Re: [PATCH] bdev: Do not return EBUSY if bdev discard races with write

[Jens Axboe <axboe@kernel.dk>]

On 1/26/21 3:02 AM, Jan Kara wrote:
> On Thu 07-01-21 16:40:34, Jan Kara wrote:
>> blkdev_fallocate() tries to detect whether a discard raced with an
>> overlapping write by calling invalidate_inode_pages2_range(). However
>> this check can give both false negatives (when writing using direct IO
>> or when writeback already writes out the written pagecache range) and
>> false positives (when write is not actually overlapping but ends in the
>> same page when blocksize < pagesize). This actually causes issues for
>> qemu which is getting confused by EBUSY errors.
>>
>> Fix the problem by removing this conflicting write detection since it is
>> inherently racy and thus of little use anyway.
>>
>> Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
>> CC: "Darrick J. Wong" <darrick.wong@oracle.com>
>> Link: https://lore.kernel.org/qemu-devel/20201111153913.41840-1-mlevitsk@redhat.com
>> Signed-off-by: Jan Kara <jack@suse.cz>
> 
> Jens, can you please pick up this patch? Thanks!

Picked it up for 5.12, hope that works. It looks simple enough but not
really meeting criteria for 5.11 at this point.

-- 
Jens Axboe