size - len;
-		if (!is_a_node(c, buf, len)) {
+		if (!is_a_node(c, p, len)) {
 			int pad_len;
 
-			pad_len = get_pad_len(c, buf, len);
+			pad_len = get_pad_len(c, p, len);
 			if (pad_len) {
 				printk(KERN_DEBUG "LEB %d:%d, pad %d bytes\n",
 				       lnum, offs, pad_len);
-				buf += pad_len;
+				p += pad_len;
 				len -= pad_len;
 				continue;
 			}
@@ -1909,7 +1915,7 @@ static void dump_lpt_leb(const struct ubifs_info *c, int lnum)
 			break;
 		}
 
-		node_type = get_lpt_node_type(c, buf, &node_num);
+		node_type = get_lpt_node_type(c, p, &node_num);
 		switch (node_type) {
 		case UBIFS_LPT_PNODE:
 		{
@@ -1934,7 +1940,7 @@ static void dump_lpt_leb(const struct ubifs_info *c, int lnum)
 			else
 				printk(KERN_DEBUG "LEB %d:%d, nnode, ",
 				       lnum, offs);
-			err = ubifs_unpack_nnode(c, buf, &nnode);
+			err = ubifs_unpack_nnode(c, p, &nnode);
 			for (i = 0; i < UBIFS_LPT_FANOUT; i++) {
 				printk(KERN_CONT "%d:%d", nnode.nbranch[i].lnum,
 				       nnode.nbranch[i].offs);
@@ -1955,15 +1961,18 @@ static void dump_lpt_leb(const struct ubifs_info *c, int lnum)
 			break;
 		default:
 			ubifs_err("LPT node type %d not recognized", node_type);
-			return;
+			goto out;
 		}
 
-		buf += node_len;
+		p += node_len;
 		len -= node_len;
 	}
 
 	printk(KERN_DEBUG "(pid %d) finish dumping LEB %d\n",
 	       current->pid, lnum);
+out:
+	vfree(buf);
+	return;
 }
 
 /**