On Thu, Apr 30 2015 at 5:07am -0400, Bart Van Assche <bart.vanassche@xxxxxxxxxxx> wrote: > On 04/29/15 21:53, Mike Snitzer wrote: > >On Wed, Apr 29 2015 at 3:11P -0400, > >Bart Van Assche <bart.vanassche@xxxxxxxxxxx> wrote: > > > >>On 04/29/15 20:53, Mike Snitzer wrote: > >>>Actually, here is the proper 4.1-only fix (Bart please verify this works > >>>for you): > >> > >>Hello Mike, > >> > >>Thanks for the patch. But against which tree has this patch been generated ? > >>It doesn't seem to apply on v4.1-rc1: > >> > >>$ git reset --hard v4.1-rc1 > >>HEAD is now at b787f68 Linux 4.1-rc1 > >>$ patch -p1 < ~/\[PATCH\]\ dm\:\ fix\ free_rq_clone\(\)\ NULL\ pointer\ > >>when\ requeueing\ unmapped\ request.eml > >>(Stripping trailing CRs from patch; use --binary to disable.) > >>patching file drivers/md/dm.c > >>Hunk #1 FAILED at 1031. > >>Hunk #2 succeeded at 1124 (offset 53 lines). > >>Hunk #3 succeeded at 1143 (offset 53 lines). > >>1 out of 3 hunks FAILED -- saving rejects to file drivers/md/dm.c.rej > > > >It was implemented against my "private" wip2 branch (since rebased): > >http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/log/?h=wip2 > > > >Anyway, here it is rebased to 4.1-rc1 (BTW, I'm open to dropping the > >WARN_ON_ONCE but I need to research further.. if you guys think that > >there are perfectly resonable ways to explain why clone->q is NULL in > >the IO completion path then I'm all ears): > > > >From: Mike Snitzer <snitzer@xxxxxxxxxx> > >Date: Wed, 29 Apr 2015 10:48:09 -0400 > >Subject: dm: fix free_rq_clone() NULL pointer when requeueing unmapped request > > > >Commit 022333427a ("dm: optimize dm_mq_queue_rq to _not_ use kthread if > >using pure blk-mq") mistakenly removed free_rq_clone()'s clone->q check > >before testing clone->q->mq_ops. It was an oversight to discontinue > >that check for 1 of the 2 use-cases for free_rq_clone(): > >1) free_rq_clone() called when an unmapped original request is requeued > >2) free_rq_clone() called in the request-based IO completion path > > > >The clone->q check made sense for case #1 but not for #2. However, we > >cannot just reinstate the check as it'd mask a serious bug in the IO > >completion case #2 -- no in-flight request should have an uninitialized > >request_queue (basic block layer refcounting _should_ ensure this). > > > >The NULL pointer seen for case #1 is detailed here: > >https://www.redhat.com/archives/dm-devel/2015-April/msg00160.html > > > >Fix this free_rq_clone() NULL pointer by simply checking if the > >mapped_device's type is DM_TYPE_MQ_REQUEST_BASED (clone's queue is > >blk-mq) rather than checking clone->q->mq_ops. This avoids the need to > >dereference clone->q, but a WARN_ON_ONCE is added to let us know if an > >uninitialized clone request is being completed. > > > >Reported-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx> > >Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> > >--- > > drivers/md/dm.c | 16 ++++++++++++---- > > 1 file changed, 12 insertions(+), 4 deletions(-) > > > >diff --git a/drivers/md/dm.c b/drivers/md/dm.c > >index 6754bbd..dfb7bde 100644 > >--- a/drivers/md/dm.c > >+++ b/drivers/md/dm.c > >@@ -1082,18 +1082,26 @@ static void rq_completed(struct mapped_device *md, int rw, bool run_queue) > > dm_put(md); > > } > > > >-static void free_rq_clone(struct request *clone) > >+static void free_rq_clone(struct request *clone, bool must_be_mapped) > > { > > struct dm_rq_target_io *tio = clone->end_io_data; > > struct mapped_device *md = tio->md; > > > >+ WARN_ON_ONCE(must_be_mapped && !clone->q); > >+ > > blk_rq_unprep_clone(clone); > > > >- if (clone->q->mq_ops) > >+ if (md->type == DM_TYPE_MQ_REQUEST_BASED) > >+ /* stacked on blk-mq queue(s) */ > > tio->ti->type->release_clone_rq(clone); > > else if (!md->queue->mq_ops) > > /* request_fn queue stacked on request_fn queue(s) */ > > free_clone_request(md, clone); > >+ /* > >+ * NOTE: for the blk-mq queue stacked on request_fn queue(s) case: > >+ * no need to call free_clone_request() because we leverage blk-mq by > >+ * allocating the clone at the end of the blk-mq pdu (see: clone_rq) > >+ */ > > > > if (!md->queue->mq_ops) > > free_rq_tio(tio); > >@@ -1124,7 +1132,7 @@ static void dm_end_request(struct request *clone, int error) > > rq->sense_len = clone->sense_len; > > } > > > >- free_rq_clone(clone); > >+ free_rq_clone(clone, true); > > if (!rq->q->mq_ops) > > blk_end_request_all(rq, error); > > else > >@@ -1143,7 +1151,7 @@ static void dm_unprep_request(struct request *rq) > > } > > > > if (clone) > >- free_rq_clone(clone); > >+ free_rq_clone(clone, false); > > } > > > > /* > > Hello Mike, > > This patch survives my SRP initiator tests without triggering any > kernel warning. Great. > Thanks ! No problem, thanks for testing. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
