linux-kernel - Re: [PATCH 1/2] staging: lustre: lprocfs: Use kstrtouint_from

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Message-ID: <9657977C-9620-4C31-9615-E4245482B5A7@intel.com>
Date:   Thu, 18 May 2017 14:48:25 +0000
From:   "Dilger, Andreas" <andreas.dilger@...el.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mathias Rav <mathiasrav@...il.com>
CC:     "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "Drokin, Oleg" <oleg.drokin@...el.com>,
        James Simmons <jsimmons@...radead.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Lustre Development List <lustre-devel@...ts.lustre.org>
Subject: Re: [PATCH 1/2] staging: lustre: lprocfs: Use kstrtouint_from_user

On May 18, 2017, at 15:53, Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> 
> On Thu, May 04, 2017 at 12:13:38PM -0400, Mathias Rav wrote:
>> Prefer kstrtouint_from_user to copy_from_user+simple_strtoul.
>> 
>> The helper function lprocfs_wr_uint() is only used to implement
>> "dump_granted_max" in debugfs.
>> 
>> Note the slight change in semantics: The previous implementation using
>> simple_strtoul allows garbage after the number, whereas kstrtox only allows
>> a trailing line break. The previous implementation allowed a write of zero
>> bytes whereas kstrtox will return -EINVAL. Since this only affects a single
>> debugfs endpoint, this should be a permissible slight change of semantics
>> in exchange for 18 fewer lines of code.
>> 
>> Signed-off-by: Mathias Rav <mathiasrav@...il.com>
>> ---
>> .../lustre/lustre/obdclass/lprocfs_status.c        | 22 +---------------------
>> 1 file changed, 1 insertion(+), 21 deletions(-)
>> 
>> diff --git a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
>> index 1ec6e3767d81..338ce34d6514 100644
>> --- a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
>> +++ b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
>> @@ -399,27 +399,7 @@ EXPORT_SYMBOL(lprocfs_rd_uint);
>> int lprocfs_wr_uint(struct file *file, const char __user *buffer,
>> 		    unsigned long count, void *data)
>> {
>> -	unsigned *p = data;
>> -	char dummy[MAX_STRING_SIZE + 1], *end;
>> -	unsigned long tmp;
>> -
>> -	if (count >= sizeof(dummy))
>> -		return -EINVAL;
>> -
>> -	if (count == 0)
>> -		return 0;
>> -
>> -	if (copy_from_user(dummy, buffer, count))
>> -		return -EFAULT;
>> -
>> -	dummy[count] = '\0';
>> -
>> -	tmp = simple_strtoul(dummy, &end, 0);
>> -	if (dummy == end)
>> -		return -EINVAL;
>> -
>> -	*p = (unsigned int)tmp;
>> -	return count;
>> +	return kstrtouint_from_user(buffer, count, 0, (unsigned int *)data);
> 
> Why not just delete this whole function and have the callers make this
> call instead?  No need for unneeded wrapper functions of core kernel
> calls.

Even better, it looks like this function has no callers on the client and could just
be deleted entirely.

Cheers, Andreas
--
Andreas Dilger
Lustre Principal Architect
Intel Corporation