Subject: Re: RFC (reassign)buf and carvinf up buffers (was Re: SCSI MMC device abstraction and UDF patch for review)
To: YAMAMOTO Takashi <>
From: Bill Studenmund <>
List: tech-kern
Date: 12/28/2005 21:45:54
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On Thu, Dec 29, 2005 at 12:36:47AM +0100, Reinoud Zandijk wrote:
> On Wed, Dec 28, 2005 at 01:33:34PM -0800, Bill Studenmund wrote:
> > On Sat, Dec 24, 2005 at 02:41:54PM +0100, Reinoud Zandijk wrote:


> true. Well part of my venturing out was to get new ways of solving the=20
> problems without resorting to the `we normally do it this way' solutions.=
> Solutions where LFS might gain from too yes.=20
> I'll try out the reassign though i wonder what problems and complexity=20
> might arise from mismatched vop_strategy() buffer sizes and disc logicl=
> block sizes. vop_strategy() now requests buffers upto say 64 kb/piece and=
> the logical block size might be 2kb. Each part of 2kb can/could be stored=
> somewhere else on disc. Normally a VOP_BMAP could determine the extent it=
> could take in one go but looking up such information can be costly.

vop_strategy() makes requests sized as the file system wants. To be=20
perfectly honest, if your 2k logical blocks are not next to each other,=20
you shouldn't be issuing a 64k request. Or at least it should be broken up=
before the vop_strategy() level.

As such, I don't think we need this support to do what you suggest. I can
think of other reasons I would like it, but the file system should only be
issuing requests (to this level of the kernel) that can make it to the
disk in contiguous blocks.

Take care,


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