On Wed, Mar 11, 2015 at 1:02 PM, Ross Zwisler <ross.zwis...@linux.intel.com> wrote: > The functions copy_from_brd() and copy_to_brd() are written with an > assumption that the bio_vec they are given has size <= PAGE_SIZE. This > assumption is not enforced in any way, and if the bio_vec has size > larger than PAGE_SIZE data will just be lost. > > Such a situation can occur with I/Os generated from in-kernel sources, > or with coalesced bio_vecs. This bug was originally reported against > the pmem driver, where it was found using the Enmotus tiering engine. > > Instead we should have brd explicitly tell the block layer that it can > handle data segments of at most PAGE_SIZE. > > Signed-off-by: Ross Zwisler <ross.zwis...@linux.intel.com> > Reported-by: Hugh Daschbach <hugh.daschb...@enmotus.com> > Cc: Roger C. Pao (Enmotus) <rcpao.enmo...@gmail.com> > Cc: Boaz Harrosh <b...@plexistor.com> > Cc: linux-nvd...@lists.01.org > Cc: Nick Piggin <npig...@kernel.dk> > --- > drivers/block/brd.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/block/brd.c b/drivers/block/brd.c > index 898b4f256782..7e4873361b64 100644 > --- a/drivers/block/brd.c > +++ b/drivers/block/brd.c > @@ -490,6 +490,7 @@ static struct brd_device *brd_alloc(int i) > blk_queue_make_request(brd->brd_queue, brd_make_request); > blk_queue_max_hw_sectors(brd->brd_queue, 1024); > blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY); > + blk_queue_max_segment_size(brd->brd_queue, PAGE_SIZE);
The block layer only honors this for request-based drivers. I think we should just fix it properly. Especially when we have in-kernel users of persistent memory allowing > PAGE_SIZE segments will be a nice feature. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
