mkfs should initialize unused fields properly

we discovered speed setting is (probably unintentionally) initialized to 1 in make_btrfs(), while being initialized to 0 in btrfs_add_to_fsid(). initialization in make_btrfs() is due to reuse of buf after pwrite() without clearing it. consequently, code like

 	btrfs_set_extent_generation(buf, extent_item, 1);

writes to the same location in buf where speed will be placed, later. It may be a good idea to clear buf after each pwrite(), though leaving the struct btrfs_header intact.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Hugo Mills <hugo@carfax.org.uk>

diff --git a/utils.c b/utils.c
index 74d2c59..46b9a2c 100644 (file)
--- a/utils.c
+++ b/utils.c
@@ -212,6 +212,8 @@ int make_btrfs(int fd, const char *device, const char *label,
        BUG_ON(ret != leafsize);
 
        /* create the items for the extent tree */
+       memset(buf->data+sizeof(struct btrfs_header), 0,
+               leafsize-sizeof(struct btrfs_header));
        nritems = 0;
        itemoff = __BTRFS_LEAF_DATA_SIZE(leafsize);
        for (i = 1; i < 7; i++) {
@@ -257,6 +259,8 @@ int make_btrfs(int fd, const char *device, const char *label,
        BUG_ON(ret != leafsize);
 
        /* create the chunk tree */
+       memset(buf->data+sizeof(struct btrfs_header), 0,
+               leafsize-sizeof(struct btrfs_header));
        nritems = 0;
        item_size = sizeof(*dev_item);
        itemoff = __BTRFS_LEAF_DATA_SIZE(leafsize) - item_size;
@@ -338,6 +342,8 @@ int make_btrfs(int fd, const char *device, const char *label,
        ret = pwrite(fd, buf->data, leafsize, blocks[3]);
 
        /* create the device tree */
+       memset(buf->data+sizeof(struct btrfs_header), 0,
+               leafsize-sizeof(struct btrfs_header));
        nritems = 0;
        itemoff = __BTRFS_LEAF_DATA_SIZE(leafsize) -
                sizeof(struct btrfs_dev_extent);
@@ -371,6 +377,8 @@ int make_btrfs(int fd, const char *device, const char *label,
        ret = pwrite(fd, buf->data, leafsize, blocks[4]);
 
        /* create the FS root */
+       memset(buf->data+sizeof(struct btrfs_header), 0,
+               leafsize-sizeof(struct btrfs_header));
        btrfs_set_header_bytenr(buf, blocks[5]);
        btrfs_set_header_owner(buf, BTRFS_FS_TREE_OBJECTID);
        btrfs_set_header_nritems(buf, 0);
@@ -379,6 +387,8 @@ int make_btrfs(int fd, const char *device, const char *label,
        BUG_ON(ret != leafsize);
 
        /* finally create the csum root */
+       memset(buf->data+sizeof(struct btrfs_header), 0,
+               leafsize-sizeof(struct btrfs_header));
        btrfs_set_header_bytenr(buf, blocks[6]);
        btrfs_set_header_owner(buf, BTRFS_CSUM_TREE_OBJECTID);
        btrfs_set_header_nritems(buf, 0);