linux-kernel - Re: [RFC 0/9] block: add llseek(SEEK_HOLE/SEEK

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Date: Tue, 2 Apr 2024 14:26:17 +0200
From: Christoph Hellwig <hch@....de>
To: Stefan Hajnoczi <stefanha@...hat.com>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
	eblake@...hat.com, Alasdair Kergon <agk@...hat.com>,
	Mikulas Patocka <mpatocka@...hat.com>, dm-devel@...ts.linux.dev,
	David Teigland <teigland@...hat.com>,
	Mike Snitzer <snitzer@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>, Joe Thornber <ejt@...hat.com>
Subject: Re: [RFC 0/9] block: add llseek(SEEK_HOLE/SEEK_DATA) support

On Thu, Mar 28, 2024 at 04:39:01PM -0400, Stefan Hajnoczi wrote:
> In the block device world there are similar concepts to holes:
> - SCSI has Logical Block Provisioning where the "mapped" state would be
>   considered data and other states would be considered holes.

But for SCSI (and ATA and NVMe) unmapped/delallocated/etc blocks do
not have to return zeroes.  They could also return some other
initialization pattern pattern.  So they are (unfortunately) not a 1:1
mapping to holes in sparse files.