linux-kernel - Re: [PATCH] proc: faster open/read/close with "permanent" files

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Message-ID: <20200219052921.GF19641@kadam>
Date:   Wed, 19 Feb 2020 08:29:21 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Alexey Dobriyan <adobriyan@...il.com>
Cc:     kbuild-all@...ts.01.org, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] proc: faster open/read/close with "permanent" files

Hi Alexey,


url:    https://github.com/0day-ci/linux/commits/Alexey-Dobriyan/proc-faster-open-read-close-with-permanent-files/20200218-231203
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux.git modules-next

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

smatch warnings:
fs/proc/generic.c:752 remove_proc_subtree() warn: inconsistent returns 'proc_subdir_lock'.

# https://github.com/0day-ci/linux/commit/3cd4ad42ca7c52d1513e7ba9f08a06197a7380c8
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout 3cd4ad42ca7c52d1513e7ba9f08a06197a7380c8
vim +/proc_subdir_lock +752 fs/proc/generic.c

8ce584c7416d8a Al Viro         2013-03-30  699  
8ce584c7416d8a Al Viro         2013-03-30  700  int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
8ce584c7416d8a Al Viro         2013-03-30  701  {
8ce584c7416d8a Al Viro         2013-03-30  702  	struct proc_dir_entry *root = NULL, *de, *next;
8ce584c7416d8a Al Viro         2013-03-30  703  	const char *fn = name;
8ce584c7416d8a Al Viro         2013-03-30  704  	unsigned int len;
8ce584c7416d8a Al Viro         2013-03-30  705  
ecf1a3dfff22bd Waiman Long     2015-09-09  706  	write_lock(&proc_subdir_lock);
8ce584c7416d8a Al Viro         2013-03-30  707  	if (__xlate_proc_name(name, &parent, &fn) != 0) {
ecf1a3dfff22bd Waiman Long     2015-09-09  708  		write_unlock(&proc_subdir_lock);
8ce584c7416d8a Al Viro         2013-03-30  709  		return -ENOENT;
8ce584c7416d8a Al Viro         2013-03-30  710  	}
8ce584c7416d8a Al Viro         2013-03-30  711  	len = strlen(fn);
8ce584c7416d8a Al Viro         2013-03-30  712  
710585d4922fd3 Nicolas Dichtel 2014-12-10  713  	root = pde_subdir_find(parent, fn, len);
8ce584c7416d8a Al Viro         2013-03-30  714  	if (!root) {
ecf1a3dfff22bd Waiman Long     2015-09-09  715  		write_unlock(&proc_subdir_lock);
8ce584c7416d8a Al Viro         2013-03-30  716  		return -ENOENT;
8ce584c7416d8a Al Viro         2013-03-30  717  	}
3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  718  	if (unlikely(pde_is_permanent(root))) {
3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  719  		WARN(1, "removing permanent /proc entry '%s/%s'",
3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  720  			root->parent->name, root->name);

unlock?

3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  721  		return -EINVAL;
3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  722  	}
4f1134370a29a5 Alexey Dobriyan 2018-04-10  723  	rb_erase(&root->subdir_node, &parent->subdir);
710585d4922fd3 Nicolas Dichtel 2014-12-10  724  
8ce584c7416d8a Al Viro         2013-03-30  725  	de = root;
8ce584c7416d8a Al Viro         2013-03-30  726  	while (1) {
710585d4922fd3 Nicolas Dichtel 2014-12-10  727  		next = pde_subdir_first(de);
8ce584c7416d8a Al Viro         2013-03-30  728  		if (next) {
3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  729  			if (unlikely(pde_is_permanent(root))) {
3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  730  				WARN(1, "removing permanent /proc entry '%s/%s'",
3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  731  					next->parent->name, next->name);
3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  732  				return -EINVAL;
3cd4ad42ca7c52 Alexey Dobriyan 2020-02-16  733  			}
4f1134370a29a5 Alexey Dobriyan 2018-04-10  734  			rb_erase(&next->subdir_node, &de->subdir);
8ce584c7416d8a Al Viro         2013-03-30  735  			de = next;
8ce584c7416d8a Al Viro         2013-03-30  736  			continue;
8ce584c7416d8a Al Viro         2013-03-30  737  		}
8ce584c7416d8a Al Viro         2013-03-30  738  		next = de->parent;
8ce584c7416d8a Al Viro         2013-03-30  739  		if (S_ISDIR(de->mode))
8ce584c7416d8a Al Viro         2013-03-30  740  			next->nlink--;
e06689bf57017a Alexey Dobriyan 2019-12-04  741  		write_unlock(&proc_subdir_lock);
e06689bf57017a Alexey Dobriyan 2019-12-04  742  
e06689bf57017a Alexey Dobriyan 2019-12-04  743  		proc_entry_rundown(de);
8ce584c7416d8a Al Viro         2013-03-30  744  		if (de == root)
8ce584c7416d8a Al Viro         2013-03-30  745  			break;
8ce584c7416d8a Al Viro         2013-03-30  746  		pde_put(de);
8ce584c7416d8a Al Viro         2013-03-30  747  
ecf1a3dfff22bd Waiman Long     2015-09-09  748  		write_lock(&proc_subdir_lock);
8ce584c7416d8a Al Viro         2013-03-30  749  		de = next;
8ce584c7416d8a Al Viro         2013-03-30  750  	}
8ce584c7416d8a Al Viro         2013-03-30  751  	pde_put(root);
8ce584c7416d8a Al Viro         2013-03-30 @752  	return 0;
8ce584c7416d8a Al Viro         2013-03-30  753  }
8ce584c7416d8a Al Viro         2013-03-30  754  EXPORT_SYMBOL(remove_proc_subtree);

---
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