Re: [PATCH] nfs: Fix nfsi->nrequests count error on nfs_inode_remove_request

From: Trond Myklebust <trondmy@hammerspace.com>
To: "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
	"zhangxiaoxu5@huawei.com" <zhangxiaoxu5@huawei.com>,
	"anna.schumaker@netapp.com" <anna.schumaker@netapp.com>
Subject: Re: [PATCH] nfs: Fix nfsi->nrequests count error on nfs_inode_remove_request
Date: Sat, 5 Oct 2019 14:07:16 +0000	[thread overview]
Message-ID: <5c50a4be3562877a5d96523e943b9976a3792e23.camel@hammerspace.com> (raw)
In-Reply-To: <08ce0101-e8df-509a-f3e5-07063aa5492e@huawei.com>

On Sat, 2019-10-05 at 09:51 +0800, zhangxiaoxu (A) wrote:
> ping.
> 
> On 2019/9/26 14:29, ZhangXiaoxu wrote:
> > When xfstests testing, there are some WARNING as below:
> > 
> > WARNING: CPU: 0 PID: 6235 at fs/nfs/inode.c:122
> > nfs_clear_inode+0x9c/0xd8
> > Modules linked in:
> > CPU: 0 PID: 6235 Comm: umount.nfs
> > Hardware name: linux,dummy-virt (DT)
> > pstate: 60000005 (nZCv daif -PAN -UAO)
> > pc : nfs_clear_inode+0x9c/0xd8
> > lr : nfs_evict_inode+0x60/0x78
> > sp : fffffc000f68fc00
> > x29: fffffc000f68fc00 x28: fffffe00c53155c0
> > x27: fffffe00c5315000 x26: fffffc0009a63748
> > x25: fffffc000f68fd18 x24: fffffc000bfaaf40
> > x23: fffffc000936d3c0 x22: fffffe00c4ff5e20
> > x21: fffffc000bfaaf40 x20: fffffe00c4ff5d10
> > x19: fffffc000c056000 x18: 000000000000003c
> > x17: 0000000000000000 x16: 0000000000000000
> > x15: 0000000000000040 x14: 0000000000000228
> > x13: fffffc000c3a2000 x12: 0000000000000045
> > x11: 0000000000000000 x10: 0000000000000000
> > x9 : 0000000000000000 x8 : 0000000000000000
> > x7 : 0000000000000000 x6 : fffffc00084b027c
> > x5 : fffffc0009a64000 x4 : fffffe00c0e77400
> > x3 : fffffc000c0563a8 x2 : fffffffffffffffb
> > x1 : 000000000000764e x0 : 0000000000000001
> > Call trace:
> >   nfs_clear_inode+0x9c/0xd8
> >   nfs_evict_inode+0x60/0x78
> >   evict+0x108/0x380
> >   dispose_list+0x70/0xa0
> >   evict_inodes+0x194/0x210
> >   generic_shutdown_super+0xb0/0x220
> >   nfs_kill_super+0x40/0x88
> >   deactivate_locked_super+0xb4/0x120
> >   deactivate_super+0x144/0x160
> >   cleanup_mnt+0x98/0x148
> >   __cleanup_mnt+0x38/0x50
> >   task_work_run+0x114/0x160
> >   do_notify_resume+0x2f8/0x308
> >   work_pending+0x8/0x14
> > 
> > The nrequest should be increased/decreased only if PG_INODE_REF
> > flag
> > was setted.
> > 
> > But in the nfs_inode_remove_request function, it maybe decrease
> > when
> > no PG_INODE_REF flag, this maybe lead nrequests count error.
> > 
> > Reported-by: Hulk Robot <hulkci@huawei.com>
> > Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@huawei.com>
> > ---
> >   fs/nfs/write.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/nfs/write.c b/fs/nfs/write.c
> > index 85ca495..52cab65 100644
> > --- a/fs/nfs/write.c
> > +++ b/fs/nfs/write.c
> > @@ -786,7 +786,6 @@ static void nfs_inode_remove_request(struct
> > nfs_page *req)
> >   	struct nfs_inode *nfsi = NFS_I(inode);
> >   	struct nfs_page *head;
> >   
> > -	atomic_long_dec(&nfsi->nrequests);
> >   	if (nfs_page_group_sync_on_bit(req, PG_REMOVE)) {
> >   		head = req->wb_head;
> >   
> > @@ -799,8 +798,10 @@ static void nfs_inode_remove_request(struct
> > nfs_page *req)
> >   		spin_unlock(&mapping->private_lock);
> >   	}
> >   
> > -	if (test_and_clear_bit(PG_INODE_REF, &req->wb_flags))
> > +	if (test_and_clear_bit(PG_INODE_REF, &req->wb_flags)) {
> >   		nfs_release_request(req);
> > +		atomic_long_dec(&nfsi->nrequests);
> > +	}
> >   }
> >   
> >   static void
> > 

Hmm... What about nfs_page_group_init()? That also bumps nfsi-
>nrequests.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com