On Fri, 7 Aug 2015 23:28:41 +0800
Kinglong Mee <kinglongmee@xxxxxxxxx> wrote:
> On 8/6/2015 05:13, Jeff Layton wrote:
> > Currently, NFSv2/3 reads and writes have to open a file, do the read or
> > write and then close it again for each RPC. This is highly inefficient,
> > especially when the underlying filesystem has a relatively slow open
> > routine.
> >
> > This patch adds a new open file cache to knfsd. Rather than doing an
> > open for each RPC, the read/write handlers can call into this cache to
> > see if there is one already there for the correct filehandle and
> > NFS_MAY_READ/WRITE flags.
> >
> > If there isn't an entry, then we create a new one and attempt to
> > perform the open. If there is, then we wait until the entry is fully
> > instantiated and return it if it is at the end of the wait. If it's
> > not, then we attempt to take over construction.
> >
> > Since the main goal is to speed up NFSv2/3 I/O, we don't want to
> > close these files on last put of these objects. We need to keep them
> > around for a little while since we never know when the next READ/WRITE
> > will come in.
> >
> > Cache entries have a hardcoded 1s timeout, and we have a recurring
> > workqueue job that walks the cache and purges any entries that have
> > expired.
> >
> > Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
> ... snip ...
> > diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
> > index 9051ee54faa3..adf7e78b8e43 100644
> > --- a/fs/nfsd/filecache.h
> > +++ b/fs/nfsd/filecache.h
> > @@ -4,6 +4,7 @@
> > #include <linux/jhash.h>
> > #include <linux/sunrpc/xdr.h>
> >
> > +#include "nfsfh.h"
> > #include "export.h"
> >
> > /* hash table for nfs4_file */
> > @@ -22,4 +23,24 @@ file_hashval(struct knfsd_fh *fh)
> > return nfsd_fh_hashval(fh) & (NFSD_FILE_HASH_SIZE - 1);
> > }
> >
> > +struct nfsd_file {
>
> There is a nfs4_file in nfsd, it's not easy to distinguish them for a new folk.
> More comments or a meaningful name is better.
>
Maybe. Again, any suggestions? My hope was that eventually we can unify
the two caches somehow but maybe that's naive.
> > + struct hlist_node nf_node;
> > + struct list_head nf_dispose;
> > + struct rcu_head nf_rcu;
> > + struct file *nf_file;
> > + unsigned long nf_time;
> > +#define NFSD_FILE_HASHED (0)
>
> Why not using hlist_unhashed()?
>
These entries are removed from the list using hlist_del_rcu(), and
hlist_unhashed will not return true after that.
> > +#define NFSD_FILE_PENDING (1)
> > + unsigned long nf_flags;
> > + struct knfsd_fh nf_handle;
> > + unsigned int nf_hashval;
> > + atomic_t nf_ref;
> > + unsigned char nf_may;
> > +};
> > +
> > +int nfsd_file_cache_init(void);
> > +void nfsd_file_cache_shutdown(void);
> > +void nfsd_file_put(struct nfsd_file *nf);
> > +__be32 nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > + unsigned int may_flags, struct nfsd_file **nfp);
> > #endif /* _FS_NFSD_FILECACHE_H */
> > diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> > index ced9944201a0..0572441e23ec 100644
> > --- a/fs/nfsd/nfssvc.c
> > +++ b/fs/nfsd/nfssvc.c
> > @@ -23,6 +23,7 @@
> > #include "cache.h"
> > #include "vfs.h"
> > #include "netns.h"
> > +#include "filecache.h"
> >
> > #define NFSDDBG_FACILITY NFSDDBG_SVC
> >
> > @@ -233,11 +234,17 @@ static int nfsd_startup_generic(int nrservs)
> > if (!nfsd_laundry_wq)
> > goto out_racache;
> >
> > - ret = nfs4_state_start();
> > + ret = nfsd_file_cache_init();
> > if (ret)
> > goto out_wq;
> > +
> > + ret = nfs4_state_start();
> > + if (ret)
> > + goto out_nfsd_file;
> > return 0;
> >
> > +out_nfsd_file:
> > + nfsd_file_cache_shutdown();
> > out_wq:
> > destroy_workqueue(nfsd_laundry_wq);
> > nfsd_laundry_wq = NULL;
> > @@ -254,6 +261,7 @@ static void nfsd_shutdown_generic(void)
> > return;
> >
> > nfs4_state_shutdown();
> > + nfsd_file_cache_shutdown();
> > nfsd_racache_shutdown();
> > }
> >
> >
--
Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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