hfsplus: fix "unused node is not erased" error

Zero newly allocated extents in the catalog tree if volume attributes
tell us to.  Not doing so we risk getting the "unused node is not
erased" error.  See kHFSUnusedNodeFix flag in Apple's source code for
reference.

There was a previous commit clearing the node when it is freed: commit
899bed05e9f6 ("hfsplus: fix issue with unzeroed unused b-tree nodes").
But it did not handle newly allocated extents (this patch fixes it).
And it zeroed nodes in all trees unconditionally which is an overkill.

This patch adds a condition and also switches to 'tree->node_size' as a
simpler method of getting the length to zero.

Signed-off-by: Sergei Antonov <saproj@gmail.com>
Cc: Anton Altaparmakov <aia21@cam.ac.uk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Hin-Tak Leung <htl10@users.sourceforge.net>
Cc: Kyle Laracey <kalaracey@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 2 deletions

diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index 285502af8df1..759708fd9331 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -646,8 +646,8 @@ void hfs_bnode_put(struct hfs_bnode *node)
                 if (test_bit(HFS_BNODE_DELETED, &node->flags)) {
                         hfs_bnode_unhash(node);
                         spin_unlock(&tree->hash_lock);
-                        hfs_bnode_clear(node, 0,
-                                PAGE_CACHE_SIZE * tree->pages_per_bnode);
+                        if (hfs_bnode_need_zeroout(tree))
+                                hfs_bnode_clear(node, 0, tree->node_size);
                         hfs_bmap_free(node);
                         hfs_bnode_free(node);
                         return;
@@ -656,3 +656,16 @@ void hfs_bnode_put(struct hfs_bnode *node)
         }
 }
 
+/*
+ * Unused nodes have to be zeroed if this is the catalog tree and
+ * a corresponding flag in the volume header is set.
+ */
+bool hfs_bnode_need_zeroout(struct hfs_btree *tree)
+{
+        struct super_block *sb = tree->inode->i_sb;
+        struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
+        const u32 volume_attr = be32_to_cpu(sbi->s_vhdr->attributes);
+
+        return tree->cnid == HFSPLUS_CAT_CNID &&
+                volume_attr & HFSPLUS_VOL_UNUSED_NODE_FIX;
+}