criu/cr-dedup.c

#include <sys/uio.h>
#include <fcntl.h>
#include <linux/falloc.h>
#include <unistd.h>

#include "crtools.h"
#include "page-read.h"
#include "restorer.h"

#define MAX_BUNCH_SIZE 256

static int cr_dedup_one_pagemap(int pid);

int cr_dedup(void)
{
	int close_ret, ret = 0;
	int pid;
	DIR * dirp;
	struct dirent *ent;

	dirp = opendir(CR_PARENT_LINK);
	if (dirp == NULL) {
		pr_perror("Can't enter previous snapshot folder, error=%d", errno);
		ret = -1;
		goto err;
	}

	while (1) {
		errno = 0;
		ent = readdir(dirp);
		if (ent == NULL) {
			if (errno) {
				pr_perror("Failed readdir, error=%d", errno);
				ret = -1;
				goto err;
			}
			break;
		}

		ret = sscanf(ent->d_name, "pagemap-%d.img", &pid);
		if (ret == 1) {
			pr_info("pid=%d\n", pid);
			ret = cr_dedup_one_pagemap(pid);
			if (ret < 0)
				break;
		}
	}

err:
	if (dirp) {
		close_ret = closedir(dirp);
		if (close_ret == -1)
			return close_ret;
	}

	if (ret < 0)
		return ret;

	pr_info("Deduplicated\n");
	return 0;
}

static int cr_dedup_one_pagemap(int pid)
{
	int ret;
	struct page_read pr;
	struct page_read * prp;
	struct iovec iov;

	ret = open_page_read(pid, &pr, PR_TASK | PR_MOD);
	if (ret <= 0) {
		ret = -1;
		goto exit;
	}

	prp = pr.parent;
	if (!prp)
		goto exit;

	ret = pr.get_pagemap(&pr, &iov);
	if (ret <= 0)
		goto exit;

	while (1) {
		pr_debug("dedup iovec base=%p, len=%zu\n", iov.iov_base, iov.iov_len);
		if (!pr.pe->in_parent) {
			ret = dedup_one_iovec(prp, &iov);
			if (ret)
				goto exit;
		}

		pr.put_pagemap(&pr);
		ret = pr.get_pagemap(&pr, &iov);
		if (ret <= 0)
			goto exit;
	}
exit:
	pr.close(&pr);

	if (ret < 0)
		return ret;

	return 0;
}

static inline bool can_extend_batch(struct iovec *bunch,
		unsigned long off, unsigned long len)
{
	return  /* The next region is the continuation of the existing */
		((unsigned long)bunch->iov_base + bunch->iov_len == off) &&
		/* The resulting region is non empty and is small enough */
		(bunch->iov_len == 0 || bunch->iov_len + len < MAX_BUNCH_SIZE * PAGE_SIZE);
}

int punch_hole(struct page_read *pr, unsigned long off, unsigned long len,
	       bool cleanup)
{
	int ret;
	struct iovec * bunch = &pr->bunch;

	if (!cleanup && can_extend_batch(bunch, off, len)) {
		pr_debug("pr%d:Extend bunch len from %zu to %lu\n", pr->id,
			 bunch->iov_len, bunch->iov_len + len);
		bunch->iov_len += len;
	} else {
		if (bunch->iov_len > 0) {
			pr_debug("Punch!/%p/%zu/\n", bunch->iov_base, bunch->iov_len);
			ret = fallocate(img_raw_fd(pr->pi), FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
					(unsigned long)bunch->iov_base, bunch->iov_len);
			if (ret != 0) {
				pr_perror("Error punching hole");
				return -1;
			}
		}
		bunch->iov_base = (void *)off;
		bunch->iov_len = len;
		pr_debug("pr%d:New bunch/%p/%zu/\n", pr->id, bunch->iov_base, bunch->iov_len);
	}
	return 0;
}

int dedup_one_iovec(struct page_read *pr, struct iovec *iov)
{
	unsigned long off;
	unsigned long off_real;
	unsigned long iov_end;

	iov_end = (unsigned long)iov->iov_base + iov->iov_len;
	off = (unsigned long)iov->iov_base;
	while (1) {
		int ret;
		struct iovec piov;
		unsigned long piov_end;
		struct iovec tiov;
		struct page_read * prp;

		ret = seek_pagemap_page(pr, off, false);
		if (ret == -1)
			return -1;

		if (ret == 0) {
			if (off < pr->cvaddr && pr->cvaddr < iov_end)
				off = pr->cvaddr;
			else
				return 0;
		}

		if (!pr->pe)
			return -1;
		pagemap2iovec(pr->pe, &piov);
		piov_end = (unsigned long)piov.iov_base + piov.iov_len;
		off_real = lseek(img_raw_fd(pr->pi), 0, SEEK_CUR);
		if (!pr->pe->in_parent) {
			ret = punch_hole(pr, off_real, min(piov_end, iov_end) - off, false);
			if (ret == -1)
				return ret;
		}

		prp = pr->parent;
		if (prp) {
			/* recursively */
			pr_debug("Go to next parent level\n");
			tiov.iov_base = (void*)off;
			tiov.iov_len = min(piov_end, iov_end) - off;
			ret = dedup_one_iovec(prp, &tiov);
			if (ret != 0)
				return -1;
		}

		if (piov_end < iov_end) {
			off = piov_end;
			continue;
		} else
			return 0;
	}
	return 0;
}