Re: [PATCH] NFS: Skip checking ds_cinfo.buckets when lseg's commit_through_mds is set

[Kinglong Mee <kinglongmee@gmail.com>]

On 9/22/2015 01:10, Trond Myklebust wrote:
> On Mon, Sep 21, 2015 at 6:03 AM, Kinglong Mee <kinglongmee@gmail.com> wrote:
>> When lseg's commit_through_mds is set, pnfs client always WARN once
>> in nfs_direct_select_verf when checking ds_cinfo.nbuckets.
>>
>> But, filelayout_alloc_commit_info will not initialize the ds_cinfo.nbuckets.
>> It's wrong of checking ds_cinfo.nbuckets, client should skip it.
>>
>> [17844.666094] ------------[ cut here ]------------
>> [17844.667071] WARNING: CPU: 0 PID: 21758 at /root/source/linux-pnfs/fs/nfs/direct.c:174 nfs_direct_select_verf+0x5a/0x70 [nfs]()
>> [17844.668650] Modules linked in: nfs_layout_nfsv41_files(OE) nfsv4(OE) nfs(OE) fscache(E) nfsd(OE) xfs libcrc32c btrfs ppdev coretemp crct10dif_pclmul auth_rpcgss crc32_pclmul crc32c_intel nfs_acl ghash_clmulni_intel lockd vmw_balloon xor vmw_vmci grace raid6_pq shpchp sunrpc parport_pc i2c_piix4 parport vmwgfx drm_kms_helper ttm drm serio_raw mptspi e1000 scsi_transport_spi mptscsih mptbase ata_generic pata_acpi [last unloaded: fscache]
>> [17844.686676] CPU: 0 PID: 21758 Comm: kworker/0:1 Tainted: G        W  OE   4.3.0-rc1-pnfs+ #245
>> [17844.687352] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/20/2014
>> [17844.698502] Workqueue: nfsiod rpc_async_release [sunrpc]
>> [17844.699212]  0000000000000009 0000000043e58010 ffff8800454fbc10 ffffffff813680c4
>> [17844.699990]  ffff8800454fbc48 ffffffff8108b49d ffff88004eb20000 ffff88004eb20000
>> [17844.700844]  ffff880062e26000 0000000000000000 0000000000000001 ffff8800454fbc58
>> [17844.701637] Call Trace:
>> [17844.725252]  [<ffffffff813680c4>] dump_stack+0x19/0x25
>> [17844.732693]  [<ffffffff8108b49d>] warn_slowpath_common+0x7d/0xb0
>> [17844.733855]  [<ffffffff8108b5da>] warn_slowpath_null+0x1a/0x20
>> [17844.735015]  [<ffffffffa04a27ca>] nfs_direct_select_verf+0x5a/0x70 [nfs]
>> [17844.735999]  [<ffffffffa04a2b83>] nfs_direct_set_hdr_verf+0x23/0x90 [nfs]
>> [17844.736846]  [<ffffffffa04a2e17>] nfs_direct_write_completion+0x227/0x260 [nfs]
>> [17844.737782]  [<ffffffffa04a433c>] nfs_pgio_release+0x1c/0x20 [nfs]
>> [17844.738597]  [<ffffffffa0502df3>] pnfs_generic_rw_release+0x23/0x30 [nfsv4]
>> [17844.739486]  [<ffffffffa01cbbea>] rpc_free_task+0x2a/0x70 [sunrpc]
>> [17844.740326]  [<ffffffffa01cbcd5>] rpc_async_release+0x15/0x20 [sunrpc]
>> [17844.741173]  [<ffffffff810a387c>] process_one_work+0x21c/0x4c0
>> [17844.741984]  [<ffffffff810a37cd>] ? process_one_work+0x16d/0x4c0
>> [17844.742837]  [<ffffffff810a3b6a>] worker_thread+0x4a/0x440
>> [17844.743639]  [<ffffffff810a3b20>] ? process_one_work+0x4c0/0x4c0
>> [17844.744399]  [<ffffffff810a3b20>] ? process_one_work+0x4c0/0x4c0
>> [17844.745176]  [<ffffffff810a8d75>] kthread+0xf5/0x110
>> [17844.745927]  [<ffffffff810a8c80>] ? kthread_create_on_node+0x240/0x240
>> [17844.747105]  [<ffffffff8172ce1f>] ret_from_fork+0x3f/0x70
>> [17844.747856]  [<ffffffff810a8c80>] ? kthread_create_on_node+0x240/0x240
>> [17844.748642] ---[ end trace 336a2845d42b83f0 ]---
>>
>> Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
>> ---
>>  fs/nfs/direct.c                | 2 +-
>>  fs/nfs/filelayout/filelayout.c | 5 ++++-
>>  include/linux/nfs_xdr.h        | 1 +
>>  3 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
>> index 38678d9..df3b6f4 100644
>> --- a/fs/nfs/direct.c
>> +++ b/fs/nfs/direct.c
>> @@ -166,7 +166,7 @@ nfs_direct_select_verf(struct nfs_direct_req *dreq,
>>         struct nfs_writeverf *verfp = &dreq->verf;
>>
>>  #ifdef CONFIG_NFS_V4_1
>> -       if (ds_clp) {
>> +       if (ds_clp && !dreq->ds_cinfo.through_mds) {
> 
> Why we can't just test for dreq->ds_cinfo.nbuckets > 0?

Yes, that's okay by checking dreq->ds_cinfo.nbuckets or dreq->ds_cinfo.buckets here.

The current code is harmless, only the noise of WARN_ONCE.
At first glance, I plan to remove the WARN_ONCE.
I add a through_mds here for stronger logical.

Without adding new values, I'd prefer using dreq->ds_cinfo.nbuckets.
A new patch will be post, thanks.

> 
>>                 /* pNFS is in use, use the DS verf */
>>                 if (commit_idx >= 0 && commit_idx < dreq->ds_cinfo.nbuckets)
>>                         verfp = &dreq->ds_cinfo.buckets[commit_idx].direct_verf;

thanks,
Kinglong Mee