[PATCH 10/9] xfs: fix dir3 freespace block corruption

Dave Chinner
2013-05-28T08:37:25Z

From: Dave Chinner <dchinner@redhat.com>

When the directory freespace index grows to a second block (2017
4k data blocks in the directory), the initialisation of the second
new block header goes wrong. The write verifier fires a corruption
error indicating that the block number in the header is zero. This
was being tripped by xfs/110.

The problem is that the initialisation of the new block is done just
fine in xfs_dir3_free_get_buf(), but the caller then users a dirv2
structure to zero on-disk header fields that xfs_dir3_free_get_buf()
has already zeroed. These lined up with the block number in the dir
v3 header format.

While looking at this, I noticed that the struct xfs_dir3_free_hdr()
had 4 bytes of padding in it that wasn't defined as padding or being
zeroed by the initialisation. Add a pad field declaration and fully
zero the on disk and in-core headers in xfs_dir3_free_get_buf() so
that this is never an issue in the future. Note that this doesn't
change the on-disk layout, just makes the 32 bits of padding in the
layout explicit.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_dir2_format.h | 1 +
fs/xfs/xfs_dir2_node.c | 13 ++++++-------
2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/xfs_dir2_format.h b/fs/xfs/xfs_dir2_format.h
index a3b1bd8..995f1f5 100644
--- a/fs/xfs/xfs_dir2_format.h
+++ b/fs/xfs/xfs_dir2_format.h
@@ -715,6 +715,7 @@ struct xfs_dir3_free_hdr {
__be32 firstdb; /* db of first entry */
__be32 nvalid; /* count of valid entries */
__be32 nused; /* count of used entries */
+ __be32 pad; /* 64 bit alignment. */
};

struct xfs_dir3_free {
diff --git a/fs/xfs/xfs_dir2_node.c b/fs/xfs/xfs_dir2_node.c
index 5246de4..2226a00 100644
--- a/fs/xfs/xfs_dir2_node.c
+++ b/fs/xfs/xfs_dir2_node.c
@@ -263,18 +263,19 @@ xfs_dir3_free_get_buf(
* Initialize the new block to be empty, and remember
* its first slot as our empty slot.
*/
- hdr.magic = XFS_DIR2_FREE_MAGIC;
- hdr.firstdb = 0;
- hdr.nused = 0;
- hdr.nvalid = 0;
+ memset(bp->b_addr, 0, sizeof(struct xfs_dir3_free_hdr));
+ memset(&hdr, 0, sizeof(hdr));
+
if (xfs_sb_version_hascrc(&mp->m_sb)) {
struct xfs_dir3_free_hdr *hdr3 = bp->b_addr;

hdr.magic = XFS_DIR3_FREE_MAGIC;
+
hdr3->hdr.blkno = cpu_to_be64(bp->b_bn);
hdr3->hdr.owner = cpu_to_be64(dp->i_ino);
uuid_copy(&hdr3->hdr.uuid, &mp->m_sb.sb_uuid);
- }
+ } else
+ hdr.magic = XFS_DIR2_FREE_MAGIC;
xfs_dir3_free_hdr_to_disk(bp->b_addr, &hdr);
*bpp = bp;
return 0;
@@ -1921,8 +1922,6 @@ xfs_dir2_node_addname_int(
*/
freehdr.firstdb = (fbno - XFS_DIR2_FREE_FIRSTDB(mp)) *
xfs_dir3_free_max_bests(mp);
- free->hdr.nvalid = 0;
- free->hdr.nused = 0;
} else {
free = fbp->b_addr;
bests = xfs_dir3_free_bests_p(mp, free);