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

Louis Rilling
2008-08-21T09:53:29Z

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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

--
Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes
http://www.kerlabs.com/ 35700 Rennes

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