Commit 5282fd72 authored by Marc Eshel's avatar Marc Eshel Committed by J. Bruce Fields
Browse files

nfsd41: sessionid hashing 



Simple sessionid hashing using its monotonically increasing sequence number.

Locking considerations:
sessionid_hashtbl access is controlled by the sessionid_lock spin lock.
It must be taken for insert, delete, and lookup.
nfsd4_sequence looks up the session id and if the session is found,
it calls nfsd4_get_session (still under the sessionid_lock).
nfsd4_destroy_session calls nfsd4_put_session after unhashing
it, so when the session's kref reaches zero it's going to get freed.

Signed-off-by: default avatarBenny Halevy <bhalevy@panasas.com>
[we don't use a prime for sessionid hash table size]
[use sessionid_lock spin lock]
Signed-off-by: default avatarBenny Halevy <bhalevy@panasas.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
parent c4bf7868

fs/nfsd/nfs4state.c

+54 −1
Original line number Diff line number Diff line
@@ -382,11 +382,62 @@ static void release_openowner(struct nfs4_stateowner *sop) 
	nfs4_put_stateowner(sop);

}



static DEFINE_SPINLOCK(sessionid_lock);

#define SESSION_HASH_SIZE	512

static struct list_head sessionid_hashtbl[SESSION_HASH_SIZE];



static inline int

hash_sessionid(struct nfs4_sessionid *sessionid)

{

	struct nfsd4_sessionid *sid = (struct nfsd4_sessionid *)sessionid;



	return sid->sequence % SESSION_HASH_SIZE;

}



static inline void

dump_sessionid(const char *fn, struct nfs4_sessionid *sessionid)

{

	u32 *ptr = (u32 *)(&sessionid->data[0]);

	dprintk("%s: %u:%u:%u:%u\n", fn, ptr[0], ptr[1], ptr[2], ptr[3]);

}



/* caller must hold sessionid_lock */

static struct nfsd4_session *

find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid)

{

	struct nfsd4_session *elem;

	int idx;



	dump_sessionid(__func__, sessionid);

	idx = hash_sessionid(sessionid);

	dprintk("%s: idx is %d\n", __func__, idx);

	/* Search in the appropriate list */

	list_for_each_entry(elem, &sessionid_hashtbl[idx], se_hash) {

		dump_sessionid("list traversal", &elem->se_sessionid);

		if (!memcmp(elem->se_sessionid.data, sessionid->data,

			    NFS4_MAX_SESSIONID_LEN)) {

			return elem;

		}

	}



	dprintk("%s: session not found\n", __func__);

	return NULL;

}



/* caller must hold sessionid_lock */

static void

release_session(struct nfsd4_session *ses)

unhash_session(struct nfsd4_session *ses)

{

	list_del(&ses->se_hash);

	list_del(&ses->se_perclnt);

}



static void

release_session(struct nfsd4_session *ses)

{

	spin_lock(&sessionid_lock);

	unhash_session(ses);

	spin_unlock(&sessionid_lock);

	nfsd4_put_session(ses);

}
@@ -3205,6 +3256,8 @@ nfs4_state_init(void) 
		INIT_LIST_HEAD(&unconf_str_hashtbl[i]);

		INIT_LIST_HEAD(&unconf_id_hashtbl[i]);

	}

	for (i = 0; i < SESSION_HASH_SIZE; i++)

		INIT_LIST_HEAD(&sessionid_hashtbl[i]);

	for (i = 0; i < FILE_HASH_SIZE; i++) {

		INIT_LIST_HEAD(&file_hashtbl[i]);

	}

include/linux/nfsd/state.h

+7 −0
Original line number Diff line number Diff line
@@ -132,6 +132,13 @@ nfsd4_get_session(struct nfsd4_session *ses) 
	kref_get(&ses->se_ref);

}



/* formatted contents of nfs4_sessionid */

struct nfsd4_sessionid {

	clientid_t	clientid;

	u32		sequence;

	u32		reserved;

};



#define HEXDIR_LEN     33 /* hex version of 16 byte md5 of cl_name plus '\0' */



/*

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