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Re: [Qemu-block] [Qemu-devel] [RFC PATCH 0/3] scsi-generic and BLKSECTGE
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From: |
Fam Zheng |
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Subject: |
Re: [Qemu-block] [Qemu-devel] [RFC PATCH 0/3] scsi-generic and BLKSECTGET |
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Date: |
Tue, 17 Jan 2017 15:08:18 +0800 |
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User-agent: |
Mutt/1.7.1 (2016-10-04) |
On Mon, 01/16 22:11, Eric Farman wrote:
> (cc'ing linux-scsi for the cover-letter; patches only to QEMU lists.)
>
> In the Linux kernel, I see two (three) places where the BLKSECTGET ioctl is
> handled:
>
> (1) block/(compat_)ioctl.c -- (compat_)blkdev_ioctl
> (2) drivers/scsi/sg.c -- sg_ioctl
>
> The former has been around forever[1], and returns a short value measured in
> sectors. A sector is generally assumed to be 512 bytes.
>
> The latter has been around for slightly less than forever[2], and returns an
> int that measures the value in bytes. A change to return the block count
> was brought up a few years ago[3] and nacked.
>
> As a convenient example, if I use the blockdev tool to drive the ioctl to a
> SCSI disk and its scsi-generic equivalent, I get different results:
Fun! :-/
The patch looks correct but I don't like how it is written a lot, but still
thanks for bringing it up so we won't be bitten in the future, and your detailed
explanation is much appreciated!
Fam