linux-kernel - Re: [PATCH] mm/vmalloc: leave lazy MMU mode on PTE mapping error

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Message-ID: <107bfdb7-c8f5-45fa-872e-3e6928dc8025@arm.com>
Date: Mon, 23 Jun 2025 13:37:11 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Alexander Gordeev <agordeev@...ux.ibm.com>,
 Dan Carpenter <dan.carpenter@...aro.org>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmalloc: leave lazy MMU mode on PTE mapping error

On 23/06/2025 08:57, Alexander Gordeev wrote:
> Function vmap_pages_pte_range() enters the lazy MMU mode,
> but fails to leave it in case an error is encountered.
> 
> 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/
> Fixes: 44562c71e2cf ("mm/vmalloc: Enter lazy mmu mode while manipulating vmalloc ptes")
> Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>

Ouch, sorry about that! The patch looks good to me so:

Reviewed-by: Ryan Roberts <ryan.roberts@....com>

I wonder an aditional Fixes: should be added for Commit 2ba3e6947aed
("mm/vmalloc: track which page-table levels were modified") though? That's the
one that added the "*mask |= PGTBL_PTE_MODIFIED;" which would have also been
skipped if an error occured before this patch.

Thanks,
Ryan


> ---
>  mm/vmalloc.c | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ab986dd09b6a..6dbcdceecae1 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -514,6 +514,7 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
>  		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
>  		pgtbl_mod_mask *mask)
>  {
> +	int err = 0;
>  	pte_t *pte;
>  
>  	/*
> @@ -530,12 +531,18 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
>  	do {
>  		struct page *page = pages[*nr];
>  
> -		if (WARN_ON(!pte_none(ptep_get(pte))))
> -			return -EBUSY;
> -		if (WARN_ON(!page))
> -			return -ENOMEM;
> -		if (WARN_ON(!pfn_valid(page_to_pfn(page))))
> -			return -EINVAL;
> +		if (WARN_ON(!pte_none(ptep_get(pte)))) {
> +			err = -EBUSY;
> +			break;
> +		}
> +		if (WARN_ON(!page)) {
> +			err = -ENOMEM;
> +			break;
> +		}
> +		if (WARN_ON(!pfn_valid(page_to_pfn(page)))) {
> +			err = -EINVAL;
> +			break;
> +		}
>  
>  		set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));
>  		(*nr)++;
> @@ -543,7 +550,8 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
>  
>  	arch_leave_lazy_mmu_mode();
>  	*mask |= PGTBL_PTE_MODIFIED;
> -	return 0;
> +
> +	return err;
>  }
>  
>  static int vmap_pages_pmd_range(pud_t *pud, unsigned long addr,