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authorKent Overstreet <kent.overstreet@gmail.com>2010-05-04 17:58:22 -0800
committerKent Overstreet <kent.overstreet@gmail.com>2010-05-04 17:58:22 -0800
commit625ca7f8fbe02b9bb9947bf821c7e6f51ab90852 (patch)
tree2315a718080cc04942e575a9369d613c88c09b7a /make-bcache.c
Initial commit
Diffstat (limited to 'make-bcache.c')
-rw-r--r--make-bcache.c108
1 files changed, 108 insertions, 0 deletions
diff --git a/make-bcache.c b/make-bcache.c
new file mode 100644
index 0000000..54828bb
--- /dev/null
+++ b/make-bcache.c
@@ -0,0 +1,108 @@
+#define _XOPEN_SOURCE 500
+
+#include <fcntl.h>
+#include <linux/fs.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+static const char bcache_magic[] = {
+ 0xc6, 0x85, 0x73, 0xf6, 0x4e, 0x1a, 0x45, 0xca,
+ 0x82, 0x65, 0xf5, 0x7f, 0x48, 0xba, 0x6d, 0x81 };
+
+struct cache_sb {
+ uint8_t magic[16];
+ uint32_t version;
+ uint16_t block_size; /* sectors */
+ uint16_t bucket_size; /* sectors */
+ uint32_t journal_start; /* buckets */
+ uint32_t first_bucket; /* start of data */
+ uint64_t nbuckets; /* device size */
+ uint64_t btree_root;
+ uint16_t btree_level;
+};
+
+struct bucket_disk {
+ uint16_t priority;
+ uint8_t generation;
+} __attribute((packed));
+
+char zero[4096];
+
+int main(int argc, char **argv)
+{
+ long n;
+ int fd, i;
+ struct stat statbuf;
+ struct cache_sb sb;
+
+ if (argc < 2) {
+ printf("Please supply a device\n");
+ exit(EXIT_FAILURE);
+ }
+
+ fd = open(argv[1], O_RDWR);
+ if (!fd) {
+ perror("Can't open dev\n");
+ exit(EXIT_FAILURE);
+ }
+
+ if (fstat(fd, &statbuf)) {
+ perror("stat error\n");
+ exit(EXIT_FAILURE);
+ }
+ if (!S_ISBLK(statbuf.st_mode))
+ n = statbuf.st_blocks;
+ else
+ if (ioctl(fd, BLKGETSIZE, &n)) {
+ perror("ioctl error");
+ exit(EXIT_FAILURE);
+ }
+
+ memcpy(sb.magic, bcache_magic, 16);
+ sb.version = 0;
+ sb.block_size = 8;
+ sb.bucket_size = 32;
+ sb.nbuckets = n / sb.bucket_size;
+
+ do
+ sb.first_bucket = ((--sb.nbuckets * sizeof(struct bucket_disk))
+ + 4096 * 3) / (sb.bucket_size * 512) + 1;
+ while ((sb.nbuckets + sb.first_bucket) * sb.bucket_size * 512
+ > statbuf.st_size);
+
+ sb.journal_start = sb.first_bucket;
+
+ sb.btree_root = sb.first_bucket * sb.bucket_size;
+ sb.btree_level = 0;
+
+ printf("block_size: %u\n"
+ "bucket_size: %u\n"
+ "journal_start: %u\n"
+ "first_bucket: %u\n"
+ "nbuckets: %ju\n",
+ sb.block_size,
+ sb.bucket_size,
+ sb.journal_start,
+ sb.first_bucket,
+ sb.nbuckets);
+
+ /* Zero out priorities */
+ lseek(fd, 4096, SEEK_SET);
+ for (i = 8; i < sb.first_bucket * sb.bucket_size; i++)
+ if (write(fd, zero, 512) != 512)
+ goto err;
+
+ if (pwrite(fd, &sb, sizeof(sb), 4096) != sizeof(sb))
+ goto err;
+
+ exit(EXIT_SUCCESS);
+err:
+ perror("write error\n");
+ return 1;
+}