linux-kernel - Re: [PATCH] fs: buffer: Modify alloc_page

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Date:   Tue, 20 Jun 2017 02:20:13 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Sean Fu <fxinrong@...il.com>
Cc:     kbuild-all@...org, viro@...iv.linux.org.uk, shli@...nel.org,
        anton@...era.com, jack@...e.cz, axboe@...com, ebiggers@...gle.com,
        rpeterso@...hat.com, bmarzins@...hat.com,
        linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        linux-ntfs-dev@...ts.sourceforge.net, Sean Fu <fxinrong@...il.com>
Subject: Re: [PATCH] fs: buffer: Modify alloc_page_buffers.

Hi Sean,

[auto build test WARNING on linus/master]
[also build test WARNING on v4.12-rc6 next-20170619]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Sean-Fu/fs-buffer-Modify-alloc_page_buffers/20170620-012328
config: x86_64-randconfig-x015-201725 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   fs/buffer.c: In function 'alloc_page_buffers':
>> fs/buffer.c:895:21: warning: 'tail' may be used uninitialized in this function [-Wmaybe-uninitialized]
      tail->b_this_page = head;
      ~~~~~~~~~~~~~~~~~~^~~~~~

vim +/tail +895 fs/buffer.c

   879	
   880			bh->b_this_page = head;
   881			bh->b_blocknr = -1;
   882	
   883			if (head == NULL)
   884				tail = bh;
   885	
   886			head = bh;
   887			bh->b_state = b_state;
   888			bh->b_size = size;
   889	
   890			/* Link the buffer to its page */
   891			set_bh_page(bh, page, offset);
   892		}
   893	
   894		if (circular)
 > 895			tail->b_this_page = head;
   896	
   897		return head;
   898	/*
   899	 * In case anything failed, we just free everything we got.
   900	 */
   901	no_grow:
   902		if (head) {
   903			do {

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0-DAY kernel test infrastructure                Open Source Technology Center
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