Re: [PATCH] selftests: get readahead size for check_file_mmap()

[Shuah Khan <skhan@linuxfoundation.org>]

On 3/30/21 6:45 AM, JeffleXu wrote:
> 
> 
> On 3/30/21 8:40 PM, Jeffle Xu wrote:
>> The readahead size used to be 2MB, thus it's reasonable to set the file
>> size as 4MB when checking check_file_mmap().
>>
>> However since commit c2e4cd57cfa1 ("block: lift setting the readahead
>> size into the block layer"), readahead could be as large as twice the
>> io_opt, and thus the hardcoded file size no longer works.
>>
>> Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> 
> Forgot to mention that otherwise, "Read-ahead pages reached the end of
> the file" is reported in check_file_mmap().
> 

Please update the change log and send v2 including the change history.

>> ---
>>   .../selftests/mincore/mincore_selftest.c      | 57 +++++++++++++++----
>>   1 file changed, 47 insertions(+), 10 deletions(-)
>>

Please include test name in the subject line

>> diff --git a/tools/testing/selftests/mincore/mincore_selftest.c b/tools/testing/selftests/mincore/mincore_selftest.c
>> index 5a1e85ff5d32..cf0c86697403 100644
>> --- a/tools/testing/selftests/mincore/mincore_selftest.c
>> +++ b/tools/testing/selftests/mincore/mincore_selftest.c
>> @@ -15,6 +15,11 @@
>>   #include <string.h>
>>   #include <fcntl.h>
>>   #include <string.h>
>> +#include <sys/types.h>
>> +#include <sys/stat.h>
>> +#include <sys/ioctl.h>
>> +#include <sys/sysmacros.h>
>> +#include <sys/mount.h>
>>   
>>   #include "../kselftest.h"
>>   #include "../kselftest_harness.h"
>> @@ -195,10 +200,42 @@ TEST(check_file_mmap)
>>   	int fd;
>>   	int i;
>>   	int ra_pages = 0;
>> +	long ra_size, filesize;
>> +	struct stat stats;
>> +	dev_t devt;
>> +	unsigned int major, minor;
>> +	char devpath[32];
>> +
>> +	retval = stat(".", &stats);
>> +	ASSERT_EQ(0, retval) {
>> +		TH_LOG("Can't stat pwd: %s", strerror(errno));
>> +	}
>> +
>> +	devt = stats.st_dev;
>> +	major = major(devt);
>> +	minor = minor(devt);
>> +	snprintf(devpath, sizeof(devpath), "/dev/block/%u:%u", major, minor);
>> +
>> +	fd = open(devpath, O_RDONLY);
>> +	ASSERT_NE(-1, fd) {
>> +		TH_LOG("Can't open underlying disk %s", strerror(errno));
>> +	}
>> +
>> +	retval = ioctl(fd, BLKRAGET, &ra_size);
>> +	ASSERT_EQ(0, retval) {
>> +		TH_LOG("Error ioctl with the underlying disk: %s", strerror(errno));
>> +	}
>> +
>> +	/*
>> +	 * BLKRAGET ioctl returns the readahead size in sectors (512 bytes).
>> +	 * Make filesize large enough to contain the readahead window.
>> +	 */
>> +	ra_size *= 512;
>> +	filesize = ra_size * 2;
>>   
>>   	page_size = sysconf(_SC_PAGESIZE);
>> -	vec_size = FILE_SIZE / page_size;
>> -	if (FILE_SIZE % page_size)
>> +	vec_size = filesize / page_size;
>> +	if (filesize % page_size)
>>   		vec_size++;
>>   
>>   	vec = calloc(vec_size, sizeof(unsigned char));
>> @@ -213,7 +250,7 @@ TEST(check_file_mmap)
>>   			strerror(errno));
>>   	}
>>   	errno = 0;
>> -	retval = fallocate(fd, 0, 0, FILE_SIZE);
>> +	retval = fallocate(fd, 0, 0, filesize);
>>   	ASSERT_EQ(0, retval) {
>>   		TH_LOG("Error allocating space for the temporary file: %s",
>>   			strerror(errno));
>> @@ -223,12 +260,12 @@ TEST(check_file_mmap)
>>   	 * Map the whole file, the pages shouldn't be fetched yet.
>>   	 */
>>   	errno = 0;
>> -	addr = mmap(NULL, FILE_SIZE, PROT_READ | PROT_WRITE,
>> +	addr = mmap(NULL, filesize, PROT_READ | PROT_WRITE,
>>   			MAP_SHARED, fd, 0);
>>   	ASSERT_NE(MAP_FAILED, addr) {
>>   		TH_LOG("mmap error: %s", strerror(errno));
>>   	}
>> -	retval = mincore(addr, FILE_SIZE, vec);
>> +	retval = mincore(addr, filesize, vec);
>>   	ASSERT_EQ(0, retval);
>>   	for (i = 0; i < vec_size; i++) {
>>   		ASSERT_EQ(0, vec[i]) {
>> @@ -240,14 +277,14 @@ TEST(check_file_mmap)
>>   	 * Touch a page in the middle of the mapping. We expect the next
>>   	 * few pages (the readahead window) to be populated too.
>>   	 */
>> -	addr[FILE_SIZE / 2] = 1;
>> -	retval = mincore(addr, FILE_SIZE, vec);
>> +	addr[filesize / 2] = 1;
>> +	retval = mincore(addr, filesize, vec);
>>   	ASSERT_EQ(0, retval);
>> -	ASSERT_EQ(1, vec[FILE_SIZE / 2 / page_size]) {
>> +	ASSERT_EQ(1, vec[filesize / 2 / page_size]) {
>>   		TH_LOG("Page not found in memory after use");
>>   	}
>>   
>> -	i = FILE_SIZE / 2 / page_size + 1;
>> +	i = filesize / 2 / page_size + 1;
>>   	while (i < vec_size && vec[i]) {
>>   		ra_pages++;
>>   		i++;
>> @@ -271,7 +308,7 @@ TEST(check_file_mmap)
>>   		}
>>   	}
>>   
>> -	munmap(addr, FILE_SIZE);
>> +	munmap(addr, filesize);
>>   	close(fd);
>>   	free(vec);
>>   }
>>
> 

thanks,
-- Shuah