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From: Eric Blake <eblake@redhat.com>
To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
	qemu-block@nongnu.org
Cc: kwolf@redhat.com, fam@euphon.net, integration@gluster.org,
	berto@igalia.com, pavel.dovgaluk@ispras.ru, dillaman@redhat.com,
	qemu-devel@nongnu.org, sw@weilnetz.de, pl@kamp.de,
	ronniesahlberg@gmail.com, mreitz@redhat.com, den@openvz.org,
	sheepdog@lists.wpkg.org, stefanha@redhat.com,
	namei.unix@gmail.com, pbonzini@redhat.com, jsnow@redhat.com,
	ari@tuxera.com
Subject: Re: [PATCH v3 05/17] block/io: support int64_t bytes in bdrv_co_do_pwrite_zeroes()
Date: Fri, 8 May 2020 13:20:29 -0500	[thread overview]
Message-ID: <d102bdad-a6aa-2153-04e7-9338e4014740@redhat.com> (raw)
In-Reply-To: <20200430111033.29980-6-vsementsov@virtuozzo.com>

On 4/30/20 6:10 AM, Vladimir Sementsov-Ogievskiy wrote:
> We are generally moving to int64_t for both offset and bytes parameters
> on all io paths.
> 
> Main motivation is realization of 64-bit write_zeroes operation for
> fast zeroing large disk chunks, up to the whole disk.
> 
> We chose signed type, to be consistent with off_t (which is signed) and
> with possibility for signed return type (where negative value means
> error).
> 
> So, prepare bdrv_co_do_pwrite_zeroes() now.
> 
> Patch-correctness audit by Eric Blake:
> 

> 
>      use of 'num' within the loop
>      compute 'int head' via % 'int alignment' - safe
>      clamp size by 'int max_write_zeroes' - safe
>      drv->bdrv_co_pwrite_zeroes(int) - safe because of clamping
>      clamp size by 'int max_transfer' - safe
>      qemu_iovec_init_buf(size_t) - safe because of clamping
>      bdrv_driver_pwritev(uint64_t) [well, int64_t after 4/17] - safe

I know you were quoting me, but the [comment] can be dropped (I wrote my 
audit on patches in isolation while reviewing the pre-series state of 
the tree, but when this commit is finally applied, the previous patch 
will already be in place)

> 
>      So even with the wider type, we aren't exceeding the contract of
>      anything we pass it on to.  Later patches may improve
>      drv->bdrv_co_pwrite_zeroes and qemu_iovec_init_buf to be 64-bit
>      clean, at which point we would want to revisit this function to use
>      64-bit clamping rather than 32-bit clamping, but it does not have
>      to happen here.
> 
> Series: 64bit-block-status
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---
>   block/io.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org



  reply	other threads:[~2020-05-08 18:21 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-30 11:10 [PATCH v3 00/17] 64bit block-layer Vladimir Sementsov-Ogievskiy
2020-04-30 11:10 ` [PATCH v3 01/17] block/throttle-groups: throttle_group_co_io_limits_intercept(): 64bit bytes Vladimir Sementsov-Ogievskiy
2020-05-11 15:28   ` Alberto Garcia
2020-04-30 11:10 ` [PATCH v3 02/17] block: use int64_t as bytes type in tracked requests Vladimir Sementsov-Ogievskiy
2020-05-11 15:32   ` Alberto Garcia
2020-05-22 19:09   ` Eric Blake
2020-04-30 11:10 ` [PATCH v3 03/17] block/io: use int64_t bytes parameter in bdrv_check_byte_request() Vladimir Sementsov-Ogievskiy
2020-05-11 15:57   ` Alberto Garcia
2020-04-30 11:10 ` [PATCH v3 04/17] block/io: use int64_t bytes in driver wrappers Vladimir Sementsov-Ogievskiy
2020-05-11 16:30   ` Alberto Garcia
2020-04-30 11:10 ` [PATCH v3 05/17] block/io: support int64_t bytes in bdrv_co_do_pwrite_zeroes() Vladimir Sementsov-Ogievskiy
2020-05-08 18:20   ` Eric Blake [this message]
2020-05-11 17:17   ` Alberto Garcia
2020-05-11 18:34     ` Eric Blake
2020-06-23 10:20       ` Vladimir Sementsov-Ogievskiy
2020-06-23 16:37         ` Eric Blake
2020-04-30 11:10 ` [PATCH v3 06/17] block/io: support int64_t bytes in bdrv_aligned_pwritev() Vladimir Sementsov-Ogievskiy
2020-05-08 20:38   ` Eric Blake
2020-06-18 14:29   ` Alberto Garcia
2020-04-30 11:10 ` [PATCH v3 07/17] block/io: support int64_t bytes in bdrv_co_do_copy_on_readv() Vladimir Sementsov-Ogievskiy
2020-05-21 22:29   ` Eric Blake
2020-05-22  6:30     ` Vladimir Sementsov-Ogievskiy
2020-04-30 11:10 ` [PATCH v3 08/17] block/io: support int64_t bytes in bdrv_aligned_preadv() Vladimir Sementsov-Ogievskiy
2020-05-22 15:14   ` Eric Blake
2020-06-18 14:35     ` Alberto Garcia
2020-06-18 14:47       ` Eric Blake
2020-04-30 11:10 ` [PATCH v3 09/17] block/io: support int64_t bytes in bdrv_co_p{read, write}v_part() Vladimir Sementsov-Ogievskiy
2020-05-22 19:34   ` [PATCH v3 09/17] block/io: support int64_t bytes in bdrv_co_p{read,write}v_part() Eric Blake
2020-04-30 11:10 ` [PATCH v3 10/17] block/io: support int64_t bytes in read/write wrappers Vladimir Sementsov-Ogievskiy
2020-04-30 11:10 ` [PATCH v3 11/17] block/io: use int64_t bytes in copy_range Vladimir Sementsov-Ogievskiy
2020-04-30 11:10 ` [PATCH v3 12/17] block/block-backend: convert blk io path to use int64_t parameters Vladimir Sementsov-Ogievskiy
2020-06-23 22:11   ` Eric Blake
2020-04-30 11:10 ` [PATCH v3 13/17] block: use int64_t instead of uint64_t in driver read handlers Vladimir Sementsov-Ogievskiy
2020-04-30 11:10 ` [PATCH v3 14/17] block: use int64_t instead of uint64_t in driver write handlers Vladimir Sementsov-Ogievskiy
2020-04-30 11:10 ` [PATCH v3 15/17] block: use int64_t instead of uint64_t in copy_range driver handlers Vladimir Sementsov-Ogievskiy
2020-04-30 11:10 ` [PATCH v3 16/17] block: use int64_t instead of int in driver write_zeroes handlers Vladimir Sementsov-Ogievskiy
2020-04-30 11:10 ` [PATCH v3 17/17] block: use int64_t instead of int in driver discard handlers Vladimir Sementsov-Ogievskiy
2020-05-06  6:40   ` Vladimir Sementsov-Ogievskiy
2020-04-30 20:51 ` [PATCH v3 00/17] 64bit block-layer no-reply
2020-05-06  6:39   ` Vladimir Sementsov-Ogievskiy
2020-04-30 20:57 ` no-reply
2020-12-01 16:07 ` Vladimir Sementsov-Ogievskiy
2020-12-01 16:56   ` Vladimir Sementsov-Ogievskiy
2020-12-01 21:50   ` Eric Blake

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