linux-kernel - Re: [PATCH v5 3/5] vmcore: Introduce remap_oldmem_pfn

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Message-ID: <CABOkKT0yk6tytN=aTSdpECQWw_30m5qrZYH-W1msovkeiSeZCA@mail.gmail.com>
Date:	Mon, 10 Jun 2013 22:40:24 +0900
From:	HATAYAMA Daisuke <d.hatayama@...il.com>
To:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
Cc:	Vivek Goyal <vgoyal@...hat.com>, Jan Willeke <willeke@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org
Subject: Re: [PATCH v5 3/5] vmcore: Introduce remap_oldmem_pfn_range()

2013/6/8 Michael Holzheu <holzheu@...ux.vnet.ibm.com>:
<cut>
> @@ -225,6 +251,56 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
>         return acc;
>  }
>
> +static ssize_t read_vmcore(struct file *file, char __user *buffer,
> +                          size_t buflen, loff_t *fpos)
> +{
> +       return __read_vmcore(buffer, buflen, fpos, 1);
> +}
> +
> +/*
> + * The vmcore fault handler uses the page cache and fills data using the
> + * standard __vmcore_read() function.
> + */
> +static int mmap_vmcore_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> +{
> +       struct address_space *mapping = vma->vm_private_data;
> +       pgoff_t index = vmf->pgoff;
> +       struct page *page;
> +       loff_t src;
> +       char *buf;
> +       int rc;
> +
> +find_page:
> +       page = find_lock_page(mapping, index);
> +       if (page) {
> +               unlock_page(page);
> +               rc = VM_FAULT_MINOR;
> +       } else {
> +               page = page_cache_alloc_cold(mapping);
> +               if (!page)
> +                       return VM_FAULT_OOM;
> +               rc = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
> +               if (rc) {
> +                       page_cache_release(page);
> +                       if (rc == -EEXIST)
> +                               goto find_page;
> +                       /* Probably ENOMEM for radix tree node */
> +                       return VM_FAULT_OOM;
> +               }
> +               buf = (void *) (page_to_pfn(page) << PAGE_SHIFT);
> +               src = index << PAGE_CACHE_SHIFT;
> +               __read_vmcore(buf, PAGE_SIZE, &src, 0);
> +               unlock_page(page);
> +               rc = VM_FAULT_MAJOR;
> +       }
> +       vmf->page = page;
> +       return rc;
> +}

How about reusing find_or_create_page()?

Thanks.
HATAYAMA, Daisuke
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