dlm: allow multiple lockspace creates

Add a count for lockspace create and release so that create can
be called multiple times to use the lockspace from different places.
Also add the new flag DLM_LSFL_NEWEXCL to create a lockspace with
the previous behavior of returning -EEXIST if the lockspace already
exists.

Signed-off-by: David Teigland <teigland@redhat.com>

4 files changed, 109 insertions, 61 deletions

diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
index 5a7ac33b629c..9e0622aff496 100644
--- a/fs/dlm/dlm_internal.h
+++ b/fs/dlm/dlm_internal.h
@@ -2,7 +2,7 @@
 *******************************************************************************
 **
 **  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
-**  Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.
+**  Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
 **
 **  This copyrighted material is made available to anyone wishing to use,
 **  modify, copy, or redistribute it subject to the terms and conditions
@@ -441,7 +441,9 @@ struct dlm_ls {
         uint32_t                ls_global_id;   /* global unique lockspace ID */
         uint32_t                ls_exflags;
         int                     ls_lvblen;
-        int                     ls_count;       /* reference count */
+        int                     ls_count;       /* refcount of processes in
+                                                   the dlm using this ls */
+        int                     ls_create_count; /* create/release refcount */
         unsigned long           ls_flags;       /* LSFL_ */
         struct kobject          ls_kobj;
 
diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
index 499e16759e96..56eae4e4a954 100644
--- a/fs/dlm/lockspace.c
+++ b/fs/dlm/lockspace.c
@@ -2,7 +2,7 @@
 *******************************************************************************
 **
 **  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
-**  Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.
+**  Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
 **
 **  This copyrighted material is made available to anyone wishing to use,
 **  modify, copy, or redistribute it subject to the terms and conditions
@@ -23,6 +23,7 @@
 #include "lock.h"
 #include "recover.h"
 #include "requestqueue.h"
+#include "user.h"
 
 static int                      ls_count;
 static struct mutex             ls_lock;
@@ -246,23 +247,6 @@ static void dlm_scand_stop(void)
         kthread_stop(scand_task);
 }
 
-static struct dlm_ls *dlm_find_lockspace_name(char *name, int namelen)
-{
-        struct dlm_ls *ls;
-
-        spin_lock(&lslist_lock);
-
-        list_for_each_entry(ls, &lslist, ls_list) {
-                if (ls->ls_namelen == namelen &&
-                    memcmp(ls->ls_name, name, namelen) == 0)
-                        goto out;
-        }
-        ls = NULL;
- out:
-        spin_unlock(&lslist_lock);
-        return ls;
-}
-
 struct dlm_ls *dlm_find_lockspace_global(uint32_t id)
 {
         struct dlm_ls *ls;
@@ -327,6 +311,7 @@ static void remove_lockspace(struct dlm_ls *ls)
         for (;;) {
                 spin_lock(&lslist_lock);
                 if (ls->ls_count == 0) {
+                        WARN_ON(ls->ls_create_count != 0);
                         list_del(&ls->ls_list);
                         spin_unlock(&lslist_lock);
                         return;
@@ -381,7 +366,7 @@ static int new_lockspace(char *name, int namelen, void **lockspace,
                          uint32_t flags, int lvblen)
 {
         struct dlm_ls *ls;
-        int i, size, error = -ENOMEM;
+        int i, size, error;
         int do_unreg = 0;
 
         if (namelen > DLM_LOCKSPACE_LEN)
@@ -393,12 +378,32 @@ static int new_lockspace(char *name, int namelen, void **lockspace,
         if (!try_module_get(THIS_MODULE))
                 return -EINVAL;
 
-        ls = dlm_find_lockspace_name(name, namelen);
-        if (ls) {
-                *lockspace = ls;
+        error = 0;
+
+        spin_lock(&lslist_lock);
+        list_for_each_entry(ls, &lslist, ls_list) {
+                WARN_ON(ls->ls_create_count <= 0);
+                if (ls->ls_namelen != namelen)
+                        continue;
+                if (memcmp(ls->ls_name, name, namelen))
+                        continue;
+                if (flags & DLM_LSFL_NEWEXCL) {
+                        error = -EEXIST;
+                        break;
+                }
+                ls->ls_create_count++;
                 module_put(THIS_MODULE);
-                return -EEXIST;
+                error = 1; /* not an error, return 0 */
+                break;
         }
+        spin_unlock(&lslist_lock);
+
+        if (error < 0)
+                goto out;
+        if (error)
+                goto ret_zero;
+
+        error = -ENOMEM;
 
         ls = kzalloc(sizeof(struct dlm_ls) + namelen, GFP_KERNEL);
         if (!ls)
@@ -418,8 +423,9 @@ static int new_lockspace(char *name, int namelen, void **lockspace,
                 ls->ls_allocation = GFP_KERNEL;
 
         /* ls_exflags are forced to match among nodes, and we don't
-           need to require all nodes to have TIMEWARN or FS set */
-        ls->ls_exflags = (flags & ~(DLM_LSFL_TIMEWARN | DLM_LSFL_FS));
+           need to require all nodes to have some flags set */
+        ls->ls_exflags = (flags & ~(DLM_LSFL_TIMEWARN | DLM_LSFL_FS |
+                                    DLM_LSFL_NEWEXCL));
 
         size = dlm_config.ci_rsbtbl_size;
         ls->ls_rsbtbl_size = size;
@@ -510,6 +516,7 @@ static int new_lockspace(char *name, int namelen, void **lockspace,
         down_write(&ls->ls_in_recovery);
 
         spin_lock(&lslist_lock);
+        ls->ls_create_count = 1;
         list_add(&ls->ls_list, &lslist);
         spin_unlock(&lslist_lock);
 
@@ -548,7 +555,7 @@ static int new_lockspace(char *name, int namelen, void **lockspace,
         dlm_create_debug_file(ls);
 
         log_debug(ls, "join complete");
-
+ ret_zero:
         *lockspace = ls;
         return 0;
 
@@ -635,11 +642,32 @@ static int release_lockspace(struct dlm_ls *ls, int force)
         struct dlm_lkb *lkb;
         struct dlm_rsb *rsb;
         struct list_head *head;
-        int i;
-        int busy = lockspace_busy(ls);
+        int i, busy, rv;
+
+        busy = lockspace_busy(ls);
+
+        spin_lock(&lslist_lock);
+        if (ls->ls_create_count == 1) {
+                if (busy > force)
+                        rv = -EBUSY;
+                else {
+                        /* remove_lockspace takes ls off lslist */
+                        ls->ls_create_count = 0;
+                        rv = 0;
+                }
+        } else if (ls->ls_create_count > 1) {
+                rv = --ls->ls_create_count;
+        } else {
+                rv = -EINVAL;
+        }
+        spin_unlock(&lslist_lock);
+
+        if (rv) {
+                log_debug(ls, "release_lockspace no remove %d", rv);
+                return rv;
+        }
 
-        if (busy > force)
-                return -EBUSY;
+        dlm_device_deregister(ls);
 
         if (force < 3)
                 do_uevent(ls, 0);
@@ -720,15 +748,10 @@ static int release_lockspace(struct dlm_ls *ls, int force)
         dlm_clear_members(ls);
         dlm_clear_members_gone(ls);
         kfree(ls->ls_node_array);
+        log_debug(ls, "release_lockspace final free");
         kobject_put(&ls->ls_kobj);
         /* The ls structure will be freed when the kobject is done with */
 
-        mutex_lock(&ls_lock);
-        ls_count--;
-        if (!ls_count)
-                threads_stop();
-        mutex_unlock(&ls_lock);
-
         module_put(THIS_MODULE);
         return 0;
 }
@@ -750,11 +773,21 @@ static int release_lockspace(struct dlm_ls *ls, int force)
 int dlm_release_lockspace(void *lockspace, int force)
 {
         struct dlm_ls *ls;
+        int error;
 
         ls = dlm_find_lockspace_local(lockspace);
         if (!ls)
                 return -EINVAL;
         dlm_put_lockspace(ls);
-        return release_lockspace(ls, force);
+
+        mutex_lock(&ls_lock);
+        error = release_lockspace(ls, force);
+        if (!error)
+                ls_count--;
+        else if (!ls_count)
+                threads_stop();
+        mutex_unlock(&ls_lock);
+
+        return error;
 }
 
diff --git a/fs/dlm/user.c b/fs/dlm/user.c
index 34f14a14fb4e..6542110c0da4 100644
--- a/fs/dlm/user.c
+++ b/fs/dlm/user.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2006-2007 Red Hat, Inc.  All rights reserved.
+ * Copyright (C) 2006-2008 Red Hat, Inc.  All rights reserved.
  *
  * This copyrighted material is made available to anyone wishing to use,
  * modify, copy, or redistribute it subject to the terms and conditions
@@ -340,10 +340,15 @@ static int device_user_deadlock(struct dlm_user_proc *proc,
         return error;
 }
 
-static int create_misc_device(struct dlm_ls *ls, char *name)
+static int dlm_device_register(struct dlm_ls *ls, char *name)
 {
         int error, len;
 
+        /* The device is already registered.  This happens when the
+           lockspace is created multiple times from userspace. */
+        if (ls->ls_device.name)
+                return 0;
+
         error = -ENOMEM;
         len = strlen(name) + strlen(name_prefix) + 2;
         ls->ls_device.name = kzalloc(len, GFP_KERNEL);
@@ -363,6 +368,22 @@ fail:
         return error;
 }
 
+int dlm_device_deregister(struct dlm_ls *ls)
+{
+        int error;
+
+        /* The device is not registered.  This happens when the lockspace
+           was never used from userspace, or when device_create_lockspace()
+           calls dlm_release_lockspace() after the register fails. */
+        if (!ls->ls_device.name)
+                return 0;
+
+        error = misc_deregister(&ls->ls_device);
+        if (!error)
+                kfree(ls->ls_device.name);
+        return error;
+}
+
 static int device_user_purge(struct dlm_user_proc *proc,
                              struct dlm_purge_params *params)
 {
@@ -397,7 +418,7 @@ static int device_create_lockspace(struct dlm_lspace_params *params)
         if (!ls)
                 return -ENOENT;
 
-        error = create_misc_device(ls, params->name);
+        error = dlm_device_register(ls, params->name);
         dlm_put_lockspace(ls);
 
         if (error)
@@ -421,31 +442,22 @@ static int device_remove_lockspace(struct dlm_lspace_params *params)
         if (!ls)
                 return -ENOENT;
 
-        /* Deregister the misc device first, so we don't have
-         * a device that's not attached to a lockspace. If
-         * dlm_release_lockspace fails then we can recreate it
-         */
-        error = misc_deregister(&ls->ls_device);
-        if (error) {
-                dlm_put_lockspace(ls);
-                goto out;
-        }
-        kfree(ls->ls_device.name);
-
         if (params->flags & DLM_USER_LSFLG_FORCEFREE)
                 force = 2;
 
         lockspace = ls->ls_local_handle;
+        dlm_put_lockspace(ls);
 
-        /* dlm_release_lockspace waits for references to go to zero,
-           so all processes will need to close their device for the ls
-           before the release will procede */
+        /* The final dlm_release_lockspace waits for references to go to
+           zero, so all processes will need to close their device for the
+           ls before the release will proceed.  release also calls the
+           device_deregister above.  Converting a positive return value
+           from release to zero means that userspace won't know when its
+           release was the final one, but it shouldn't need to know. */
 
-        dlm_put_lockspace(ls);
         error = dlm_release_lockspace(lockspace, force);
-        if (error)
-                create_misc_device(ls, ls->ls_name);
- out:
+        if (error > 0)
+                error = 0;
         return error;
 }
 
diff --git a/fs/dlm/user.h b/fs/dlm/user.h
index d38e9f3e4151..c528b6b2991b 100644
--- a/fs/dlm/user.h
+++ b/fs/dlm/user.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2006 Red Hat, Inc.  All rights reserved.
+ * Copyright (C) 2006-2008 Red Hat, Inc.  All rights reserved.
  *
  * This copyrighted material is made available to anyone wishing to use,
  * modify, copy, or redistribute it subject to the terms and conditions
@@ -12,5 +12,6 @@
 void dlm_user_add_ast(struct dlm_lkb *lkb, int type);
 int dlm_user_init(void);
 void dlm_user_exit(void);
+int dlm_device_deregister(struct dlm_ls *ls);
 
 #endif