linux-kernel - Re: [PATCH 2/6] mm: Lock kernel page tables before entering lazy MMU mode

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Message-ID: <0be7d42e-5898-4b94-829b-59c661c2f07b@suswa.mountain>
Date: Wed, 18 Jun 2025 20:32:28 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: oe-kbuild@...ts.linux.dev, Alexander Gordeev <agordeev@...ux.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc: lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
	Linux Memory Management List <linux-mm@...ck.org>,
	linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
	xen-devel@...ts.xenproject.org, linuxppc-dev@...ts.ozlabs.org,
	linux-s390@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	Nicholas Piggin <npiggin@...il.com>,
	Guenter Roeck <linux@...ck-us.net>, Juergen Gross <jgross@...e.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Ryan Roberts <ryan.roberts@....com>
Subject: Re: [PATCH 2/6] mm: Lock kernel page tables before entering lazy MMU
 mode

Hi Alexander,

kernel test robot noticed the following build warnings:

url:    https://github.com/intel-lab-lkp/linux/commits/Alexander-Gordeev/mm-Cleanup-apply_to_pte_range-routine/20250613-013835
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/7bd3a45dbc375dc2c15cebae09cb2bb972d6039f.1749747752.git.agordeev%40linux.ibm.com
patch subject: [PATCH 2/6] mm: Lock kernel page tables before entering lazy MMU mode
config: x86_64-randconfig-161-20250613 (https://download.01.org/0day-ci/archive/20250613/202506132017.T1l1l6ME-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
| Closes: https://lore.kernel.org/r/202506132017.T1l1l6ME-lkp@intel.com/

smatch warnings:
mm/vmalloc.c:552 vmap_pages_pte_range() warn: inconsistent returns 'global &init_mm.page_table_lock'.

vim +552 mm/vmalloc.c

0a264884046f1ab Nicholas Piggin   2021-04-29  517  static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
2ba3e6947aed9bb Joerg Roedel      2020-06-01  518  		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
2ba3e6947aed9bb Joerg Roedel      2020-06-01  519  		pgtbl_mod_mask *mask)
^1da177e4c3f415 Linus Torvalds    2005-04-16  520  {
^1da177e4c3f415 Linus Torvalds    2005-04-16  521  	pte_t *pte;
^1da177e4c3f415 Linus Torvalds    2005-04-16  522  
db64fe02258f150 Nicholas Piggin   2008-10-18  523  	/*
db64fe02258f150 Nicholas Piggin   2008-10-18  524  	 * nr is a running index into the array which helps higher level
db64fe02258f150 Nicholas Piggin   2008-10-18  525  	 * callers keep track of where we're up to.
db64fe02258f150 Nicholas Piggin   2008-10-18  526  	 */
db64fe02258f150 Nicholas Piggin   2008-10-18  527  
2ba3e6947aed9bb Joerg Roedel      2020-06-01  528  	pte = pte_alloc_kernel_track(pmd, addr, mask);
^1da177e4c3f415 Linus Torvalds    2005-04-16  529  	if (!pte)
^1da177e4c3f415 Linus Torvalds    2005-04-16  530  		return -ENOMEM;
44562c71e2cfc9e Ryan Roberts      2025-04-22  531  
dac0cc793368851 Alexander Gordeev 2025-06-12  532  	spin_lock(&init_mm.page_table_lock);
44562c71e2cfc9e Ryan Roberts      2025-04-22  533  	arch_enter_lazy_mmu_mode();
44562c71e2cfc9e Ryan Roberts      2025-04-22  534  
^1da177e4c3f415 Linus Torvalds    2005-04-16  535  	do {
db64fe02258f150 Nicholas Piggin   2008-10-18  536  		struct page *page = pages[*nr];
db64fe02258f150 Nicholas Piggin   2008-10-18  537  
c33c794828f2121 Ryan Roberts      2023-06-12  538  		if (WARN_ON(!pte_none(ptep_get(pte))))
db64fe02258f150 Nicholas Piggin   2008-10-18  539  			return -EBUSY;
db64fe02258f150 Nicholas Piggin   2008-10-18  540  		if (WARN_ON(!page))
^1da177e4c3f415 Linus Torvalds    2005-04-16  541  			return -ENOMEM;
4fcdcc12915c707 Yury Norov        2022-04-28  542  		if (WARN_ON(!pfn_valid(page_to_pfn(page))))
4fcdcc12915c707 Yury Norov        2022-04-28  543  			return -EINVAL;

These error paths don't unlock &init_mm.page_table_lock?

4fcdcc12915c707 Yury Norov        2022-04-28  544  
^1da177e4c3f415 Linus Torvalds    2005-04-16  545  		set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));
db64fe02258f150 Nicholas Piggin   2008-10-18  546  		(*nr)++;
^1da177e4c3f415 Linus Torvalds    2005-04-16  547  	} while (pte++, addr += PAGE_SIZE, addr != end);
44562c71e2cfc9e Ryan Roberts      2025-04-22  548  
44562c71e2cfc9e Ryan Roberts      2025-04-22  549  	arch_leave_lazy_mmu_mode();
dac0cc793368851 Alexander Gordeev 2025-06-12  550  	spin_unlock(&init_mm.page_table_lock);
2ba3e6947aed9bb Joerg Roedel      2020-06-01  551  	*mask |= PGTBL_PTE_MODIFIED;
^1da177e4c3f415 Linus Torvalds    2005-04-16 @552  	return 0;
^1da177e4c3f415 Linus Torvalds    2005-04-16  553  }

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