[dm-devel] [PATCH v3 1/4] dm dust: report some message results back to user directly

[Bryan Gurney]

On Fri, Jun 19, 2020 at 8:37 AM yangerkun <yangerkun at huawei.com> wrote:
>
> Some type of message(queryblock/countbadblocks/removebadblock) may better
> report results to user directly. Do it with DMEMIT.
>
> Signed-off-by: yangerkun <yangerkun at huawei.com>
> ---
>  drivers/md/dm-dust.c | 31 ++++++++++++++++++-------------
>  1 file changed, 18 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/md/dm-dust.c b/drivers/md/dm-dust.c
> index ff03b90072c5..a0c75c104de0 100644
> --- a/drivers/md/dm-dust.c
> +++ b/drivers/md/dm-dust.c
> @@ -138,20 +138,22 @@ static int dust_add_block(struct dust_device *dd, unsigned long long block,
>         return 0;
>  }
>
> -static int dust_query_block(struct dust_device *dd, unsigned long long block)
> +static int dust_query_block(struct dust_device *dd, unsigned long long block, char *result,
> +                           unsigned int maxlen, unsigned int *sz_ptr)
>  {
>         struct badblock *bblock;
>         unsigned long flags;
> +       unsigned int sz = *sz_ptr;
>
>         spin_lock_irqsave(&dd->dust_lock, flags);
>         bblock = dust_rb_search(&dd->badblocklist, block);
>         if (bblock != NULL)
> -               DMINFO("%s: block %llu found in badblocklist", __func__, block);
> +               DMEMIT("block %llu found in badblocklist", block);
>         else
> -               DMINFO("%s: block %llu not found in badblocklist", __func__, block);
> +               DMEMIT("block %llu not found in badblocklist", block);
>         spin_unlock_irqrestore(&dd->dust_lock, flags);
>
> -       return 0;
> +       return 1;

First, thank you very much for this patch.  After the concerns to
convert some functions to use DMEMIT were brought up, I was trying to
start the conversion, when this patch arrived, so I installed it, and
tested it.

I do have a question, though:

First, I see that in dust_query_block() (above) and
dust_clear_badblocks(), the "return 0" statement is changed to "return
1".

(Additionally, there is a change from "r = 0" to  "r = 1", in the
"countbadblocks" message handler)

On testing the functions, they still work, but why was this change
made?  Is it related to the use of DMEMIT?


Thanks,

Bryan

>  }
>
>  static int __dust_map_read(struct dust_device *dd, sector_t thisblock)
> @@ -259,11 +261,13 @@ static bool __dust_clear_badblocks(struct rb_root *tree,
>         return true;
>  }
>
> -static int dust_clear_badblocks(struct dust_device *dd)
> +static int dust_clear_badblocks(struct dust_device *dd, char *result, unsigned int maxlen,
> +                               unsigned int *sz_ptr)
>  {
>         unsigned long flags;
>         struct rb_root badblocklist;
>         unsigned long long badblock_count;
> +       unsigned int sz = *sz_ptr;
>
>         spin_lock_irqsave(&dd->dust_lock, flags);
>         badblocklist = dd->badblocklist;
> @@ -273,11 +277,11 @@ static int dust_clear_badblocks(struct dust_device *dd)
>         spin_unlock_irqrestore(&dd->dust_lock, flags);
>
>         if (!__dust_clear_badblocks(&badblocklist, badblock_count))
> -               DMINFO("%s: no badblocks found", __func__);
> +               DMEMIT("no badblocks found");
>         else
> -               DMINFO("%s: badblocks cleared", __func__);
> +               DMEMIT("badblocks cleared");
>
> -       return 0;
> +       return 1;
>  }
>
>  /*
> @@ -383,7 +387,7 @@ static void dust_dtr(struct dm_target *ti)
>  }
>
>  static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
> -                       char *result_buf, unsigned int maxlen)
> +                       char *result, unsigned int maxlen)
>  {
>         struct dust_device *dd = ti->private;
>         sector_t size = i_size_read(dd->dev->bdev->bd_inode) >> SECTOR_SHIFT;
> @@ -393,6 +397,7 @@ static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
>         unsigned char wr_fail_cnt;
>         unsigned int tmp_ui;
>         unsigned long flags;
> +       unsigned int sz = 0;
>         char dummy;
>
>         if (argc == 1) {
> @@ -410,12 +415,12 @@ static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
>                         r = 0;
>                 } else if (!strcasecmp(argv[0], "countbadblocks")) {
>                         spin_lock_irqsave(&dd->dust_lock, flags);
> -                       DMINFO("countbadblocks: %llu badblock(s) found",
> +                       DMEMIT("countbadblocks: %llu badblock(s) found",
>                                dd->badblock_count);
>                         spin_unlock_irqrestore(&dd->dust_lock, flags);
> -                       r = 0;
> +                       r = 1;
>                 } else if (!strcasecmp(argv[0], "clearbadblocks")) {
> -                       r = dust_clear_badblocks(dd);
> +                       r = dust_clear_badblocks(dd, result, maxlen, &sz);
>                 } else if (!strcasecmp(argv[0], "quiet")) {
>                         if (!dd->quiet_mode)
>                                 dd->quiet_mode = true;
> @@ -441,7 +446,7 @@ static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
>                 else if (!strcasecmp(argv[0], "removebadblock"))
>                         r = dust_remove_block(dd, block);
>                 else if (!strcasecmp(argv[0], "queryblock"))
> -                       r = dust_query_block(dd, block);
> +                       r = dust_query_block(dd, block, result, maxlen, &sz);
>                 else
>                         invalid_msg = true;
>
> --
> 2.25.4
>