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Date:   Mon, 29 Nov 2021 08:32:35 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Joao Martins <joao.m.martins@oracle.com>
Cc:     linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
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        Matthew Wilcox <willy@infradead.org>,
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        Muchun Song <songmuchun@bytedance.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Christoph Hellwig <hch@lst.de>, nvdimm@lists.linux.dev,
        linux-doc@vger.kernel.org
Subject: Re: [PATCH v6 09/10] device-dax: set mapping prior to
 vmf_insert_pfn{,_pmd,pud}()
Message-ID: <20211129073235.GA23843@lst.de>
References: <20211124191005.20783-1-joao.m.martins@oracle.com> <20211124191005.20783-10-joao.m.martins@oracle.com> <0439eb48-1688-a4f4-5feb-8eb2680d652f@oracle.com> <96b53b3c-5c18-5f93-c595-a7d509d58f92@oracle.com>
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On Fri, Nov 26, 2021 at 06:39:39PM +0000, Joao Martins wrote:
> @@ -230,23 +235,18 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
>  	id = dax_read_lock();
>  	switch (pe_size) {
>  	case PE_SIZE_PTE:
> -		fault_size = PAGE_SIZE;
>  		rc = __dev_dax_pte_fault(dev_dax, vmf, &pfn);
>  		break;
>  	case PE_SIZE_PMD:
> -		fault_size = PMD_SIZE;
>  		rc = __dev_dax_pmd_fault(dev_dax, vmf, &pfn);
>  		break;
>  	case PE_SIZE_PUD:
> -		fault_size = PUD_SIZE;
>  		rc = __dev_dax_pud_fault(dev_dax, vmf, &pfn);
>  		break;
>  	default:
>  		rc = VM_FAULT_SIGBUS;
>  	}
> 
>  	dax_read_unlock(id);

I wonder if if would make sense to move dax_read_lock / dax_read_unlock
іnto the individul helpers as well now.  That way you could directly
return from the switch.  Aso it seems like pfn is only an input
parameter now and doesn't need to be passed by reference.