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Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii fi
From: |
Eric Blake |
Subject: |
Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse |
Date: |
Tue, 31 Jul 2012 11:27:51 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 |
On 07/31/2012 09:33 AM, Paul Eggert wrote:
> On 07/31/2012 12:05 AM, Jim Meyering wrote:
>> Given the knowledge that we're using one of those non-compressing file
>> systems, the legacy heuristic will work.
>
> I originally coded it up that way, using the st_fstype member
> that Solaris has -- this is more convenient and more accurate
> than the dance with statvfs. But I gave it up on the grounds
> that any system sane enough to have st_fstype already has
> a working SEEK_HOLE (or is so old that we don't care about it....).
>
> Maybe while we're asking for SEEK_HOLE, we can also ask for
> st_fstype? The problem with the statvfs dance is that it opens
> up race conditions when some other process is doing mounts.
I think Linux' 'struct stat' is full already; the best we can hope for
is an implementation of xstat() that gives us the information we want
(other nice fields to add would be st_btim for birth-time on file
systems that support it, matching what BSD and cygwin already had room
to provide as part of stat()). But I certainly want xstat(); I'm
surprised to see that the discussion about the new interface in 2010
appears to have died off, rather than proceeding all the way to getting
it in the kernel.
--
Eric Blake address@hidden +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, (continued)
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Jim Meyering, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Paul Eggert, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Jim Meyering, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Paul Eggert, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Jim Meyering, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Paul Eggert, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Jim Meyering, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Paul Eggert, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Jim Meyering, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Paul Eggert, 2012/07/31
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse,
Eric Blake <=
- Re: SEEK_HOLE defined but useless on linux-3.4+/ext4 [Re: small ascii files can be sparse, Jim Meyering, 2012/07/31