Re: [PATCH] file-posix: allow -EBUSY errors during write zeros on block

[Nir Soffer]

On Tue, Mar 2, 2021 at 4:08 AM ChangLimin <changlm@chinatelecom.cn> wrote:
>
> After Linux 5.10, write zeros to a multipath device using
> ioctl(fd, BLKZEROOUT, range) with cache none or directsync will return EBUSY.
>
> Similar to handle_aiocb_write_zeroes_unmap, handle_aiocb_write_zeroes_block
> allow -EBUSY errors during ioctl(fd, BLKZEROOUT, range).
>
> Reference commit in Linux 5.10:
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=384d87ef2c954fc58e6c5fd8253e4a1984f5fe02

But this can happen only when the block device is used by a file system or
maybe someone else. In qemu we assume that we are the only user of the
block device, so EBUSY is a fatal error that should never happen, no?

Can you explain a real world use case when we get EBUSY?

Nir

> Signed-off-by: ChangLimin <changlm@chinatelecom.cn>
> ---
>  block/file-posix.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 05079b40ca..3e60c96214 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1629,8 +1629,13 @@ static ssize_t 
> handle_aiocb_write_zeroes_block(RawPosixAIOData *aiocb)
>          } while (errno == EINTR);
>
>          ret = translate_err(-errno);
> -        if (ret == -ENOTSUP) {
> +        switch (ret) {
> +        case -ENOTSUP:
> +        case -EINVAL:
> +        case -EBUSY:
>              s->has_write_zeroes = false;
> +            return -ENOTSUP;
> +            break;
>          }
>      }
>  #endif
> --
> 2.27.0
>