Re: [LTP] [PATCH 2/2] fill_fs: Ensure written data is not easily compressed

Cyril Hrubis
2022-12-06T16:14:42Z

Hi!
> I suppose that instead of writing random lengths we could just copy
> /dev/urandom to <path> in static chunks of a reasonable size.

Actually it would make sense to do random length writes as well, at
least for a subset of files. I guess that in real life scenario we would
encounter both, block writes and randomly sized writes for files.

I would do something as:

#define BLOCK_SIZE 4096

..
char buf[2*BLOCK_SIZE];

fd = SAFE_OPEN("/dev/urandom", O_RDONLY);
SAFE_READ(1, fd, buf, sizeof(buf));
SAFE_CLOSE(fd);

...

random_size = random() % 2;

while (len) {
if (random_size)
len = random() % BOCK_SIZE;
else
len = BLOCK_SIZE;

off = random() % BLOCK_SIZE;

ret = write(fd, buf + off, len);

...

But feel free to implement anything that you find sensible.

--
Cyril Hrubis
chrubis@suse.cz