[stgt] stgt: how to avoid WARNING at block/blk-core.c:1080
FUJITA Tomonori
fujita.tomonori at lab.ntt.co.jp
Thu Aug 5 10:09:31 CEST 2010
On Tue, 03 Aug 2010 17:23:32 -0700
Joe Eykholt <jeykholt at cisco.com> wrote:
> On 8/3/10 12:40 PM, Joe Eykholt wrote:
> > On 7/31/10 6:49 PM, FUJITA Tomonori wrote:
> >> On Fri, 30 Jul 2010 10:32:34 -0700
> >> Joe Eykholt<jeykholt at cisco.com> wrote:
> >>
> >>> Hi All,
> >>>
> >>> I'm working on a target module for scsi_tgt to work with libfc / fcoe
> >>> in Linux 2.6.33.5. I'm missing some step in handling completion of
> >>> a request.
> >>>
> >>> After each Inquiry or READ operation, in the transfer_response
> >>> callback I send the data and response and then call the (*done)()
> >>> routine.
> >>>
> >>> I figure I must be missing something, because I get this WARNING:
> >>>
> >>> [ 271.521650] ------------[ cut here ]------------
> >>> [ 271.521658] WARNING: at block/blk-core.c:1080
> >>> __blk_put_request+0x4f/0xbe()
> >>> [ 271.521660] Hardware name:<snip>
> >>> [ 271.521662] Modules linked in: libfc_tgt scsi_tgt nfs lockd nfs_acl
> >>> auth_rpcgss autofs4 sunrpc ip6t_REJECT
> >>> nf_conntrack_ipv6 ip6table_filter ip6_tables ipv6 dm_multipath uinput
> >>> fnic libfcoe libfc enic i2c_i801
> >>> iTCO_wdt serio_raw scsi_transport_fc iTCO_vendor_support pcspkr
> >>> e1000e shpchp radeon ttm drm_kms_helper drm
> >>> i2c_algo_bit i2c_core
> >>> [ 271.521705] Pid: 2769, comm: scsi_tgtd/2 Tainted: G W 2.6.33.5-ftgt #9
> >>> [ 271.521708] Call Trace:
> >>> [ 271.521715] [<ffffffff811696ae>] ? __blk_put_request+0x4f/0xbe
> >>> [ 271.521720] [<ffffffff81041462>] warn_slowpath_common+0x77/0xa4
> >>> [ 271.521724] [<ffffffff8104149e>] warn_slowpath_null+0xf/0x11
> >>> [ 271.521728] [<ffffffff811696ae>] __blk_put_request+0x4f/0xbe
> >>> [ 271.521735] [<ffffffffa02b14b7>] scsi_host_put_command+0x52/0x80
> >>> [scsi_tgt]
> >>> [ 271.521740] [<ffffffffa02b14e5>] ? scsi_tgt_cmd_destroy+0x0/0x3f
> >>> [scsi_tgt]
> >>> [ 271.521745] [<ffffffffa02b151f>] scsi_tgt_cmd_destroy+0x3a/0x3f
> >>> [scsi_tgt]
> >>> [ 271.521751] [<ffffffff810513a0>] worker_thread+0x131/0x1bd
> >>> [ 271.521756] [<ffffffff81054bfc>] ? autoremove_wake_function+0x0/0x38
> >>> [ 271.521760] [<ffffffff8105126f>] ? worker_thread+0x0/0x1bd
> >>> [ 271.521764] [<ffffffff810547fe>] kthread+0x7d/0x85
> >>> [ 271.521770] [<ffffffff810099a4>] kernel_thread_helper+0x4/0x10
> >>> [ 271.521774] [<ffffffff81054781>] ? kthread+0x0/0x85
> >>> [ 271.521779] [<ffffffff810099a0>] ? kernel_thread_helper+0x0/0x10
> >>> [ 271.521782] ---[ end trace 096013af4d0a82a0 ]---
> >>>
> >>> It's this code in block/blk-core.c:
> >>>
> >>> void __blk_put_request(struct request_queue *q, struct request *req)
> >>> {
> >>> if (unlikely(!q))
> >>> return;
> >>> if (unlikely(--req->ref_count))
> >>> return;
> >>>
> >>> elv_completed_request(q, req);
> >>>
> >>> /* this is a bio leak */
> >>> WARN_ON(req->bio != NULL);
> >>>
> >>> ...
> >>>
> >>> So, what should I be doing to tell the block layer that the request
> >>> is done?
> >>> Or, is there something that scsi_tgt should be doing to disassociate
> >>> the bio
> >>> from the req?
> >>
> >> Maybe we should call blk_end_request_all().
> >>
> >> But I don't think that bio is leaked in our case. So setting req->bio
> >> to NULL might be fine.
> >>
> >> I can't access to my IBM POWER box now but I'll try later.
> >
> > I tried it with my module (not with ibmvstgt) and it seems to work better.
> > Here's the patch I used (cut-and-paste from stg so for illustration only).
> > Feel free to do something different. If setting rq->bio = NULL is OK,
> > it might be better. I haven't researched this enough to know what's best.
> >
> > Author: Joe Eykholt <jeykholt at cisco.com>
> > Date: Tue Aug 3 12:33:07 2010 -0700
> >
> > stgt: fix warning from __blk_put_request()
> >
> > Every ftgt I/O ending was getting a WARNING and stack dump
> > from block/blk-core:1080 __blk_put_request() because a request
> > still had a bio associated with it.
> >
> > Call blk_end_request_all() after unmapping the user pages.
> >
> > Signed-off-by: Joe Eykholt <jeykholt at cisco.com>
> >
> > diff --git a/drivers/scsi/scsi_tgt_lib.c b/drivers/scsi/scsi_tgt_lib.c
> > index 1030327..a454ed0 100644
> > --- a/drivers/scsi/scsi_tgt_lib.c
> > +++ b/drivers/scsi/scsi_tgt_lib.c
> > @@ -151,6 +151,7 @@ void scsi_host_put_command(struct Scsi_Host *shost,
> > struct scsi_cmnd *cmd)
> > kmem_cache_free(scsi_tgt_cmd_cache, tcmd);
> >
> > spin_lock_irqsave(q->queue_lock, flags);
> > + __blk_end_request_all(rq, 0);
> > __blk_put_request(q, rq);
> > spin_unlock_irqrestore(q->queue_lock, flags);
> >
>
> Although that seemed to work on 2.6.35, when I tried it on
> the fcoe-next tree, which is 2.6.35-rc3, it caused a crash due to
> blk_update_request referencing a freed bio. So, maybe just setting
> rq->bio to NULL is correct. If we freed the bio, we should do that
> at the same place. Just wanted to let you know that there's a
> problem with the patch at this point.
I think that we need to call blk_end_request_all before calling
blk_rq_unmap_user.
I've just updated the kernel version to the latest git and confirmed
that this patch works for my IBM POWER box.
=
From: FUJITA Tomonori <fujita.tomonori at lab.ntt.co.jp>
Date: Thu, 5 Aug 2010 17:02:42 +0900
Subject: [PATCH] tgt: fix warning
We don't set rq->bio to NULL so we get the following warnings:
Badness at /home/fujita/git/linux-2.6/block/blk-core.c:1108
NIP: c0000000001bfb58 LR: c0000000001bfb48 CTR: c0000000001bfb08
We don't leak bios (blk_rq_unmap_user should free them). We don't need
to call blk_end_request_all but let's finish a request like everyone.
Signed-off-by: FUJITA Tomonori <fujita.tomonori at lab.ntt.co.jp>
---
drivers/scsi/scsi_tgt_lib.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/drivers/scsi/scsi_tgt_lib.c b/drivers/scsi/scsi_tgt_lib.c
index 66241dd..fff1b61 100644
--- a/drivers/scsi/scsi_tgt_lib.c
+++ b/drivers/scsi/scsi_tgt_lib.c
@@ -184,6 +184,7 @@ static void scsi_tgt_cmd_destroy(struct work_struct *work)
dprintk("cmd %p %d %u\n", cmd, cmd->sc_data_direction,
rq_data_dir(cmd->request));
+ blk_end_request_all(cmd->request, 0);
scsi_unmap_user_pages(tcmd);
scsi_host_put_command(scsi_tgt_cmd_to_host(cmd), cmd);
}
--
1.6.5
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