re: mm: frontswap: core code

re: mm: frontswap: core code

[Dan Carpenter]

Hello Dan Magenheimer,

This is a semi-automatic email to let you know that df0aade19b6a:
"mm: frontswap: core code" leads to the following Smatch complaint.

mm/frontswap.c +250 frontswap_curr_pages(7)
	 error: we previously assumed 'si' could be null (see line 252)

mm/frontswap.c
   249		spin_lock(&swap_lock);
   250		for (type = swap_list.head; type >= 0; type = si->next) {
                                                              ^^^^^^^^
Dereference.

   251			si = swap_info[type];
   252			if (si != NULL)
                            ^^^^^^^^^^
Check for NULL.

   253				totalpages += atomic_read(&si->frontswap_pages);
   254		}

These semi-automatic emails are in testing.  Let me know how they can
be improved.

regards,
dan carpenter

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RE: mm: frontswap: core code

[Dan Magenheimer]

> From: Dan Carpenter [mailto:error27@gmail.com]
> Sent: Tuesday, August 30, 2011 3:47 PM
> To: Dan Magenheimer
> Cc: linux-mm@kvack.org
> Subject: re: mm: frontswap: core code
> 
> Hello Dan Magenheimer,
> 
> This is a semi-automatic email to let you know that df0aade19b6a:
> "mm: frontswap: core code" leads to the following Smatch complaint.
> 
> mm/frontswap.c +250 frontswap_curr_pages(7)
> 	 error: we previously assumed 'si' could be null (see line 252)
> 
> mm/frontswap.c
>    249		spin_lock(&swap_lock);
>    250		for (type = swap_list.head; type >= 0; type = si->next) {
>                                                               ^^^^^^^^
> Dereference.
> 
>    251			si = swap_info[type];
>    252			if (si != NULL)
>                             ^^^^^^^^^^
> Check for NULL.
> 
>    253				totalpages += atomic_read(&si->frontswap_pages);
>    254		}
> 
> These semi-automatic emails are in testing.  Let me know how they can
> be improved.
> 
> regards,
> dan carpenter

Thanks Dan!  On second look, the check for si against NULL is
unnecessary.  The "type >=0" guarantees that (and this idiom
for walking the list of swap devices is used elsewhere in the
swap subsystem).

Will fix it.

Dan

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