2 files changed, 227 insertions, 9 deletions

diff --git a/Documentation/md.txt b/Documentation/md.txt
index b19978e035fc..df0b45515775 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -216,6 +216,45 @@ All md devices contain:
      period as a number of seconds.  The default is 200msec (0.200).
      Writing a value of 0 disables safemode.
 
+   array_state
+     This file contains a single word which describes the current
+     state of the array.  In many cases, the state can be set by
+     writing the word for the desired state, however some states
+     cannot be explicitly set, and some transitions are not allowed.
+
+     clear
+         No devices, no size, no level
+         Writing is equivalent to STOP_ARRAY ioctl
+     inactive
+         May have some settings, but array is not active
+            all IO results in error
+         When written, doesn't tear down array, but just stops it
+     suspended (not supported yet)
+         All IO requests will block. The array can be reconfigured.
+         Writing this, if accepted, will block until array is quiessent
+     readonly
+         no resync can happen.  no superblocks get written.
+         write requests fail
+     read-auto
+         like readonly, but behaves like 'clean' on a write request.
+
+     clean - no pending writes, but otherwise active.
+         When written to inactive array, starts without resync
+         If a write request arrives then
+           if metadata is known, mark 'dirty' and switch to 'active'.
+           if not known, block and switch to write-pending
+         If written to an active array that has pending writes, then fails.
+     active
+         fully active: IO and resync can be happening.
+         When written to inactive array, starts with resync
+
+     write-pending
+         clean, but writes are blocked waiting for 'active' to be written.
+
+     active-idle
+         like active, but no writes have been seen for a while (safe_mode_delay).
+
+
    sync_speed_min
    sync_speed_max
      This are similar to /proc/sys/dev/raid/speed_limit_{min,max}
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 34b6902cda46..f6562ee4c6fc 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2185,6 +2185,176 @@ chunk_size_store(mddev_t *mddev, const char *buf, size_t len)
 static struct md_sysfs_entry md_chunk_size =
 __ATTR(chunk_size, 0644, chunk_size_show, chunk_size_store);
 
+/*
+ * The array state can be:
+ *
+ * clear
+ *     No devices, no size, no level
+ *     Equivalent to STOP_ARRAY ioctl
+ * inactive
+ *     May have some settings, but array is not active
+ *        all IO results in error
+ *     When written, doesn't tear down array, but just stops it
+ * suspended (not supported yet)
+ *     All IO requests will block. The array can be reconfigured.
+ *     Writing this, if accepted, will block until array is quiessent
+ * readonly
+ *     no resync can happen.  no superblocks get written.
+ *     write requests fail
+ * read-auto
+ *     like readonly, but behaves like 'clean' on a write request.
+ *
+ * clean - no pending writes, but otherwise active.
+ *     When written to inactive array, starts without resync
+ *     If a write request arrives then
+ *       if metadata is known, mark 'dirty' and switch to 'active'.
+ *       if not known, block and switch to write-pending
+ *     If written to an active array that has pending writes, then fails.
+ * active
+ *     fully active: IO and resync can be happening.
+ *     When written to inactive array, starts with resync
+ *
+ * write-pending
+ *     clean, but writes are blocked waiting for 'active' to be written.
+ *
+ * active-idle
+ *     like active, but no writes have been seen for a while (100msec).
+ *
+ */
+enum array_state { clear, inactive, suspended, readonly, read_auto, clean, active,
+                   write_pending, active_idle, bad_word};
+char *array_states[] = {
+        "clear", "inactive", "suspended", "readonly", "read-auto", "clean", "active",
+        "write-pending", "active-idle", NULL };
+
+static int match_word(const char *word, char **list)
+{
+        int n;
+        for (n=0; list[n]; n++)
+                if (cmd_match(word, list[n]))
+                        break;
+        return n;
+}
+
+static ssize_t
+array_state_show(mddev_t *mddev, char *page)
+{
+        enum array_state st = inactive;
+
+        if (mddev->pers)
+                switch(mddev->ro) {
+                case 1:
+                        st = readonly;
+                        break;
+                case 2:
+                        st = read_auto;
+                        break;
+                case 0:
+                        if (mddev->in_sync)
+                                st = clean;
+                        else if (mddev->safemode)
+                                st = active_idle;
+                        else
+                                st = active;
+                }
+        else {
+                if (list_empty(&mddev->disks) &&
+                    mddev->raid_disks == 0 &&
+                    mddev->size == 0)
+                        st = clear;
+                else
+                        st = inactive;
+        }
+        return sprintf(page, "%s\n", array_states[st]);
+}
+
+static int do_md_stop(mddev_t * mddev, int ro);
+static int do_md_run(mddev_t * mddev);
+static int restart_array(mddev_t *mddev);
+
+static ssize_t
+array_state_store(mddev_t *mddev, const char *buf, size_t len)
+{
+        int err = -EINVAL;
+        enum array_state st = match_word(buf, array_states);
+        switch(st) {
+        case bad_word:
+                break;
+        case clear:
+                /* stopping an active array */
+                if (mddev->pers) {
+                        if (atomic_read(&mddev->active) > 1)
+                                return -EBUSY;
+                        err = do_md_stop(mddev, 0);
+                }
+                break;
+        case inactive:
+                /* stopping an active array */
+                if (mddev->pers) {
+                        if (atomic_read(&mddev->active) > 1)
+                                return -EBUSY;
+                        err = do_md_stop(mddev, 2);
+                }
+                break;
+        case suspended:
+                break; /* not supported yet */
+        case readonly:
+                if (mddev->pers)
+                        err = do_md_stop(mddev, 1);
+                else {
+                        mddev->ro = 1;
+                        err = do_md_run(mddev);
+                }
+                break;
+        case read_auto:
+                /* stopping an active array */
+                if (mddev->pers) {
+                        err = do_md_stop(mddev, 1);
+                        if (err == 0)
+                                mddev->ro = 2; /* FIXME mark devices writable */
+                } else {
+                        mddev->ro = 2;
+                        err = do_md_run(mddev);
+                }
+                break;
+        case clean:
+                if (mddev->pers) {
+                        restart_array(mddev);
+                        spin_lock_irq(&mddev->write_lock);
+                        if (atomic_read(&mddev->writes_pending) == 0) {
+                                mddev->in_sync = 1;
+                                mddev->sb_dirty = 1;
+                        }
+                        spin_unlock_irq(&mddev->write_lock);
+                } else {
+                        mddev->ro = 0;
+                        mddev->recovery_cp = MaxSector;
+                        err = do_md_run(mddev);
+                }
+                break;
+        case active:
+                if (mddev->pers) {
+                        restart_array(mddev);
+                        mddev->sb_dirty = 0;
+                        wake_up(&mddev->sb_wait);
+                        err = 0;
+                } else {
+                        mddev->ro = 0;
+                        err = do_md_run(mddev);
+                }
+                break;
+        case write_pending:
+        case active_idle:
+                /* these cannot be set */
+                break;
+        }
+        if (err)
+                return err;
+        else
+                return len;
+}
+static struct md_sysfs_entry md_array_state = __ATTR(array_state, 0644, array_state_show, array_state_store);
+
 static ssize_t
 null_show(mddev_t *mddev, char *page)
 {
@@ -2553,6 +2723,7 @@ static struct attribute *md_default_attrs[] = {
         &md_metadata.attr,
         &md_new_device.attr,
         &md_safe_delay.attr,
+        &md_array_state.attr,
         NULL,
 };
 
@@ -2919,11 +3090,8 @@ static int restart_array(mddev_t *mddev)
                 md_wakeup_thread(mddev->thread);
                 md_wakeup_thread(mddev->sync_thread);
                 err = 0;
-        } else {
-                printk(KERN_ERR "md: %s has no personality assigned.\n",
-                        mdname(mddev));
+        } else
                 err = -EINVAL;
-        }
 
 out:
         return err;
@@ -2955,7 +3123,12 @@ static void restore_bitmap_write_access(struct file *file)
         spin_unlock(&inode->i_lock);
 }
 
-static int do_md_stop(mddev_t * mddev, int ro)
+/* mode:
+ *   0 - completely stop and dis-assemble array
+ *   1 - switch to readonly
+ *   2 - stop but do not disassemble array
+ */
+static int do_md_stop(mddev_t * mddev, int mode)
 {
         int err = 0;
         struct gendisk *disk = mddev->gendisk;
@@ -2977,12 +3150,15 @@ static int do_md_stop(mddev_t * mddev, int ro)
 
                 invalidate_partition(disk, 0);
 
-                if (ro) {
+                switch(mode) {
+                case 1: /* readonly */
                         err  = -ENXIO;
                         if (mddev->ro==1)
                                 goto out;
                         mddev->ro = 1;
-                } else {
+                        break;
+                case 0: /* disassemble */
+                case 2: /* stop */
                         bitmap_flush(mddev);
                         md_super_wait(mddev);
                         if (mddev->ro)
@@ -3002,7 +3178,7 @@ static int do_md_stop(mddev_t * mddev, int ro)
                         mddev->in_sync = 1;
                         md_update_sb(mddev);
                 }
-                if (ro)
+                if (mode == 1)
                         set_disk_ro(disk, 1);
                 clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
         }
@@ -3010,7 +3186,7 @@ static int do_md_stop(mddev_t * mddev, int ro)
         /*
          * Free resources if final stop
          */
-        if (!ro) {
+        if (mode == 0) {
                 mdk_rdev_t *rdev;
                 struct list_head *tmp;
                 struct gendisk *disk;
@@ -3034,6 +3210,9 @@ static int do_md_stop(mddev_t * mddev, int ro)
                 export_array(mddev);
 
                 mddev->array_size = 0;
+                mddev->size = 0;
+                mddev->raid_disks = 0;
+
                 disk = mddev->gendisk;
                 if (disk)
                         set_capacity(disk, 0);