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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: SF Markus Elfring <elfring@users.sourceforge.net>
Cc: linux-mm@kvack.org, Minchan Kim <minchan@kernel.org>,
	Nitin Gupta <ngupta@vflare.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	kernel-janitors@vger.kernel.org,
	Julia Lawall <julia.lawall@lip6.fr>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] zsmalloc: Delete an unnecessary check before the function call "iput"
Date: Mon, 25 Jul 2016 09:49:56 +0900
Message-ID: <20160725004956.GA430@swordfish> (raw)
In-Reply-To: <559cf499-4a01-25f9-c87f-24d906626a57@users.sourceforge.net>

On (07/22/16 20:02), SF Markus Elfring wrote:
> The iput() function tests whether its argument is NULL and then
> returns immediately. Thus the test around the call is not needed.
> 
> This issue was detected by using the Coccinelle software.

there is no issue; the change is just cosmetic.


> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>



alloc_anon_inode() returns ERR_PTR, so I'd probably rather
change iput() to do IS_ERR_OR_NULL instead of !NULL.

	inode = alloc_anon_inode();
	if (IS_ERR(inode)) {
		inode = NULL;
		^^^^^^^^^^^^^
	}
	...
	iput(inode);

this NULL assignment on error path is a bit fragile.

IOW, something like this

---

diff --git a/fs/inode.c b/fs/inode.c
index 559a9da..f1b7bd2 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1497,7 +1497,7 @@ static void iput_final(struct inode *inode)
  */
 void iput(struct inode *inode)
 {
-       if (!inode)
+       if (IS_ERR_OR_NULL(inode))
                return;
        BUG_ON(inode->i_state & I_CLEAR);
 retry:


---

	-ss

> ---
>  mm/zsmalloc.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 5e5237c..7b5fd2b 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -2181,8 +2181,7 @@ static int zs_register_migration(struct zs_pool *pool)
>  static void zs_unregister_migration(struct zs_pool *pool)
>  {
>  	flush_work(&pool->free_work);
> -	if (pool->inode)
> -		iput(pool->inode);
> +	iput(pool->inode);
>  }
>  
>  /*
> -- 
> 2.9.2
> 

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Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <5307CAA2.8060406@users.sourceforge.net>
     [not found] ` <alpine.DEB.2.02.1402212321410.2043@localhost6.localdomain6>
     [not found]   ` <530A086E.8010901@users.sourceforge.net>
     [not found]     ` <alpine.DEB.2.02.1402231635510.1985@localhost6.localdomain6>
     [not found]       ` <530A72AA.3000601@users.sourceforge.net>
     [not found]         ` <alpine.DEB.2.02.1402240658210.2090@localhost6.localdomain6>
     [not found]           ` <530B5FB6.6010207@users.sourceforge.net>
     [not found]             ` <alpine.DEB.2.10.1402241710370.2074@hadrien>
     [not found]               ` <530C5E18.1020800@users.sourceforge.net>
     [not found]                 ` <alpine.DEB.2.10.1402251014170.2080@hadrien>
     [not found]                   ` <530CD2C4.4050903@users.sourceforge.net>
     [not found]                     ` <alpine.DEB.2.10.1402251840450.7035@hadrien>
     [not found]                       ` <530CF8FF.8080600@users.sourceforge.net>
     [not found]                         ` <alpine.DEB.2.02.1402252117150.2047@localhost6.localdomain6>
     [not found]                           ` <530DD06F.4090703@users.sourceforge.net>
     [not found]                             ` <alpine.DEB.2.02.1402262129250.2221@localhost6.localdomain6>
     [not found]                               ` <5317A59D.4@users.sourceforge.net>
2014-11-17 17:40                                 ` [PATCH 1/1] mm/zswap: Deletion of an unnecessary check before the function call "free_percpu" SF Markus Elfring
2014-11-18 22:17                                   ` Seth Jennings
2016-07-22 18:02                                 ` [PATCH] zsmalloc: Delete an unnecessary check before the function call "iput" SF Markus Elfring
2016-07-25  0:49                                   ` Sergey Senozhatsky [this message]
2016-07-25  9:08                                   ` Minchan Kim

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