Hi Jeff, On Mon, Dec 2, 2013 at 11:20 PM, Jeff Moyer <[email protected]> wrote: > Ming Lei <[email protected]> writes: > >> blk_mq_alloc_request_pinned() may return NULL request in case of >> !__GFP_WAIT, so cause its callers to derefence NULL pointer for >> releasing current context. >> >> This patch introduces two flags to address the issue. > > Hi, Ming, > > > Good catch, but your patch seems overly complicated. How about > something like the following (compile-tested only), instead? Note that
Looks your patch is better and simpler, :-) > I did not touch blk_make_request, as the put_ctx there seems to > correlate to a get_ctx earlier in the function (not a leaked reference > from __blk_mq_alloc_request). > > -Jeff > > p.s. Jens, every time I see GFP_ATOMIC|__GFP_WAIT, my head explodes. Just > sayin'. > > Signed-off-by: Jeff Moyer <[email protected]> Reported-by: Ming Lei <[email protected]> > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index cdc629c..70fd6f9 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -202,10 +202,12 @@ static struct request > *blk_mq_alloc_request_pinned(struct request_queue *q, > if (rq) { > blk_mq_rq_ctx_init(q, ctx, rq, rw); > break; > - } else if (!(gfp & __GFP_WAIT)) > - break; > + } > > blk_mq_put_ctx(ctx); > + if (!(gfp & __GFP_WAIT)) > + break; > + > __blk_mq_run_hw_queue(hctx); > blk_mq_wait_for_tags(hctx->tags); > } while (1); > @@ -222,7 +224,8 @@ struct request *blk_mq_alloc_request(struct request_queue > *q, int rw, > return NULL; > > rq = blk_mq_alloc_request_pinned(q, rw, gfp, reserved); > - blk_mq_put_ctx(rq->mq_ctx); > + if (rq) > + blk_mq_put_ctx(rq->mq_ctx); > return rq; > } > > @@ -235,7 +238,8 @@ struct request *blk_mq_alloc_reserved_request(struct > request_queue *q, int rw, > return NULL; > > rq = blk_mq_alloc_request_pinned(q, rw, gfp, true); > - blk_mq_put_ctx(rq->mq_ctx); > + if (rq) > + blk_mq_put_ctx(rq->mq_ctx); > return rq; > } > EXPORT_SYMBOL(blk_mq_alloc_reserved_request); Thanks, -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
