Re: [REVIEW] Fix unaligned accesses in IA64 in xfsprogs

Barry Naujok
2008-12-02T00:37:20Z

On Tue, 02 Dec 2008 00:42:05 +1100, Christoph Hellwig <hch@infradead.org>
wrote:

> On Mon, Dec 01, 2008 at 05:34:39PM +1100, Barry Naujok wrote:
>> xfs_repair is the main culprit when getting disk extents which aren't
>> properly aligned in memory. This patch does not call
>> xfs_bmbt_disk_get_all directly anymore but does an unaligned get on
>> the disk extent record and calls xfs_bmbt_get_all which is host-based
>> like the rest of the kernel routines do.
>
> What about just doin the get_unaligned in xfs_bmbt_disk_get_all? That
> way we could just use it everywhere. The only users that don't need
> the get_unaligned are in the tracing code, and I don't think we should
> be worried about that little bit of overhead.
>
>> @@ -277,21 +277,17 @@ convert_extent(
>> xfs_dfilblks_t *cp,
>> int *fp)
>> {
>
> And then we could replace this helper with a direct call to
> xfs_bmbt_disk_get_all as the caller would be much cleaner with a
> xfs_bmbt_irec_t on the stack anyway..

Obviously modifying xfs_bmbt_disk_get_all yields a much smaller patch:

===========================================================================
xfsprogs/db/bmap.c
===========================================================================

--- a/xfsprogs/db/bmap.c 2008-12-02 11:21:00.000000000 +1100
+++ b/xfsprogs/db/bmap.c 2008-12-02 11:20:41.324928232 +1100
@@ -277,21 +277,14 @@ convert_extent(
xfs_dfilblks_t *cp,
int *fp)
{
- xfs_bmbt_irec_t irec, *s = &irec;
- xfs_bmbt_rec_t rpcopy, *p = &rpcopy;
+ xfs_bmbt_irec_t irec;

- memmove(&rpcopy, rp, sizeof(rpcopy));
- libxfs_bmbt_disk_get_all(p, s);
+ libxfs_bmbt_disk_get_all(rp, &irec);

- if (s->br_state == XFS_EXT_UNWRITTEN) {
- *fp = 1;
- } else {
- *fp = 0;
- }
-
- *op = s->br_startoff;
- *sp = s->br_startblock;
- *cp = s->br_blockcount;
+ *fp = irec.br_state == XFS_EXT_UNWRITTEN;
+ *op = irec.br_startoff;
+ *sp = irec.br_startblock;
+ *cp = irec.br_blockcount;
}

void

===========================================================================
xfsprogs/libxfs/xfs_bmap_btree.c
===========================================================================

--- a/xfsprogs/libxfs/xfs_bmap_btree.c 2008-12-02 11:21:00.000000000 +1100
+++ b/xfsprogs/libxfs/xfs_bmap_btree.c 2008-12-02 11:20:09.553355392 +1100
@@ -181,7 +181,8 @@ xfs_bmbt_disk_get_all(
xfs_bmbt_rec_t *r,
xfs_bmbt_irec_t *s)
{
- __xfs_bmbt_get_all(be64_to_cpu(r->l0), be64_to_cpu(r->l1), s);
+ __xfs_bmbt_get_all(get_unaligned_be64(&r->l0),
+ get_unaligned_be64(&r->l1), s);
}

/*