| Message ID | 20171020015907.25430-4-wqu@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Oct 20, 2017 at 09:59:03AM +0800, Qu Wenruo wrote: > 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> Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/mkfs/main.c b/mkfs/main.c index 1355089505ca..7b78cfe3550e 100644 --- a/mkfs/main.c +++ b/mkfs/main.c @@ -404,18 +404,25 @@ 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; }
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> --- mkfs/main.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-)