Re: [PATCH V3] fuse: Fix VM_BUG_ON_PAGE issue while accessing zero ref count page

[Dan Carpenter <dan.carpenter@oracle.com>]

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Hi Pradeep,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on fuse/for-next]
[also build test WARNING on v5.9-rc4 next-20200903]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Pradeep-P-V-K/fuse-Fix-VM_BUG_ON_PAGE-issue-while-accessing-zero-ref-count-page/20200907-111835
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git for-next
config: i386-randconfig-m021-20200907 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

New smatch warnings:
fs/fuse/dev.c:904 fuse_ref_page() warn: inconsistent returns 'fc->lock'.

Old smatch warnings:
fs/fuse/dev.c:1223 fuse_dev_do_read() warn: inconsistent returns 'fiq->lock'.

# https://github.com/0day-ci/linux/commit/f99df00de1b2265fba75dceb63724c2a9b0f1e52
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Pradeep-P-V-K/fuse-Fix-VM_BUG_ON_PAGE-issue-while-accessing-zero-ref-count-page/20200907-111835
git checkout f99df00de1b2265fba75dceb63724c2a9b0f1e52
vim +904 fs/fuse/dev.c

c3021629a0d820 Miklos Szeredi     2010-05-25  877  static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page,
f99df00de1b226 Pradeep P V K      2020-09-06  878  			 unsigned offset, unsigned count, struct fuse_conn *fc)
c3021629a0d820 Miklos Szeredi     2010-05-25  879  {
c3021629a0d820 Miklos Szeredi     2010-05-25  880  	struct pipe_buffer *buf;
0d8e84b0432beb Miklos Szeredi     2015-07-01  881  	int err;
c3021629a0d820 Miklos Szeredi     2010-05-25  882  
6718b6f855a0b4 David Howells      2019-10-16  883  	if (cs->nr_segs >= cs->pipe->max_usage)
c3021629a0d820 Miklos Szeredi     2010-05-25  884  		return -EIO;
c3021629a0d820 Miklos Szeredi     2010-05-25  885  
f99df00de1b226 Pradeep P V K      2020-09-06  886  	spin_lock(&fc->lock);
dc00809a53edd1 Miklos Szeredi     2015-07-01  887  	err = unlock_request(cs->req);
0d8e84b0432beb Miklos Szeredi     2015-07-01  888  	if (err)
0d8e84b0432beb Miklos Szeredi     2015-07-01  889  		return err;
                                                                ^^^^^^^^^^
Unlock before returning?

0d8e84b0432beb Miklos Szeredi     2015-07-01  890  
c3021629a0d820 Miklos Szeredi     2010-05-25  891  	fuse_copy_finish(cs);
c3021629a0d820 Miklos Szeredi     2010-05-25  892  
c3021629a0d820 Miklos Szeredi     2010-05-25  893  	buf = cs->pipebufs;
09cbfeaf1a5a67 Kirill A. Shutemov 2016-04-01  894  	get_page(page);
c3021629a0d820 Miklos Szeredi     2010-05-25  895  	buf->page = page;
f99df00de1b226 Pradeep P V K      2020-09-06  896  	spin_unlock(&fc->lock);
c3021629a0d820 Miklos Szeredi     2010-05-25  897  	buf->offset = offset;
c3021629a0d820 Miklos Szeredi     2010-05-25  898  	buf->len = count;
c3021629a0d820 Miklos Szeredi     2010-05-25  899  
c3021629a0d820 Miklos Szeredi     2010-05-25  900  	cs->pipebufs++;
c3021629a0d820 Miklos Szeredi     2010-05-25  901  	cs->nr_segs++;
c3021629a0d820 Miklos Szeredi     2010-05-25  902  	cs->len = 0;
c3021629a0d820 Miklos Szeredi     2010-05-25  903  
c3021629a0d820 Miklos Szeredi     2010-05-25 @904  	return 0;
c3021629a0d820 Miklos Szeredi     2010-05-25  905  }

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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