NFSv4: Fix a race between open() and close()
We must not remove the nfs4_state structure from the inode open lists
before we are in sequence lock.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 2d5a6a2..959374d 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -366,6 +366,23 @@
return state;
}
+void
+nfs4_state_set_mode_locked(struct nfs4_state *state, mode_t mode)
+{
+ if (state->state == mode)
+ return;
+ /* NB! List reordering - see the reclaim code for why. */
+ if ((mode & FMODE_WRITE) != (state->state & FMODE_WRITE)) {
+ if (mode & FMODE_WRITE)
+ list_move(&state->open_states, &state->owner->so_states);
+ else
+ list_move_tail(&state->open_states, &state->owner->so_states);
+ }
+ if (mode == 0)
+ list_del_init(&state->inode_states);
+ state->state = mode;
+}
+
static struct nfs4_state *
__nfs4_find_state(struct inode *inode, struct rpc_cred *cred, mode_t mode)
{
@@ -376,10 +393,6 @@
list_for_each_entry(state, &nfsi->open_states, inode_states) {
if (state->owner->so_cred != cred)
continue;
- if ((mode & FMODE_READ) != 0 && state->nreaders == 0)
- continue;
- if ((mode & FMODE_WRITE) != 0 && state->nwriters == 0)
- continue;
if ((state->state & mode) != mode)
continue;
atomic_inc(&state->count);
@@ -400,7 +413,7 @@
list_for_each_entry(state, &nfsi->open_states, inode_states) {
/* Is this in the process of being freed? */
- if (state->nreaders == 0 && state->nwriters == 0)
+ if (state->state == 0)
continue;
if (state->owner == owner) {
atomic_inc(&state->count);
@@ -481,7 +494,6 @@
spin_unlock(&inode->i_lock);
spin_unlock(&owner->so_lock);
iput(inode);
- BUG_ON (state->state != 0);
nfs4_free_open_state(state);
nfs4_put_state_owner(owner);
}
@@ -493,7 +505,7 @@
{
struct inode *inode = state->inode;
struct nfs4_state_owner *owner = state->owner;
- int newstate;
+ int oldstate, newstate = 0;
atomic_inc(&owner->so_count);
/* Protect against nfs4_find_state() */
@@ -503,30 +515,20 @@
state->nreaders--;
if (mode & FMODE_WRITE)
state->nwriters--;
- if (state->nwriters == 0) {
- if (state->nreaders == 0)
- list_del_init(&state->inode_states);
- /* See reclaim code */
- list_move_tail(&state->open_states, &owner->so_states);
+ oldstate = newstate = state->state;
+ if (state->nreaders == 0)
+ newstate &= ~FMODE_READ;
+ if (state->nwriters == 0)
+ newstate &= ~FMODE_WRITE;
+ if (test_bit(NFS_DELEGATED_STATE, &state->flags)) {
+ nfs4_state_set_mode_locked(state, newstate);
+ oldstate = newstate;
}
spin_unlock(&inode->i_lock);
spin_unlock(&owner->so_lock);
- newstate = 0;
- if (state->state != 0) {
- if (state->nreaders)
- newstate |= FMODE_READ;
- if (state->nwriters)
- newstate |= FMODE_WRITE;
- if (state->state == newstate)
- goto out;
- if (test_bit(NFS_DELEGATED_STATE, &state->flags)) {
- state->state = newstate;
- goto out;
- }
- if (nfs4_do_close(inode, state, newstate) == 0)
- return;
- }
-out:
+
+ if (oldstate != newstate && nfs4_do_close(inode, state) == 0)
+ return;
nfs4_put_open_state(state);
nfs4_put_state_owner(owner);
}