Subject: Re: bug#8001: cp (8.10) sparse handling fails on compressed btrfs (cp/fiemap-2)

From: Pádraig Brady <[email-masked]>
Date: Sun, 20 Feb 2011 00:39:47 +0000

On 19/02/11 23:22, Pádraig Brady wrote:
> On 19/02/11 18:28, Mike Frysinger wrote:
>> based on other threads (which i havent been following too closely), did we 
>> settle on this being a btrfs bug ?
>> -mike
> 
> Nope, cp 8.10 is not absolved yet.
> It may be btrfs not honoring FIEMAP_FLAG_SYNC,
> and/or it may be cp needing to handle FIEMAP_EXTENT_ENCODED
> specially.
> 
> It would help if you ran `sync` before the copy,
> to exclude that as a possible issue.
> 
> Also `filefrag -v` output for the file on
> the compressed BTRFS file system would be helpful.

Hmm I just tried the latest Fedora 15 live image
and was tripped up a bit by https://bugzilla.redhat.com/show_bug.c

Anyway it uses 2.6.38 rc4 and "compress" doesn't
seem to be implemented for BTRFS there?
Writing a file of zeros showed a normal disk usage,
and filefrag -v didn't report any flags for the extents.

In any case, cp/fiemap-2 passed on each of
about 100 runs, even without introducing
and syncs.

cheers,
Pádraig.