linux-kernel - Re: [PATCH] mm/memory: print also a_ops->readpage in print_bad

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Date:	Fri, 3 Apr 2015 20:33:12 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/memory: print also a_ops->readpage in print_bad_pte

On Fri, Apr 03, 2015 at 08:18:18PM +0300, Konstantin Khlebnikov wrote:
> A lot of filesystems use generic_file_mmap() and filemap_fault(),
> f_op->mmap and vm_ops->fault aren't enough to identify filesystem.
> 
> This prints file name, vm_ops->fault, f_op->mmap and a_ops->readpage
> (which is almost always implemented and filesystem-specific).
> 
> Example:
> 
> [   23.676410] BUG: Bad page map in process sh  pte:1b7e6025 pmd:19bbd067
> [   23.676887] page:ffffea00006df980 count:4 mapcount:1 mapping:ffff8800196426c0 index:0x97
> [   23.677481] flags: 0x10000000000000c(referenced|uptodate)
> [   23.677896] page dumped because: bad pte
> [   23.678205] addr:00007f52fcb17000 vm_flags:00000075 anon_vma:          (null) mapping:ffff8800196426c0 index:97
> [   23.678922] file:libc-2.19.so fault:filemap_fault mmap:generic_file_readonly_mmap readpage:v9fs_vfs_readpage
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> ---
>  mm/memory.c |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 411144f977b1..ea868eea0c88 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -690,12 +690,12 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
>  	/*
>  	 * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
>  	 */
> -	if (vma->vm_ops)
> -		printk(KERN_ALERT "vma->vm_ops->fault: %pSR\n",
> -		       vma->vm_ops->fault);
> -	if (vma->vm_file)
> -		printk(KERN_ALERT "vma->vm_file->f_op->mmap: %pSR\n",
> -		       vma->vm_file->f_op->mmap);
> +	printk(KERN_ALERT

pr_alert() ?

Otherwise,

Acked-by: Kirill A. Shutemov <kirill@...temov.name>

It would be nice to patch dump_vma() to display this information too.

> +		"file:%pD fault:%pf mmap:%pf readpage:%pf\n",
> +		vma->vm_file,
> +		vma->vm_ops ? vma->vm_ops->fault : NULL,
> +		vma->vm_file ? vma->vm_file->f_op->mmap : NULL,
> +		mapping ? mapping->a_ops->readpage : NULL);
>  	dump_stack();
>  	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
>  }
> 
> --
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-- 
 Kirill A. Shutemov
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