Fix wrong name_len and file_type in intermediate htree nodes

Hello,

while testing the dirshrink patch, I found that sometimes intermediate htree nodes end up with their fake_dirent's name_len and file_type not being zero. e2fsck will then consider the htree to be corrupted as it doesn't recognise that these blocks contain dx_nodes.

As far as I understand it, this happens sometimes when ext4_dx_add_entry() has to create a new index node and calls ext4_append(). In the end ext4_getblk() is called and it might get a buffer that has BH_Uptodate set, causing ext4_getblk() to not zero it out and leave the old content intact.

I can reproduce this with plain linux-2.6.30.5. To produce this I use a nearly full filesystem and continuously create new files in one directory while removing other directories/files at the same time.

Do I understand it correctly, that it happens when the newly allocated block (for the new index node) was very recently used by another file/directory, so that it is still in the buffer cache? But it surprises me that it doesn't happen more often.

Andreas Schlick

When ext4_dx_add_entry() has to split an index node, it has to ensure that name_len of dx_node's fake_dirent is also zero, because otherwise e2fsck won't recognise it as an intermediate htree node and consider the htree to be corrupted.

---
 fs/ext4/namei.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

index 22098e1..682a488 100644
@@ -1590,9 +1590,9 @@ static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
 			goto cleanup;
 		node2 = (struct dx_node *)(bh2->b_data);
 		entries2 = node2->entries;
+		memset(&node2->fake, 0, sizeof(struct fake_dirent));
 		node2->fake.rec_len = ext4_rec_len_to_disk(sb->s_blocksize,
 							   sb->s_blocksize);
-		node2->fake.inode = 0;
 		BUFFER_TRACE(frame->bh, "get_write_access");
 		err = ext4_journal_get_write_access(handle, frame->bh);
 		if (err)

1.6.4

When ext3_dx_add_entry() has to split an index node, it has to ensure that name_len of dx_node's fake_dirent is also zero, because otherwise e2fsck won't recognise it as an intermediate htree node and consider the htree to be corrupted.

---
 fs/ext3/namei.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

index 6ff7b97..877dd2b 100644
@@ -1550,8 +1550,8 @@ static int ext3_dx_add_entry(handle_t *handle, struct dentry *dentry,
 			goto cleanup;
 		node2 = (struct dx_node *)(bh2->b_data);
 		entries2 = node2->entries;
+		memset(&node2->fake, 0, sizeof(struct fake_dirent));
 		node2->fake.rec_len = ext3_rec_len_to_disk(sb->s_blocksize);
-		node2->fake.inode = 0;
 		BUFFER_TRACE(frame->bh, "get_write_access");
 		err = ext3_journal_get_write_access(handle, frame->bh);
 		if (err)

1.6.4

Added to the ext4 patch queue, thanks.

- Ted