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From: Markus Armbruster <armbru@redhat.com>
To: lishan <lishan24@huawei.com>
Cc: qemu-devel@nongnu.org, eric.fangyi@huawei.com
Subject: Re: [PATCH] block/file-posix: Limit max_iov to IOV_MAX
Date: Mon, 20 Sep 2021 06:47:10 +0200	[thread overview]
Message-ID: <87lf3rn99t.fsf@dusky.pond.sub.org> (raw)
In-Reply-To: <20210918040658.19484-1-lishan24@huawei.com> (lishan's message of "Sat, 18 Sep 2021 12:06:58 +0800")

lishan <lishan24@huawei.com> writes:

> AIO read/write. The size of iocb->aio_nbytes in the kernel cannot exceed UIO_MAXIOV = 1024.
> max_segments read from the block device layer may be greater than UIO_MAXIOV,
> this causes the ioq_submit interface to return a -22(-EINVAL) error result.
> ---
>  block/file-posix.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/file-posix.c b/block/file-posix.c
> index d81e15efa4..137e27e47b 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1273,7 +1273,8 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
>  
>          ret = hdev_get_max_segments(s->fd, &st);
>          if (ret > 0) {
> -            bs->bl.max_iov = ret;
> +            /* The maximum segment size allowed by the kernel is UIO_MAXIOV = 1024. */
> +            bs->bl.max_iov = MIN(ret, IOV_MAX);
>          }
>      }
>  }

I didn't check your assertion we always need to cap at IOV_MAX.
Assuming you're right, why not do it in hdev_get_max_segments()?



  reply	other threads:[~2021-09-20  4:48 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-18  4:06 lishan
2021-09-20  4:47 ` Markus Armbruster [this message]
2021-09-20  9:03 ` Daniel P. Berrangé
2021-09-18  7:33 lishan
2021-09-20  8:14 ` Kevin Wolf

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