Re: INFO: task hung in generic_file_write_iter

From: Tetsuo Handa
Date: Wed Jan 02 2019 - 11:08:24 EST

On 2019/01/02 23:40, Jan Kara wrote:
> I had a look into this and the only good explanation for this I have is
> that sb->s_blocksize is different from (1 << sb->s_bdev->bd_inode->i_blkbits).
> If that would happen, we'd get exactly the behavior syzkaller observes
> because grow_buffers() would populate different page than
> __find_get_block() then looks up.
> However I don't see how that's possible since the filesystem has the block
> device open exclusively and blkdev_bszset() makes sure we also have
> exclusive access to the block device before changing the block device size.
> So changing block device block size after filesystem gets access to the
> device should be impossible.
> Anyway, could you perhaps add to your debug patch a dump of 'size' passed
> to __getblk_slow() and bdev->bd_inode->i_blkbits? That should tell us
> whether my theory is right or not. Thanks!

OK. Andrew, will you add (or fold into) this change?