Re: [PATCH v2 1/1] mkfs: Break block discard into chunks of 2 GB

[Pavel Reichl <preichl@redhat.com>]

Oh,  I forgot to add '\n' to one of the printf statements. I'll send
fixed patch immediately.

On Wed, Nov 27, 2019 at 10:23 PM Pavel Reichl <preichl@redhat.com> wrote:
>
> Some users are not happy about the BLKDISCARD taking too long and at the same
> time not being informed about that - so they think that the command actually
> hung.
>
> This commit changes code so that progress reporting is possible and also typing
> the ^C will cancel the ongoing BLKDISCARD.
>
> Signed-off-by: Pavel Reichl <preichl@redhat.com>
> ---
>  mkfs/xfs_mkfs.c | 50 ++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 37 insertions(+), 13 deletions(-)
>
> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> index 18338a61..7fa4af0e 100644
> --- a/mkfs/xfs_mkfs.c
> +++ b/mkfs/xfs_mkfs.c
> @@ -1240,17 +1240,40 @@ done:
>  }
>
>  static void
> -discard_blocks(dev_t dev, uint64_t nsectors)
> +discard_blocks(dev_t dev, uint64_t nsectors, int quiet)
>  {
> -       int fd;
> +       int             fd;
> +       uint64_t        offset = 0;
> +       /* Discard the device 2G at a time */
> +       const uint64_t  step = 2ULL << 30;
> +       const uint64_t  count = BBTOB(nsectors);
>
> -       /*
> -        * We intentionally ignore errors from the discard ioctl.  It is
> -        * not necessary for the mkfs functionality but just an optimization.
> -        */
>         fd = libxfs_device_to_fd(dev);
> -       if (fd > 0)
> -               platform_discard_blocks(fd, 0, nsectors << 9);
> +       if (fd <= 0)
> +               return;
> +       if (!quiet) {
> +               printf("Discarding blocks...");
> +               printf("...");
> +       }
> +
> +       /* The block discarding happens in smaller batches so it can be
> +        * interrupted prematurely
> +        */
> +       while (offset < count) {
> +               uint64_t        tmp_step = min(step, count - offset);
> +
> +               /*
> +                * We intentionally ignore errors from the discard ioctl. It is
> +                * not necessary for the mkfs functionality but just an
> +                * optimization. However we should stop on error.
> +                */
> +               if (platform_discard_blocks(fd, offset, tmp_step))
> +                       return;
> +
> +               offset += tmp_step;
> +       }
> +       if (!quiet)
> +               printf("Done.\n");
>  }
>
>  static __attribute__((noreturn)) void
> @@ -2507,18 +2530,19 @@ open_devices(
>
>  static void
>  discard_devices(
> -       struct libxfs_xinit     *xi)
> +       struct libxfs_xinit     *xi,
> +       int                     quiet)
>  {
>         /*
>          * This function has to be called after libxfs has been initialized.
>          */
>
>         if (!xi->disfile)
> -               discard_blocks(xi->ddev, xi->dsize);
> +               discard_blocks(xi->ddev, xi->dsize, quiet);
>         if (xi->rtdev && !xi->risfile)
> -               discard_blocks(xi->rtdev, xi->rtsize);
> +               discard_blocks(xi->rtdev, xi->rtsize, quiet);
>         if (xi->logdev && xi->logdev != xi->ddev && !xi->lisfile)
> -               discard_blocks(xi->logdev, xi->logBBsize);
> +               discard_blocks(xi->logdev, xi->logBBsize, quiet);
>  }
>
>  static void
> @@ -3749,7 +3773,7 @@ main(
>          * All values have been validated, discard the old device layout.
>          */
>         if (discard && !dry_run)
> -               discard_devices(&xi);
> +               discard_devices(&xi, quiet);
>
>         /*
>          * we need the libxfs buffer cache from here on in.
> --
> 2.23.0
>