mkfs: Zero 2MB at the start and end of the device

But, on sparc, don't zero the first 1k.

diff --git a/mkfs.c b/mkfs.c
index 28d6184..c3a84c0 100644 (file)
--- a/mkfs.c
+++ b/mkfs.c
@@ -67,6 +67,43 @@ static u64 parse_size(char *s)
        return atol(s) * mult;
 }
 
+static int zero_blocks(int fd, off_t start, size_t len)
+{
+       char *buf = malloc(len);
+       int ret = 0;
+       ssize_t written;
+
+       if (!buf)
+               return -ENOMEM;
+       memset(buf, 0, len);
+       written = pwrite(fd, buf, len, start);
+       if (written != len)
+               ret = -EIO;
+       free(buf);
+       return ret;
+}
+
+static int zero_dev_start(int fd)
+{
+       off_t start = 0;
+       size_t len = 2 * 1024 * 1024;
+
+#ifdef __sparc__
+       /* don't overwrite the disk labels on sparc */
+       start = 1024;
+       len -= 1024;
+#endif
+       return zero_blocks(fd, start, len);
+}
+
+static int zero_dev_end(int fd, u64 dev_size)
+{
+       size_t len = 2 * 1024 * 1024;
+       off_t start = dev_size - len;
+
+       return zero_blocks(fd, start, len);
+}
+
 static int make_root_dir(int fd) {
        struct btrfs_root *root;
        struct btrfs_trans_handle *trans;
@@ -143,7 +180,7 @@ int main(int ac, char **av)
        u32 nodesize = 16 * 1024;
        u32 stripesize = 4096;
        u64 blocks[4];
-       char *buf = malloc(sectorsize);
+       int zero_end = 0;
 
        while(1) {
                int c;
@@ -201,6 +238,7 @@ int main(int ac, char **av)
                        fprintf(stderr, "unable to find %s size\n", file);
                        exit(1);
                }
+               zero_end = 1;
        }
        block_count /= sectorsize;
        block_count *= sectorsize;
@@ -209,16 +247,23 @@ int main(int ac, char **av)
                fprintf(stderr, "device %s is too small\n", file);
                exit(1);
        }
-       memset(buf, 0, sectorsize);
-       for(i = 0; i < 64; i++) {
-               ret = write(fd, buf, sectorsize);
-               if (ret != sectorsize) {
-                       fprintf(stderr, "unable to zero fill device\n");
+       ret = zero_dev_start(fd);
+       if (ret) {
+               fprintf(stderr, "failed to zero device start %d\n", ret);
+               exit(1);
+       }
+
+       if (zero_end) {
+               ret = zero_dev_end(fd, block_count);
+               if (ret) {
+                       fprintf(stderr, "failed to zero device end %d\n", ret);
                        exit(1);
                }
        }
+
        for (i = 0; i < 4; i++)
                blocks[i] = BTRFS_SUPER_INFO_OFFSET + leafsize * i;
+
        ret = make_btrfs(fd, blocks, block_count, nodesize, leafsize,
                         sectorsize, stripesize);
        if (ret) {