Michael L. Semon has been testing CRC patches on a 32 bit system and
been seeing assert failures in the directory code from xfs/080.
Thanks to Michael's heroic efforts with printk debugging, we found
that the problem was that the last free space being left in the
directory structure was too small to fit a unused tag structure and
it was being corrupted and attempting to log a region out of bounds.
Hence the assert failure looked something like:
.....
#5 calling xfs_dir2_data_log_unused() 36 32
#1 4092 4095 4096
#2 8182 8183 4096
XFS: Assertion failed: first <= last && last < BBTOB(bp->b_length), file: fs/xfs/xfs_trans_buf.c, line: 568
Where #1 showed the first region of the dup being logged (i.e. the
last 4 bytes of a directory buffer) and #2 shows the corrupt values
being calculated from the length of the dup entry which overflowed
the size of the buffer.
It turns out that the problem was not in the logging code, nor in
the freespace handling code. It is an initial condition bug that
only shows up on 32 bit systems. When a new buffer is initialised,
where's the freespace that is set up:
[ 172.316249] calling xfs_dir2_leaf_addname() from xfs_dir_createname()
[ 172.316346] #9 calling xfs_dir2_data_log_unused()
[ 172.316351] #1 calling xfs_trans_log_buf() 60 63 4096
[ 172.316353] #2 calling xfs_trans_log_buf() 4094 4095 4096
Note the offset of the first region being logged? It's 60 bytes into
the buffer. Once I saw that, I pretty much knew that the bug was
going to be caused by this.
Essentially, all direct entries are rounded to 8 bytes in length,
and all entries start with an 8 byte alignment. This means that we
can decode inplace as variables are naturally aligned. With the
directory data supposedly starting on a 8 byte boundary, and all
entries padded to 8 bytes, the minimum freespace in a directory
block is supposed to be 8 bytes, which is large enough to fit a
unused data entry structure (6 bytes in size). The fact we only have
4 bytes of free space indicates a directory data block alignment
problem.
And what do you know - there's an implicit hole in the directory
data block header for the CRC format, which means the header is 60
byte on 32 bit intel systems and 64 bytes on 64 bit systems. Needs
padding. And while looking at the structures, I found the same
problem in the attr leaf header. Fix them both.
Note that this only affects 32 bit systems with CRCs enabled.
Everything else is just fine. Note that CRC enabled filesystems created
before this fix on such systems will not be readable with this fix
applied.
Reported-by: Michael L. Semon <mlsemon35@gmail.com>
Debugged-by: Michael L. Semon <mlsemon35@gmail.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
(cherry picked from commit 8a1fd2950e)
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>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
(cherry picked from commit 5ae6e6a401)
Because the header size for the CRC enabled directory blocks is
larger, the offset of the first entry into a directory block is
different to the dir2 format. The shortform directory stores the
dirent's offset so that it doesn't change when moving from shortform
to block form and back again, and hence it needs to take into
account the different header sizes to maintain the correct offsets.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
This addition follows the same pattern as the dir2 block CRCs.
Seeing as both LEAF1 and LEAFN types need to changed at the same
time, this is a pretty large amount of change. leaf block headers
need to be abstracted away from the on-disk structures (struct
xfs_dir3_icleaf_hdr), as do the base leaf entry locations.
This header abstract allows the in-core header and leaf entry
location to be passed around instead of the leaf block itself. This
saves a lot of converting individual variables from on-disk format
to host format where they are used, so there's a good chance that
the compiler will be able to produce much more optimal code as it's
not having to byteswap variables all over the place.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
This addition follows the same pattern as the dir2 block CRCs.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
This addition follows the same pattern as the dir2 block CRCs, but
with a few differences. The main difference is that the free block
header is different between the v2 and v3 formats, so an "in-core"
free block header has been added and _todisk/_from_disk functions
used to abstract the differences in structure format from the code.
This is similar to the on-disk superblock versus the in-core
superblock setup. The in-core strucutre is populated when the buffer
is read from disk, all the in memory checks and modifications are
done on the in-core version of the structure which is written back
to the buffer before the buffer is logged.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
Now that directory buffers are made from a single struct xfs_buf, we
can add CRC calculation and checking callbacks. While there, add all
the fields to the on disk structures for future functionality such
as d_type support, uuids, block numbers, owner inode, etc.
To distinguish between the different on disk formats, change the
magic numbers for the new format directory blocks.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
Change the bests array to be a proper variable sized entry. This is done
easily as no one relies on the size of the structure. Also change
XFS_DIR2_MAX_FREE_BESTS to an inline function while we're at it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Replace the current mess of dir2 headers with just three that have a clear
purpose:
- xfs_dir2_format.h for all format definitions, including the inline helpers
to access our variable size structures
- xfs_dir2_priv.h for all prototypes that are internal to the dir2 code
and not needed by anything outside of the directory code. For this
purpose xfs_da_btree.c, and phase6.c in xfs_repair are considered part
of the directory code.
- xfs_dir2.h for the public interface to the directory code
In addition to the reshuffle I have also update the comments to not only
match the new file structure, but also to describe the directory format
better.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Dave Chinner