diff --git a/daemon/delegation.c b/daemon/delegation.c
index 6d436b6..c10bdcf 100644
--- a/daemon/delegation.c
+++ b/daemon/delegation.c
@@ -84,43 +84,8 @@ void nfs41_delegation_deref(
         free(state);
 }
 
-
-/* delegation return */
 #define open_entry(pos) list_container(pos, nfs41_open_state, client_entry)
 
-static int open_deleg_cmp(const struct list_entry *entry, const void *value)
-{
-    nfs41_open_state *open = open_entry(entry);
-    int result = -1;
-
-    /* open must match the delegation and have no open stateid */
-    AcquireSRWLockShared(&open->lock);
-    if (open->delegation.state != value) goto out;
-    if (open->do_close) goto out;
-    result = 0;
-out:
-    ReleaseSRWLockShared(&open->lock);
-    return result;
-}
-
-/* find the first open that needs recovery */
-static nfs41_open_state* deleg_open_find(
-    IN struct client_state *state,
-    IN const nfs41_delegation_state *deleg)
-{
-    struct list_entry *entry;
-    nfs41_open_state *open = NULL;
-
-    EnterCriticalSection(&state->lock);
-    entry = list_search(&state->opens, deleg, open_deleg_cmp);
-    if (entry) {
-        open = open_entry(entry);
-        nfs41_open_state_ref(open); /* return a reference */
-    }
-    LeaveCriticalSection(&state->lock);
-    return open;
-}
-
 static void delegation_remove(
     IN nfs41_client *client,
     IN nfs41_delegation_state *deleg)
@@ -154,6 +119,145 @@ static void delegation_remove(
     nfs41_delegation_deref(deleg);
 }
 
+
+/* delegation return */
+#define lock_entry(pos) list_container(pos, nfs41_lock_state, open_entry)
+
+static bool_t has_delegated_locks(
+    IN nfs41_open_state *open)
+{
+    struct list_entry *entry;
+    list_for_each(entry, &open->locks.list) {
+        if (lock_entry(entry)->delegated)
+            return TRUE;
+    }
+    return FALSE;
+}
+
+static int open_deleg_cmp(const struct list_entry *entry, const void *value)
+{
+    nfs41_open_state *open = open_entry(entry);
+    int result = -1;
+
+    /* open must match the delegation and have state to reclaim */
+    AcquireSRWLockShared(&open->lock);
+    if (open->delegation.state != value) goto out;
+    if (open->do_close && !has_delegated_locks(open)) goto out;
+    result = 0;
+out:
+    ReleaseSRWLockShared(&open->lock);
+    return result;
+}
+
+/* find the first open that needs recovery */
+static nfs41_open_state* deleg_open_find(
+    IN struct client_state *state,
+    IN const nfs41_delegation_state *deleg)
+{
+    struct list_entry *entry;
+    nfs41_open_state *open = NULL;
+
+    EnterCriticalSection(&state->lock);
+    entry = list_search(&state->opens, deleg, open_deleg_cmp);
+    if (entry) {
+        open = open_entry(entry);
+        nfs41_open_state_ref(open); /* return a reference */
+    }
+    LeaveCriticalSection(&state->lock);
+    return open;
+}
+
+/* find the first lock that needs recovery */
+static bool_t deleg_lock_find(
+    IN nfs41_open_state *open,
+    OUT nfs41_lock_state *lock_out)
+{
+    struct list_entry *entry;
+    bool_t found = FALSE;
+
+    AcquireSRWLockShared(&open->lock);
+    list_for_each(entry, &open->locks.list) {
+        nfs41_lock_state *lock = lock_entry(entry);
+        if (lock->delegated) {
+            /* copy offset, length, type */
+            lock_out->offset = lock->offset;
+            lock_out->length = lock->length;
+            lock_out->exclusive = lock->exclusive;
+            lock_out->id = lock->id;
+            found = TRUE;
+            break;
+        }
+    }
+    ReleaseSRWLockShared(&open->lock);
+    return found;
+}
+
+/* find the matching lock by id, and reset lock.delegated */
+static void deleg_lock_update(
+    IN nfs41_open_state *open,
+    IN const nfs41_lock_state *source)
+{
+    struct list_entry *entry;
+
+    AcquireSRWLockExclusive(&open->lock);
+    list_for_each(entry, &open->locks.list) {
+        nfs41_lock_state *lock = lock_entry(entry);
+        if (lock->id == source->id) {
+            lock->delegated = FALSE;
+            break;
+        }
+    }
+    ReleaseSRWLockExclusive(&open->lock);
+}
+
+static int delegation_flush_locks(
+    IN nfs41_open_state *open,
+    IN bool_t try_recovery)
+{
+    stateid_arg stateid;
+    nfs41_lock_state lock;
+    int status = NFS4_OK;
+
+    stateid.open = open;
+    stateid.delegation = NULL;
+
+    /* get the starting open/lock stateid */
+    AcquireSRWLockShared(&open->lock);
+    if (open->locks.stateid.seqid) {
+        memcpy(&stateid.stateid, &open->locks.stateid, sizeof(stateid4));
+        stateid.type = STATEID_LOCK;
+    } else {
+        memcpy(&stateid.stateid, &open->stateid, sizeof(stateid4));
+        stateid.type = STATEID_OPEN;
+    }
+    ReleaseSRWLockShared(&open->lock);
+
+    /* send LOCK requests for each delegated lock range */
+    while (deleg_lock_find(open, &lock)) {
+        status = nfs41_lock(open->session, &open->file,
+            &open->owner, lock.exclusive ? WRITE_LT : READ_LT,
+            lock.offset, lock.length, FALSE, try_recovery, &stateid);
+        if (status)
+            break;
+        deleg_lock_update(open, &lock);
+    }
+
+    /* save the updated lock stateid */
+    if (stateid.type == STATEID_LOCK) {
+        AcquireSRWLockExclusive(&open->lock);
+        if (open->locks.stateid.seqid == 0) {
+            /* if it's a new lock stateid, copy it in */
+            memcpy(&open->locks.stateid, &stateid.stateid, sizeof(stateid4));
+        } else if (stateid.stateid.seqid > open->locks.stateid.seqid) {
+            /* update the seqid if it's more recent */
+            open->locks.stateid.seqid = stateid.stateid.seqid;
+        }
+        ReleaseSRWLockExclusive(&open->lock);
+    }
+out:
+    return status;
+}
+
 #pragma warning (disable : 4706) /* assignment within conditional expression */
 
 static int delegation_return(
@@ -163,16 +267,18 @@ static int delegation_return(
     IN bool_t try_recovery)
 {
     stateid_arg stateid;
-    int status = NFS4_OK;
-
-    /* recover opens associated with the delegation */
     nfs41_open_state *open;
+    int status;
+
+    /* recover opens and locks associated with the delegation */
     while (open = deleg_open_find(&client->state, deleg)) {
         status = nfs41_delegation_to_open(open, try_recovery);
+        if (status == NFS4_OK)
+            status = delegation_flush_locks(open, try_recovery);
         nfs41_open_state_deref(open);
 
-        if (status == NFS4ERR_BADSESSION)
-            goto out;
+        if (status)
+            break;
     }
 
     /* return the delegation */
@@ -494,7 +600,7 @@ int nfs41_delegation_return(
         }
     } else {
         /* the delegation is being returned, wait for it to finish */
-        while (deleg->status != DELEGATION_RETURNED)
+        while (deleg->status == DELEGATION_RETURNING)
             SleepConditionVariableSRW(&deleg->cond, &deleg->lock, INFINITE, 0);
         status = NFS4ERR_BADHANDLE;
     }
diff --git a/daemon/lock.c b/daemon/lock.c
index c0889c3..4cd52b2 100644
--- a/daemon/lock.c
+++ b/daemon/lock.c
@@ -41,10 +41,6 @@ static void lock_stateid_arg(
     arg->open = state;
     arg->delegation = NULL;
 
-    /* open_to_lock_owner4 requires an open stateid; if we
-     * have a delegation, convert it to an open stateid */
-    nfs41_delegation_to_open(state, TRUE);
-
     AcquireSRWLockShared(&state->lock);
     if (state->locks.stateid.seqid) {
         memcpy(&arg->stateid, &state->locks.stateid, sizeof(stateid4));
@@ -60,7 +56,7 @@ static void lock_stateid_arg(
 }
 
 /* expects the caller to hold an exclusive lock on nfs41_open_state.lock */
-static void update_lock_state(
+static void lock_stateid_update(
     OUT nfs41_open_state *state,
     IN const stateid4 *stateid)
 {
@@ -74,54 +70,118 @@ static void update_lock_state(
 }
 
 static int open_lock_add(
-    IN nfs41_open_state *state,
-    IN const stateid4 *stateid,
-    IN uint64_t offset,
-    IN uint64_t length,
-    IN uint32_t type)
+    IN nfs41_open_state *open,
+    IN const stateid_arg *stateid,
+    IN const nfs41_lock_state *input)
 {
     nfs41_lock_state *lock;
     int status = NO_ERROR;
 
-    AcquireSRWLockExclusive(&state->lock);
-    update_lock_state(state, stateid);
+    AcquireSRWLockExclusive(&open->lock);
+    if (stateid->type == STATEID_LOCK)
+        lock_stateid_update(open, &stateid->stateid);
 
-    lock = malloc(sizeof(nfs41_lock_state));
+    lock = calloc(1, sizeof(nfs41_lock_state));
     if (lock == NULL) {
         status = GetLastError();
         goto out;
     }
-    lock->offset = offset;
-    lock->length = length;
-    lock->type = type;
+    lock->offset = input->offset;
+    lock->length = input->length;
+    lock->exclusive = input->exclusive;
+    lock->id = open->locks.counter++;
 
-    list_add_tail(&state->locks.list, &lock->open_entry);
+    list_add_tail(&open->locks.list, &lock->open_entry);
 out:
-    ReleaseSRWLockExclusive(&state->lock);
+    ReleaseSRWLockExclusive(&open->lock);
     return status;
 }
 
-static void open_lock_remove(
-    IN nfs41_open_state *state,
-    IN const stateid4 *stateid,
-    IN uint64_t offset,
-    IN uint64_t length)
+static bool_t open_lock_delegate(
+    IN nfs41_open_state *open,
+    IN const nfs41_lock_state *input)
+{
+    bool_t delegated = FALSE;
+
+    AcquireSRWLockExclusive(&open->lock);
+    if (open->delegation.state) {
+        nfs41_delegation_state *deleg = open->delegation.state;
+        AcquireSRWLockShared(&deleg->lock);
+        if (deleg->state.type == OPEN_DELEGATE_WRITE
+            && deleg->status == DELEGATION_GRANTED) {
+            nfs41_lock_state *lock = calloc(1, sizeof(nfs41_lock_state));
+            if (lock) {
+                lock->offset = input->offset;
+                lock->length = input->length;
+                lock->exclusive = input->exclusive;
+                lock->delegated = 1;
+                lock->id = open->locks.counter++;
+                list_add_tail(&open->locks.list, &lock->open_entry);
+                delegated = TRUE;
+            }
+        }
+        ReleaseSRWLockShared(&deleg->lock);
+    }
+    ReleaseSRWLockExclusive(&open->lock);
+
+    return delegated;
+}
+
+#define lock_entry(pos) list_container(pos, nfs41_lock_state, open_entry)
+
+static int lock_range_cmp(const struct list_entry *entry, const void *value)
+{
+    const nfs41_lock_state *lhs = lock_entry(entry);
+    const nfs41_lock_state *rhs = (const nfs41_lock_state*)value;
+    if (lhs->offset != rhs->offset) return -1;
+    if (lhs->length != rhs->length) return -1;
+    return 0;
+}
+
+static int open_unlock_delegate(
+    IN nfs41_open_state *open,
+    IN const nfs41_lock_state *input)
 {
     struct list_entry *entry;
-    nfs41_lock_state *lock;
+    int status = ERROR_NOT_LOCKED;
 
-    AcquireSRWLockExclusive(&state->lock);
-    update_lock_state(state, stateid);
+    AcquireSRWLockExclusive(&open->lock);
 
-    list_for_each(entry, &state->locks.list) {
-        lock = list_container(entry, nfs41_lock_state, open_entry);
-        if (lock->offset == offset && lock->length == length) {
+    /* find lock state that matches this range */
+    entry = list_search(&open->locks.list, input, lock_range_cmp);
+    if (entry) {
+        nfs41_lock_state *lock = lock_entry(entry);
+        if (lock->delegated) {
+            /* if the lock was delegated, remove/free it and return success */
             list_remove(entry);
             free(lock);
-            break;
-        }
+            status = NO_ERROR;
+        } else
+            status = ERROR_LOCKED;
     }
-    ReleaseSRWLockExclusive(&state->lock);
+
+    ReleaseSRWLockExclusive(&open->lock);
+    return status;
+}
+
+static void open_unlock_remove(
+    IN nfs41_open_state *open,
+    IN const stateid_arg *stateid,
+    IN const nfs41_lock_state *input)
+{
+    struct list_entry *entry;
+
+    AcquireSRWLockExclusive(&open->lock);
+    if (stateid->type == STATEID_LOCK)
+        lock_stateid_update(open, &stateid->stateid);
+
+    /* find and remove the unlocked range */
+    entry = list_search(&open->locks.list, input, lock_range_cmp);
+    if (entry) {
+        list_remove(entry);
+        free(lock_entry(entry));
+    }
+    ReleaseSRWLockExclusive(&open->lock);
 }
 
 
@@ -156,13 +216,12 @@ static __inline uint32_t get_lock_type(BOOLEAN exclusive, BOOLEAN blocking)
 
 static int handle_lock(nfs41_upcall *upcall)
 {
+    nfs41_lock_state input;
     stateid_arg stateid;
     lock_upcall_args *args = &upcall->args.lock;
     nfs41_open_state *state = upcall->state_ref;
     const uint32_t type = get_lock_type(args->exclusive, args->blocking);
-    int status;
-
-    lock_stateid_arg(state, &stateid);
+    int status = NO_ERROR;
 
     /* 18.10.3. Operation 12: LOCK - Create Lock
      * "To lock the file from a specific offset through the end-of-file
@@ -171,8 +230,29 @@ static int handle_lock(nfs41_upcall *upcall)
     if (args->length >= NFS4_UINT64_MAX - args->offset)
         args->length = NFS4_UINT64_MAX;
 
+    input.offset = args->offset;
+    input.length = args->length;
+    input.exclusive = args->exclusive;
+
+    /* if we hold a write delegation, handle the lock locally */
+    if (open_lock_delegate(state, &input)) {
+        dprintf(LKLVL, "delegated lock { %llu, %llu }\n",
+            input.offset, input.length);
+        goto out;
+    }
+
+    /* open_to_lock_owner4 requires an open stateid; if we
+     * have a delegation, convert it to an open stateid */
+    status = nfs41_delegation_to_open(state, TRUE);
+    if (status) {
+        status = ERROR_FILE_INVALID;
+        goto out;
+    }
+
+    lock_stateid_arg(state, &stateid);
+
     status = nfs41_lock(state->session, &state->file, &state->owner,
-        type, args->offset, args->length, FALSE, TRUE, &stateid);
+        type, input.offset, input.length, FALSE, TRUE, &stateid);
     if (status) {
         dprintf(LKLVL, "nfs41_lock failed with %s\n",
             nfs_error_string(status));
@@ -182,7 +262,7 @@ static int handle_lock(nfs41_upcall *upcall)
 
     /* ignore errors from open_lock_add(); they just mean we
      * won't be able to recover the lock after reboot */
-    open_lock_add(state, &stateid.stateid, args->offset, args->length, type);
+    open_lock_add(state, &stateid, &input);
 out:
     return status;
 }
@@ -190,6 +270,7 @@ out:
 static void cancel_lock(IN nfs41_upcall *upcall)
 {
     stateid_arg stateid;
+    nfs41_lock_state input;
     lock_upcall_args *args = &upcall->args.lock;
     nfs41_open_state *state = upcall->state_ref;
     int status = NO_ERROR;
@@ -199,18 +280,21 @@ static void cancel_lock(IN nfs41_upcall *upcall)
     if (upcall->status)
         goto out;
 
+    input.offset = args->offset;
+    input.length = args->length;
+
+    /* search for the range to unlock, and remove if delegated */
+    status = open_unlock_delegate(state, &input);
+    if (status != ERROR_LOCKED)
+        goto out;
+
     lock_stateid_arg(state, &stateid);
 
     status = nfs41_unlock(state->session, &state->file,
         args->offset, args->length, &stateid);
-    if (status) {
-        dprintf(LKLVL, "cancel_lock: nfs41_unlock() failed with %s\n",
-            nfs_error_string(status));
-        status = nfs_to_windows_error(status, ERROR_BAD_NET_RESP);
-        goto out;
-    }
 
-    open_lock_remove(state, &stateid.stateid, args->offset, args->length);
+    open_unlock_remove(state, &stateid, &input);
+    status = nfs_to_windows_error(status, ERROR_BAD_NET_RESP);
 out:
     dprintf(1, "<-- cancel_lock() returning %d\n", status);
 }
@@ -235,48 +319,36 @@ out:
 
 static int handle_unlock(nfs41_upcall *upcall)
 {
+    nfs41_lock_state input;
     stateid_arg stateid;
     unlock_upcall_args *args = &upcall->args.unlock;
     nfs41_open_state *state = upcall->state_ref;
-    uint32_t i, nsuccess = 0;
     unsigned char *buf = args->buf;
     uint32_t buf_len = args->buf_len;
-    uint64_t offset;
-    uint64_t length;
+    uint32_t i;
     int status = NO_ERROR;
 
     lock_stateid_arg(state, &stateid);
-    if (stateid.type != STATEID_LOCK) {
-        eprintf("attempt to unlock a file with no lock state\n");
-        status = ERROR_NOT_LOCKED;
-        goto out;
-    }
 
     for (i = 0; i < args->count; i++) {
-        if (safe_read(&buf, &buf_len, &offset, sizeof(LONGLONG))) break;
-        if (safe_read(&buf, &buf_len, &length, sizeof(LONGLONG))) break;
+        if (safe_read(&buf, &buf_len, &input.offset, sizeof(LONGLONG))) break;
+        if (safe_read(&buf, &buf_len, &input.length, sizeof(LONGLONG))) break;
 
         /* do the same translation as LOCK, or the ranges won't match */
-        if (length >= NFS4_UINT64_MAX - offset)
-            length = NFS4_UINT64_MAX;
+        if (input.length >= NFS4_UINT64_MAX - input.offset)
+            input.length = NFS4_UINT64_MAX;
 
-        status = nfs41_unlock(state->session,
-            &state->file, offset, length, &stateid);
-        if (status == NFS4_OK) {
-            open_lock_remove(state, &stateid.stateid, offset, length);
-            nsuccess++;
-        } else {
-            dprintf(LKLVL, "nfs41_unlock failed with %s\n",
-                nfs_error_string(status));
-            status = nfs_to_windows_error(status, ERROR_BAD_NET_RESP);
-        }
-    }
+        /* search for the range to unlock, and remove if delegated */
+        status = open_unlock_delegate(state, &input);
+        if (status != ERROR_LOCKED)
+            continue;
 
-    if (nsuccess) {
-        update_lock_state(state, &stateid.stateid);
-        status = NO_ERROR;
+        status = nfs41_unlock(state->session, &state->file,
+            input.offset, input.length, &stateid);
+
+        open_unlock_remove(state, &stateid, &input);
+        status = nfs_to_windows_error(status, ERROR_BAD_NET_RESP);
     }
-out:
     return status;
 }
 
diff --git a/daemon/nfs41.h b/daemon/nfs41.h
index 514b5e0..d0b36c9 100644
--- a/daemon/nfs41.h
+++ b/daemon/nfs41.h
@@ -105,7 +105,9 @@ typedef struct __nfs41_lock_state {
     struct list_entry open_entry; /* entry in nfs41_open_state.locks */
     uint64_t offset;
     uint64_t length;
-    uint32_t type;
+    uint32_t exclusive : 1;
+    uint32_t delegated : 1; /* whether or not there is state on the server */
+    uint32_t id : 30;
 } nfs41_lock_state;
 
 /* nfs41_open_state reference counting:
@@ -140,6 +142,7 @@ typedef struct __nfs41_open_state {
     struct { /* list of open lock state for recovery */
         stateid4 stateid;
         struct list_entry list;
+        uint32_t counter;
     } locks;
 } nfs41_open_state;
 
diff --git a/daemon/recovery.c b/daemon/recovery.c
index ff994e1..edd8877 100644
--- a/daemon/recovery.c
+++ b/daemon/recovery.c
@@ -233,18 +233,22 @@ static int recover_locks(
     /* recover any locks for this open */
     list_for_each(entry, &open->locks.list) {
         lock = list_container(entry, nfs41_lock_state, open_entry);
+        if (lock->delegated)
+            continue;
 
         if (*grace)
-            status = nfs41_lock(session, &open->file, &open->owner,
-                lock->type, lock->offset, lock->length, TRUE, FALSE, &stateid);
+            status = nfs41_lock(session, &open->file,
+                &open->owner, lock->exclusive ? WRITE_LT : READ_LT,
+                lock->offset, lock->length, TRUE, FALSE, &stateid);
         else
             status = NFS4ERR_NO_GRACE;
 
         if (status == NFS4ERR_NO_GRACE) {
             *grace = FALSE;
             /* attempt out-of-grace recovery with a normal LOCK */
-            status = nfs41_lock(session, &open->file, &open->owner,
-                lock->type, lock->offset, lock->length, FALSE, FALSE, &stateid);
+            status = nfs41_lock(session, &open->file,
+                &open->owner, lock->exclusive ? WRITE_LT : READ_LT,
+                lock->offset, lock->length, FALSE, FALSE, &stateid);
         }
         if (status == NFS4ERR_BADSESSION)
             break;