From b9b1dae19b2155c07d8ffb6d6283f3a5fd2d4b2c Mon Sep 17 00:00:00 2001
From: Vitaliy Filippov <vitalif@yourcmc.ru>
Date: Tue, 19 Feb 2019 00:49:07 +0300
Subject: [PATCH] era_copy for dm-era

---
 Makefile   |   3 ++
 era_copy.c | 135 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 138 insertions(+)
 create mode 100644 Makefile
 create mode 100644 era_copy.c

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..caf4618
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,3 @@
+all: era_copy
+era_copy:
+	gcc -o era_copy -Wall era_copy.c
diff --git a/era_copy.c b/era_copy.c
new file mode 100644
index 0000000..ec7daf5
--- /dev/null
+++ b/era_copy.c
@@ -0,0 +1,135 @@
+/**
+ * Parses XML block lists produced by dm-era `era_invalidate` tool
+ * from `thin-provisioning-tools` and copies these blocks from/to
+ * specified device(s)
+ *
+ * Author: Vitaliy Filippov <vitalif@yourcmc.ru>, 2019
+ * License: GNU GPLv3.0 or later
+ */
+
+#define _LARGEFILE64_SOURCE
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/sendfile.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define XML_BUFSIZE 1024
+#define MAX_COPY 0x10000000
+
+void copy_blocks(int src, int dst, off64_t start, off64_t length)
+{
+	off64_t copied = 0, cur = start;
+	ssize_t fact = 0;
+	if (lseek64(dst, start, 0) < 0)
+	{
+		fprintf(stderr, "Failed to lseek output file: %s\n", strerror(errno));
+		exit(1);
+	}
+	while (length > copied)
+	{
+		fact = sendfile64(dst, src, &cur, length-copied > MAX_COPY ? MAX_COPY : length-copied);
+		if (fact < 0)
+		{
+			fprintf(stderr, "Failed to copy data: %s\n", strerror(errno));
+			exit(1);
+		}
+		cur += fact;
+		copied += fact;
+	}
+}
+
+void read_era_invalidate_and_copy(FILE *fp, int src, int dst, int metadata_block_size)
+{
+	// read input XML
+	char buf[XML_BUFSIZE] = { 0 };
+	off64_t start = 0, length = 0;
+	if (fgets(buf, XML_BUFSIZE, fp) == NULL)
+	{
+		fprintf(stderr, "Input block list is empty\n");
+		exit(0);
+	}
+	if (sscanf(buf, " <blocks >") == 0)
+	{
+		fprintf(stderr, "<blocks> expected, but \"%s\" found\n", buf);
+		exit(1);
+	}
+	while (fgets(buf, XML_BUFSIZE, fp) != NULL)
+	{
+		if (sscanf(buf, " <range begin = \" %lld \" end = \" %lld \" />", &start, &length) == 2)
+		{
+			copy_blocks(src, dst, start*metadata_block_size*512, length*metadata_block_size*512);
+		}
+		else if (sscanf(buf, " <block block = \" %lld \" />", &start) == 1)
+		{
+			copy_blocks(src, dst, start*metadata_block_size*512, metadata_block_size*512);
+		}
+		else
+		{
+			fprintf(stderr, "<range begin=NUMBER end=NUMBER /> or <block block=NUMBER /> expected, but \"%s\" found\n", buf);
+			exit(1);
+		}
+	}
+	buf[0] = '\0';
+	if (fgets(buf, XML_BUFSIZE, fp) == NULL ||
+		sscanf(buf, " </blocks >") == 0)
+	{
+		fprintf(stderr, "</blocks> expected, but \"%s\" found\n", buf);
+		exit(1);
+	}
+}
+
+void era_copy(char *src_path, const char *dst_path, int metadata_block_size)
+{
+	int src, dst;
+	struct stat statbuf;
+	src = open(src_path, O_RDONLY|O_LARGEFILE);
+	if (src < 0)
+	{
+		fprintf(stderr, "Failed to open %s for reading: %s\n", src_path, strerror(errno));
+		exit(1);
+	}
+	if (stat(dst_path, &statbuf) != 0)
+	{
+		fprintf(stderr, "Failed to stat %s: %s\n", dst_path, strerror(errno));
+		exit(1);
+	}
+	// prevent writing to mounted devices
+	dst = open(dst_path, ((statbuf.st_mode & S_IFBLK) ? O_EXCL : 0) | O_WRONLY | O_LARGEFILE);
+	if (src < 0)
+	{
+		fprintf(stderr, "Failed to open %s for writing: %s\n", dst_path, strerror(errno));
+		exit(1);
+	}
+	read_era_invalidate_and_copy(stdin, src, dst, metadata_block_size);
+	// fsync and close
+	fsync(dst);
+	close(dst);
+	close(src);
+}
+
+int main(int narg, char *args[])
+{
+	if (narg < 4)
+	{
+		fprintf(stderr,
+			"era_copy - parses era_invalidate output and copies specified blocks from one file/device to another\n"
+			"(c) Vitaliy Filippov, 2019+, distributed under the terms of GNU GPLv3.0 or later license\n"
+			"USAGE:\nera_invalidate --metadata-snapshot --written-since <ERA> <META_DEVICE> |\\\n"
+			"    era_copy <METADATA_BLOCK_SIZE> <DATA_DEVICE> <DEST_DEVICE>\n"
+		);
+		exit(1);
+	}
+	int bs = atoi(args[1]);
+	if (bs < 1)
+	{
+		fprintf(stderr, "Incorrect metadata_block_size = %d\n", bs);
+		exit(1);
+	}
+	era_copy(args[2], args[3], bs);
+	return 0;
+}