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From: "Myklebust, Trond" <Trond.Myklebust@netapp.com>
To: fanchaoting <fanchaoting@cn.fujitsu.com>,
        "bfields@fieldses.org" <bfields@fieldses.org>
CC: "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: RE: [PATCH] umount oops when remove  blocklayoutdriver first
Date: Mon, 4 Feb 2013 14:03:43 +0000
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> -----Original Message-----
> From: linux-nfs-owner@vger.kernel.org [mailto:linux-nfs-
> owner@vger.kernel.org] On Behalf Of fanchaoting
> Sent: Monday, February 04, 2013 8:15 AM
> To: bfields@fieldses.org; Myklebust, Trond
> Cc: linux-nfs@vger.kernel.org
> Subject: [PATCH] umount oops when remove blocklayoutdriver first
> 
> now pnfs client uses block layout, maybe we can remove blocklayoutdriver
> first. if we umount later, it can cause oops in unset_pnfs_layoutdriver.
> because nfss->pnfs_curr_ld->clear_layoutdriver is invalid.
> 
> reproduce it:
>  modprobe  blocklayoutdriver
>  mount -t nfs4 -o minorversion=1 pnfsip:/ /mnt/  rmmod blocklayoutdriver
> umount /mnt
> 
> then you can see following
> 
> ##########################################################
> ###
> CPU 0
> Pid: 17023, comm: umount.nfs4 Tainted: GF          O 3.7.0-rc6-pnfs #1 VMware,
> Inc. VMware Virtual Platform/440BX Desktop Reference Platform
> RIP: 0010:[<ffffffffa04cfe6d>]  [<ffffffffa04cfe6d>]
> unset_pnfs_layoutdriver+0x1d/0x70 [nfsv4]
> RSP: 0018:ffff8800022d9e48  EFLAGS: 00010286
> RAX: ffffffffa04a1b00 RBX: ffff88000b013800 RCX: 0000000000000001
> RDX: ffffffff81ae8ee0 RSI: ffff880001ee94b8 RDI: ffff88000b013800
> RBP: ffff8800022d9e58 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffff880001ee9400
> R13: ffff8800105978c0 R14: 00007fff25846c08 R15: 0000000001bba550
> FS:  00007f45ae7f0700(0000) GS:ffff880012c00000(0000)
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: ffffffffa04a1b38 CR3: 0000000002c0c000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process umount.nfs4 (pid: 17023, threadinfo ffff8800022d8000, task
> ffff880006e48aa0)
> Stack:
> ffff8800105978c0 ffff88000b013800 ffff8800022d9e78 ffffffffa04cd0ce
> ffff8800022d9e78 ffff88000b013800 ffff8800022d9ea8 ffffffffa04755a7
> ffff8800022d9ea8 ffff880002f96400 ffff88000b013800 ffff880002f96400 Call
> Trace:
> [<ffffffffa04cd0ce>] nfs4_destroy_server+0x1e/0x30 [nfsv4]
> [<ffffffffa04755a7>] nfs_free_server+0xb7/0x150 [nfs] [<ffffffffa047d4d5>]
> nfs_kill_super+0x35/0x40 [nfs] [<ffffffff81178d35>]
> deactivate_locked_super+0x45/0x70 [<ffffffff8117986a>]
> deactivate_super+0x4a/0x70 [<ffffffff81193ee2>]
> mntput_no_expire+0xd2/0x130 [<ffffffff81194d62>]
> sys_umount+0x72/0xe0 [<ffffffff8154af59>]
> system_call_fastpath+0x16/0x1b
> Code: 06 e1 b8 ea ff ff ff eb 9e 0f 1f 44 00 00 55 48 89 e5 53 48 83 ec 08 66 66 66
> 66 90 48 8b 87 80 03 00 00 48 89 fb 48 85 c0 74 29 <48> 8b 40 38 48 85 c0 74 02 ff
> d0 48 8b 03 3e ff 48 04 0f 94 c2 RIP  [<ffffffffa04cfe6d>]
> unset_pnfs_layoutdriver+0x1d/0x70 [nfsv4] RSP <ffff8800022d9e48>
> CR2: ffffffffa04a1b38
> ---[ end trace 29f75aaedda058bf ]---
> 
> ##########################################################
> ###
> 
> 
> Signed-off-by: fanchaoting<fanchaoting@cn.fujitsu.com>
> ---

Ooh... That's bad... I never knew that try_module_get() will return success if the argument is a NULL pointer. Anyhow, thanks! I will apply.

Trond