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Date:      Thu, 29 Mar 2012 06:56:31 -0700
From:      mdf@FreeBSD.org
To:        Konstantin Belousov <kostikbel@gmail.com>
Cc:        fs@freebsd.org
Subject:   Re: RFC: SEEK_HOLE/SEEK_DATA common implementation
Message-ID:  <CAMBSHm8Qoj-Qhr_uXXYMe_M17ngU89ToK=ZLfKCs1TZCkYSM2w@mail.gmail.com>
In-Reply-To: <20120329093427.GA2358@deviant.kiev.zoral.com.ua>
References:  <20120327183440.GS2358@deviant.kiev.zoral.com.ua> <20120329091415.GA1316@reks> <20120329093427.GA2358@deviant.kiev.zoral.com.ua>

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On Thu, Mar 29, 2012 at 2:34 AM, Konstantin Belousov
<kostikbel@gmail.com> wrote:
> Filesystem probably should always fall back to calling vop_stdioctl()
> manually if it ever implements VOP_IOCTL, regardless of seek_hole/data.

We can't if there's a use of VOP_BMAP() in one of the ioctls.  For
OneFS, a call to VOP_BMAP is fatal.  That operation doesn't work with
our system.

We could implement SEEK_HOLE/SEEK_DATA semi-efficiently, but
implementing a custom filesystem becomes very complex once one has not
only to manage replacing all VOPs where the default doesn't work but
also has to know there's a bunch of ioctls in VOP_IOCTL that must be
handled as well.

Thanks,
matthew



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