From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
To: HATAYAMA Daisuke <d.hatayama@gmail.com>
Cc: Vivek Goyal <vgoyal@redhat.com>, Jan Willeke <willeke@de.ibm.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
linux-kernel@vger.kernel.org, kexec@lists.infradead.org
Subject: Re: [PATCH v5 3/5] vmcore: Introduce remap_oldmem_pfn_range()
Date: Wed, 12 Jun 2013 11:13:03 +0200 [thread overview]
Message-ID: <20130612111303.3323f24f@holzheu> (raw)
In-Reply-To: <CABOkKT05VR3V9rEz1LWnEJSEvkevhBFfQVVX5_DS0Z4rBG9EyA@mail.gmail.com>
On Tue, 11 Jun 2013 21:42:15 +0900
HATAYAMA Daisuke <d.hatayama@gmail.com> wrote:
> 2013/6/11 Michael Holzheu <holzheu@linux.vnet.ibm.com>:
> > On Mon, 10 Jun 2013 22:40:24 +0900
> > HATAYAMA Daisuke <d.hatayama@gmail.com> wrote:
> >
> >> 2013/6/8 Michael Holzheu <holzheu@linux.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()?
> >
> > The function would then look like the following:
> >
> > 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;
> >
> > page = find_or_create_page(mapping, index, GFP_KERNEL);
> > if (!page)
> > return VM_FAULT_OOM;
> > src = index << PAGE_CACHE_SHIFT;
> > buf = (void *) (page_to_pfn(page) << PAGE_SHIFT);
> > __read_vmcore(buf, PAGE_SIZE, &src, 0);
> > unlock_page(page);
> > vmf->page = page;
> > return 0;
> > }
> >
> > I agree that this makes the function simpler but we have to copy
> > the page also if it has already been filled, correct?
> >
>
> You can use for the purpose PG_uptodate flag.
Thanks for that hint! So together with your other comment regarding
error checking for __read_vmcore() the function would look like the
following:
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;
page = find_or_create_page(mapping, index, GFP_KERNEL);
if (!page)
return VM_FAULT_OOM;
if (!PageUptodate(page)) {
src = index << PAGE_CACHE_SHIFT;
buf = (void *) (page_to_pfn(page) << PAGE_SHIFT);
if (__read_vmcore(buf, PAGE_SIZE, &src, 0) < 0) {
unlock_page(page);
return VM_FAULT_SIGBUS;
}
SetPageUptodate(page);
}
unlock_page(page);
vmf->page = page;
return 0;
}
Perhaps one open issue remains:
Can we remove the page from the page cache if __read_vmcore() fails?
Thanks!
Michael
next prev parent reply other threads:[~2013-06-12 9:13 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-07 16:55 [PATCH v5 0/5] kdump: Allow ELF header creation in new kernel Michael Holzheu
2013-06-07 16:55 ` [PATCH v5 1/5] vmcore: Introduce ELF header in new memory feature Michael Holzheu
2013-06-10 13:35 ` HATAYAMA Daisuke
2013-06-10 13:53 ` Michael Holzheu
2013-06-14 18:54 ` Vivek Goyal
2013-06-21 14:17 ` Michael Holzheu
2013-06-27 19:32 ` Vivek Goyal
2013-06-27 20:10 ` Cliff Wickman
2013-06-27 20:23 ` Vivek Goyal
2013-06-28 8:15 ` Michael Holzheu
2013-07-01 17:37 ` Vivek Goyal
2013-07-01 18:29 ` Michael Holzheu
2013-06-07 16:55 ` [PATCH v5 2/5] s390/vmcore: Use " Michael Holzheu
2013-06-10 13:36 ` HATAYAMA Daisuke
2013-06-10 13:48 ` Michael Holzheu
2013-06-14 19:16 ` Vivek Goyal
2013-06-07 16:55 ` [PATCH v5 3/5] vmcore: Introduce remap_oldmem_pfn_range() Michael Holzheu
[not found] ` <CAJGZr0+_W0dp2f9VtVAiUT2fqiwe91gHXd9zYzfMMzBZSZogww@mail.gmail.com>
2013-06-10 8:00 ` Michael Holzheu
2013-06-10 13:40 ` HATAYAMA Daisuke
2013-06-10 14:03 ` Michael Holzheu
2013-06-10 15:37 ` Michael Holzheu
2013-06-11 12:42 ` HATAYAMA Daisuke
2013-06-12 9:13 ` Michael Holzheu [this message]
2013-06-13 1:32 ` HATAYAMA Daisuke
2013-06-13 8:54 ` Michael Holzheu
2013-06-13 4:00 ` HATAYAMA Daisuke
2013-06-11 13:20 ` HATAYAMA Daisuke
2013-06-07 16:56 ` [PATCH v5 4/5] s390/vmcore: Implement remap_oldmem_pfn_range for s390 Michael Holzheu
2013-06-14 20:08 ` Vivek Goyal
2013-06-07 16:56 ` [PATCH v5 5/5] s390/vmcore: Use vmcore for zfcpdump Michael Holzheu
2013-06-11 23:47 ` HATAYAMA Daisuke
2013-06-12 9:14 ` Michael Holzheu
2013-06-14 18:54 ` [PATCH v5 0/5] kdump: Allow ELF header creation in new kernel Vivek Goyal
2013-06-21 13:39 ` Michael Holzheu
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