[JFFS2] Improve read_inode memory usage, v2.

We originally used to read every node and allocate a jffs2_tmp_dnode_info
structure for each, before processing them in (reverse) version order
and discarding the ones which are obsoleted by later nodes.

With huge logfiles, this behaviour caused memory problems. For example, a
file involved in OLPC trac #1292 has 1822391 nodes, and would cause the XO
machine to run out of memory during the first stage of read_inode().

Instead of just inserting nodes into a tree in version order as we find
them, we now put them into a tree in order of their offset within the
file, which allows us to immediately discard nodes which are completely
obsoleted.

We don't use a full tree with 'fragments' pointing to the real data
structure, as we do in the normal fragtree. We sort only on the start
address, and add an 'overlapped' flag to the tmp_dnode_info to indicate
that the node in question is (partially) overlapped by another.

When the scan is complete, we start at the end of the file, adding each
node to a real fragtree as before. Where the node is non-overlapped, we
just add it (it doesn't matter that it's not the latest version; there is
no overlap). When the node at the end of the tree _is_ overlapped, we sort
it and all its overlapping nodes into version order and then add them to
the fragtree in that order.

This 'early discard' reduces the peak allocation of tmp_dnode_info
structures from 1.8M to a mere 62872 (3.5%) in the degenerate case
referenced above.

This version of the patch also correctly rememembers the highest node
version# seen for an inode when it's scanned.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

1 files changed, 595 insertions, 137 deletions

diff --git a/fs/jffs2/readinode.c b/fs/jffs2/readinode.c
index 1298848336b..49d4b0a67c5 100644
--- a/fs/jffs2/readinode.c
+++ b/fs/jffs2/readinode.c
@@ -22,30 +22,510 @@
 #include "nodelist.h"
 
 /*
- * Put a new tmp_dnode_info into the temporaty RB-tree, keeping the list in
- * order of increasing version.
+ * Check the data CRC of the node.
+ *
+ * Returns: 0 if the data CRC is correct;
+ * 	    1 - if incorrect;
+ *	    error code if an error occured.
  */
-static void jffs2_add_tn_to_tree(struct jffs2_tmp_dnode_info *tn, struct rb_root *list)
+static int check_node_data(struct jffs2_sb_info *c, struct jffs2_tmp_dnode_info *tn)
 {
-	struct rb_node **p = &list->rb_node;
-	struct rb_node * parent = NULL;
-	struct jffs2_tmp_dnode_info *this;
-
-	while (*p) {
-		parent = *p;
-		this = rb_entry(parent, struct jffs2_tmp_dnode_info, rb);
-
-		/* There may actually be a collision here, but it doesn't
-		   actually matter. As long as the two nodes with the same
-		   version are together, it's all fine. */
-		if (tn->version > this->version)
-			p = &(*p)->rb_left;
+	struct jffs2_raw_node_ref *ref = tn->fn->raw;
+	int err = 0, pointed = 0;
+	struct jffs2_eraseblock *jeb;
+	unsigned char *buffer;
+	uint32_t crc, ofs, len;
+	size_t retlen;
+
+	BUG_ON(tn->csize == 0);
+
+	if (!jffs2_is_writebuffered(c))
+		goto adj_acc;
+
+	/* Calculate how many bytes were already checked */
+	ofs = ref_offset(ref) + sizeof(struct jffs2_raw_inode);
+	len = ofs % c->wbuf_pagesize;
+	if (likely(len))
+		len = c->wbuf_pagesize - len;
+
+	if (len >= tn->csize) {
+		dbg_readinode("no need to check node at %#08x, data length %u, data starts at %#08x - it has already been checked.\n",
+			ref_offset(ref), tn->csize, ofs);
+		goto adj_acc;
+	}
+
+	ofs += len;
+	len = tn->csize - len;
+
+	dbg_readinode("check node at %#08x, data length %u, partial CRC %#08x, correct CRC %#08x, data starts at %#08x, start checking from %#08x - %u bytes.\n",
+		ref_offset(ref), tn->csize, tn->partial_crc, tn->data_crc, ofs - len, ofs, len);
+
+#ifndef __ECOS
+	/* TODO: instead, incapsulate point() stuff to jffs2_flash_read(),
+	 * adding and jffs2_flash_read_end() interface. */
+	if (c->mtd->point) {
+		err = c->mtd->point(c->mtd, ofs, len, &retlen, &buffer);
+		if (!err && retlen < tn->csize) {
+			JFFS2_WARNING("MTD point returned len too short: %zu instead of %u.\n", retlen, tn->csize);
+			c->mtd->unpoint(c->mtd, buffer, ofs, len);
+		} else if (err)
+			JFFS2_WARNING("MTD point failed: error code %d.\n", err);
 		else
-			p = &(*p)->rb_right;
+			pointed = 1; /* succefully pointed to device */
+	}
+#endif
+
+	if (!pointed) {
+		buffer = kmalloc(len, GFP_KERNEL);
+		if (unlikely(!buffer))
+			return -ENOMEM;
+
+		/* TODO: this is very frequent pattern, make it a separate
+		 * routine */
+		err = jffs2_flash_read(c, ofs, len, &retlen, buffer);
+		if (err) {
+			JFFS2_ERROR("can not read %d bytes from 0x%08x, error code: %d.\n", len, ofs, err);
+			goto free_out;
+		}
+
+		if (retlen != len) {
+			JFFS2_ERROR("short read at %#08x: %zd instead of %d.\n", ofs, retlen, len);
+			err = -EIO;
+			goto free_out;
+		}
+	}
+
+	/* Continue calculating CRC */
+	crc = crc32(tn->partial_crc, buffer, len);
+	if(!pointed)
+		kfree(buffer);
+#ifndef __ECOS
+	else
+		c->mtd->unpoint(c->mtd, buffer, ofs, len);
+#endif
+
+	if (crc != tn->data_crc) {
+		JFFS2_NOTICE("wrong data CRC in data node at 0x%08x: read %#08x, calculated %#08x.\n",
+			ofs, tn->data_crc, crc);
+		return 1;
 	}
 
-	rb_link_node(&tn->rb, parent, p);
-	rb_insert_color(&tn->rb, list);
+adj_acc:
+	jeb = &c->blocks[ref->flash_offset / c->sector_size];
+	len = ref_totlen(c, jeb, ref);
+	/* If it should be REF_NORMAL, it'll get marked as such when
+	   we build the fragtree, shortly. No need to worry about GC
+	   moving it while it's marked REF_PRISTINE -- GC won't happen
+	   till we've finished checking every inode anyway. */
+	ref->flash_offset |= REF_PRISTINE;
+	/*
+	 * Mark the node as having been checked and fix the
+	 * accounting accordingly.
+	 */
+	spin_lock(&c->erase_completion_lock);
+	jeb->used_size += len;
+	jeb->unchecked_size -= len;
+	c->used_size += len;
+	c->unchecked_size -= len;
+	jffs2_dbg_acct_paranoia_check_nolock(c, jeb);
+	spin_unlock(&c->erase_completion_lock);
+
+	return 0;
+
+free_out:
+	if(!pointed)
+		kfree(buffer);
+#ifndef __ECOS
+	else
+		c->mtd->unpoint(c->mtd, buffer, ofs, len);
+#endif
+	return err;
+}
+
+/*
+ * Helper function for jffs2_add_older_frag_to_fragtree().
+ *
+ * Checks the node if we are in the checking stage.
+ */
+static int check_tn_node(struct jffs2_sb_info *c, struct jffs2_tmp_dnode_info *tn)
+{
+	int ret;
+
+	BUG_ON(ref_obsolete(tn->fn->raw));
+
+	/* We only check the data CRC of unchecked nodes */
+	if (ref_flags(tn->fn->raw) != REF_UNCHECKED)
+		return 0;
+
+	dbg_readinode("check node %#04x-%#04x, phys offs %#08x\n",
+		      tn->fn->ofs, tn->fn->ofs + tn->fn->size, ref_offset(tn->fn->raw));
+
+	ret = check_node_data(c, tn);
+	if (unlikely(ret < 0)) {
+		JFFS2_ERROR("check_node_data() returned error: %d.\n",
+			ret);
+	} else if (unlikely(ret > 0)) {
+		dbg_readinode("CRC error, mark it obsolete.\n");
+		jffs2_mark_node_obsolete(c, tn->fn->raw);
+	}
+
+	return ret;
+}
+
+static struct jffs2_tmp_dnode_info *jffs2_lookup_tn(struct rb_root *tn_root, uint32_t offset)
+{
+	struct rb_node *next;
+	struct jffs2_tmp_dnode_info *tn = NULL;
+
+	dbg_readinode("root %p, offset %d\n", tn_root, offset);
+
+	next = tn_root->rb_node;
+
+	while (next) {
+		tn = rb_entry(next, struct jffs2_tmp_dnode_info, rb);
+
+		if (tn->fn->ofs < offset)
+			next = tn->rb.rb_right;
+		else if (tn->fn->ofs >= offset)
+			next = tn->rb.rb_left;
+		else
+			break;
+	}
+
+	return tn;
+}
+
+
+static void jffs2_kill_tn(struct jffs2_sb_info *c, struct jffs2_tmp_dnode_info *tn)
+{
+	jffs2_mark_node_obsolete(c, tn->fn->raw);
+	jffs2_free_full_dnode(tn->fn);
+	jffs2_free_tmp_dnode_info(tn);
+}
+/*
+ * This function is used when we read an inode. Data nodes arrive in
+ * arbitrary order -- they may be older or newer than the nodes which
+ * are already in the tree. Where overlaps occur, the older node can
+ * be discarded as long as the newer passes the CRC check. We don't
+ * bother to keep track of holes in this rbtree, and neither do we deal
+ * with frags -- we can have multiple entries starting at the same
+ * offset, and the one with the smallest length will come first in the
+ * ordering.
+ *
+ * Returns 0 if the node was inserted
+ *         1 if the node is obsolete (because we can't mark it so yet)
+ *         < 0 an if error occurred
+ */
+static int jffs2_add_tn_to_tree(struct jffs2_sb_info *c,
+				struct jffs2_readinode_info *rii,
+				struct jffs2_tmp_dnode_info *tn)
+{
+	uint32_t fn_end = tn->fn->ofs + tn->fn->size;
+	struct jffs2_tmp_dnode_info *insert_point = NULL, *this;
+
+	dbg_readinode("insert fragment %#04x-%#04x, ver %u\n", tn->fn->ofs, fn_end, tn->version);
+
+	/* If a node has zero dsize, we only have to keep if it if it might be the
+	   node with highest version -- i.e. the one which will end up as f->metadata.
+	   Note that such nodes won't be REF_UNCHECKED since there are no data to
+	   check anyway. */
+	if (!tn->fn->size) {
+		if (rii->mdata_tn) {
+			/* We had a candidate mdata node already */
+			dbg_readinode("kill old mdata with ver %d\n", rii->mdata_tn->version);
+			jffs2_kill_tn(c, rii->mdata_tn);
+		}
+		rii->mdata_tn = tn;
+		dbg_readinode("keep new mdata with ver %d\n", tn->version);
+		return 0;
+	}
+
+	/* Find the earliest node which _may_ be relevant to this one */
+	this = jffs2_lookup_tn(&rii->tn_root, tn->fn->ofs);
+	if (!this) {
+		/* First addition to empty tree. $DEITY how I love the easy cases */
+		rb_link_node(&tn->rb, NULL, &rii->tn_root.rb_node);
+		rb_insert_color(&tn->rb, &rii->tn_root);
+		dbg_readinode("keep new frag\n");
+		return 0;
+	}
+
+	/* If we add a new node it'll be somewhere under here. */
+	insert_point = this;
+
+	/* If the node is coincident with another at a lower address,
+	   back up until the other node is found. It may be relevant */
+	while (tn->overlapped)
+		tn = tn_prev(tn);
+
+	dbg_readinode("'this' found %#04x-%#04x (%s)\n", this->fn->ofs, this->fn->ofs + this->fn->size, this->fn ? "data" : "hole");
+
+	while (this) {
+		if (this->fn->ofs > fn_end)
+			break;
+		dbg_readinode("Ponder this ver %d, 0x%x-0x%x\n",
+			      this->version, this->fn->ofs, this->fn->size);
+
+		if (this->version == tn->version) {
+			/* Version number collision means REF_PRISTINE GC. Accept either of them
+			   as long as the CRC is correct. Check the one we have already...  */
+			if (!check_tn_node(c, this)) {
+				/* The one we already had was OK. Keep it and throw away the new one */
+				dbg_readinode("Like old node. Throw away new\n");
+				jffs2_kill_tn(c, tn);
+				return 0;
+			} else {
+				/* Who cares if the new one is good; keep it for now anyway. */
+				rb_replace_node(&this->rb, &tn->rb, &rii->tn_root);
+				/* Same overlapping from in front and behind */
+				tn->overlapped = this->overlapped;
+				jffs2_kill_tn(c, this);
+				dbg_readinode("Like new node. Throw away old\n");
+				return 0;
+			}
+		}
+		if (this->version < tn->version &&
+		    this->fn->ofs >= tn->fn->ofs &&
+		    this->fn->ofs + this->fn->size <= fn_end) {
+			/* New node entirely overlaps 'this' */
+			if (check_tn_node(c, tn)) {
+				dbg_readinode("new node bad CRC\n");
+				jffs2_kill_tn(c, tn);
+				return 0;
+			}
+			/* ... and is good. Kill 'this'... */
+			rb_replace_node(&this->rb, &tn->rb, &rii->tn_root);
+			tn->overlapped = this->overlapped;
+			jffs2_kill_tn(c, this);
+			/* ... and any subsequent nodes which are also overlapped */
+			this = tn_next(tn);
+			while (this && this->fn->ofs + this->fn->size < fn_end) {
+				struct jffs2_tmp_dnode_info *next = tn_next(this);
+				if (this->version < tn->version) {
+					tn_erase(this, &rii->tn_root);
+					dbg_readinode("Kill overlapped ver %d, 0x%x-0x%x\n",
+						      this->version, this->fn->ofs,
+						      this->fn->ofs+this->fn->size);
+					jffs2_kill_tn(c, this);
+				}
+				this = next;
+			}
+			dbg_readinode("Done inserting new\n");
+			return 0;
+		}
+		if (this->version > tn->version &&
+		    this->fn->ofs <= tn->fn->ofs &&
+		    this->fn->ofs+this->fn->size >= fn_end) {
+			/* New node entirely overlapped by 'this' */
+			if (!check_tn_node(c, this)) {
+				dbg_readinode("Good CRC on old node. Kill new\n");
+				jffs2_kill_tn(c, tn);
+				return 0;
+			}
+			/* ... but 'this' was bad. Replace it... */
+			rb_replace_node(&this->rb, &tn->rb, &rii->tn_root);
+			dbg_readinode("Bad CRC on old overlapping node. Kill it\n");
+			jffs2_kill_tn(c, this);
+			return 0;
+		}
+		/* We want to be inserted under the last node which is
+		   either at a lower offset _or_ has a smaller range */
+		if (this->fn->ofs < tn->fn->ofs ||
+		    (this->fn->ofs == tn->fn->ofs &&
+		     this->fn->size <= tn->fn->size))
+			insert_point = this;
+
+		this = tn_next(this);
+	}
+	dbg_readinode("insert_point %p, ver %d, 0x%x-0x%x, ov %d\n",
+		      insert_point, insert_point->version, insert_point->fn->ofs,
+		      insert_point->fn->ofs+insert_point->fn->size,
+		      insert_point->overlapped);
+	/* We neither completely obsoleted nor were completely
+	   obsoleted by an earlier node. Insert under insert_point */
+	{
+		struct rb_node *parent = &insert_point->rb;
+		struct rb_node **link = &parent;
+
+		while (*link) {
+			parent = *link;
+			insert_point = rb_entry(parent, struct jffs2_tmp_dnode_info, rb);
+			if (tn->fn->ofs > insert_point->fn->ofs)
+				link = &insert_point->rb.rb_right;
+			else if (tn->fn->ofs < insert_point->fn->ofs ||
+				 tn->fn->size < insert_point->fn->size)
+				link = &insert_point->rb.rb_left;
+			else
+				link = &insert_point->rb.rb_right;
+		}
+		rb_link_node(&tn->rb, &insert_point->rb, link);
+		rb_insert_color(&tn->rb, &rii->tn_root);
+	}
+	/* If there's anything behind that overlaps us, note it */
+	this = tn_prev(tn);
+	if (this) {
+		while (1) {
+			if (this->fn->ofs + this->fn->size > tn->fn->ofs) {
+				dbg_readinode("Node is overlapped by %p (v %d, 0x%x-0x%x)\n",
+					      this, this->version, this->fn->ofs,
+					      this->fn->ofs+this->fn->size);
+				tn->overlapped = 1;
+				break;
+			}
+			if (!this->overlapped)
+				break;
+			this = tn_prev(this);
+		}
+	}
+
+	/* If the new node overlaps anything ahead, note it */
+	this = tn_next(tn);
+	while (this && this->fn->ofs < fn_end) {
+		this->overlapped = 1;
+		dbg_readinode("Node ver %d, 0x%x-0x%x is overlapped\n",
+			      this->version, this->fn->ofs,
+			      this->fn->ofs+this->fn->size);
+		this = tn_next(this);
+	}
+	return 0;
+}
+
+/* Trivial function to remove the last node in the tree. Which by definition
+   has no right-hand -- so can be removed just by making its only child (if
+   any) take its place under its parent. */
+static void eat_last(struct rb_root *root, struct rb_node *node)
+{
+	struct rb_node *parent = rb_parent(node);
+	struct rb_node **link;
+
+	/* LAST! */
+	BUG_ON(node->rb_right);
+
+	if (!parent)
+		link = &root->rb_node;
+	else if (node == parent->rb_left)
+		link = &parent->rb_left;
+	else
+		link = &parent->rb_right;
+
+	*link = node->rb_left;
+	/* Colour doesn't matter now. Only the parent pointer. */
+	if (node->rb_left)
+		node->rb_left->rb_parent_color = node->rb_parent_color;
+}
+
+/* We put this in reverse order, so we can just use eat_last */
+static void ver_insert(struct rb_root *ver_root, struct jffs2_tmp_dnode_info *tn)
+{
+	struct rb_node **link = &ver_root->rb_node;
+	struct rb_node *parent = NULL;
+	struct jffs2_tmp_dnode_info *this_tn;
+
+	while (*link) {
+		parent = *link;
+		this_tn = rb_entry(parent, struct jffs2_tmp_dnode_info, rb);
+
+		if (tn->version > this_tn->version)
+			link = &parent->rb_left;
+		else
+			link = &parent->rb_right;
+	}
+	dbg_readinode("Link new node at %p (root is %p)\n", link, ver_root);
+	rb_link_node(&tn->rb, parent, link);
+	rb_insert_color(&tn->rb, ver_root);
+}
+
+/* Build final, normal fragtree from tn tree. It doesn't matter which order
+   we add nodes to the real fragtree, as long as they don't overlap. And
+   having thrown away the majority of overlapped nodes as we went, there
+   really shouldn't be many sets of nodes which do overlap. If we start at
+   the end, we can use the overlap markers -- we can just eat nodes which
+   aren't overlapped, and when we encounter nodes which _do_ overlap we
+   sort them all into a temporary tree in version order before replaying them. */
+static int jffs2_build_inode_fragtree(struct jffs2_sb_info *c,
+				      struct jffs2_inode_info *f,
+				      struct jffs2_readinode_info *rii)
+{
+	struct jffs2_tmp_dnode_info *pen, *last, *this;
+	struct rb_root ver_root = RB_ROOT;
+	uint32_t high_ver = 0;
+
+	if (rii->mdata_tn) {
+		dbg_readinode("potential mdata is ver %d at %p\n", rii->mdata_tn->version, rii->mdata_tn);
+		high_ver = rii->mdata_tn->version;
+		rii->latest_ref = rii->mdata_tn->fn->raw;
+	}
+#ifdef JFFS2_DBG_READINODE_MESSAGES
+	this = tn_last(&rii->tn_root);
+	while (this) {
+		dbg_readinode("tn %p ver %d range 0x%x-0x%x ov %d\n", this, this->version, this->fn->ofs,
+			     this->fn->ofs+this->fn->size, this->overlapped);
+		this = tn_prev(this);
+	}
+#endif
+	pen = tn_last(&rii->tn_root);
+	while ((last = pen)) {
+		pen = tn_prev(last);
+
+		eat_last(&rii->tn_root, &last->rb);
+		ver_insert(&ver_root, last);
+
+		if (unlikely(last->overlapped))
+			continue;
+
+		/* Now we have a bunch of nodes in reverse version
+		   order, in the tree at ver_root. Most of the time,
+		   there'll actually be only one node in the 'tree',
+		   in fact. */
+		this = tn_last(&ver_root);
+
+		while (this) {
+			struct jffs2_tmp_dnode_info *vers_next;
+			int ret;
+			vers_next = tn_prev(this);
+			eat_last(&ver_root, &this->rb);
+			if (check_tn_node(c, this)) {
+				dbg_readinode("node ver %x, 0x%x-0x%x failed CRC\n",
+					     this->version, this->fn->ofs,
+					     this->fn->ofs+this->fn->size);
+				jffs2_kill_tn(c, this);
+			} else {
+				if (this->version > high_ver) {
+					/* Note that this is different from the other
+					   highest_version, because this one is only
+					   counting _valid_ nodes which could give the
+					   latest inode metadata */
+					high_ver = this->version;
+					rii->latest_ref = this->fn->raw;
+				}
+				dbg_readinode("Add %p (v %x, 0x%x-0x%x, ov %d) to fragtree\n",
+					     this, this->version, this->fn->ofs,
+					     this->fn->ofs+this->fn->size, this->overlapped);
+
+				ret = jffs2_add_full_dnode_to_inode(c, f, this->fn);
+				if (ret) {
+					/* Free the nodes in vers_root; let the caller
+					   deal with the rest */
+					JFFS2_ERROR("Add node to tree failed %d\n", ret);
+					while (1) {
+						vers_next = tn_prev(this);
+						if (check_tn_node(c, this))
+							jffs2_mark_node_obsolete(c, this->fn->raw);
+						jffs2_free_full_dnode(this->fn);
+						jffs2_free_tmp_dnode_info(this);
+						this = vers_next;
+						if (!this)
+							break;
+						eat_last(&ver_root, &vers_next->rb);
+					}
+					return ret;
+				}
+				jffs2_free_tmp_dnode_info(this);
+			}
+			this = vers_next;
+		}
+	}
+	return 0;
 }
 
 static void jffs2_free_tmp_dnode_info_list(struct rb_root *list)
@@ -112,8 +592,8 @@ static struct jffs2_raw_node_ref *jffs2_first_valid_node(struct jffs2_raw_node_r
  * 	    negative error code on failure.
  */
 static inline int read_direntry(struct jffs2_sb_info *c, struct jffs2_raw_node_ref *ref,
-				struct jffs2_raw_dirent *rd, size_t read, struct jffs2_full_dirent **fdp,
-				uint32_t *latest_mctime, uint32_t *mctime_ver)
+				struct jffs2_raw_dirent *rd, size_t read,
+				struct jffs2_readinode_info *rii)
 {
 	struct jffs2_full_dirent *fd;
 	uint32_t crc;
@@ -125,7 +605,8 @@ static inline int read_direntry(struct jffs2_sb_info *c, struct jffs2_raw_node_r
 	if (unlikely(crc != je32_to_cpu(rd->node_crc))) {
 		JFFS2_NOTICE("header CRC failed on dirent node at %#08x: read %#08x, calculated %#08x\n",
 			     ref_offset(ref), je32_to_cpu(rd->node_crc), crc);
-		return 1;
+		jffs2_mark_node_obsolete(c, ref);
+		return 0;
 	}
 
 	/* If we've never checked the CRCs on this node, check them now */
@@ -137,7 +618,8 @@ static inline int read_direntry(struct jffs2_sb_info *c, struct jffs2_raw_node_r
 		if (unlikely(PAD((rd->nsize + sizeof(*rd))) != PAD(je32_to_cpu(rd->totlen)))) {
 			JFFS2_ERROR("illegal nsize in node at %#08x: nsize %#02x, totlen %#04x\n",
 				    ref_offset(ref), rd->nsize, je32_to_cpu(rd->totlen));
-			return 1;
+			jffs2_mark_node_obsolete(c, ref);
+			return 0;
 		}
 
 		jeb = &c->blocks[ref->flash_offset / c->sector_size];
@@ -161,10 +643,13 @@ static inline int read_direntry(struct jffs2_sb_info *c, struct jffs2_raw_node_r
 	fd->ino = je32_to_cpu(rd->ino);
 	fd->type = rd->type;
 
+	if (fd->version > rii->highest_version)
+		rii->highest_version = fd->version;
+
 	/* Pick out the mctime of the latest dirent */
-	if(fd->version > *mctime_ver && je32_to_cpu(rd->mctime)) {
-		*mctime_ver = fd->version;
-		*latest_mctime = je32_to_cpu(rd->mctime);
+	if(fd->version > rii->mctime_ver && je32_to_cpu(rd->mctime)) {
+		rii->mctime_ver = fd->version;
+		rii->latest_mctime = je32_to_cpu(rd->mctime);
 	}
 
 	/*
@@ -201,7 +686,7 @@ static inline int read_direntry(struct jffs2_sb_info *c, struct jffs2_raw_node_r
 	 * Wheee. We now have a complete jffs2_full_dirent structure, with
 	 * the name in it and everything. Link it into the list
 	 */
-	jffs2_add_fd_to_list(c, fd, fdp);
+	jffs2_add_fd_to_list(c, fd, &rii->fds);
 
 	return 0;
 }
@@ -210,13 +695,13 @@ static inline int read_direntry(struct jffs2_sb_info *c, struct jffs2_raw_node_r
  * Helper function for jffs2_get_inode_nodes().
  * It is called every time an inode node is found.
  *
- * Returns: 0 on succes;
+ * Returns: 0 on success;
  * 	    1 if the node should be marked obsolete;
  * 	    negative error code on failure.
  */
 static inline int read_dnode(struct jffs2_sb_info *c, struct jffs2_raw_node_ref *ref,
-			     struct jffs2_raw_inode *rd, struct rb_root *tnp, int rdlen,
-			     uint32_t *latest_mctime, uint32_t *mctime_ver)
+			     struct jffs2_raw_inode *rd, int rdlen,
+			     struct jffs2_readinode_info *rii)
 {
 	struct jffs2_tmp_dnode_info *tn;
 	uint32_t len, csize;
@@ -230,7 +715,8 @@ static inline int read_dnode(struct jffs2_sb_info *c, struct jffs2_raw_node_ref
 	if (unlikely(crc != je32_to_cpu(rd->node_crc))) {
 		JFFS2_NOTICE("node CRC failed on dnode at %#08x: read %#08x, calculated %#08x\n",
 			     ref_offset(ref), je32_to_cpu(rd->node_crc), crc);
-		return 1;
+		jffs2_mark_node_obsolete(c, ref);
+		return 0;
 	}
 
 	tn = jffs2_alloc_tmp_dnode_info();
@@ -342,6 +828,10 @@ static inline int read_dnode(struct jffs2_sb_info *c, struct jffs2_raw_node_ref
 	tn->data_crc = je32_to_cpu(rd->data_crc);
 	tn->csize = csize;
 	tn->fn->raw = ref;
+	tn->overlapped = 0;
+
+	if (tn->version > rii->highest_version)
+		rii->highest_version = tn->version;
 
 	/* There was a bug where we wrote hole nodes out with
 	   csize/dsize swapped. Deal with it */
@@ -353,13 +843,25 @@ static inline int read_dnode(struct jffs2_sb_info *c, struct jffs2_raw_node_ref
 	dbg_readinode("dnode @%08x: ver %u, offset %#04x, dsize %#04x, csize %#04x\n",
 		  ref_offset(ref), je32_to_cpu(rd->version), je32_to_cpu(rd->offset), je32_to_cpu(rd->dsize), csize);
 
-	jffs2_add_tn_to_tree(tn, tnp);
+	ret = jffs2_add_tn_to_tree(c, rii, tn);
 
+	if (ret) {
+		jffs2_free_full_dnode(tn->fn);
+	free_out:
+		jffs2_free_tmp_dnode_info(tn);
+		return ret;
+	}
+#ifdef JFFS2_DBG_READINODE_MESSAGES
+	dbg_readinode("After adding ver %d:\n", tn->version);
+	tn = tn_first(&rii->tn_root);
+	while (tn) {
+		dbg_readinode("%p: v %d r 0x%x-0x%x ov %d\n",
+			     tn, tn->version, tn->fn->ofs,
+			     tn->fn->ofs+tn->fn->size, tn->overlapped);
+		tn = tn_next(tn);
+	}
+#endif
 	return 0;
-
-free_out:
-	jffs2_free_tmp_dnode_info(tn);
-	return ret;
 }
 
 /*
@@ -379,7 +881,8 @@ static inline int read_unknown(struct jffs2_sb_info *c, struct jffs2_raw_node_re
 		JFFS2_ERROR("Node is {%04x,%04x,%08x,%08x}. Please report this error.\n",
                             je16_to_cpu(un->magic), je16_to_cpu(un->nodetype),
                             je32_to_cpu(un->totlen), je32_to_cpu(un->hdr_crc));
-		return 1;
+		jffs2_mark_node_obsolete(c, ref);
+		return 0;
 	}
 
 	un->nodetype = cpu_to_je16(JFFS2_NODE_ACCURATE | je16_to_cpu(un->nodetype));
@@ -407,7 +910,8 @@ static inline int read_unknown(struct jffs2_sb_info *c, struct jffs2_raw_node_re
 	case JFFS2_FEATURE_RWCOMPAT_DELETE:
 		JFFS2_NOTICE("unknown RWCOMPAT_DELETE nodetype %#04X at %#08x\n",
 			     je16_to_cpu(un->nodetype), ref_offset(ref));
-		return 1;
+		jffs2_mark_node_obsolete(c, ref);
+		return 0;
 	}
 
 	return 0;
@@ -457,21 +961,20 @@ static int read_more(struct jffs2_sb_info *c, struct jffs2_raw_node_ref *ref,
 }
 
 /* Get tmp_dnode_info and full_dirent for all non-obsolete nodes associated
-   with this ino, returning the former in order of version */
+   with this ino. Perform a preliminary ordering on data nodes, throwing away
+   those which are completely obsoleted by newer ones. The naïve approach we
+   use to take of just returning them _all_ in version order will cause us to
+   run out of memory in certain degenerate cases. */
 static int jffs2_get_inode_nodes(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
-				 struct rb_root *tnp, struct jffs2_full_dirent **fdp,
-				 uint32_t *highest_version, uint32_t *latest_mctime,
-				 uint32_t *mctime_ver)
+				 struct jffs2_readinode_info *rii)
 {
 	struct jffs2_raw_node_ref *ref, *valid_ref;
-	struct rb_root ret_tn = RB_ROOT;
-	struct jffs2_full_dirent *ret_fd = NULL;
 	unsigned char *buf = NULL;
 	union jffs2_node_union *node;
 	size_t retlen;
 	int len, err;
 
-	*mctime_ver = 0;
+	rii->mctime_ver = 0;
 
 	dbg_readinode("ino #%u\n", f->inocache->ino);
 
@@ -569,16 +1072,10 @@ static int jffs2_get_inode_nodes(struct jffs2_sb_info *c, struct jffs2_inode_inf
 					goto free_out;
 			}
 
-			err = read_direntry(c, ref, &node->d, retlen, &ret_fd, latest_mctime, mctime_ver);
-			if (err == 1) {
-				jffs2_mark_node_obsolete(c, ref);
-				break;
-			} else if (unlikely(err))
+			err = read_direntry(c, ref, &node->d, retlen, rii);
+			if (unlikely(err))
 				goto free_out;
 
-			if (je32_to_cpu(node->d.version) > *highest_version)
-				*highest_version = je32_to_cpu(node->d.version);
-
 			break;
 
 		case JFFS2_NODETYPE_INODE:
@@ -589,16 +1086,10 @@ static int jffs2_get_inode_nodes(struct jffs2_sb_info *c, struct jffs2_inode_inf
 					goto free_out;
 			}
 
-			err = read_dnode(c, ref, &node->i, &ret_tn, len, latest_mctime, mctime_ver);
-			if (err == 1) {
-				jffs2_mark_node_obsolete(c, ref);
-				break;
-			} else if (unlikely(err))
+			err = read_dnode(c, ref, &node->i, len, rii);
+			if (unlikely(err))
 				goto free_out;
 
-			if (je32_to_cpu(node->i.version) > *highest_version)
-				*highest_version = je32_to_cpu(node->i.version);
-
 			break;
 
 		default:
@@ -621,17 +1112,19 @@ static int jffs2_get_inode_nodes(struct jffs2_sb_info *c, struct jffs2_inode_inf
 	}
 
 	spin_unlock(&c->erase_completion_lock);
-	*tnp = ret_tn;
-	*fdp = ret_fd;
 	kfree(buf);
 
+	f->highest_version = rii->highest_version;
+
 	dbg_readinode("nodes of inode #%u were read, the highest version is %u, latest_mctime %u, mctime_ver %u.\n",
-			f->inocache->ino, *highest_version, *latest_mctime, *mctime_ver);
+		      f->inocache->ino, rii->highest_version, rii->latest_mctime,
+		      rii->mctime_ver);
 	return 0;
 
  free_out:
-	jffs2_free_tmp_dnode_info_list(&ret_tn);
-	jffs2_free_full_dirent_list(ret_fd);
+	jffs2_free_tmp_dnode_info_list(&rii->tn_root);
+	jffs2_free_full_dirent_list(rii->fds);
+	rii->fds = NULL;
 	kfree(buf);
 	return err;
 }
@@ -640,20 +1133,17 @@ static int jffs2_do_read_inode_internal(struct jffs2_sb_info *c,
 					struct jffs2_inode_info *f,
 					struct jffs2_raw_inode *latest_node)
 {
-	struct jffs2_tmp_dnode_info *tn;
-	struct rb_root tn_list;
-	struct rb_node *rb, *repl_rb;
-	struct jffs2_full_dirent *fd_list;
-	struct jffs2_full_dnode *fn, *first_fn = NULL;
+	struct jffs2_readinode_info rii;
 	uint32_t crc;
-	uint32_t latest_mctime, mctime_ver;
 	size_t retlen;
 	int ret;
 
 	dbg_readinode("ino #%u nlink is %d\n", f->inocache->ino, f->inocache->nlink);
 
+	memset(&rii, 0, sizeof(rii));
+
 	/* Grab all nodes relevant to this ino */
-	ret = jffs2_get_inode_nodes(c, f, &tn_list, &fd_list, &f->highest_version, &latest_mctime, &mctime_ver);
+	ret = jffs2_get_inode_nodes(c, f, &rii);
 
 	if (ret) {
 		JFFS2_ERROR("cannot read nodes for ino %u, returned error is %d\n", f->inocache->ino, ret);
@@ -661,74 +1151,42 @@ static int jffs2_do_read_inode_internal(struct jffs2_sb_info *c,
 			jffs2_set_inocache_state(c, f->inocache, INO_STATE_CHECKEDABSENT);
 		return ret;
 	}
-	f->dents = fd_list;
-
-	rb = rb_first(&tn_list);
 
-	while (rb) {
-		cond_resched();
-		tn = rb_entry(rb, struct jffs2_tmp_dnode_info, rb);
-		fn = tn->fn;
-		ret = 1;
-		dbg_readinode("consider node ver %u, phys offset "
-			"%#08x(%d), range %u-%u.\n", tn->version,
-			ref_offset(fn->raw), ref_flags(fn->raw),
-			fn->ofs, fn->ofs + fn->size);
-
-		if (fn->size) {
-			ret = jffs2_add_older_frag_to_fragtree(c, f, tn);
-			/* TODO: the error code isn't checked, check it */
-			jffs2_dbg_fragtree_paranoia_check_nolock(f);
-			BUG_ON(ret < 0);
-			if (!first_fn && ret == 0)
-				first_fn = fn;
-		} else if (!first_fn) {
-			first_fn = fn;
-			f->metadata = fn;
-			ret = 0; /* Prevent freeing the metadata update node */
-		} else
-			jffs2_mark_node_obsolete(c, fn->raw);
-
-		BUG_ON(rb->rb_left);
-		if (rb_parent(rb) && rb_parent(rb)->rb_left == rb) {
-			/* We were then left-hand child of our parent. We need
-			 * to move our own right-hand child into our place. */
-			repl_rb = rb->rb_right;
-			if (repl_rb)
-				rb_set_parent(repl_rb, rb_parent(rb));
-		} else
-			repl_rb = NULL;
-
-		rb = rb_next(rb);
-
-		/* Remove the spent tn from the tree; don't bother rebalancing
-		 * but put our right-hand child in our own place. */
-		if (rb_parent(&tn->rb)) {
-			if (rb_parent(&tn->rb)->rb_left == &tn->rb)
-				rb_parent(&tn->rb)->rb_left = repl_rb;
-			else if (rb_parent(&tn->rb)->rb_right == &tn->rb)
-				rb_parent(&tn->rb)->rb_right = repl_rb;
-			else BUG();
-		} else if (tn->rb.rb_right)
-			rb_set_parent(tn->rb.rb_right, NULL);
+	ret = jffs2_build_inode_fragtree(c, f, &rii);
+	if (ret) {
+		JFFS2_ERROR("Failed to build final fragtree for inode #%u: error %d\n",
+			    f->inocache->ino, ret);
+		if (f->inocache->state == INO_STATE_READING)
+			jffs2_set_inocache_state(c, f->inocache, INO_STATE_CHECKEDABSENT);
+		jffs2_free_tmp_dnode_info_list(&rii.tn_root);
+		/* FIXME: We could at least crc-check them all */
+		if (rii.mdata_tn) {
+			jffs2_free_full_dnode(rii.mdata_tn->fn);
+			jffs2_free_tmp_dnode_info(rii.mdata_tn);
+			rii.mdata_tn = NULL;
+		}
+		return ret;
+	}
 
-		jffs2_free_tmp_dnode_info(tn);
-		if (ret) {
-			dbg_readinode("delete dnode %u-%u.\n",
-				fn->ofs, fn->ofs + fn->size);
-			jffs2_free_full_dnode(fn);
+	if (rii.mdata_tn) {
+		if (rii.mdata_tn->fn->raw == rii.latest_ref) {
+			f->metadata = rii.mdata_tn->fn;
+			jffs2_free_tmp_dnode_info(rii.mdata_tn);
+		} else {
+			jffs2_kill_tn(c, rii.mdata_tn);
 		}
+		rii.mdata_tn = NULL;
 	}
-	jffs2_dbg_fragtree_paranoia_check_nolock(f);
 
-	BUG_ON(first_fn && ref_obsolete(first_fn->raw));
+	f->dents = rii.fds;
+
+	jffs2_dbg_fragtree_paranoia_check_nolock(f);
 
-	fn = first_fn;
-	if (unlikely(!first_fn)) {
+	if (unlikely(!rii.latest_ref)) {
 		/* No data nodes for this inode. */
 		if (f->inocache->ino != 1) {
 			JFFS2_WARNING("no data nodes found for ino #%u\n", f->inocache->ino);
-			if (!fd_list) {
+			if (!rii.fds) {
 				if (f->inocache->state == INO_STATE_READING)
 					jffs2_set_inocache_state(c, f->inocache, INO_STATE_CHECKEDABSENT);
 				return -EIO;
@@ -746,7 +1204,7 @@ static int jffs2_do_read_inode_internal(struct jffs2_sb_info *c,
 		return 0;
 	}
 
-	ret = jffs2_flash_read(c, ref_offset(fn->raw), sizeof(*latest_node), &retlen, (void *)latest_node);
+	ret = jffs2_flash_read(c, ref_offset(rii.latest_ref), sizeof(*latest_node), &retlen, (void *)latest_node);
 	if (ret || retlen != sizeof(*latest_node)) {
 		JFFS2_ERROR("failed to read from flash: error %d, %zd of %zd bytes read\n",
 			ret, retlen, sizeof(*latest_node));
@@ -759,7 +1217,7 @@ static int jffs2_do_read_inode_internal(struct jffs2_sb_info *c,
 	crc = crc32(0, latest_node, sizeof(*latest_node)-8);
 	if (crc != je32_to_cpu(latest_node->node_crc)) {
 		JFFS2_ERROR("CRC failed for read_inode of inode %u at physical location 0x%x\n",
-			f->inocache->ino, ref_offset(fn->raw));
+			f->inocache->ino, ref_offset(rii.latest_ref));
 		up(&f->sem);
 		jffs2_do_clear_inode(c, f);
 		return -EIO;
@@ -767,10 +1225,10 @@ static int jffs2_do_read_inode_internal(struct jffs2_sb_info *c,
 
 	switch(jemode_to_cpu(latest_node->mode) & S_IFMT) {
 	case S_IFDIR:
-		if (mctime_ver > je32_to_cpu(latest_node->version)) {
+		if (rii.mctime_ver > je32_to_cpu(latest_node->version)) {
 			/* The times in the latest_node are actually older than
 			   mctime in the latest dirent. Cheat. */
-			latest_node->ctime = latest_node->mtime = cpu_to_je32(latest_mctime);
+			latest_node->ctime = latest_node->mtime = cpu_to_je32(rii.latest_mctime);
 		}
 		break;
 
@@ -800,7 +1258,7 @@ static int jffs2_do_read_inode_internal(struct jffs2_sb_info *c,
 				return -ENOMEM;
 			}
 
-			ret = jffs2_flash_read(c, ref_offset(fn->raw) + sizeof(*latest_node),
+			ret = jffs2_flash_read(c, ref_offset(rii.latest_ref) + sizeof(*latest_node),
 						je32_to_cpu(latest_node->csize), &retlen, (char *)f->target);
 
 			if (ret  || retlen != je32_to_cpu(latest_node->csize)) {