nfsd: add a new struct file caching facility to nfsd

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@primarydata.com>
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Richard Sharpe <richard.sharpe@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 43 insertions, 22 deletions

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index c85783e536d5..5983206ab036 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -699,7 +699,7 @@ nfsd_access(struct svc_rqst *rqstp, struct svc_fh *fhp, u32 *access, u32 *suppor
 }
 #endif /* CONFIG_NFSD_V3 */
 
-static int nfsd_open_break_lease(struct inode *inode, int access)
+int nfsd_open_break_lease(struct inode *inode, int access)
 {
         unsigned int mode;
 
@@ -715,8 +715,8 @@ static int nfsd_open_break_lease(struct inode *inode, int access)
  * and additional flags.
  * N.B. After this call fhp needs an fh_put
  */
-__be32
-nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
+static __be32
+__nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
                         int may_flags, struct file **filp)
 {
         struct path     path;
@@ -726,25 +726,6 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
         __be32          err;
         int             host_err = 0;
 
-        validate_process_creds();
-
-        /*
-         * If we get here, then the client has already done an "open",
-         * and (hopefully) checked permission - so allow OWNER_OVERRIDE
-         * in case a chmod has now revoked permission.
-         *
-         * Arguably we should also allow the owner override for
-         * directories, but we never have and it doesn't seem to have
-         * caused anyone a problem.  If we were to change this, note
-         * also that our filldir callbacks would need a variant of
-         * lookup_one_len that doesn't check permissions.
-         */
-        if (type == S_IFREG)
-                may_flags |= NFSD_MAY_OWNER_OVERRIDE;
-        err = fh_verify(rqstp, fhp, type, may_flags);
-        if (err)
-                goto out;
-
         path.mnt = fhp->fh_export->ex_path.mnt;
         path.dentry = fhp->fh_dentry;
         inode = d_inode(path.dentry);
@@ -798,10 +779,50 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
 out_nfserr:
         err = nfserrno(host_err);
 out:
+        return err;
+}
+
+__be32
+nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
+                int may_flags, struct file **filp)
+{
+        __be32 err;
+
+        validate_process_creds();
+        /*
+         * If we get here, then the client has already done an "open",
+         * and (hopefully) checked permission - so allow OWNER_OVERRIDE
+         * in case a chmod has now revoked permission.
+         *
+         * Arguably we should also allow the owner override for
+         * directories, but we never have and it doesn't seem to have
+         * caused anyone a problem.  If we were to change this, note
+         * also that our filldir callbacks would need a variant of
+         * lookup_one_len that doesn't check permissions.
+         */
+        if (type == S_IFREG)
+                may_flags |= NFSD_MAY_OWNER_OVERRIDE;
+        err = fh_verify(rqstp, fhp, type, may_flags);
+        if (!err)
+                err = __nfsd_open(rqstp, fhp, type, may_flags, filp);
+        validate_process_creds();
+        return err;
+}
+
+__be32
+nfsd_open_verified(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
+                int may_flags, struct file **filp)
+{
+        __be32 err;
+
+        validate_process_creds();
+        err = __nfsd_open(rqstp, fhp, type, may_flags, filp);
         validate_process_creds();
         return err;
 }
 
+
+
 struct raparms *
 nfsd_init_raparms(struct file *file)
 {