From: Max Reitz <mreitz@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Kevin Wolf <kwolf@redhat.com>,
qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v2] block/raw-posix: Try both FIEMAP and SEEK_HOLE
Date: Thu, 15 May 2014 01:13:12 +0200 [thread overview]
Message-ID: <5373F888.5030100@redhat.com> (raw)
In-Reply-To: <20140511172605.GA9761@lst.de>
On 11.05.2014 19:26, Christoph Hellwig wrote:
> On Tue, May 06, 2014 at 09:00:54PM +0200, Max Reitz wrote:
>> The current version of raw-posix always uses ioctl(FS_IOC_FIEMAP) if
>> FIEMAP is available; lseek with SEEK_HOLE/SEEK_DATA are not even
>> compiled in in this case. However, there may be implementations which
>> support the latter but not the former (e.g., NFSv4.2) as well as vice
>> versa.
>>
>> To cover both cases, always try SEEK_HOLE/SEEK_DATA (as this will
>> probably be covered by POSIX soon) and if that does not work, fall back
>> to FIEMAP; and if that does not work either, treat everything as
>> allocated.
> Btw, while I think that SEEK_HOLE/SEEK_DATA generally is the better API
> for qemu, the NFS 4.2 SEEK operation will be sufficient for a proper FIEMAP
> implementation, and we'll implement it for the Linux NFS client.
Hm, great, in that case this patch will probably never be put to the
test. *g*
Max
prev parent reply other threads:[~2014-05-14 23:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-06 19:00 [Qemu-devel] [PATCH v2] block/raw-posix: Try both FIEMAP and SEEK_HOLE Max Reitz
2014-05-06 21:18 ` Eric Blake
2014-05-06 21:35 ` Max Reitz
2014-05-06 21:47 ` Eric Blake
2014-05-06 21:48 ` Max Reitz
2014-05-07 5:56 ` Markus Armbruster
2014-05-08 18:35 ` Max Reitz
2014-05-09 8:03 ` Paolo Bonzini
2014-05-11 17:26 ` Christoph Hellwig
2014-05-14 23:13 ` Max Reitz [this message]
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