On Mon, Nov 11, 2019 at 03:19:40AM -0500, Jan Stancek wrote:
loff_t length, if (pad) iomap_dio_zero(dio, iomap, pos, fs_block_size - pad); }
return copied ? copied : ret;
return copied ? (loff_t) copied : ret;I'm a little confused on this proposed fix -- why does casting size_t (aka unsigned long) to loff_t (long long) on a 32-bit system change the test outcome?
Ternary operator has a return type and an attempt is made to convert each of operands to the type of the other. So, in this case "ret" appears to be converted to type of "copied" first. Both have size of 4 bytes on 32-bit x86:
Sounds like we should use a good old if here to avoid that whole problem spacE:
if (copied) return copied; return ret;
size_t copied = 0; int ret = -14; long long actor_ret = copied ? copied : ret;
On x86_64: actor_ret == -14; On x86 : actor_ret == 4294967282
Does this same diotest4 failure happen with XFS? I ask because XFS has been using iomap for directio for ages.
Yes, it fails on XFS too.
Is this a new test? If not why was this never reported? Sounds like we should add this test case to xfstests.