diff options
author | Qu Wenruo <wqu@suse.com> | 2017-10-19 14:16:17 +0800 |
---|---|---|
committer | David Sterba <dsterba@suse.com> | 2018-01-03 17:29:19 +0100 |
commit | 6dd8669a1c52cae1d827d934fbe6171f4893f1ba (patch) | |
tree | 9fe479a09b0a2aa61c2d666e2177d5b0d7533121 | |
parent | 31d228a2eb98d95637338bf77b5abcd375614d15 (diff) |
btrfs-progs: mkfs: Only zero out the first 1M for rootdir
It's a waste of IO to fill the whole image before creating btrfs on it,
just wiping the first 1M, and then write 1 byte to the last position to
create a sparse file.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
-rw-r--r-- | mkfs/main.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/mkfs/main.c b/mkfs/main.c index 90fab59b..d817ad8d 100644 --- a/mkfs/main.c +++ b/mkfs/main.c @@ -1161,18 +1161,25 @@ static int zero_output_file(int out_fd, u64 size) { int loop_num; u64 location = 0; - char buf[4096]; + char buf[SZ_4K]; int ret = 0, i; ssize_t written; - memset(buf, 0, 4096); - loop_num = size / 4096; + memset(buf, 0, SZ_4K); + + /* Only zero out the first 1M */ + loop_num = SZ_1M / SZ_4K; for (i = 0; i < loop_num; i++) { - written = pwrite64(out_fd, buf, 4096, location); - if (written != 4096) + written = pwrite64(out_fd, buf, SZ_4K, location); + if (written != SZ_4K) ret = -EIO; - location += 4096; + location += SZ_4K; } + + /* Then enlarge the file to size */ + written = pwrite64(out_fd, buf, 1, size - 1); + if (written < 1) + ret = -EIO; return ret; } |