linux-kernel - Re: [PATCH v3 1/8] mm/dax: Dump start address in fault handler

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Message-ID: <bca7a510-4f66-42b2-b4a7-40b3bd37ead6@redhat.com>
Date: Wed, 31 Jul 2024 14:04:38 +0200
From: David Hildenbrand <david@...hat.com>
To: Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Cc: Dave Jiang <dave.jiang@...el.com>, Rik van Riel <riel@...riel.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Michael Ellerman <mpe@...erman.id.au>, linuxppc-dev@...ts.ozlabs.org,
 Matthew Wilcox <willy@...radead.org>,
 Rick P Edgecombe <rick.p.edgecombe@...el.com>,
 Oscar Salvador <osalvador@...e.de>, Mel Gorman
 <mgorman@...hsingularity.net>, Andrew Morton <akpm@...ux-foundation.org>,
 Borislav Petkov <bp@...en8.de>,
 Christophe Leroy <christophe.leroy@...roup.eu>,
 Huang Ying <ying.huang@...el.com>, "Kirill A . Shutemov"
 <kirill@...temov.name>, "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
 Dan Williams <dan.j.williams@...el.com>, Thomas Gleixner
 <tglx@...utronix.de>, Hugh Dickins <hughd@...gle.com>, x86@...nel.org,
 Nicholas Piggin <npiggin@...il.com>, Vlastimil Babka <vbabka@...e.cz>,
 Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v3 1/8] mm/dax: Dump start address in fault handler

On 15.07.24 21:21, Peter Xu wrote:
> Currently the dax fault handler dumps the vma range when dynamic debugging
> enabled.  That's mostly not useful.  Dump the (aligned) address instead
> with the order info.
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>   drivers/dax/device.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dax/device.c b/drivers/dax/device.c
> index eb61598247a9..714174844ca5 100644
> --- a/drivers/dax/device.c
> +++ b/drivers/dax/device.c
> @@ -235,9 +235,9 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf, unsigned int order)
>   	int id;
>   	struct dev_dax *dev_dax = filp->private_data;
>   
> -	dev_dbg(&dev_dax->dev, "%s: %s (%#lx - %#lx) order:%d\n", current->comm,
> -			(vmf->flags & FAULT_FLAG_WRITE) ? "write" : "read",
> -			vmf->vma->vm_start, vmf->vma->vm_end, order);
> +	dev_dbg(&dev_dax->dev, "%s: op=%s addr=%#lx order=%d\n", current->comm,
> +		(vmf->flags & FAULT_FLAG_WRITE) ? "write" : "read",
> +		vmf->address & ~((1UL << (order + PAGE_SHIFT)) - 1), order);
>   
>   	id = dax_read_lock();
>   	if (order == 0)

Agreed, the address of the fault is better. Just wondering, would the 
unmasked address be even better? Using the order we can figure out the 
to-be-aligned address.

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb