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nfsd: fix race with open / open upgrade stateids

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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>
This commit is contained in:
Andrew Elble 2015-11-05 20:42:43 -05:00 committed by J. Bruce Fields
parent 34ed9872e7
commit 7fc0564e3a
1 changed files with 54 additions and 26 deletions
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80
fs/nfsd/nfs4state.c
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@ -3392,6 +3392,27 @@ static const struct nfs4_stateowner_operations openowner_ops = {
.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 @@ alloc_init_open_stateowner(unsigned int strhashval, struct nfsd4_open *open,
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 @@ static void init_open_stateid(struct nfs4_ol_stateid *stp, struct nfs4_file *fp,
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 @@ out:
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 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
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 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
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 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
} 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 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
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);