Re: [RFC v2][PATCH 4/9] Memory management - dump state

Oren Laadan
2008-08-22T21:26:53Z

Thanks Louis for all the comments. Will fix in v3.

Oren.

Louis Rilling wrote:
> On Wed, Aug 20, 2008 at 11:05:15PM -0400, Oren Laadan wrote:
>> For each VMA, there is a 'struct cr_vma'; if the VMA is file-mapped,
>> it will be followed by the file name. The cr_vma->npages will tell
>> how many pages were dumped for this VMA. Then it will be followed
>> by the actual data: first a dump of the addresses of all dumped
>> pages (npages entries) followed by a dump of the contents of all
>> dumped pages (npages pages). Then will come the next VMA and so on.
>
> [...]
>
>> diff --git a/checkpoint/ckpt_mem.c b/checkpoint/ckpt_mem.c
>> new file mode 100644
>> index 0000000..a23aa29
>> --- /dev/null
>> +++ b/checkpoint/ckpt_mem.c
>
> [...]
>
>> +/**
>> + * cr_vma_fill_pgarr - fill a page-array with addr/page tuples for a vma
>> + * @ctx - checkpoint context
>> + * @pgarr - page-array to fill
>> + * @vma - vma to scan
>> + * @start - start address (updated)
>> + */
>> +static int cr_vma_fill_pgarr(struct cr_ctx *ctx, struct cr_pgarr *pgarr,
>> + struct vm_area_struct *vma, unsigned long *start)
>> +{
>> + unsigned long end = vma->vm_end;
>> + unsigned long addr = *start;
>> + struct page **pagep;
>> + unsigned long *addrp;
>> + int cow, nr, ret = 0;
>> +
>> + nr = pgarr->nleft;
>> + pagep = &pgarr->pages[pgarr->nused];
>> + addrp = &pgarr->addrs[pgarr->nused];
>> + cow = !!vma->vm_file;
>> +
>> + while (addr < end) {
>> + struct page *page;
>> +
>> + /* simplified version of get_user_pages(): already have vma,
>> + * only need FOLL_TOUCH, and (for now) ignore fault stats */
>> +
>> + cond_resched();
>> + while (!(page = follow_page(vma, addr, FOLL_TOUCH))) {
>> + ret = handle_mm_fault(vma->vm_mm, vma, addr, 0);
>> + if (ret & VM_FAULT_ERROR) {
>> + if (ret & VM_FAULT_OOM)
>> + ret = -ENOMEM;
>> + else if (ret & VM_FAULT_SIGBUS)
>> + ret = -EFAULT;
>> + else
>> + BUG();
>> + break;
>> + }
>
> + ret = 0;
>
>> + cond_resched();
>> + }
>> +
>> + if (IS_ERR(page)) {
>> + ret = PTR_ERR(page);
>> + break;
>> + }
>
> Need to check ret here:
>
> + if (ret)
> break;
>
>> +
>> + if (page == ZERO_PAGE(0))
>> + page = NULL; /* zero page: ignore */
>> + else if (cow && page_mapping(page) != NULL)
>> + page = NULL; /* clean cow: ignore */
>> + else {
>> + get_page(page);
>> + *(addrp++) = addr;
>> + *(pagep++) = page;
>> + if (--nr == 0) {
>> + addr += PAGE_SIZE;
>> + break;
>> + }
>> + }
>> +
>> + addr += PAGE_SIZE;
>> + }
>> +
>> + if (unlikely(ret < 0)) {
>> + nr = pgarr->nleft - nr;
>> + while (nr--)
>> + page_cache_release(*(--pagep));
>> + return ret;
>> + }
>> +
>> + *start = addr;
>> + return (pgarr->nleft - nr);
>> +}
>
> [...]
>
> Thanks,
>
> Louis
>