[PATCH v6 3/5] vmcore: Introduce remap_oldmem_pfn_range()
Vivek Goyal
vgoyal at redhat.com
Tue Jul 2 11:42:14 EDT 2013
On Mon, Jul 01, 2013 at 09:32:37PM +0200, Michael Holzheu wrote:
> For zfcpdump we can't map the HSA storage because it is only available
> via a read interface. Therefore, for the new vmcore mmap feature we have
> introduce a new mechanism to create mappings on demand.
>
> This patch introduces a new architecture function remap_oldmem_pfn_range()
> that should be used to create mappings with remap_pfn_range() for oldmem
> areas that can be directly mapped. For zfcpdump this is everything besides
> of the HSA memory. For the areas that are not mapped by remap_oldmem_pfn_range()
> a generic vmcore a new generic vmcore fault handler mmap_vmcore_fault()
> is called.
>
> This handler works as follows:
>
> * Get already available or new page from page cache (find_or_create_page)
> * Check if /proc/vmcore page is filled with data (PageUptodate)
> * If yes:
> Return that page
> * If no:
> Fill page using __vmcore_read(), set PageUptodate, and return page
>
> Signed-off-by: Michael Holzheu <holzheu at linux.vnet.ibm.com>
In general vmcore related changes look fine to me. I am not very familiar
with the logic of finding pages in page cache and using page uptodate
flag.
Hatayama, can you please review it.
Acked-by: Vivek Goyal <vgoyal at redhat.com>
Thanks
Vivek
> ---
> fs/proc/vmcore.c | 84 +++++++++++++++++++++++++++++++++++++++++-----
> include/linux/crash_dump.h | 3 ++
> 2 files changed, 79 insertions(+), 8 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index c28189c..77312c7 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -21,6 +21,7 @@
> #include <linux/crash_dump.h>
> #include <linux/list.h>
> #include <linux/vmalloc.h>
> +#include <linux/pagemap.h>
> #include <asm/uaccess.h>
> #include <asm/io.h>
> #include "internal.h"
> @@ -153,11 +154,35 @@ ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
> return read_from_oldmem(buf, count, ppos, 0);
> }
>
> +/*
> + * Architectures may override this function to map oldmem
> + */
> +int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
> + unsigned long from, unsigned long pfn,
> + unsigned long size, pgprot_t prot)
> +{
> + return remap_pfn_range(vma, from, pfn, size, prot);
> +}
> +
> +/*
> + * Copy to either kernel or user space
> + */
> +static int copy_to(void *target, void *src, size_t size, int userbuf)
> +{
> + if (userbuf) {
> + if (copy_to_user(target, src, size))
> + return -EFAULT;
> + } else {
> + memcpy(target, src, size);
> + }
> + return 0;
> +}
> +
> /* Read from the ELF header and then the crash dump. On error, negative value is
> * returned otherwise number of bytes read are returned.
> */
> -static ssize_t read_vmcore(struct file *file, char __user *buffer,
> - size_t buflen, loff_t *fpos)
> +static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
> + int userbuf)
> {
> ssize_t acc = 0, tmp;
> size_t tsz;
> @@ -174,7 +199,7 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
> /* Read ELF core header */
> if (*fpos < elfcorebuf_sz) {
> tsz = min(elfcorebuf_sz - (size_t)*fpos, buflen);
> - if (copy_to_user(buffer, elfcorebuf + *fpos, tsz))
> + if (copy_to(buffer, elfcorebuf + *fpos, tsz, userbuf))
> return -EFAULT;
> buflen -= tsz;
> *fpos += tsz;
> @@ -192,7 +217,7 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
>
> tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, buflen);
> kaddr = elfnotes_buf + *fpos - elfcorebuf_sz;
> - if (copy_to_user(buffer, kaddr, tsz))
> + if (copy_to(buffer, kaddr, tsz, userbuf))
> return -EFAULT;
> buflen -= tsz;
> *fpos += tsz;
> @@ -208,7 +233,7 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
> if (*fpos < m->offset + m->size) {
> tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
> start = m->paddr + *fpos - m->offset;
> - tmp = read_from_oldmem(buffer, tsz, &start, 1);
> + tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
> if (tmp < 0)
> return tmp;
> buflen -= tsz;
> @@ -225,6 +250,48 @@ 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_file->f_mapping;
> + pgoff_t index = vmf->pgoff;
> + struct page *page;
> + loff_t src;
> + char *buf;
> + int rc;
> +
> + 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);
> + rc = __read_vmcore(buf, PAGE_SIZE, &src, 0);
> + if (rc < 0) {
> + unlock_page(page);
> + page_cache_release(page);
> + return (rc == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS;
> + }
> + SetPageUptodate(page);
> + }
> + unlock_page(page);
> + vmf->page = page;
> + return 0;
> +}
> +
> +static const struct vm_operations_struct vmcore_mmap_ops = {
> + .fault = mmap_vmcore_fault,
> +};
> +
> static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
> {
> size_t size = vma->vm_end - vma->vm_start;
> @@ -242,6 +309,7 @@ static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
>
> vma->vm_flags &= ~(VM_MAYWRITE | VM_MAYEXEC);
> vma->vm_flags |= VM_MIXEDMAP;
> + vma->vm_ops = &vmcore_mmap_ops;
>
> len = 0;
>
> @@ -283,9 +351,9 @@ static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
>
> tsz = min_t(size_t, m->offset + m->size - start, size);
> paddr = m->paddr + start - m->offset;
> - if (remap_pfn_range(vma, vma->vm_start + len,
> - paddr >> PAGE_SHIFT, tsz,
> - vma->vm_page_prot))
> + if (remap_oldmem_pfn_range(vma, vma->vm_start + len,
> + paddr >> PAGE_SHIFT, tsz,
> + vma->vm_page_prot))
> goto fail;
> size -= tsz;
> start += tsz;
> diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
> index 6571f82..fe68a5a 100644
> --- a/include/linux/crash_dump.h
> +++ b/include/linux/crash_dump.h
> @@ -17,6 +17,9 @@ extern int __weak elfcorehdr_alloc(unsigned long long *addr,
> extern void __weak elfcorehdr_free(unsigned long long addr);
> extern ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos);
> extern ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos);
> +extern int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
> + unsigned long from, unsigned long pfn,
> + unsigned long size, pgprot_t prot);
>
> extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
> unsigned long, int);
> --
> 1.8.2.2
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