From: Sergey Senozhatsky Date: Mon, 25 Jul 2016 00:49:56 +0000 Subject: Re: [PATCH] zsmalloc: Delete an unnecessary check before the function call "iput" Message-Id: <20160725004956.GA430@swordfish> List-Id: References: <530C5E18.1020800@users.sourceforge.net> <530CD2C4.4050903@users.sourceforge.net> <530CF8FF.8080600@users.sourceforge.net> <530DD06F.4090703@users.sourceforge.net> <5317A59D.4@users.sourceforge.net> <559cf499-4a01-25f9-c87f-24d906626a57@users.sourceforge.net> In-Reply-To: <559cf499-4a01-25f9-c87f-24d906626a57@users.sourceforge.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: SF Markus Elfring Cc: linux-mm@kvack.org, Minchan Kim , Nitin Gupta , Sergey Senozhatsky , LKML , kernel-janitors@vger.kernel.org, Julia Lawall , Andrew Morton 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 Reviewed-by: Sergey Senozhatsky 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 >