initial commit

6 files changed, 212 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..59a4ba5
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/cow-*
+*.o
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..10ebe01
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,13 @@
+CFLAGS += -std=c11
+CPPFLAGS += -I$(CURDIR)/lib
+CFLAGS += -Wall -Werror -Wextra
+CPPFLAGS += -O2 -D_FORTIFY_SOURCE=2
+
+all: cow-dedupe-range
+.PHONY: all
+
+cow-dedupe-range: src/cow-dedupe-range.o lib/dedupe-range.o
+	$(CC) $(LDFLAGS) -o $@ $^
+
+.SECONDARY:
+.DELETE_ON_ERROR:
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..bd7afd9
--- /dev/null
+++ b/README.md
@@ -0,0 +1,4 @@
+- ioctl
+  * FICLONE
+  * FICLONERANGE
+  * FIDEDUPERANGE
diff --git a/lib/dedupe-range.c b/lib/dedupe-range.c
new file mode 100644
index 0000000..dea70c7
--- /dev/null
+++ b/lib/dedupe-range.c
@@ -0,0 +1,86 @@
+#include <assert.h>    /* for assert(3p) */
+#include <errno.h>     /* for errno */
+#include <error.h>     /* for error(3gnu) */
+#include <fcntl.h>     /* for open(2) */
+#include <inttypes.h>  /* for uint64_t, PRIu64 */
+#include <linux/fs.h>  /* for FIDEDUPRANGE and related */
+#include <stdbool.h>   /* for bool, true, false */
+#include <stdlib.h>    /* for exit(3p), EXIT_SUCCESS, EXIT_FAILURE */
+#include <sys/ioctl.h> /* for ioctl(2) */
+#include <unistd.h>    /* for sysconf(3p), _SC_PAGESIZE */
+
+#include "dedupe-range.h"
+
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
+void dedupe_range(struct range src, struct range *dsts) {
+	size_t dst_count;
+	for (dst_count = 0; dsts[dst_count].filename; dst_count++);
+
+	const size_t max_dst_count = (sysconf(_SC_PAGESIZE) - sizeof(struct file_dedupe_range))
+		/ sizeof(struct file_dedupe_range_info);
+
+	int src_fd = open(src.filename, src.flags);
+	if (src_fd < 0)
+		error(EXIT_FAILURE, errno, "open src: %s", src.filename);
+
+	struct file_dedupe_range_info *range_info =
+		calloc(dst_count, sizeof(struct file_dedupe_range_info));
+	for (size_t i = 0; i < dst_count; i++) {
+		int dst_fd = open(dsts[i].filename, dsts[i].flags);
+		if (dst_fd < 0)
+			error(EXIT_FAILURE, errno, "open dst: %s", dsts[i].filename);
+		range_info[i].dest_fd = dst_fd;
+		range_info[i].dest_offset = dsts[i].offset;
+	}
+
+	for (size_t files_deduped = 0; files_deduped < dst_count; ) {
+		uint16_t dest_count = MIN(dst_count - files_deduped, max_dst_count);
+		struct file_dedupe_range *range = malloc(sizeof(struct file_dedupe_range) + dest_count * sizeof(struct file_dedupe_range_info));
+		*range = (struct file_dedupe_range){
+			.src_offset = src.offset,
+			.src_length = src.length,
+			.dest_count = dest_count,
+			.reserved1 = 0,
+			.reserved2 = 0,
+		};
+		for (size_t i = 0; i < dest_count; i++)
+			range->info[i] = range_info[files_deduped+i];
+
+		bool erred = false;
+		while (range->src_length > 0) {
+			if (ioctl(src_fd, FIDEDUPERANGE, &range) < 0)
+				error(EXIT_FAILURE, errno, "ioctl (FIDEDUPERANGE)");
+			uint64_t bytes_deduped = range->info[0].bytes_deduped;
+			assert(bytes_deduped <= range->src_length);
+			for (size_t i = 0; i < range->dest_count; i ++) {
+				if (range->info[i].bytes_deduped != bytes_deduped) {
+					error(0, errno, "dedupe: %"PRIu64" != %"PRIu64": %s",
+					      bytes_deduped,
+					      /* on platforms where both "long" and "long long" 
+					       * are 64 bits, linux __u64 might disagree with 
+					       * glibc uint64_t and thus PRIu64  */
+					      (uint64_t)range->info[i].bytes_deduped,
+					      dsts[files_deduped+i].filename);
+					erred = true;
+				}
+				switch (range->info[i].status) {
+				case FILE_DEDUPE_RANGE_DIFFERS:
+					error(0, 0, "dedupe: range differs: %s", dsts[files_deduped+i].filename);
+					erred = true;
+					break;
+				case FILE_DEDUPE_RANGE_SAME:
+					range->info[i].dest_offset += range->info[i].bytes_deduped;
+					break;
+				default:
+					assert(false);
+				}
+			}
+			if (erred == true)
+				exit(EXIT_FAILURE);
+			range->src_offset += bytes_deduped;
+			range->src_length -= bytes_deduped;
+		}
+		files_deduped += range->dest_count;
+	}
+}
diff --git a/lib/dedupe-range.h b/lib/dedupe-range.h
new file mode 100644
index 0000000..028fe08
--- /dev/null
+++ b/lib/dedupe-range.h
@@ -0,0 +1,10 @@
+#include <stdint.h>
+
+struct range {
+	char *filename;
+	int flags; /* to pass to open(2) */
+	uint64_t offset;
+	uint64_t length;
+};
+
+void dedupe_range(struct range src, struct range *dsts);
diff --git a/src/cow-dedupe-range.c b/src/cow-dedupe-range.c
new file mode 100644
index 0000000..7508f04
--- /dev/null
+++ b/src/cow-dedupe-range.c
@@ -0,0 +1,97 @@
+#define _GNU_SOURCE  /* for program_invocation_name */
+#include <assert.h>  /* for assert(3p) */
+#include <errno.h>   /* for errno, program_invocation_name */
+#include <error.h>   /* for error(3gnu) */
+#include <fcntl.h>   /* for O_RDONLY, O_RDWR */
+#include <getopt.h>  /* for getopt_long(3gnu), struct option, optind */
+#include <stdbool.h> /* for bool, true, false */
+#include <stdint.h>  /* for uint64_t */
+#include <stdio.h>   /* for printf(3gnu), fprintf(3p), stderr */
+#include <stdlib.h>  /* for strtoll(3p), calloc(3p), free(3p) */
+#include <string.h>  /* for strlen(3p) */
+#include <unistd.h>  /* for dup2(3p) */
+
+#include "dedupe-range.h" /* for dedupe_range, struct range */
+
+bool atou64(const char *str, uint64_t *ret) {
+	assert(sizeof(uint64_t) <= sizeof(unsigned long long int));
+	if (!('0' <= str[0] && str[0] <= '9'))
+		return false;
+	errno = 0;
+	char *end;
+	unsigned long long int n = strtoll(str, &end, 10);
+	if (end[0] != '\0' || errno != 0)
+		return false;
+	*ret = (uint64_t)n;
+	return true;
+}
+
+void usage() {
+	printf("Usage: %2$*1$s [OPTIONS] SRC_FILENAME SRC_OFFSET SRC_LENGTH \\\n"
+	       "       %3$*1$s           DST_FILENAME DST_OFFSET \\\n"
+	       "       %3$*1$s          [DST_FILENAME DST_OFFSET]...\n"
+	       "Submit a file deduplication request to the kernel.\n"
+	       "If the file ranges are not duplicates, the kernel will ignore this request.\n"
+	       "\n"
+	       "OPTIONS:\n"
+	       "   -r, --readonly  Open destination files read-only, rather than read/write.\n"
+	       "                   Generically, the destination must be open for writing.\n"
+	       "                   However, on Btrfs, this allows deduplication to be done\n"
+	       "                   on read-only subvolumes when invoked as root.\n"
+	       "   -h, --help      Display this help and exit.\n",
+	       (int)strlen(program_invocation_name), program_invocation_name, "");
+}
+
+int main(int argc, char *argv[]) {
+	int ro = 0;
+	struct option long_options[] = {
+		{"readonly", no_argument, &ro,  1},
+		{"help",     no_argument, NULL, 'h'},
+		{0}
+	};
+	int flag;
+	while ((flag = getopt_long(argc, argv, "rh", long_options, NULL)) >= 0) {
+		switch (flag) {
+		case 0:
+			break;
+		case 'r':
+			ro = 1;
+			break;
+		case 'h':
+			usage();
+			return 0;
+		case '?':
+			fprintf(stderr, "Try '%s --help' for more information.\n", program_invocation_name);
+			return 2;
+		default:
+			assert(false);
+		}
+	}
+
+	if (argc - optind < 5) {
+		error(0, 0, "too few arguments");
+		fprintf(stderr, "Try '%s --help' for more information.\n", program_invocation_name);
+		return 2;
+	}
+
+	struct range src;
+	src.filename = argv[optind];
+	src.flags = O_RDONLY;
+	if (!atou64(argv[optind+1], &src.offset))
+		error(2, errno, "invalid offset '%s'", argv[optind+1]);
+	if (!atou64(argv[optind+2], &src.length))
+		error(2, errno, "invalid length '%s'", argv[optind+2]);
+	
+	const size_t dst_count = (argc - optind - 3) / 2;
+	struct range *dsts = calloc(dst_count + 1, sizeof(struct range));
+	for (size_t i = 0; i < dst_count; i++) {
+		dsts[i].filename = argv[optind+3+(i*2)];
+		dsts[i].flags = ro ? O_RDONLY : O_RDWR;
+		if (!atou64(argv[optind+3+(i*2)+1], &dsts[i].offset))
+			error(2, errno, "invalid offset '%s'", argv[optind+3+(i*2)+1]);
+	}
+
+	dedupe_range(src, dsts);
+	free(dsts);
+	return 0;
+}