JFS: Better RAS when btstack is overrun

The current warning and/or trap when the btstack is overrun in
dtSearch or dtReadFirst are not very helpful.  Add code to detect
the stack overrun earlier, print something useful, and return
gracefully.

I've found that dbFree being called with blkno == 0 can lead to this
error, so I put in a specific check for that.
Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>

fs/jfs/jfs_btree.h

 /*
- *   Copyright (c) International Business Machines Corp., 2000-2001
+ *   Copyright (C) International Business Machines Corp., 2000-2004
  *
  *   This program is free software;  you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -108,13 +108,12 @@ struct btpage {
  * record the path traversed during the search;
  * top frame record the leaf page/entry selected.
  */
-#define	MAXTREEHEIGHT		8
 struct btframe {	/* stack frame */
 	s64 bn;			/* 8: */
 	s16 index;		/* 2: */
-	s16 lastindex;		/* 2: */
-	struct metapage *mp;	/* 4: */
-};				/* (16) */
+	s16 lastindex;		/* 2: unused */
+	struct metapage *mp;	/* 4/8: */
+};				/* (16/24) */
 
 struct btstack {
 	struct btframe *top;
@@ -125,12 +124,15 @@ struct btstack {
 #define BT_CLR(btstack)\
 	(btstack)->top = (btstack)->stack
 
+#define BT_STACK_FULL(btstack)\
+	( (btstack)->top == &((btstack)->stack[MAXTREEHEIGHT-1]))
+
 #define BT_PUSH(BTSTACK, BN, INDEX)\
 {\
+	assert(!BT_STACK_FULL(BTSTACK));\
 	(BTSTACK)->top->bn = BN;\
 	(BTSTACK)->top->index = INDEX;\
 	++(BTSTACK)->top;\
-	assert((BTSTACK)->top != &((BTSTACK)->stack[MAXTREEHEIGHT]));\
 }
 
 #define BT_POP(btstack)\
@@ -139,6 +141,16 @@ struct btstack {
 #define BT_STACK(btstack)\
 	( (btstack)->top == (btstack)->stack ? NULL : (btstack)->top )
 
+static inline void BT_STACK_DUMP(struct btstack *btstack)
+{
+	int i;
+	printk("btstack dump:\n");
+	for (i = 0; i < MAXTREEHEIGHT; i++)
+		printk(KERN_ERR "bn = %Lx, index = %d\n",
+		       btstack->stack[i].bn,
+		       btstack->stack[i].index);
+}
+
 /* retrieve search results */
 #define BT_GETSEARCH(IP, LEAF, BN, MP, TYPE, P, INDEX, ROOT)\
 {\

fs/jfs/jfs_dmap.c

 /*
- *   Copyright (C) International Business Machines Corp., 2000-2003
+ *   Copyright (C) International Business Machines Corp., 2000-2004
  *
  *   This program is free software;  you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -382,7 +382,7 @@ int dbFree(struct inode *ip, s64 blkno, s64 nblocks)
 	IREAD_LOCK(ipbmap);
 
 	/* block to be freed better be within the mapsize. */
-	if (blkno + nblocks > bmp->db_mapsize) {
+	if (unlikely((blkno == 0) || (blkno + nblocks > bmp->db_mapsize))) {
 		IREAD_UNLOCK(ipbmap);
 		printk(KERN_ERR "blkno = %Lx, nblocks = %Lx\n",
 		       (unsigned long long) blkno,

fs/jfs/jfs_dtree.c

 /*
- *   Copyright (C) International Business Machines Corp., 2000-2003
+ *   Copyright (C) International Business Machines Corp., 2000-2004
  *
  *   This program is free software;  you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -766,11 +766,12 @@ int dtSearch(struct inode *ip, struct component_name * key, ino_t * data,
 		 */
 	      getChild:
 		/* update max. number of pages to split */
-		if (btstack->nsplit >= 8) {
+		if (BT_STACK_FULL(btstack)) {
 			/* Something's corrupted, mark filesytem dirty so
 			 * chkdsk will fix it.
 			 */
 			jfs_error(sb, "stack overrun in dtSearch!");
+			BT_STACK_DUMP(btstack);
 			rc = -EIO;
 			goto out;
 		}
@@ -3346,6 +3347,12 @@ static int dtReadFirst(struct inode *ip, struct btstack * btstack)
 		/*
 		 * descend down to leftmost child page
 		 */
+		if (BT_STACK_FULL(btstack)) {
+			DT_PUTPAGE(mp);
+			jfs_error(ip->i_sb, "dtReadFirst: btstack overrun");
+			BT_STACK_DUMP(btstack);
+			return -EIO;
+		}
 		/* push (bn, index) of the parent page/entry */
 		BT_PUSH(btstack, bn, 0);
 

fs/jfs/jfs_types.h

@@ -113,11 +113,12 @@ typedef struct {
 #define	addressPXD(pxd)\
 	( ((s64)((pxd)->addr1)) << 32 | __le32_to_cpu((pxd)->addr2))
 
+#define MAXTREEHEIGHT 8
 /* pxd list */
 struct pxdlist {
 	s16 maxnpxd;
 	s16 npxd;
-	pxd_t pxd[8];
+	pxd_t pxd[MAXTREEHEIGHT];
 };