From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cyril Hrubis <chrubis@suse.cz>
Date: Tue, 5 Mar 2019 15:19:03 +0100
Subject: [LTP] [PATCH v2 1/2] syscalls/sync_file_range: add partial file
 sync test-case
In-Reply-To: <1551770065-20444-1-git-send-email-sumit.garg@linaro.org>
References: <1551770065-20444-1-git-send-email-sumit.garg@linaro.org>
Message-ID: <20190305141903.GD13703@rei>
List-Id: <ltp.lists.linux.it>
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To: ltp@lists.linux.it

Hi!
> +static void verify_sync_partial_file(void)
> +{
> +	int fd;
> +	unsigned long written;
> +
> +	fd = SAFE_OPEN(FNAME, O_RDWR|O_CREAT, MODE);
> +
> +	tst_dev_bytes_written(tst_device->dev);
> +
> +	tst_fill_fd(fd, 0xff, TST_MB, FILE_SIZE_MB);
> +
> +	TEST(sync_file_range(fd, FILE_SIZE/4, FILE_SIZE/2,
> +			     SYNC_FILE_RANGE_WAIT_BEFORE |
> +			     SYNC_FILE_RANGE_WRITE |
> +			     SYNC_FILE_RANGE_WAIT_AFTER));
> +
> +	if (TST_RET)
> +		tst_brk(TFAIL | TTERRNO, "sync_file_range() failed");
> +
> +	written = tst_dev_bytes_written(tst_device->dev);
> +
> +	SAFE_CLOSE(fd);
> +
> +	if (written >= FILE_SIZE/2)
> +		tst_res(TPASS, "Test file range synced to device");
> +	else
> +		tst_res(TFAIL, "Synced %li, expected %i", written,
> +			FILE_SIZE/2);
> +}


Looking at this the function is nearly the same as the other one, I
guess that we may as well define the function as:

static void verify_sync_file_range(off64_t off, off64_t size, char byte)
{
	...
}

Also I'm not sure I was clear enough, but I was suggesting to check for
upper bound for the synced size as well, which is why I suggested to do
full write, sync only part of it, then check that the size was within
bounds, i.e. >= size and  <= size + epsilon.

I guess that we can even extend this to call the sync over a range that
has been only partially written, but for that we would have to be
careful and make sure all the data has been either synced@the end of
the test function or use a different file for each test.

-- 
Cyril Hrubis
chrubis@suse.cz