linux-ext4 - Re: [PATCH 1/5] fallocate() implementation in i86, x86

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070509165402.GO6375@schatzie.adilger.int>
Date:	Wed, 9 May 2007 09:54:02 -0700
From:	Andreas Dilger <adilger@...sterfs.com>
To:	"Amit K. Arora" <aarora@...ux.vnet.ibm.com>
Cc:	torvalds@...l.org, akpm@...ux-foundation.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-ext4@...r.kernel.org, xfs@....sgi.com, suparna@...ibm.com,
	cmm@...ibm.com
Subject: Re: [PATCH 1/5] fallocate() implementation in i86, x86_64 and powerpc

On May 09, 2007  21:31 +0530, Amit K. Arora wrote:
> 2) For FA_UNALLOCATE mode, should the file system allow unallocation
>    of normal (non-preallocated) blocks (blocks allocated via
>    regular write/truncate operations) also (i.e. work as punch()) ?
>    - Though FA_UNALLOCATE mode is yet to be implemented on ext4, still
>      we need to finalize on the convention here as a general guideline
>      to all the filesystems that implement fallocate.

I would only allow this on FA_ALLOCATE extents.  That means it won't be
possible to do this for filesystems that don't understand unwritten
extents unless there are blocks allocated beyond EOF.

> 3) If above is true, the file size will need to be changed
>    for "unallocation" when block holding the EOF gets unallocated.
>    - If we do not "unallocate" normal (non-preallocated) blocks and we
>      do not change the file size on preallocation, then this is a
>      non-issue.

Not necessarily.  That will just make the file sparse.  If FA_ALLOCATE
does not change the file size, why should FA_UNALLOCATE.

> 4) Should we update mtime & ctime on a successfull allocation/
>    unallocation ?

I would say yes.  If glibc does the fallback fallocate via write() the
mtime/ctime will be updated, so it makes sense to be consistent for
both methods.  Also, it just makes sense from the "this file was modified"
point of view.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

-
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html