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Commit 81b82965 authored by J. Bruce Fields's avatar J. Bruce Fields
Browse files

nfsd4: simplify stateid generation code, fix wraparound 



Follow the recommendation from rfc3530bis for stateid generation number
wraparound, simplify some code, and fix or remove incorrect comments.

Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent b79abadd

fs/nfsd/nfs4state.c

+23 −29
Original line number Diff line number Diff line
@@ -3168,6 +3168,12 @@ grace_disallows_io(struct inode *inode) 
	return locks_in_grace() && mandatory_lock(inode);

}



/* Returns true iff a is later than b: */

static bool stateid_generation_after(stateid_t *a, stateid_t *b)

{

	return (s32)a->si_generation - (s32)b->si_generation > 0;

}



static int check_stateid_generation(stateid_t *in, stateid_t *ref, bool has_session)

{

	/*
@@ -3175,25 +3181,25 @@ static int check_stateid_generation(stateid_t *in, stateid_t *ref, bool has_sess 
	 * when it is zero.

	 */

	if (has_session && in->si_generation == 0)

		goto out;

		return nfs_ok;



	if (in->si_generation == ref->si_generation)

		return nfs_ok;



	/* If the client sends us a stateid from the future, it's buggy: */

	if (in->si_generation > ref->si_generation)

	if (stateid_generation_after(in, ref))

		return nfserr_bad_stateid;

	/*

	 * The following, however, can happen.  For example, if the

	 * client sends an open and some IO at the same time, the open

	 * may bump si_generation while the IO is still in flight.

	 * Thanks to hard links and renames, the client never knows what

	 * file an open will affect.  So it could avoid that situation

	 * only by serializing all opens and IO from the same open

	 * owner.  To recover from the old_stateid error, the client

	 * will just have to retry the IO:

	 * However, we could see a stateid from the past, even from a

	 * non-buggy client.  For example, if the client sends a lock

	 * while some IO is outstanding, the lock may bump si_generation

	 * while the IO is still in flight.  The client could avoid that

	 * situation by waiting for responses on all the IO requests,

	 * but better performance may result in retrying IO that

	 * receives an old_stateid error if requests are rarely

	 * reordered in flight:

	 */

	if (in->si_generation < ref->si_generation)

	return nfserr_old_stateid;

out:

	return nfs_ok;

}



static int is_delegation_stateid(stateid_t *stateid)
@@ -3353,16 +3359,9 @@ nfsd4_free_stateid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, 
		ret = nfserr_bad_stateid;

		goto out;

	}

	if (stateid->si_generation != 0) {

		if (stateid->si_generation < stp->st_stateid.si_generation) {

			ret = nfserr_old_stateid;

			goto out;

		}

		if (stateid->si_generation > stp->st_stateid.si_generation) {

			ret = nfserr_bad_stateid;

	ret = check_stateid_generation(stateid, &stp->st_stateid, 1);

	if (ret)

		goto out;

		}

	}



	if (stp->st_type == NFS4_OPEN_STID) {

		ret = nfserr_locks_held;
@@ -3439,11 +3438,6 @@ nfs4_preprocess_seqid_op(struct nfsd4_compound_state *cstate, u32 seqid, 
		return nfserr_bad_stateid;

	}



	/*

	*  We now validate the seqid and stateid generation numbers.

	*  For the moment, we ignore the possibility of 

	*  generation number wraparound.

	*/

	if (!nfsd4_has_session(cstate) && seqid != sop->so_seqid)

		goto check_replay;

fs/nfsd/state.h

+3 −0
Original line number Diff line number Diff line
@@ -293,6 +293,9 @@ static inline void 
update_stateid(stateid_t *stateid)

{

	stateid->si_generation++;

	/* Wraparound recommendation from 3530bis-13 9.1.3.2: */

	if (stateid->si_generation == 0)

		stateid->si_generation = 1;

}



/* A reasonable value for REPLAY_ISIZE was estimated as follows: