Re: REVIEW: Fix for incore extent corruption.

Russell Cattelan
2008-09-19T15:14:08Z

Eric Sandeen wrote:
> Lachlan McIlroy wrote:
>
>> Here's a patch to remove xfs_iext_irec_compact_full() like Russell
>> did in his original patch - are you guys happy with this?
>>
>> I'm putting it through it's paces now and so far it looks good.
>>
>
> I'll have to think more about it, honestly. Probably fine, but I've not
> looked at all the surrounding code, I was so far just looking for the
> original bug.
>
Once I started looking at the pattern of extent buffer reductions before
and after calling compact_page/full
I noticed even when we did a partial move the number of total buffers
didn't go down.
I suppose you could end up with the stars and moon lining up just right
and you would
do enough partial moves to free up a page.

Since this is all incore buffers space we are talking about all these
space optimizations are
moot once the inode goes inactive and is flushed from cache.

I can't really think of a situation where not doing partial extent moves
is really going to
create an issue but I might be missing something.

-Russell

> (FWIW, compact_full *does* get called reasonably frequently, but the
> memmove case is what's hard to hit...)
>
> -Eric
>
>
>> --- a/fs/xfs/xfs_inode.c 2008-09-19 13:08:08.000000000 +1000
>> +++ b/fs/xfs/xfs_inode.c 2008-09-19 13:16:34.000000000 +1000
>> @@ -4157,7 +4166,7 @@ xfs_iext_indirect_to_direct(
>> ASSERT(nextents <= XFS_LINEAR_EXTS);
>> size = nextents * sizeof(xfs_bmbt_rec_t);
>>
>> - xfs_iext_irec_compact_full(ifp);
>> + xfs_iext_irec_compact_pages(ifp);
>> ASSERT(ifp->if_real_bytes == XFS_IEXT_BUFSZ);
>>
>> ep = ifp->if_u1.if_ext_irec->er_extbuf;
>>
>
> ...
>
>