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Jeff LaytonJ. Bruce Fields
Jeff Layton
authored and
J. Bruce Fields
committed
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: Jeff Layton <jlayton@primarydata.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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‎fs/nfsd/nfs4state.c

Lines changed: 49 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -4719,20 +4719,15 @@ alloc_init_lock_stateowner(unsigned int strhashval, struct nfs4_client *clp, str
47194719
return lo;
47204720
}
47214721

4722-
static struct nfs4_ol_stateid *
4723-
alloc_init_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp,
4724-
struct inode *inode,
4725-
struct nfs4_ol_stateid *open_stp)
4722+
static void
4723+
init_lock_stateid(struct nfs4_ol_stateid *stp, struct nfs4_lockowner *lo,
4724+
struct nfs4_file *fp, struct inode *inode,
4725+
struct nfs4_ol_stateid *open_stp)
47264726
{
4727-
struct nfs4_stid *s;
4728-
struct nfs4_openowner *oo = openowner(open_stp->st_stateowner);
4729-
struct nfs4_ol_stateid *stp;
47304727
struct nfs4_client *clp = lo->lo_owner.so_client;
47314728

4732-
s = nfs4_alloc_stid(clp, stateid_slab);
4733-
if (s == NULL)
4734-
return NULL;
4735-
stp = openlockstateid(s);
4729+
lockdep_assert_held(&clp->cl_lock);
4730+
47364731
stp->st_stid.sc_type = NFS4_LOCK_STID;
47374732
stp->st_stateowner = &lo->lo_owner;
47384733
get_nfs4_file(fp);
@@ -4741,20 +4736,20 @@ alloc_init_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp,
47414736
stp->st_access_bmap = 0;
47424737
stp->st_deny_bmap = open_stp->st_deny_bmap;
47434738
stp->st_openstp = open_stp;
4744-
spin_lock(&oo->oo_owner.so_client->cl_lock);
47454739
list_add(&stp->st_locks, &open_stp->st_locks);
47464740
list_add(&stp->st_perstateowner, &lo->lo_owner.so_stateids);
47474741
spin_lock(&fp->fi_lock);
47484742
list_add(&stp->st_perfile, &fp->fi_stateids);
47494743
spin_unlock(&fp->fi_lock);
4750-
spin_unlock(&oo->oo_owner.so_client->cl_lock);
4751-
return stp;
47524744
}
47534745

47544746
static struct nfs4_ol_stateid *
47554747
find_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp)
47564748
{
47574749
struct nfs4_ol_stateid *lst;
4750+
struct nfs4_client *clp = lo->lo_owner.so_client;
4751+
4752+
lockdep_assert_held(&clp->cl_lock);
47584753

47594754
list_for_each_entry(lst, &lo->lo_owner.so_stateids, st_perstateowner) {
47604755
if (lst->st_stid.sc_file == fp)
@@ -4763,6 +4758,38 @@ find_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fp)
47634758
return NULL;
47644759
}
47654760

4761+
static struct nfs4_ol_stateid *
4762+
find_or_create_lock_stateid(struct nfs4_lockowner *lo, struct nfs4_file *fi,
4763+
struct inode *inode, struct nfs4_ol_stateid *ost,
4764+
bool *new)
4765+
{
4766+
struct nfs4_stid *ns = NULL;
4767+
struct nfs4_ol_stateid *lst;
4768+
struct nfs4_openowner *oo = openowner(ost->st_stateowner);
4769+
struct nfs4_client *clp = oo->oo_owner.so_client;
4770+
4771+
spin_lock(&clp->cl_lock);
4772+
lst = find_lock_stateid(lo, fi);
4773+
if (lst == NULL) {
4774+
spin_unlock(&clp->cl_lock);
4775+
ns = nfs4_alloc_stid(clp, stateid_slab);
4776+
if (ns == NULL)
4777+
return NULL;
4778+
4779+
spin_lock(&clp->cl_lock);
4780+
lst = find_lock_stateid(lo, fi);
4781+
if (likely(!lst)) {
4782+
lst = openlockstateid(ns);
4783+
init_lock_stateid(lst, lo, fi, inode, ost);
4784+
ns = NULL;
4785+
*new = true;
4786+
}
4787+
}
4788+
spin_unlock(&clp->cl_lock);
4789+
if (ns)
4790+
nfs4_put_stid(ns);
4791+
return lst;
4792+
}
47664793

47674794
static int
47684795
check_lock_length(u64 offset, u64 length)
@@ -4783,7 +4810,11 @@ static void get_lock_access(struct nfs4_ol_stateid *lock_stp, u32 access)
47834810
set_access(access, lock_stp);
47844811
}
47854812

4786-
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)
4813+
static __be32
4814+
lookup_or_create_lock_state(struct nfsd4_compound_state *cstate,
4815+
struct nfs4_ol_stateid *ost,
4816+
struct nfsd4_lock *lock,
4817+
struct nfs4_ol_stateid **lst, bool *new)
47874818
{
47884819
struct nfs4_file *fi = ost->st_stid.sc_file;
47894820
struct nfs4_openowner *oo = openowner(ost->st_stateowner);
@@ -4807,14 +4838,10 @@ static __be32 lookup_or_create_lock_state(struct nfsd4_compound_state *cstate, s
48074838
return nfserr_bad_seqid;
48084839
}
48094840

4810-
*lst = find_lock_stateid(lo, fi);
4841+
*lst = find_or_create_lock_stateid(lo, fi, inode, ost, new);
48114842
if (*lst == NULL) {
4812-
*lst = alloc_init_lock_stateid(lo, fi, inode, ost);
4813-
if (*lst == NULL) {
4814-
release_lockowner_if_empty(lo);
4815-
return nfserr_jukebox;
4816-
}
4817-
*new = true;
4843+
release_lockowner_if_empty(lo);
4844+
return nfserr_jukebox;
48184845
}
48194846
return nfs_ok;
48204847
}

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