Re: [PATCH 2/2] src/attr_replace_test: dynamically adjust the max xattr size

["Luís Henriques" <lhenriques@suse.de>]

"Darrick J. Wong" <djwong@kernel.org> writes:

> On Tue, Jun 07, 2022 at 04:15:13PM +0100, Luís Henriques wrote:
>> CephFS doesn't had a maximum xattr size.  Instead, it imposes a maximum
>> size for the full set of an inode's xattrs names+values, which by default
>> is 64K but it can be changed by a cluster admin.
>> 
>> Test generic/486 started to fail after fixing a ceph bug where this limit
>> wasn't being imposed.  Adjust dynamically the size of the xattr being set
>> if the error returned is -ENOSPC.
>> 
>> Signed-off-by: Luís Henriques <lhenriques@suse.de>
>> ---
>>  src/attr_replace_test.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>> 
>> diff --git a/src/attr_replace_test.c b/src/attr_replace_test.c
>> index cca8dcf8ff60..de18e643f469 100644
>> --- a/src/attr_replace_test.c
>> +++ b/src/attr_replace_test.c
>> @@ -62,7 +62,10 @@ int main(int argc, char *argv[])
>>  
>>  	/* Then, replace it with bigger one, forcing short form to leaf conversion. */
>>  	memset(value, '1', size);
>> -	ret = fsetxattr(fd, name, value, size, XATTR_REPLACE);
>> +	do {
>> +		ret = fsetxattr(fd, name, value, size, XATTR_REPLACE);
>> +		size -= 256;
>> +	} while ((ret < 0) && (errno == ENOSPC) && (size > 0));
>
> Isn't @size a size_t?  Which means that it can't be less than zero?  I
> wouldn't count on st_blksize (or XATTR_SIZE_MAX) always being a multiple
> of 256.

*sigh*

You're right, of course.  Do you think it would be acceptable to do this
instead:

	} while ((ret < 0) && (errno == ENOSPC) && (size > 256));

It's still a magic number, but it should do the trick.  Although it's
still a bit ugly, I know.  My initial idea was to add an arg to this
program that would be then used as the value for 'size'; this way I could
add a ceph-specific value.  But not sure that's less ugly...

Cheers,
-- 
Luís

>
> --D
>
>>  	if (ret < 0) die();
>>  	close(fd);
>>