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Re: [PATCH v4 12/16] block/io: support int64_t bytes in bdrv_co_do_copy_
From: |
Eric Blake |
Subject: |
Re: [PATCH v4 12/16] block/io: support int64_t bytes in bdrv_co_do_copy_on_readv() |
Date: |
Fri, 22 Jan 2021 10:34:18 -0600 |
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Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 |
On 12/11/20 12:39 PM, 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_copy_on_readv() now.
>
> 'bytes' type widening, so callers are safe. Look at the function
> itself:
>
> bytes, skip_bytes and progress become int64_t.
>
> bdrv_round_to_clusters() is OK, cluster_bytes now may be large.
> trace_bdrv_co_do_copy_on_readv() is OK
>
> looping through cluster_bytes is still OK.
>
> pnum is still capped to max_transfer, and to MAX_BOUNCE_BUFFER when we
> are going to do COR operation. Therefor calculations in
> qemu_iovec_from_buf() and bdrv_driver_preadv() should not change.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
> block/io.c | 8 +++++---
> block/trace-events | 2 +-
> 2 files changed, 6 insertions(+), 4 deletions(-)
>
Reviewed-by: Eric Blake <eblake@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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