Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934260Ab2FHKGm (ORCPT ); Fri, 8 Jun 2012 06:06:42 -0400 Received: from smtp.ctxuk.citrix.com ([62.200.22.115]:50216 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754344Ab2FHKGj (ORCPT ); Fri, 8 Jun 2012 06:06:39 -0400 X-IronPort-AV: E=Sophos;i="4.75,737,1330905600"; d="scan'208";a="12905440" Date: Fri, 8 Jun 2012 11:06:20 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Konrad Rzeszutek Wilk CC: Stefano Stabellini , "axboe@kernel.dk" , "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" , Jan Beulich Subject: Re: [Xen-devel] [PATCH 2/2] xen/blkfront: Add BUG_ON to deal with misbehaving backends. In-Reply-To: <20120607215942.GA13592@phenom.dumpdata.com> Message-ID: References: <1337982603-15692-1-git-send-email-konrad.wilk@oracle.com> <1337982603-15692-3-git-send-email-konrad.wilk@oracle.com> <4FC4A10F0200007800086842@nat28.tlf.novell.com> <20120531181712.GA19700@phenom.dumpdata.com> <20120607215942.GA13592@phenom.dumpdata.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9546 Lines: 251 On Thu, 7 Jun 2012, Konrad Rzeszutek Wilk wrote: > On Fri, Jun 01, 2012 at 11:16:29AM +0100, Stefano Stabellini wrote: > > On Thu, 31 May 2012, Konrad Rzeszutek Wilk wrote: > > > The blkfront_remove part is .. that is going to take some surgery to do > > > and I don't think I am going to be able to attempt that within the next couple > > > of weeks. So lets put that on the TODO list and just do this one? > > > > OK > > > > > >From 4aabb5b44778fc0c0b8d4f5a2e2cd8e8490064d7 Mon Sep 17 00:00:00 2001 > > > From: Konrad Rzeszutek Wilk > > > Date: Fri, 25 May 2012 17:34:51 -0400 > > > Subject: [PATCH] xen/blkfront: Add WARN to deal with misbehaving backends. > > > > > > Part of the ring structure is the 'id' field which is under > > > control of the frontend. The frontend stamps it with "some" > > > value (this some in this implementation being a value less > > > than BLK_RING_SIZE), and when it gets a response expects > > > said value to be in the response structure. We have a check > > > for the id field when spolling new requests but not when > > > de-spolling responses. > > > > > > We also add an extra check in add_id_to_freelist to make > > > sure that the 'struct request' was not NULL - as we cannot > > > pass a NULL to __blk_end_request_all, otherwise that crashes > > > (and all the operations that the response is dealing with > > > end up with __blk_end_request_all). > > > > > > Lastly we also print the name of the operation that failed. > > > > > > [v1: s/BUG/WARN/ suggested by Stefano] > > > [v2: Add extra check in add_id_to_freelist] > > > Signed-off-by: Konrad Rzeszutek Wilk > > > --- > > > drivers/block/xen-blkfront.c | 39 +++++++++++++++++++++++++++++---------- > > > 1 files changed, 29 insertions(+), 10 deletions(-) > > > > > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > > > index 60eed4b..c7ef8a4 100644 > > > --- a/drivers/block/xen-blkfront.c > > > +++ b/drivers/block/xen-blkfront.c > > > @@ -144,11 +144,22 @@ static int get_id_from_freelist(struct blkfront_info *info) > > > static void add_id_to_freelist(struct blkfront_info *info, > > > unsigned long id) > > > { > > > + BUG_ON(info->shadow[id].req.u.rw.id != id); > > > info->shadow[id].req.u.rw.id = info->shadow_free; > > > + BUG_ON(info->shadow[id].request == NULL); > > > info->shadow[id].request = NULL; > > > info->shadow_free = id; > > > } > > > > Like Jan said, it would be best to change the two BUG_ON into WARN_ON > > and return an error. > > Yes. I missed that. > > > > > > > +static const char *op_name(int op) > > > +{ > > > + const char *names[BLKIF_OP_DISCARD+1] = { > > > + "read" , "write", "barrier", "flush", "reserved", "discard"}; > > > + > > > + if (op > BLKIF_OP_DISCARD) > > > + return "unknown"; > > > + return names[op]; > > > +} > > > > Considering that op is an int, shoudn't we check for negative values > > too? > > Yes! I also converted this per Jan's excellent idea. > > Please see: > > > >From 3877611c3096423a7741e99e9c9b9e63a9f2e557 Mon Sep 17 00:00:00 2001 > From: Konrad Rzeszutek Wilk > Date: Fri, 25 May 2012 17:34:51 -0400 > Subject: [PATCH] xen/blkfront: Add WARN to deal with misbehaving backends. > > Part of the ring structure is the 'id' field which is under > control of the frontend. The frontend stamps it with "some" > value (this some in this implementation being a value less > than BLK_RING_SIZE), and when it gets a response expects > said value to be in the response structure. We have a check > for the id field when spolling new requests but not when > de-spolling responses. > > We also add an extra check in add_id_to_freelist to make > sure that the 'struct request' was not NULL - as we cannot > pass a NULL to __blk_end_request_all, otherwise that crashes > (and all the operations that the response is dealing with > end up with __blk_end_request_all). > > Lastly we also print the name of the operation that failed. > > [v1: s/BUG/WARN/ suggested by Stefano] > [v2: Add extra check in add_id_to_freelist] > [v3: Redid op_name per Jan's suggestion] > Signed-off-by: Konrad Rzeszutek Wilk Acked-by: Stefano Stabellini > drivers/block/xen-blkfront.c | 58 +++++++++++++++++++++++++++++-------- > include/xen/interface/io/blkif.h | 6 ++++ > 2 files changed, 51 insertions(+), 13 deletions(-) > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > index 2f22874..ae8e3b7 100644 > --- a/drivers/block/xen-blkfront.c > +++ b/drivers/block/xen-blkfront.c > @@ -141,14 +141,33 @@ static int get_id_from_freelist(struct blkfront_info *info) > return free; > } > > -static void add_id_to_freelist(struct blkfront_info *info, > +static int add_id_to_freelist(struct blkfront_info *info, > unsigned long id) > { > + if (info->shadow[id].req.u.rw.id != id) > + return -EINVAL; > + if (info->shadow[id].request == NULL) > + return -EINVAL; > info->shadow[id].req.u.rw.id = info->shadow_free; > info->shadow[id].request = NULL; > info->shadow_free = id; > + return 0; > } > > +static const char *op_name(int op) > +{ > + static const char *names[] = { > + [BLKIF_OP_READ] = "read", > + [BLKIF_OP_WRITE] = "write", > + [BLKIF_OP_WRITE_BARRIER] = "barrier", > + [BLKIF_OP_FLUSH_DISKCACHE] = "flush", > + [BLKIF_OP_RESERVED_1] = "reserved", > + [BLKIF_OP_DISCARD] = "discard" }; > + > + if (op < 0 || op >= ARRAY_SIZE(names)) > + return "unknown"; > + return names[op]; > +} > static int xlbd_reserve_minors(unsigned int minor, unsigned int nr) > { > unsigned int end = minor + nr; > @@ -744,20 +763,31 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) > > bret = RING_GET_RESPONSE(&info->ring, i); > id = bret->id; > + /* > + * The backend has messed up and given us an id that we would > + * never have given to it (we stamp it up to BLK_RING_SIZE - > + * look in get_id_from_freelist. > + */ > + if (id >= BLK_RING_SIZE) > + /* We can't safely get the 'struct request' as > + * the id is busted. So limp along. */ > + goto err_out; > + > req = info->shadow[id].request; > > if (bret->operation != BLKIF_OP_DISCARD) > blkif_completion(&info->shadow[id]); > > - add_id_to_freelist(info, id); > + if (add_id_to_freelist(info, id)) > + goto err_out; > > error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO; > switch (bret->operation) { > case BLKIF_OP_DISCARD: > if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) { > struct request_queue *rq = info->rq; > - printk(KERN_WARNING "blkfront: %s: discard op failed\n", > - info->gd->disk_name); > + printk(KERN_WARNING "blkfront: %s: %s op failed\n", > + info->gd->disk_name, op_name(bret->operation)); > error = -EOPNOTSUPP; > info->feature_discard = 0; > info->feature_secdiscard = 0; > @@ -769,18 +799,14 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) > case BLKIF_OP_FLUSH_DISKCACHE: > case BLKIF_OP_WRITE_BARRIER: > if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) { > - printk(KERN_WARNING "blkfront: %s: write %s op failed\n", > - info->flush_op == BLKIF_OP_WRITE_BARRIER ? > - "barrier" : "flush disk cache", > - info->gd->disk_name); > + printk(KERN_WARNING "blkfront: %s: %s op failed\n", > + info->gd->disk_name, op_name(bret->operation)); > error = -EOPNOTSUPP; > } > if (unlikely(bret->status == BLKIF_RSP_ERROR && > info->shadow[id].req.u.rw.nr_segments == 0)) { > - printk(KERN_WARNING "blkfront: %s: empty write %s op failed\n", > - info->flush_op == BLKIF_OP_WRITE_BARRIER ? > - "barrier" : "flush disk cache", > - info->gd->disk_name); > + printk(KERN_WARNING "blkfront: %s: empty %s op failed\n", > + info->gd->disk_name, op_name(bret->operation)); > error = -EOPNOTSUPP; > } > if (unlikely(error)) { > @@ -813,12 +839,18 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) > goto again; > } else > info->ring.sring->rsp_event = i + 1; > - > kick_pending_request_queues(info); > > spin_unlock_irqrestore(&blkif_io_lock, flags); > > return IRQ_HANDLED; > +err_out: > + WARN(1, "%s: response to %s has incorrect id\n", > + info->gd->disk_name, op_name(bret->operation)); > + > + spin_unlock_irqrestore(&info->io_lock, flags); > + > + return IRQ_HANDLED; > } > > > diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h > index ee338bf..bc75c75 100644 > --- a/include/xen/interface/io/blkif.h > +++ b/include/xen/interface/io/blkif.h > @@ -59,6 +59,12 @@ typedef uint64_t blkif_sector_t; > #define BLKIF_OP_FLUSH_DISKCACHE 3 > > /* > + * Used in SLES sources for device specific command packet > + * contained within the request. Reserved for that purpose. > + */ > +#define BLKIF_OP_RESERVED_1 4 > + > +/* > * Recognised only if "feature-discard" is present in backend xenbus info. > * The "feature-discard" node contains a boolean indicating whether trim > * (ATA) or unmap (SCSI) - conviently called discard requests are likely > -- > 1.7.7.6 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/