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Commit eab7e2e6 authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
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[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: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent efc36aa5

fs/nfsd/export.c

+40 −20
Original line number Diff line number Diff line
@@ -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 @@ exp_rootfh(svc_client *clp, char *path, struct knfsd_fh *f, int maxsize) 
	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;

}

include/linux/nfsd/export.h

+4 −16
Original line number Diff line number Diff line
@@ -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__ */