[PATCH] knfsd: Break the hard linkage from svc_expkey to svc_export

Current svc_expkey holds a pointer to the svc_export structure, so updates to
that structure have to be in-place, which is a wart on the whole cache
infrastruct.  So we break that linkage and just do a second lookup.

If this became a performance issue, it would be possible to put a direct link
back in which was only used conditionally.  i.e.  when an object is replaced
in the cache, we set a flag in the old object.  When dereferencing the link
from svc_expkey, if the flag is set, we drop the reference and do a fresh
lookup.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index ac09977..587829e 100644 (file)
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -73,8 +73,10 @@ void expkey_put(struct cache_head *item, struct cache_detail *cd)
        if (cache_put(item, cd)) {
                struct svc_expkey *key = container_of(item, struct svc_expkey, h);
                if (test_bit(CACHE_VALID, &item->flags) &&
-                   !test_bit(CACHE_NEGATIVE, &item->flags))
-                       exp_put(key->ek_export);
+                   !test_bit(CACHE_NEGATIVE, &item->flags)) {
+                       dput(key->ek_dentry);
+                       mntput(key->ek_mnt);
+               }
                auth_domain_put(key->ek_client);
                kfree(key);
        }
@@ -164,26 +166,18 @@ static int expkey_parse(struct cache_detail *cd, char *mesg, int mlen)
        } else {
                struct nameidata nd;
                struct svc_expkey *ek;
-               struct svc_export *exp;
                err = path_lookup(buf, 0, &nd);
                if (err)
                        goto out;
 
                dprintk("Found the path %s\n", buf);
-               exp = exp_get_by_name(dom, nd.mnt, nd.dentry, NULL);
-
-               err = -ENOENT;
-               if (!exp)
-                       goto out_nd;
-               key.ek_export = exp;
-               dprintk("And found export\n");
+               key.ek_mnt = nd.mnt;
+               key.ek_dentry = nd.dentry;
                
                ek = svc_expkey_lookup(&key, 1);
                if (ek)
                        expkey_put(&ek->h, &svc_expkey_cache);
-               exp_put(exp);
                err = 0;
-       out_nd:
                path_release(&nd);
        }
        cache_flush();
@@ -214,7 +208,7 @@ static int expkey_show(struct seq_file *m,
        if (test_bit(CACHE_VALID, &h->flags) && 
            !test_bit(CACHE_NEGATIVE, &h->flags)) {
                seq_printf(m, " ");
-               seq_path(m, ek->ek_export->ex_mnt, ek->ek_export->ex_dentry, "\\ \t\n");
+               seq_path(m, ek->ek_mnt, ek->ek_dentry, "\\ \t\n");
        }
        seq_printf(m, "\n");
        return 0;
@@ -252,8 +246,8 @@ static inline void svc_expkey_init(struct svc_expkey *new, struct svc_expkey *it
 
 static inline void svc_expkey_update(struct svc_expkey *new, struct svc_expkey *item)
 {
-       cache_get(&item->ek_export->h);
-       new->ek_export = item->ek_export;
+       new->ek_mnt = mntget(item->ek_mnt);
+       new->ek_dentry = dget(item->ek_dentry);
 }
 
 static DefineSimpleCacheLookup(svc_expkey,0) /* no inplace updates */
@@ -519,7 +513,8 @@ static int exp_set_key(svc_client *clp, int fsid_type, u32 *fsidv,
        key.ek_client = clp;
        key.ek_fsidtype = fsid_type;
        memcpy(key.ek_fsid, fsidv, key_len(fsid_type));
-       key.ek_export = exp;
+       key.ek_mnt = exp->ex_mnt;
+       key.ek_dentry = exp->ex_dentry;
        key.h.expiry_time = NEVER;
        key.h.flags = 0;
 
@@ -741,8 +736,8 @@ exp_export(struct nfsctl_export *nxp)
        if ((nxp->ex_flags & NFSEXP_FSID) &&
            (fsid_key = exp_get_fsid_key(clp, nxp->ex_dev)) &&
            !IS_ERR(fsid_key) &&
-           fsid_key->ek_export &&
-           fsid_key->ek_export != exp)
+           fsid_key->ek_mnt &&
+           (fsid_key->ek_mnt != nd.mnt || fsid_key->ek_dentry != nd.dentry) )
                goto finish;
 
        if (exp) {
@@ -912,6 +907,24 @@ out:
        return err;
 }
 
+struct svc_export *
+exp_find(struct auth_domain *clp, int fsid_type, u32 *fsidv,
+        struct cache_req *reqp)
+{
+       struct svc_export *exp;
+       struct svc_expkey *ek = exp_find_key(clp, fsid_type, fsidv, reqp);
+       if (!ek || IS_ERR(ek))
+               return ERR_PTR(PTR_ERR(ek));
+
+       exp = exp_get_by_name(clp, ek->ek_mnt, ek->ek_dentry, reqp);
+       expkey_put(&ek->h, &svc_expkey_cache);
+
+       if (!exp || IS_ERR(exp))
+               return ERR_PTR(PTR_ERR(exp));
+       return exp;
+}
+
+
 /*
  * Called when we need the filehandle for the root of the pseudofs,
  * for a given NFSv4 client.   The root is defined to be the
@@ -922,6 +935,7 @@ exp_pseudoroot(struct auth_domain *clp, struct svc_fh *fhp,
               struct cache_req *creq)
 {
        struct svc_expkey *fsid_key;
+       struct svc_export *exp;
        int rv;
        u32 fsidv[2];
 
@@ -933,8 +947,14 @@ exp_pseudoroot(struct auth_domain *clp, struct svc_fh *fhp,
        if (!fsid_key || IS_ERR(fsid_key))
                return nfserr_perm;
 
-       rv = fh_compose(fhp, fsid_key->ek_export, 
-                         fsid_key->ek_export->ex_dentry, NULL);
+       exp = exp_get_by_name(clp, fsid_key->ek_mnt, fsid_key->ek_dentry, creq);
+       if (exp == NULL)
+               rv = nfserr_perm;
+       else if (IS_ERR(exp))
+               rv = nfserrno(PTR_ERR(exp));
+       else
+               rv = fh_compose(fhp, exp,
+                               fsid_key->ek_dentry, NULL);
        expkey_put(&fsid_key->h, &svc_expkey_cache);
        return rv;
 }

diff --git a/include/linux/nfsd/export.h b/include/linux/nfsd/export.h
index 6bad476..d52e0b7 100644 (file)
--- a/include/linux/nfsd/export.h
+++ b/include/linux/nfsd/export.h
@@ -67,7 +67,8 @@ struct svc_expkey {
        int                     ek_fsidtype;
        u32                     ek_fsid[3];
 
-       struct svc_export *     ek_export;
+       struct vfsmount *       ek_mnt;
+       struct dentry *         ek_dentry;
 };
 
 #define EX_SECURE(exp)         (!((exp)->ex_flags & NFSEXP_INSECURE_PORT))
@@ -114,22 +115,9 @@ static inline void exp_get(struct svc_export *exp)
 {
        cache_get(&exp->h);
 }
-static inline struct svc_export *
+extern struct svc_export *
 exp_find(struct auth_domain *clp, int fsid_type, u32 *fsidv,
-        struct cache_req *reqp)
-{
-       struct svc_expkey *ek = exp_find_key(clp, fsid_type, fsidv, reqp);
-       if (ek && !IS_ERR(ek)) {
-               struct svc_export *exp = ek->ek_export;
-               int err;
-               exp_get(exp);
-               expkey_put(&ek->h, &svc_expkey_cache);
-               if ((err = cache_check(&svc_export_cache, &exp->h, reqp)))
-                       exp = ERR_PTR(err);
-               return exp;
-       } else
-               return ERR_PTR(PTR_ERR(ek));
-}
+        struct cache_req *reqp);
 
 #endif /* __KERNEL__ */