[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH v2] block/raw-posix: Try both FIEMAP and SEEK_HO

From: Christoph Hellwig
Subject: Re: [Qemu-devel] [PATCH v2] block/raw-posix: Try both FIEMAP and SEEK_HOLE
Date: Sun, 11 May 2014 19:26:05 +0200
User-agent: Mutt/1.5.17 (2007-11-01)

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.

reply via email to

[Prev in Thread] Current Thread [Next in Thread]