nfsd: fix race with open / open upgrade stateids
We observed multiple open stateids on the server for files that
seemingly should have been closed.
nfsd4_process_open2() tests for the existence of a preexisting
stateid. If one is not found, the locks are dropped and a new
one is created. The problem is that init_open_stateid(), which
is also responsible for hashing the newly initialized stateid,
doesn't check to see if another open has raced in and created
a matching stateid. This fix is to enable init_open_stateid() to
return the matching stateid and have nfsd4_process_open2()
swap to that stateid and switch to the open upgrade path.
In testing this patch, coverage to the newly created
path indicates that the race was indeed happening.
Signed-off-by: Andrew Elble <aweits@rit.edu>
Reviewed-by: Jeff Layton <jlayton@poochiereds.net>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 6411c34..6b800b5b 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3392,6 +3392,27 @@
.so_free = nfs4_free_openowner,
};
+static struct nfs4_ol_stateid *
+nfsd4_find_existing_open(struct nfs4_file *fp, struct nfsd4_open *open)
+{
+ struct nfs4_ol_stateid *local, *ret = NULL;
+ struct nfs4_openowner *oo = open->op_openowner;
+
+ lockdep_assert_held(&fp->fi_lock);
+
+ list_for_each_entry(local, &fp->fi_stateids, st_perfile) {
+ /* ignore lock owners */
+ if (local->st_stateowner->so_is_open_owner == 0)
+ continue;
+ if (local->st_stateowner == &oo->oo_owner) {
+ ret = local;
+ atomic_inc(&ret->st_stid.sc_count);
+ break;
+ }
+ }
+ return ret;
+}
+
static struct nfs4_openowner *
alloc_init_open_stateowner(unsigned int strhashval, struct nfsd4_open *open,
struct nfsd4_compound_state *cstate)
@@ -3423,9 +3444,20 @@
return ret;
}
-static void init_open_stateid(struct nfs4_ol_stateid *stp, struct nfs4_file *fp, struct nfsd4_open *open) {
- struct nfs4_openowner *oo = open->op_openowner;
+static struct nfs4_ol_stateid *
+init_open_stateid(struct nfs4_ol_stateid *stp, struct nfs4_file *fp,
+ struct nfsd4_open *open)
+{
+ struct nfs4_openowner *oo = open->op_openowner;
+ struct nfs4_ol_stateid *retstp = NULL;
+
+ spin_lock(&oo->oo_owner.so_client->cl_lock);
+ spin_lock(&fp->fi_lock);
+
+ retstp = nfsd4_find_existing_open(fp, open);
+ if (retstp)
+ goto out_unlock;
atomic_inc(&stp->st_stid.sc_count);
stp->st_stid.sc_type = NFS4_OPEN_STID;
INIT_LIST_HEAD(&stp->st_locks);
@@ -3436,12 +3468,13 @@
stp->st_deny_bmap = 0;
stp->st_openstp = NULL;
init_rwsem(&stp->st_rwsem);
- spin_lock(&oo->oo_owner.so_client->cl_lock);
list_add(&stp->st_perstateowner, &oo->oo_owner.so_stateids);
- spin_lock(&fp->fi_lock);
list_add(&stp->st_perfile, &fp->fi_stateids);
+
+out_unlock:
spin_unlock(&fp->fi_lock);
spin_unlock(&oo->oo_owner.so_client->cl_lock);
+ return retstp;
}
/*
@@ -3852,27 +3885,6 @@
return nfs_ok;
}
-static struct nfs4_ol_stateid *
-nfsd4_find_existing_open(struct nfs4_file *fp, struct nfsd4_open *open)
-{
- struct nfs4_ol_stateid *local, *ret = NULL;
- struct nfs4_openowner *oo = open->op_openowner;
-
- spin_lock(&fp->fi_lock);
- list_for_each_entry(local, &fp->fi_stateids, st_perfile) {
- /* ignore lock owners */
- if (local->st_stateowner->so_is_open_owner == 0)
- continue;
- if (local->st_stateowner == &oo->oo_owner) {
- ret = local;
- atomic_inc(&ret->st_stid.sc_count);
- break;
- }
- }
- spin_unlock(&fp->fi_lock);
- return ret;
-}
-
static inline int nfs4_access_to_access(u32 nfs4_access)
{
int flags = 0;
@@ -4258,6 +4270,7 @@
struct nfs4_client *cl = open->op_openowner->oo_owner.so_client;
struct nfs4_file *fp = NULL;
struct nfs4_ol_stateid *stp = NULL;
+ struct nfs4_ol_stateid *swapstp = NULL;
struct nfs4_delegation *dp = NULL;
__be32 status;
@@ -4271,7 +4284,9 @@
status = nfs4_check_deleg(cl, open, &dp);
if (status)
goto out;
+ spin_lock(&fp->fi_lock);
stp = nfsd4_find_existing_open(fp, open);
+ spin_unlock(&fp->fi_lock);
} else {
open->op_file = NULL;
status = nfserr_bad_stateid;
@@ -4294,7 +4309,19 @@
} else {
stp = open->op_stp;
open->op_stp = NULL;
- init_open_stateid(stp, fp, open);
+ swapstp = init_open_stateid(stp, fp, open);
+ if (swapstp) {
+ nfs4_put_stid(&stp->st_stid);
+ stp = swapstp;
+ down_read(&stp->st_rwsem);
+ status = nfs4_upgrade_open(rqstp, fp, current_fh,
+ stp, open);
+ if (status) {
+ up_read(&stp->st_rwsem);
+ goto out;
+ }
+ goto upgrade_out;
+ }
down_read(&stp->st_rwsem);
status = nfs4_get_vfs_file(rqstp, fp, current_fh, stp, open);
if (status) {
@@ -4308,6 +4335,7 @@
if (stp->st_clnt_odstate == open->op_odstate)
open->op_odstate = NULL;
}
+upgrade_out:
nfs4_inc_and_copy_stateid(&open->op_stateid, &stp->st_stid);
up_read(&stp->st_rwsem);