Commit 356a95ec authored by Jeff Layton's avatar Jeff Layton Committed by J. Bruce Fields
Browse files

nfsd: clean up races in lock stateid searching and creation 



Preparation for removal of the client_mutex.

Currently, no lock aside from the client_mutex is held when calling
find_lock_state. Ensure that the cl_lock is held by adding a lockdep
assertion.

Once we remove the client_mutex, it'll be possible for another thread to
race in and insert a lock state for the same file after we search but
before we insert a new one. Ensure that doesn't happen by redoing the
search after allocating a new stid that we plan to insert. If one is
found just put the one that was allocated.

Signed-off-by: default avatarJeff Layton <jlayton@primarydata.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent 1c755dc1

fs/nfsd/nfs4state.c

+49 −22
Original line number Diff line number Diff line
@@ -4719,20 +4719,15 @@ alloc_init_lock_stateowner(unsigned int strhashval, struct nfs4_client *clp, str 
	return lo;

}



static struct nfs4_ol_stateid *

alloc_init_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp,

		struct inode *inode,

static void

init_lock_stateid(struct nfs4_ol_stateid *stp, struct nfs4_lockowner *lo,

		  struct nfs4_file *fp, struct inode *inode,

		  struct nfs4_ol_stateid *open_stp)

{

	struct nfs4_stid *s;

	struct nfs4_openowner *oo = openowner(open_stp->st_stateowner);

	struct nfs4_ol_stateid *stp;

	struct nfs4_client *clp = lo->lo_owner.so_client;



	s = nfs4_alloc_stid(clp, stateid_slab);

	if (s == NULL)

		return NULL;

	stp = openlockstateid(s);

	lockdep_assert_held(&clp->cl_lock);



	stp->st_stid.sc_type = NFS4_LOCK_STID;

	stp->st_stateowner = &lo->lo_owner;

	get_nfs4_file(fp);
@@ -4741,20 +4736,20 @@ alloc_init_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp, 
	stp->st_access_bmap = 0;

	stp->st_deny_bmap = open_stp->st_deny_bmap;

	stp->st_openstp = open_stp;

	spin_lock(&oo->oo_owner.so_client->cl_lock);

	list_add(&stp->st_locks, &open_stp->st_locks);

	list_add(&stp->st_perstateowner, &lo->lo_owner.so_stateids);

	spin_lock(&fp->fi_lock);

	list_add(&stp->st_perfile, &fp->fi_stateids);

	spin_unlock(&fp->fi_lock);

	spin_unlock(&oo->oo_owner.so_client->cl_lock);

	return stp;

}



static struct nfs4_ol_stateid *

find_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp)

{

	struct nfs4_ol_stateid *lst;

	struct nfs4_client *clp = lo->lo_owner.so_client;



	lockdep_assert_held(&clp->cl_lock);



	list_for_each_entry(lst, &lo->lo_owner.so_stateids, st_perstateowner) {

		if (lst->st_stid.sc_file == fp)
@@ -4763,6 +4758,38 @@ find_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp) 
	return NULL;

}



static struct nfs4_ol_stateid *

find_or_create_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fi,

			    struct inode *inode, struct nfs4_ol_stateid *ost,

			    bool *new)

{

	struct nfs4_stid *ns = NULL;

	struct nfs4_ol_stateid *lst;

	struct nfs4_openowner *oo = openowner(ost->st_stateowner);

	struct nfs4_client *clp = oo->oo_owner.so_client;



	spin_lock(&clp->cl_lock);

	lst = find_lock_stateid(lo, fi);

	if (lst == NULL) {

		spin_unlock(&clp->cl_lock);

		ns = nfs4_alloc_stid(clp, stateid_slab);

		if (ns == NULL)

			return NULL;



		spin_lock(&clp->cl_lock);

		lst = find_lock_stateid(lo, fi);

		if (likely(!lst)) {

			lst = openlockstateid(ns);

			init_lock_stateid(lst, lo, fi, inode, ost);

			ns = NULL;

			*new = true;

		}

	}

	spin_unlock(&clp->cl_lock);

	if (ns)

		nfs4_put_stid(ns);

	return lst;

}



static int

check_lock_length(u64 offset, u64 length)
@@ -4783,7 +4810,11 @@ static void get_lock_access(struct nfs4_ol_stateid *lock_stp, u32 access) 
	set_access(access, lock_stp);

}



static __be32 lookup_or_create_lock_state(struct nfsd4_compound_state *cstate, struct nfs4_ol_stateid *ost, struct nfsd4_lock *lock, struct nfs4_ol_stateid **lst, bool *new)

static __be32

lookup_or_create_lock_state(struct nfsd4_compound_state *cstate,

			    struct nfs4_ol_stateid *ost,

			    struct nfsd4_lock *lock,

			    struct nfs4_ol_stateid **lst, bool *new)

{

	struct nfs4_file *fi = ost->st_stid.sc_file;

	struct nfs4_openowner *oo = openowner(ost->st_stateowner);
@@ -4807,15 +4838,11 @@ static __be32 lookup_or_create_lock_state(struct nfsd4_compound_state *cstate, s 
			return nfserr_bad_seqid;

	}



	*lst = find_lock_stateid(lo, fi);

	if (*lst == NULL) {

		*lst = alloc_init_lock_stateid(lo, fi, inode, ost);

	*lst = find_or_create_lock_stateid(lo, fi, inode, ost, new);

	if (*lst == NULL) {

		release_lockowner_if_empty(lo);

		return nfserr_jukebox;

	}

		*new = true;

	}

	return nfs_ok;

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE