NFSv4: Fix up stateid locking...

We really don't need to grab both the state->so_owner and the
inode->i_lock.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

3 files changed, 19 insertions, 20 deletions

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 4a1c4d80a577..dd1aa2b598ce 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -139,9 +139,11 @@ struct nfs4_state {
         unsigned long flags;            /* Do we hold any locks? */
         spinlock_t state_lock;          /* Protects the lock_states list */
 
+        seqlock_t seqlock;              /* Protects the stateid/open_stateid */
         nfs4_stateid stateid;           /* Current stateid: may be delegation */
         nfs4_stateid open_stateid;      /* OPEN stateid */
 
+        /* The following 3 fields are protected by owner->so_lock */
         unsigned int n_rdonly;          /* Number of read-only references */
         unsigned int n_wronly;          /* Number of write-only references */
         unsigned int n_rdwr;            /* Number of read/write references */
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 3a2af8053767..ba86ec654c2e 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -385,29 +385,28 @@ static void nfs_set_open_stateid_locked(struct nfs4_state *state, nfs4_stateid *
 
 static void nfs_set_open_stateid(struct nfs4_state *state, nfs4_stateid *stateid, int open_flags)
 {
-        spin_lock(&state->owner->so_lock);
-        spin_lock(&state->inode->i_lock);
+        write_seqlock(&state->seqlock);
         nfs_set_open_stateid_locked(state, stateid, open_flags);
-        spin_unlock(&state->inode->i_lock);
-        spin_unlock(&state->owner->so_lock);
+        write_sequnlock(&state->seqlock);
 }
 
 static void update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_stateid, nfs4_stateid *deleg_stateid, int open_flags)
 {
-        struct inode *inode = state->inode;
-
         open_flags &= (FMODE_READ|FMODE_WRITE);
-        /* Protect against nfs4_find_state_byowner() */
-        spin_lock(&state->owner->so_lock);
-        spin_lock(&inode->i_lock);
+        /*
+         * Protect the call to nfs4_state_set_mode_locked and
+         * serialise the stateid update
+         */
+        write_seqlock(&state->seqlock);
         if (deleg_stateid != NULL) {
                 memcpy(state->stateid.data, deleg_stateid->data, sizeof(state->stateid.data));
                 set_bit(NFS_DELEGATED_STATE, &state->flags);
         }
         if (open_stateid != NULL)
                 nfs_set_open_stateid_locked(state, open_stateid, open_flags);
+        write_sequnlock(&state->seqlock);
+        spin_lock(&state->owner->so_lock);
         update_open_stateflags(state, open_flags);
-        spin_unlock(&inode->i_lock);
         spin_unlock(&state->owner->so_lock);
 }
 
@@ -608,12 +607,10 @@ static int nfs4_open_recover(struct nfs4_opendata *opendata, struct nfs4_state *
          */
         if (test_bit(NFS_DELEGATED_STATE, &state->flags) == 0 &&
             memcmp(state->stateid.data, state->open_stateid.data, sizeof(state->stateid.data)) != 0) {
-                spin_lock(&state->owner->so_lock);
-                spin_lock(&state->inode->i_lock);
+                write_seqlock(&state->seqlock);
                 if (test_bit(NFS_DELEGATED_STATE, &state->flags) == 0)
                         memcpy(state->stateid.data, state->open_stateid.data, sizeof(state->stateid.data));
-                spin_unlock(&state->inode->i_lock);
-                spin_unlock(&state->owner->so_lock);
+                write_sequnlock(&state->seqlock);
         }
         return 0;
 }
@@ -1280,7 +1277,6 @@ static void nfs4_close_prepare(struct rpc_task *task, void *data)
         mode = FMODE_READ|FMODE_WRITE;
         clear_rd = clear_wr = clear_rdwr = 0;
         spin_lock(&state->owner->so_lock);
-        spin_lock(&calldata->inode->i_lock);
         /* Calculate the change in open mode */
         if (state->n_rdwr == 0) {
                 if (state->n_rdonly == 0) {
@@ -1294,7 +1290,6 @@ static void nfs4_close_prepare(struct rpc_task *task, void *data)
                         clear_rdwr |= test_and_clear_bit(NFS_O_RDWR_STATE, &state->flags);
                 }
         }
-        spin_unlock(&calldata->inode->i_lock);
         spin_unlock(&state->owner->so_lock);
         if (!clear_rd && !clear_wr && !clear_rdwr) {
                 /* Note: exit _without_ calling nfs4_close_done */
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 4fa4054cdf34..523cc2cbb5e1 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -307,6 +307,7 @@ nfs4_alloc_open_state(void)
         atomic_set(&state->count, 1);
         INIT_LIST_HEAD(&state->lock_states);
         spin_lock_init(&state->state_lock);
+        seqlock_init(&state->seqlock);
         return state;
 }
 
@@ -411,7 +412,6 @@ void nfs4_put_open_state(struct nfs4_state *state)
  */
 void nfs4_close_state(struct path *path, struct nfs4_state *state, mode_t mode)
 {
-        struct inode *inode = state->inode;
         struct nfs4_state_owner *owner = state->owner;
         int call_close = 0;
         int newstate;
@@ -419,7 +419,6 @@ void nfs4_close_state(struct path *path, struct nfs4_state *state, mode_t mode)
         atomic_inc(&owner->so_count);
         /* Protect against nfs4_find_state() */
         spin_lock(&owner->so_lock);
-        spin_lock(&inode->i_lock);
         switch (mode & (FMODE_READ | FMODE_WRITE)) {
                 case FMODE_READ:
                         state->n_rdonly--;
@@ -446,7 +445,6 @@ void nfs4_close_state(struct path *path, struct nfs4_state *state, mode_t mode)
                         clear_bit(NFS_DELEGATED_STATE, &state->flags);
         }
         nfs4_state_set_mode_locked(state, newstate);
-        spin_unlock(&inode->i_lock);
         spin_unlock(&owner->so_lock);
 
         if (!call_close) {
@@ -599,8 +597,12 @@ int nfs4_set_lock_state(struct nfs4_state *state, struct file_lock *fl)
 void nfs4_copy_stateid(nfs4_stateid *dst, struct nfs4_state *state, fl_owner_t fl_owner)
 {
         struct nfs4_lock_state *lsp;
+        int seq;
 
-        memcpy(dst, &state->stateid, sizeof(*dst));
+        do {
+                seq = read_seqbegin(&state->seqlock);
+                memcpy(dst, &state->stateid, sizeof(*dst));
+        } while (read_seqretry(&state->seqlock, seq));
         if (test_bit(LK_STATE_IN_USE, &state->flags) == 0)
                 return;