Re: [RPC] nfsd: NFSv4 close a file completely

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

Hi,

> > On Jun 12, 2022, at 3:22 AM, Wang Yugui <wangyugui@e16-tech.com> wrote:
> > 
> > NFSv4 need to close a file completely (no lingering open) when it does
> > a CLOSE or DELEGRETURN.
> > 
> > When multiple NFSv4/OPEN from different clients, we need to check the
> > reference count. The flowing reference-count-check change the behavior
> > of NFSv3 nfsd_rename()/nfsd_unlink() too.
> > 
> > Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=387
> > Signed-off-by: Wang Yugui <wangyugui@e16-tech.com>
> > ---
> > TO-CHECK:
> > 1) NFSv3 nfsd_rename()/nfsd_unlink() feature change is OK?
> > 2) Can we do better performance than nfsd_file_close_inode_sync()?
> > 3) nfsd_file_close_inode_sync()->nfsd_file_close_inode() in nfsd4_delegreturn()
> > 	=> 'Text file busy' about 4s
> > 4) reference-count-check : refcount_read(&nf->nf_ref) <= 1 or ==0?
> > 	nfsd_file_alloc()	refcount_set(&nf->nf_ref, 1);
> > 
> > fs/nfsd/filecache.c | 2 +-
> > fs/nfsd/nfs4state.c | 4 ++++
> > 2 files changed, 5 insertions(+), 1 deletion(-)
> 
> I suppose I owe you (and Frank) a progress report on #386. I've fixed
> the LRU algorithm and added some observability features to measure
> how the fix impacts the cache's efficiency for NFSv3 workloads.
> 
> These new features show that the hit rate and average age of cache
> items goes down after the fix is applied. I'm trying to understand
> if I've done something wrong or if the fix is supposed to do that.
> 
> To handle the case of hundreds of thousands of open files more
> efficiently, I'd like to convert the filecache to use rhashtable.

A question about the comming rhashtable.

Now multiple nfsd export share a cache pool.

In the coming rhashtable, a nfsd export could use a private cache pool
to improve scale out?

Best Regards
Wang Yugui (wangyugui@e16-tech.com)
2022/06/15