[lustre-devel] [PATCH] staging/lustre/lnet: correctly casts value for arithmetic

[Lidza Louina]

----- Original Message -----
From: oleg.drokin at intel.com
To: lidza.louina at oracle.com
Cc: devel at driverdev.osuosl.org, andreas.dilger at intel.com, lustre-devel at lists.lustre.org, gregkh at linuxfoundation.org
Sent: Thursday, June 23, 2016 11:11:06 AM GMT -08:00 US/Canada Pacific
Subject: Re: [lustre-devel] [PATCH] staging/lustre/lnet: correctly casts value for arithmetic


On Jun 23, 2016, at 2:07 PM, Lidza Louina wrote:

> The smatch warning was "drivers/staging/lustre/lnet/lnet/api-ni.c:516 
> lnet_res_lh_initialize() warn: should '1 << ibits' be a 64 bit type?"

I think you misinterpreted it, it has nothing to do with the addition.

What it actually means is:
1 is a 32bit integer, you do a right shift by some variable number
of bits. So please check if there's risk to overflow the 32 bits
unexpectedly.
The way to fix this warning is to replace 1 with 1ULL (unsigned long long)
and that is fine to do as a way of future proofing this stuff even if it's
not yet broken yet, I guess.

Ahh, okay, I see what you're saying and I see what I did wrong.

I'm going to update the patch to:

-        rec->rec_lh_cookie += 1 << ibits;
+        rec->rec_lh_cookie += (1ULL << ibits);

Lidza

> 
>> 
>> 	hash = (lh->lh_cookie >> ibits) & LNET_LH_HASH_MASK;
>> 
>> -- 
>> 1.9.1
>> 
>> 
>> 
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