Discard the whole device before starting to create the filesystem structures. Modelled after similar support in mkfs.xfs.
Signed-off-by: Christoph Hellwig <[email protected]> Index: btrfs-progs-unstable/utils.c =================================================================== --- btrfs-progs-unstable.orig/utils.c 2009-10-30 09:34:00.000000000 +0000 +++ btrfs-progs-unstable/utils.c 2009-10-30 09:38:01.000000000 +0000 @@ -46,6 +46,20 @@ static inline int ioctl(int fd, int define, u64 *size) { return 0; } #endif +#ifndef BLKDISCARD +#define BLKDISCARD _IO(0x12,119) +#endif + +static int +discard_blocks(int fd, u64 start, u64 len) +{ + u64 range[2] = { start, len }; + + if (ioctl(fd, BLKDISCARD, &range) < 0) + return errno; + return 0; +} + static u64 reference_root_table[] = { [1] = BTRFS_ROOT_TREE_OBJECTID, [2] = BTRFS_EXTENT_TREE_OBJECTID, @@ -532,6 +546,13 @@ int btrfs_prepare_device(int fd, char *f "(must be at least 256 MB)\n", file); exit(1); } + + /* + * We intentionally ignore errors from the discard ioctl. It is + * not necessary for the mkfs functionality but just an optimization. + */ + discard_blocks(fd, 0, block_count); + ret = zero_dev_start(fd); if (ret) { fprintf(stderr, "failed to zero device start %d\n", ret); -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
