Re: a nfsd_file_free panic when shudown

[Wang Yugui <wangyugui@e16-tech.com>]

Hi, Jeff Layton 

> Hi,
> > a nfsd_file_free panic when shudown.
> > 
> > This is a kernel 6.1.1 with some nfsd 6.2 pathes.
> > It happened when os shutdown.
> > 
> > but the reproducer is yet not clear.
> > we just gather the info of the attachment file.
> 
> Now I can reproduce it.
> 1)  'tail -f xxx' to keep a file is open from nfs4 client
> 2) 'shutdow -r now' the nfs server.
> 
> more panic info in the attachment files (panic-2.txt/panic-3.txt)
> 
> Best Regards
> Wang Yugui (wangyugui@e16-tech.com)
> 2022/12/22
> 
> > 
> > the path list that applied to kernel 6.1.1.
> > Subject: nfsd: don't call nfsd_file_put from client states seqfile display
> > Subject: NFSD: Pass the target nfsd_file to nfsd_commit()
> > Subject: NFSD: Revert "NFSD: NFSv4 CLOSE should release an nfsd_file
> > Subject: NFSD: Add an NFSD_FILE_GC flag to enable nfsd_file garbage collection
> > Subject: nfsd: fix up the filecache laundrette scheduling
> > Subject: NFSD: Flesh out a documenting comment for filecache.c
> > Subject: NFSD: Clean up nfs4_preprocess_stateid_op() call sites
> > Subject: NFSD: Trace stateids returned via DELEGRETURN
> > Subject: NFSD: Trace delegation revocations
> > Subject: NFSD: Use const pointers as parameters to fh_ helpers
> > Subject: NFSD: Update file_hashtbl() helpers
> > Subject: NFSD: Clean up nfsd4_init_file()
> > Subject: NFSD: Add a nfsd4_file_hash_remove() helper
> > Subject: NFSD: Clean up find_or_add_file()
> > Subject: NFSD: Refactor find_file()
> > Subject: NFSD: Use rhashtable for managing nfs4_file objects
> > Subject: NFSD: Fix licensing header in filecache.c
> > Subject: nfsd: remove the pages_flushed statistic from filecache
> > Subject: nfsd: reorganize filecache.c
> > Subject: NFSD: Add an nfsd_file_fsync tracepoint
> > Subject: nfsd: rework refcounting in filecache
> > Subject: nfsd: under NFSv4.1, fix double svc_xprt_put on rpc_create failure
> > Subject: NFSD: fix use-after-free in __nfs42_ssc_open()
> > 
> > 
> > It happened just after 'Subject: nfsd: rework refcounting in filecache'
> > is added, so this patch maybe related.

It is confirmed that this panic is caused by the patch
'nfsd: rework refcounting in filecache'.

the problem is 100% reproduced when this patch is applied.
the problem is yet not reproduced when this patch is not applied.

Best Regards
Wang Yugui (wangyugui@e16-tech.com)
2022/12/22