marko10_000
/
btrfs-progs
forked from Mirrors/btrfs-progs
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

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>
master
Qu Wenruo 2017-10-19 14:16:17 +08:00 committed by David Sterba
parent 31d228a2eb
commit 6dd8669a1c
1 changed files with 13 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
mkfs/main.c
View File

@ -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;
}