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nfsd: clean up races in lock stateid searching and creation

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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>
This commit is contained in:
Jeff Layton 2014-07-29 21:34:13 -04:00 committed by J. Bruce Fields
parent 1c755dc1ad
commit 356a95ece7
1 changed files with 49 additions and 22 deletions
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65
fs/nfsd/nfs4state.c
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@ -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;
}