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

[Oren Laadan]

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
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