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Subject: Re: [PATCH v5 3/5] writeback: fix build problems of "writeback:
 support retrieving per group debug writeback stats of bdi"
From: Kemeng Shi <shikemeng@huaweicloud.com>
To: akpm@linux-foundation.org, willy@infradead.org, jack@suse.cz,
 bfoster@redhat.com, tj@kernel.org
Cc: dsterba@suse.com, mjguzik@gmail.com, dhowells@redhat.com,
 linux-kernel@vger.kernel.org, linux-mm@kvack.org,
 linux-fsdevel@vger.kernel.org, sj@kernel.org, sfr@canb.auug.org.au
References: <20240423034643.141219-1-shikemeng@huaweicloud.com>
 <20240423034643.141219-4-shikemeng@huaweicloud.com>
Message-ID: <085442bc-68c8-4d91-952f-c321c4d81825@huaweicloud.com>
Date: Tue, 23 Apr 2024 11:53:45 +0800
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on 4/23/2024 11:46 AM, Kemeng Shi wrote:
> Fix two build problems:
> 1. implicit declaration of function 'cgroup_ino'.
> 2. unused variable 'stats'.
> 
> After this fix, No build problem is found when CGROUPS is disabled.
> The wb_stats could be successfully retrieved when CGROUP_WRITEBACK is
> disabled:
> cat wb_stats
> WbCgIno:                    1
> WbWriteback:                0 kB
> WbReclaimable:         685440 kB
> WbDirtyThresh:      195530960 kB
> WbDirtied:             691488 kB
> WbWritten:               6048 kB
> WbWriteBandwidth:      102400 kBps
> b_dirty:                    2
> b_io:                       0
> b_more_io:                  0
> b_dirty_time:               0
> state:                      5
> 
> cat wb_stats
> WbCgIno:                    1
> WbWriteback:                0 kB
> WbReclaimable:         818944 kB
> WbDirtyThresh:      195527484 kB
> WbDirtied:             824992 kB
> WbWritten:               6048 kB
> WbWriteBandwidth:      102400 kBps
> b_dirty:                    2
> b_io:                       0
> b_more_io:                  0
> b_dirty_time:               0
> state:                      5
> 
> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reported-by: SeongJae Park <sj@kernel.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Sorry for missing reported-by tags.

> ---
>  mm/backing-dev.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index 6ecd11bdce6e..e61bbb1bd622 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -172,7 +172,11 @@ static void wb_stats_show(struct seq_file *m, struct bdi_writeback *wb,
>  		   "b_more_io:         %10lu\n"
>  		   "b_dirty_time:      %10lu\n"
>  		   "state:             %10lx\n\n",
> +#ifdef CONFIG_CGROUP_WRITEBACK
>  		   cgroup_ino(wb->memcg_css->cgroup),
> +#else
> +		   1ul,
> +#endif
>  		   K(stats->nr_writeback),
>  		   K(stats->nr_reclaimable),
>  		   K(stats->wb_thresh),
> @@ -192,7 +196,6 @@ static int cgwb_debug_stats_show(struct seq_file *m, void *v)
>  	unsigned long background_thresh;
>  	unsigned long dirty_thresh;
>  	struct bdi_writeback *wb;
> -	struct wb_stats stats;
>  
>  	global_dirty_limits(&background_thresh, &dirty_thresh);
>  
>