v3 deduplication: look up for old pages in previous snapshot

old snapshot from "parent" symlink, and pids from pagemap-PID.img files
Signed-off-by: Tikhomirov Pavel <snorcht@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-dedup.c

+#include <sys/uio.h>
 #include <unistd.h>
 
 #include "crtools.h"
+#include "page-read.h"
+#include "restorer.h"
+
+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;
+}
+
+int cr_dedup_one_pagemap(int pid)
+{
+	int ret;
+	struct page_read pr;
+	struct page_read * prp;
+	struct iovec iov;
+
+	ret = open_page_rw(pid, &pr);
+	if (ret) {
+		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=%lu, len=%lu\n", (unsigned long)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;
+}
+
+int dedup_one_iovec(struct page_read *pr, struct iovec *iov)
+{
+	unsigned long off;
+	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;
+		ret = seek_pagemap_page(pr, off, false);
+		if (ret == -1) {
+			if(off < pr->cvaddr) {
+				if(pr->cvaddr < iov_end)
+					off = pr->cvaddr;
+				else
+					return 0;
+			} else
+				return ret;
+		}
+
+		if (!pr->pe)
+			return -1;
+		pagemap2iovec(pr->pe, &piov);
+		piov_end = (unsigned long)piov.iov_base + piov.iov_len;
+
+		if (piov_end < iov_end) {
+			off = piov_end;
+			continue;
+		} else
+			return 0;
+	}
 	return 0;
 }

include/page-read.h

@@ -70,4 +70,6 @@ extern int open_page_read(int pid, struct page_read *);
 extern int open_page_rw(int pid, struct page_read *);
 extern void pagemap2iovec(PagemapEntry *pe, struct iovec *iov);
 extern int seek_pagemap_page(struct page_read *pr, unsigned long vaddr, bool warn);
+
+extern int dedup_one_iovec(struct page_read *pr, struct iovec *iov);
 #endif /* __CR_PAGE_READ_H__ */