linux-kernel - Re: [PATCH] cpumask: Omit terminating null byte in cpumap_print_{list,bitmask}_to

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Date:   Thu, 30 Sep 2021 12:43:41 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Antti Kervinen <antti.kervinen@...el.com>
Cc:     tklauser@...tanz.ch, Jonathan.Cameron@...wei.com,
        akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        song.bao.hua@...ilicon.com, tiantao6@...ilicon.com,
        yury.norov@...il.com
Subject: Re: [PATCH] cpumask: Omit terminating null byte in
 cpumap_print_{list,bitmask}_to_buf

On Thu, Sep 30, 2021 at 01:30:10PM +0300, Antti Kervinen wrote:
> 
> An original function, bitmap_print_to_pagebuf() in lib/bitmap.c,
> returns the number of printed characters, excluding terminating null.
> 
> Commit 1fae5629, a cause of this regression, introduced new functions
> to lib/bitmap.c:
> 
> - bitmap_print_to_buf()
>   (return value doc missing)
> 
> - bitmap_print_bitmask_to_buf()
>   (return value doc not explicit about terminating null, but
>   can be considered misleading)
> 
> - bitmap_print_list_to_buf()
>   (the same as above)
> 
> Unlike the original function, the return value of new functions
> include the terminating null.
> 
> As this behavior is clearly opposite to the original function, and
> functions that print to buffers in general, I would suggest fixing
> this problem by alignign these new functions with the original one:
> excluding the terminating null. And documenting this behavior
> unambiguously.
> 
> The suggested change to cpumask_print_{bitmask,list}_to_buf()
> functions decrements possible errors (like -ENOMEM) returned by
> bitmap_print_to_buf(). This must not happen.

I already pointed you at
	https://lore.kernel.org/r/20210916222705.13554-1-tklauser@distanz.ch
a few hours ago.

Why not test the patch there (and in linux-next) and let us know if it
resolves the issue you see or not.

thanks,

greg k-h