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Date:   Thu, 11 May 2023 13:55:57 +0300
From:   Dan Carpenter <dan.carpenter@linaro.org>
To:     oe-kbuild@lists.linux.dev,
        Dominique Martinet <asmadeus@codewreck.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        Jens Axboe <axboe@kernel.dk>,
        Pavel Begunkov <asml.silence@gmail.com>,
        Stefan Roesch <shr@fb.com>
Cc:     lkp@intel.com, oe-kbuild-all@lists.linux.dev,
        Clay Harris <bugs@claycon.org>,
        Dave Chinner <david@fromorbit.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        io-uring@vger.kernel.org,
        Dominique Martinet <asmadeus@codewreck.org>
Subject: Re: [PATCH v2 4/6] kernfs: implement readdir FMODE_NOWAIT
Message-ID: <4e88ec58-be22-4b0c-968d-fa9a52764c98@kili.mountain>
MIME-Version: 1.0
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In-Reply-To: <20230422-uring-getdents-v2-4-2db1e37dc55e@codewreck.org>
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Hi Dominique,

kernel test robot noticed the following build warnings:

url:    https://github.com/intel-lab-lkp/linux/commits/Dominique-Martinet/fs-split-off-vfs_getdents-function-of-getdents64-syscall/20230510-185542
base:   58390c8ce1bddb6c623f62e7ed36383e7fa5c02f
patch link:    https://lore.kernel.org/r/20230422-uring-getdents-v2-4-2db1e37dc55e%40codewreck.org
patch subject: [PATCH v2 4/6] kernfs: implement readdir FMODE_NOWAIT
config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20230511/202305110647.eSnSEulg-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-12) 11.3.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Link: https://lore.kernel.org/r/202305110647.eSnSEulg-lkp@intel.com/

smatch warnings:
fs/kernfs/dir.c:1863 kernfs_fop_readdir() warn: inconsistent returns '&root->kernfs_rwsem'.

vim +1863 fs/kernfs/dir.c

c637b8acbe079e Tejun Heo          2013-12-11  1815  static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1816  {
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1817  	struct dentry *dentry = file->f_path.dentry;
319ba91d352a74 Shaohua Li         2017-07-12  1818  	struct kernfs_node *parent = kernfs_dentry_node(dentry);
324a56e16e44ba Tejun Heo          2013-12-11  1819  	struct kernfs_node *pos = file->private_data;
393c3714081a53 Minchan Kim        2021-11-18  1820  	struct kernfs_root *root;
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1821  	const void *ns = NULL;
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1822  
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1823  	if (!dir_emit_dots(file, ctx))
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1824  		return 0;
393c3714081a53 Minchan Kim        2021-11-18  1825  
393c3714081a53 Minchan Kim        2021-11-18  1826  	root = kernfs_root(parent);
a551138c4b3b9f Dominique Martinet 2023-05-10  1827  	if (ctx->flags & DIR_CONTEXT_F_NOWAIT) {
a551138c4b3b9f Dominique Martinet 2023-05-10  1828  		if (!down_read_trylock(&root->kernfs_rwsem))
a551138c4b3b9f Dominique Martinet 2023-05-10  1829  			return -EAGAIN;
a551138c4b3b9f Dominique Martinet 2023-05-10  1830  	} else {
393c3714081a53 Minchan Kim        2021-11-18  1831  		down_read(&root->kernfs_rwsem);
a551138c4b3b9f Dominique Martinet 2023-05-10  1832  	}
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1833  
324a56e16e44ba Tejun Heo          2013-12-11  1834  	if (kernfs_ns_enabled(parent))
c525aaddc366df Tejun Heo          2013-12-11  1835  		ns = kernfs_info(dentry->d_sb)->ns;
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1836  
c637b8acbe079e Tejun Heo          2013-12-11  1837  	for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos);
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1838  	     pos;
c637b8acbe079e Tejun Heo          2013-12-11  1839  	     pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) {
adc5e8b58f4886 Tejun Heo          2013-12-11  1840  		const char *name = pos->name;
364595a6851bf6 Jeff Layton        2023-03-30  1841  		unsigned int type = fs_umode_to_dtype(pos->mode);
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1842  		int len = strlen(name);
67c0496e87d193 Tejun Heo          2019-11-04  1843  		ino_t ino = kernfs_ino(pos);
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1844  
adc5e8b58f4886 Tejun Heo          2013-12-11  1845  		ctx->pos = pos->hash;
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1846  		file->private_data = pos;
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1847  		kernfs_get(pos);
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1848  
393c3714081a53 Minchan Kim        2021-11-18  1849  		up_read(&root->kernfs_rwsem);
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1850  		if (!dir_emit(ctx, name, len, ino, type))
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1851  			return 0;
393c3714081a53 Minchan Kim        2021-11-18  1852  		down_read(&root->kernfs_rwsem);
                                                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Needs to be deleted.

a551138c4b3b9f Dominique Martinet 2023-05-10  1853  		if (ctx->flags & DIR_CONTEXT_F_NOWAIT) {
a551138c4b3b9f Dominique Martinet 2023-05-10  1854  			if (!down_read_trylock(&root->kernfs_rwsem))
a551138c4b3b9f Dominique Martinet 2023-05-10  1855  				return 0;

It's a bit strange the this doesn't return -EAGAIN;

a551138c4b3b9f Dominique Martinet 2023-05-10  1856  		} else {
a551138c4b3b9f Dominique Martinet 2023-05-10  1857  			down_read(&root->kernfs_rwsem);
a551138c4b3b9f Dominique Martinet 2023-05-10  1858  		}
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1859  	}
393c3714081a53 Minchan Kim        2021-11-18  1860  	up_read(&root->kernfs_rwsem);
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1861  	file->private_data = NULL;
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1862  	ctx->pos = INT_MAX;
fd7b9f7b9776b1 Tejun Heo          2013-11-28 @1863  	return 0;
fd7b9f7b9776b1 Tejun Heo          2013-11-28  1864  }

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests