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Date:      Thu, 29 Mar 2012 21:28:47 +0300
From:      Konstantin Belousov <kostikbel@gmail.com>
To:        mdf@freebsd.org
Cc:        fs@freebsd.org
Subject:   Re: RFC: SEEK_HOLE/SEEK_DATA common implementation
Message-ID:  <20120329182847.GD2358@deviant.kiev.zoral.com.ua>
In-Reply-To: <CAMBSHm8Qoj-Qhr_uXXYMe_M17ngU89ToK=ZLfKCs1TZCkYSM2w@mail.gmail.com>
References:  <20120327183440.GS2358@deviant.kiev.zoral.com.ua> <20120329091415.GA1316@reks> <20120329093427.GA2358@deviant.kiev.zoral.com.ua> <CAMBSHm8Qoj-Qhr_uXXYMe_M17ngU89ToK=ZLfKCs1TZCkYSM2w@mail.gmail.com>

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On Thu, Mar 29, 2012 at 06:56:31AM -0700, mdf@freebsd.org wrote:
> 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.
>=20
> 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.
But you had to already take some measure to disable the call to VOP_BMAP()
for your filesystem, otherwise mmap() is fatal too (whatever the word
fatal means) ?

>=20
> 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.

Does anything change if VOP_SEEKDATA() is added which default implementation
using VOP_BMAP() ?

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