linux-kernel - Re: [PATCH] staging: lustre: fix sparse warning on LPROC_SEQ

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Message-ID: <20141206223429.GA17675@dunderer>
Date:	Sat, 6 Dec 2014 14:34:29 -0800
From:	Tristan Lelong <tristan@...ong.xyz>
To:	"Dilger, Andreas" <andreas.dilger@...el.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
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Subject: Re: [PATCH] staging: lustre: fix sparse warning on LPROC_SEQ_FOPS
 macros

Andreas,

On Sat, Dec 06, 2014 at 05:05:14PM +0000, Dilger, Andreas wrote:
> On 2014/12/05, 3:41 PM, "Tristan Lelong" <tristan@...ong.xyz> wrote:
> 
> 
> Sorry, but I don't see where you get 80 from?  fh_name is declared as a
> "const char *", and initialized in the declaration of fld_hash[].  I'd
> thought to reply that sizeof(fh_name) would even be better than a #define,
> but sizeof(const char *) doesn't actually make sense.
> 

You are right, I got confused with the names trying to follow the declaration of the variable.

> The longest declared fh_name is 4 characters, but I'm not sure of an easy
> way to determine this at compile time.  I guess one option is to change
> the declaration of struct lu_fld_hash to use "const char fh_name[4];" and
> then use sizeof(fh_name), but I don't know if that is better than just
> declaring a small buffer (8 chars) for this usage.  IMHO that is small
> enough to fit on the stack, since it is at the top of a very short
> callchain (userspace->sys_write->vfs_write->fld_proc_hash_seq_write())
> that just saves the value so the chance of stack overflow is basically nil.
> 

I can implement any of those 2 options. If somebody as a strong preference, let me know,
otherwise I'll follow Andreas idea and will redo the patch with a stack name variable of size 8.

> 
> Cheers, Andreas
> -- 
> Andreas Dilger
> 
> Lustre Software Architect
> Intel High Performance Data Division
> 
> 

Thanks for your comment and help.
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