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Subject: Re: [PATCH RFC 0/3] block,ext4: Introduce REQ_OP_ASSIGN_RANGE to
 reflect extents allocation in block device internals
To:     Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
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        Damien Le Moal <Damien.LeMoal@wdc.com>,
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        Ajay Joshi <Ajay.Joshi@wdc.com>,
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From:   Kirill Tkhai <ktkhai@virtuozzo.com>
Message-ID: <a96e7af6-a807-1ca9-af50-4e0a7d771ac8@virtuozzo.com>
Date:   Wed, 11 Dec 2019 11:50:52 +0300
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On 11.12.2019 10:42, Chaitanya Kulkarni wrote:
>> Here is a simple test I did:
>> https://gist.github.com/tkhai/5b788651cdb74c1dbff3500745878856
>>
> 
> Somehow I'm not able to open this link, can you please share results
> in plain text on the email ?

#define _GNU_SOURCE
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>

#define BLOCK_SIZE 4096
#define STEP (BLOCK_SIZE * 16)
#define SIZE (4ULL * 1024 * 1024 * 1024)

int main(int argc)
{
	int fd, step, ret = 0;
	unsigned long i;
	void *buf;

	if (posix_memalign(&buf, BLOCK_SIZE, SIZE)) {
		perror("alloc");
		exit(1);
	}

	fd = open("file2.img", O_RDWR|O_CREAT|O_DIRECT);
	if (fd < 0) {
		perror("open");
		exit(1);
	}

	if (ftruncate(fd, SIZE)) {
		perror("ftruncate");
		exit(1);
	}

	ret = fallocate(fd, 0, 0, SIZE);
	if (ret) {
		perror("fallocate");
		exit(1);
	}
	
	for (step = STEP - BLOCK_SIZE; step >= 0; step -= BLOCK_SIZE) {
		printf("step=%u\n", step);
		for (i = step; i < SIZE; i += STEP) {
			errno = 0;
			if (pwrite(fd, buf, BLOCK_SIZE, i) != BLOCK_SIZE) {
				perror("pwrite");
				exit(1);
			}
		}

		if (fsync(fd)) {
			perror("fsync");
			exit(1);
		}
	}

	return 0;
}