On 2020-08-06 17:28, Bart Van Assche wrote:
> On 2020-08-06 14:58, Keith Busch wrote:
>> A previous commit aligning splits to physical block sizes inadvertently
>> modified one return case such that that it now returns 0 length splits
>> when the number of sectors doesn't exceed the physical offset. This
>> later hits a BUG in bio_split(). Restore the previous working behavior.
>>
>> Reported-by: Eric Deal <eric.deal@xxxxxxx>
>> Cc: Bart Van Assche <bvanassche@xxxxxxx>
>> Cc: stable@xxxxxxxxxxxxxxx
>> Fixes: 9cc5169cd478b ("block: Improve physical block alignment of split bios")
>> Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx>
>> ---
>> block/blk-merge.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/block/blk-merge.c b/block/blk-merge.c
>> index 5196dc145270..d7fef954d42f 100644
>> --- a/block/blk-merge.c
>> +++ b/block/blk-merge.c
>> @@ -154,7 +154,7 @@ static inline unsigned get_max_io_size(struct request_queue *q,
>> if (max_sectors > start_offset)
>> return max_sectors - start_offset;
>>
>> - return sectors & (lbs - 1);
>> + return sectors & ~(lbs - 1);
>> }
>
> I think we agree that get_max_io_size() should never return zero. However, the above
> change seems wrong to me because it will cause get_max_io_size() to return zero if
> the logical block size is larger than 512 bytes and if sectors < lbs. How about
> changing the return statement as follows (untested):
This should work better than what was mentioned in my previous email:
- return sectors & (lbs - 1);
+ return sectors;
Thanks,
Bart.
