Re: [PATCH 2/2] xfs: Add new constant to mark start of xqmstat

[Eric Sandeen <sandeen@sandeen.net>]

On 10/3/18 7:35 AM, Carlos Maiolino wrote:
> xqmstat information under __xfsstats is used directly by the
> /proc/fs/xfs/xqmstat show method, which makes use of struct offsets to
> print out the values.
> 
> Currently, the function is setup to start printing values from the offset of
> the last marker before xqmstat, so, an update to __xfsstats structure
> may also require an update of xqmstat_proc_show() function.
> 
> By adding a new constant, we concentrate any updates do __xfsstats
> structure fields locally to the file xfs_stats.h, reducing the
> likelyhood of future bugs if an update to xqmstat_proc_show is
> forgotten as have happened before.

did 

BUILD_BUG_ON(offsetof(struct __xfsstats, xs_qm_dqreclaims)/sizeof(uint32_t)) != XFSSTAT_START_XQMSTAT);

and/or

#define XFSSTAT_START_XQMSTAT	(offsetof(struct __xfsstats, xs_qm_dqreclaims)/sizeof(uint32_t))

not work out?

> Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
> ---
>  fs/xfs/xfs_stats.c | 2 +-
>  fs/xfs/xfs_stats.h | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_stats.c b/fs/xfs/xfs_stats.c
> index 740ac9674848..09121c36a062 100644
> --- a/fs/xfs/xfs_stats.c
> +++ b/fs/xfs/xfs_stats.c
> @@ -119,7 +119,7 @@ static int xqmstat_proc_show(struct seq_file *m, void *v)
>  	int j;
>  
>  	seq_printf(m, "qm");
> -	for (j = XFSSTAT_END_REFCOUNT; j < XFSSTAT_END_XQMSTAT; j++)
> +	for (j = XFSSTAT_START_XQMSTAT; j < XFSSTAT_END_XQMSTAT; j++)
>  		seq_printf(m, " %u", counter_val(xfsstats.xs_stats, j));
>  	seq_putc(m, '\n');
>  	return 0;
> diff --git a/fs/xfs/xfs_stats.h b/fs/xfs/xfs_stats.h
> index 130db070e4d8..102e794addac 100644
> --- a/fs/xfs/xfs_stats.h
> +++ b/fs/xfs/xfs_stats.h
> @@ -147,6 +147,7 @@ struct __xfsstats {
>  	uint32_t		xs_rmap_2[__XBTS_MAX];
>  #define XFSSTAT_END_REFCOUNT		(XFSSTAT_END_RMAP_V2 + __XBTS_MAX)
>  	uint32_t		xs_refcbt_2[__XBTS_MAX];
> +#define XFSSTAT_START_XQMSTAT		XFSSTAT_END_REFCOUNT
>  #define XFSSTAT_END_XQMSTAT		(XFSSTAT_END_REFCOUNT + 6)
>  	uint32_t		xs_qm_dqreclaims;
>  	uint32_t		xs_qm_dqreclaim_misses;
>