[dm-devel] [PATCH] dm integrity: reinitialize __bi_remaining when reusing bio

[Christoph Hellwig]

On Tue, Feb 25, 2020 at 06:07:44PM +0100, Daniel Glöckner wrote:
> In cases where dec_in_flight has to requeue the integrity_bio_wait work
> to transfer the rest of the data, the __bi_remaining field of the bio
> might already have been decremented to zero. Reusing the bio without
> reinitializing that counter to 1 can then result in integrity_end_io
> being called too early when the BIO_CHAIN flag is set, f.ex. due to
> blk_queue_split. In our case this triggered the BUG() in
> blk_mq_end_request when the hardware signalled completion of the bio
> after integrity_end_io had modified it.
> 
> Signed-off-by: Daniel Glöckner <dg at emlix.com>

Drivers have no business poking into these internals.  If a bio is
reused the caller needs to use bio_reset instead.