[RFC PATCH mtd-utils 064/110] fsck.ubifs: rebuild_fs: Remove deleted nodes from valid node tree

[Zhihao Cheng]

This is the 2/12 step of rebuilding. Traverse nodes from del_inos and
del_dents trees, remove inode nodes and dentry nodes with smaller sqnum
from valid trees.

This step handles deleting case, for example, file A is deleted, deleted
inode node and deleted dentry node are written, if we ignore the deleted
nodes, file A can be recovered after rebuilding because undeleted inode
node and undeleted dentry node can be scanned. There's an exception, if
deleted inode node and deleted dentry node are reclaimed(by gc) after
deletion, file A is recovered. UBIFS rebuild_fs cannot solve it, because
the real existence information of nodes depends on TNC, but TNC should
not be depended for UBIFS rebuild_fs.

Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
---
 ubifs-utils/fsck.ubifs/rebuild_fs.c | 120 +++++++++++++++++++++++++++++++++++-
 1 file changed, 119 insertions(+), 1 deletion(-)

diff --git a/ubifs-utils/fsck.ubifs/rebuild_fs.c b/ubifs-utils/fsck.ubifs/rebuild_fs.c
index 3ca94869..dbb0f3bc 100644
--- a/ubifs-utils/fsck.ubifs/rebuild_fs.c
+++ b/ubifs-utils/fsck.ubifs/rebuild_fs.c
@@ -364,6 +364,117 @@ out:
 	return err;
 }
 
+static struct scanned_ino_node *
+lookup_valid_ino_node(struct ubifs_info *c, struct scanned_info *si,
+		      struct scanned_ino_node *target)
+{
+	int cmp;
+	struct scanned_ino_node *ino_node;
+	struct rb_node *p;
+
+	p = si->valid_inos.rb_node;
+	while (p) {
+		ino_node = rb_entry(p, struct scanned_ino_node, rb);
+		cmp = keys_cmp(c, &target->key, &ino_node->key);
+		if (cmp < 0) {
+			p = p->rb_left;
+		} else if (cmp > 0) {
+			p = p->rb_right;
+		} else {
+			if (target->header.sqnum > ino_node->header.sqnum)
+				return ino_node;
+			else
+				return NULL;
+		}
+	}
+
+	return NULL;
+}
+
+static struct scanned_dent_node *
+lookup_valid_dent_node(struct ubifs_info *c, struct scanned_info *si,
+		       struct scanned_dent_node *target)
+{
+	int cmp, nlen;
+	struct scanned_dent_node *dent_node;
+	struct rb_node *p;
+
+	p = si->valid_dents.rb_node;
+	while (p) {
+		dent_node = rb_entry(p, struct scanned_dent_node, rb);
+		cmp = keys_cmp(c, &target->key, &dent_node->key);
+		if (cmp < 0) {
+			p = p->rb_left;
+		} else if (cmp > 0) {
+			p = p->rb_right;
+		} else {
+			nlen = min(target->nlen, dent_node->nlen);
+			cmp = strncmp(target->name, dent_node->name, nlen) ? :
+				      target->nlen - dent_node->nlen;
+			if (cmp < 0) {
+				p = p->rb_left;
+			} else if (cmp > 0) {
+				p = p->rb_right;
+			} else {
+				if (target->header.sqnum >
+				    dent_node->header.sqnum)
+					return dent_node;
+				else
+					return NULL;
+			}
+		}
+	}
+
+	return NULL;
+}
+
+/**
+ * remove_del_nodes - remove deleted nodes from valid node tree.
+ * @c: UBIFS file-system description object
+ * @si: records nodes and files information during scanning
+ *
+ * This function compares sqnum between deleted node and corresponding valid
+ * node, removes valid node from tree if the sqnum of deleted node is bigger.
+ * Deleted ino/dent nodes will be removed from @si->del_inos/@si->del_dents
+ * after this function finished.
+ */
+static void remove_del_nodes(struct ubifs_info *c, struct scanned_info *si)
+{
+	struct scanned_ino_node *del_ino_node, *valid_ino_node;
+	struct scanned_dent_node *del_dent_node, *valid_dent_node;
+	struct rb_node *this;
+
+	this = rb_first(&si->del_inos);
+	while (this) {
+		del_ino_node = rb_entry(this, struct scanned_ino_node, rb);
+		this = rb_next(this);
+
+		valid_ino_node = lookup_valid_ino_node(c, si, del_ino_node);
+		if (valid_ino_node) {
+			rb_erase(&valid_ino_node->rb, &si->valid_inos);
+			kfree(valid_ino_node);
+		}
+
+		rb_erase(&del_ino_node->rb, &si->del_inos);
+		kfree(del_ino_node);
+	}
+
+	this = rb_first(&si->del_dents);
+	while (this) {
+		del_dent_node = rb_entry(this, struct scanned_dent_node, rb);
+		this = rb_next(this);
+
+		valid_dent_node = lookup_valid_dent_node(c, si, del_dent_node);
+		if (valid_dent_node) {
+			rb_erase(&valid_dent_node->rb, &si->valid_dents);
+			kfree(valid_dent_node);
+		}
+
+		rb_erase(&del_dent_node->rb, &si->del_dents);
+		kfree(del_dent_node);
+	}
+}
+
 /**
  * ubifs_rebuild_filesystem - Rebuild filesystem.
  * @c: UBIFS file-system description object
@@ -389,9 +500,16 @@ int ubifs_rebuild_filesystem(struct ubifs_info *c)
 	/* Step 1: Scan valid/deleted nodes from volume. */
 	log_out(c, "Scan nodes");
 	err = scan_nodes(c, &si);
-	if (err)
+	if (err) {
 		exit_code |= FSCK_ERROR;
+		goto out;
+	}
+
+	/* Step 2: Remove deleted nodes from valid node tree. */
+	log_out(c, "Remove deleted nodes");
+	remove_del_nodes(c, &si);
 
+out:
 	destroy_scanned_info(c, &si);
 	destroy_rebuild_info(c);
 
-- 
2.13.6