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From: Eric Blake <eblake@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kwolf@redhat.com, vsementsov@virtuozzo.com,
	qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: [PATCH v4 2/7] scsi-generic: pass max_segments via max_iov field in BlockLimits
Date: Tue, 8 Jun 2021 12:42:21 -0500	[thread overview]
Message-ID: <20210608174221.lu6pgbpai6xtaqwk@redhat.com> (raw)
In-Reply-To: <20210608131634.423904-3-pbonzini@redhat.com>

On Tue, Jun 08, 2021 at 03:16:29PM +0200, Paolo Bonzini wrote:
> I/O to a disk via read/write is not limited by the number of segments allowed
> by the host adapter; the kernel can split requests if needed, and the limit
> imposed by the host adapter can be very low (256k or so) to avoid that SG_IO
> returns EINVAL if memory is heavily fragmented.

to avoid SG_IO returning EINVAL

> 
> Since this value is only interesting for SG_IO-based I/O, do not include
> it in the max_transfer and only take it into account when patching the
> block limits VPD page in the scsi-generic device.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  block/file-posix.c     | 3 +--
>  hw/scsi/scsi-generic.c | 6 ++++--
>  2 files changed, 5 insertions(+), 4 deletions(-)
>

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org



  reply	other threads:[~2021-06-08 17:45 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-08 13:16 [PATCH v4 0/7] block: file-posix queue Paolo Bonzini
2021-06-08 13:16 ` [PATCH v4 1/7] file-posix: fix max_iov for /dev/sg devices Paolo Bonzini
2021-06-08 17:34   ` Eric Blake
2021-06-08 19:14   ` Vladimir Sementsov-Ogievskiy
2021-06-09 16:08     ` Maxim Levitsky
2021-06-23 15:42     ` Max Reitz
2021-06-24  7:33       ` Vladimir Sementsov-Ogievskiy
2021-06-08 13:16 ` [PATCH v4 2/7] scsi-generic: pass max_segments via max_iov field in BlockLimits Paolo Bonzini
2021-06-08 17:42   ` Eric Blake [this message]
2021-06-09 16:10   ` Maxim Levitsky
2021-06-08 13:16 ` [PATCH v4 3/7] block: add max_hw_transfer to BlockLimits Paolo Bonzini
2021-06-08 17:48   ` Eric Blake
2021-06-09 16:12   ` Maxim Levitsky
2021-06-08 13:16 ` [PATCH v4 4/7] file-posix: try BLKSECTGET on block devices too, do not round to power of 2 Paolo Bonzini
2021-06-08 17:53   ` Eric Blake
2021-06-09 16:15   ` Maxim Levitsky
2021-06-08 13:16 ` [PATCH v4 5/7] block: feature detection for host block support Paolo Bonzini
2021-06-23 15:44   ` Max Reitz
2021-06-08 13:16 ` [PATCH v4 6/7] block: check for sys/disk.h Paolo Bonzini
2021-06-08 13:16 ` [PATCH v4 7/7] block: detect DKIOCGETBLOCKCOUNT/SIZE before use Paolo Bonzini
2021-06-23 15:47   ` Max Reitz

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