1 files changed, 76 insertions, 5 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 1364a1c97e6f..6101879a730f 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -42,6 +42,7 @@
 #include <linux/devfs_fs_kernel.h>
 #include <linux/buffer_head.h> /* for invalidate_bdev */
 #include <linux/suspend.h>
+#include <linux/poll.h>
 
 #include <linux/init.h>
 
@@ -134,6 +135,24 @@ static struct block_device_operations md_fops;
 static int start_readonly;
 
 /*
+ * We have a system wide 'event count' that is incremented
+ * on any 'interesting' event, and readers of /proc/mdstat
+ * can use 'poll' or 'select' to find out when the event
+ * count increases.
+ *
+ * Events are:
+ *  start array, stop array, error, add device, remove device,
+ *  start build, activate spare
+ */
+DECLARE_WAIT_QUEUE_HEAD(md_event_waiters);
+static atomic_t md_event_count;
+void md_new_event(mddev_t *mddev)
+{
+        atomic_inc(&md_event_count);
+        wake_up(&md_event_waiters);
+}
+
+/*
  * Enables to iterate over all existing md arrays
  * all_mddevs_lock protects this list.
  */
@@ -2111,6 +2130,7 @@ static int do_md_run(mddev_t * mddev)
         mddev->queue->make_request_fn = mddev->pers->make_request;
 
         mddev->changed = 1;
+        md_new_event(mddev);
         return 0;
 }
 
@@ -2238,6 +2258,7 @@ static int do_md_stop(mddev_t * mddev, int ro)
                 printk(KERN_INFO "md: %s switched to read-only mode.\n",
                         mdname(mddev));
         err = 0;
+        md_new_event(mddev);
 out:
         return err;
 }
@@ -2712,6 +2733,7 @@ static int hot_remove_disk(mddev_t * mddev, dev_t dev)
 
         kick_rdev_from_array(rdev);
         md_update_sb(mddev);
+        md_new_event(mddev);
 
         return 0;
 busy:
@@ -2802,7 +2824,7 @@ static int hot_add_disk(mddev_t * mddev, dev_t dev)
          */
         set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
         md_wakeup_thread(mddev->thread);
-
+        md_new_event(mddev);
         return 0;
 
 abort_unbind_export:
@@ -3531,6 +3553,7 @@ void md_error(mddev_t *mddev, mdk_rdev_t *rdev)
         set_bit(MD_RECOVERY_INTR, &mddev->recovery);
         set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
         md_wakeup_thread(mddev->thread);
+        md_new_event(mddev);
 }
 
 /* seq_file implementation /proc/mdstat */
@@ -3671,12 +3694,17 @@ static void md_seq_stop(struct seq_file *seq, void *v)
                 mddev_put(mddev);
 }
 
+struct mdstat_info {
+        int event;
+};
+
 static int md_seq_show(struct seq_file *seq, void *v)
 {
         mddev_t *mddev = v;
         sector_t size;
         struct list_head *tmp2;
         mdk_rdev_t *rdev;
+        struct mdstat_info *mi = seq->private;
         int i;
         struct bitmap *bitmap;
 
@@ -3689,6 +3717,7 @@ static int md_seq_show(struct seq_file *seq, void *v)
 
                 spin_unlock(&pers_lock);
                 seq_printf(seq, "\n");
+                mi->event = atomic_read(&md_event_count);
                 return 0;
         }
         if (v == (void*)2) {
@@ -3797,16 +3826,52 @@ static struct seq_operations md_seq_ops = {
 static int md_seq_open(struct inode *inode, struct file *file)
 {
         int error;
+        struct mdstat_info *mi = kmalloc(sizeof(*mi), GFP_KERNEL);
+        if (mi == NULL)
+                return -ENOMEM;
 
         error = seq_open(file, &md_seq_ops);
+        if (error)
+                kfree(mi);
+        else {
+                struct seq_file *p = file->private_data;
+                p->private = mi;
+                mi->event = atomic_read(&md_event_count);
+        }
         return error;
 }
 
+static int md_seq_release(struct inode *inode, struct file *file)
+{
+        struct seq_file *m = file->private_data;
+        struct mdstat_info *mi = m->private;
+        m->private = NULL;
+        kfree(mi);
+        return seq_release(inode, file);
+}
+
+static unsigned int mdstat_poll(struct file *filp, poll_table *wait)
+{
+        struct seq_file *m = filp->private_data;
+        struct mdstat_info *mi = m->private;
+        int mask;
+
+        poll_wait(filp, &md_event_waiters, wait);
+
+        /* always allow read */
+        mask = POLLIN | POLLRDNORM;
+
+        if (mi->event != atomic_read(&md_event_count))
+                mask |= POLLERR | POLLPRI;
+        return mask;
+}
+
 static struct file_operations md_seq_fops = {
         .open           = md_seq_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
-        .release        = seq_release,
+        .release        = md_seq_release,
+        .poll           = mdstat_poll,
 };
 
 int register_md_personality(int pnum, mdk_personality_t *p)
@@ -4076,7 +4141,11 @@ static void md_do_sync(mddev_t *mddev)
 
                 j += sectors;
                 if (j>1) mddev->curr_resync = j;
-
+                if (last_check == 0)
+                        /* this is the earliers that rebuilt will be
+                         * visible in /proc/mdstat
+                         */
+                        md_new_event(mddev);
 
                 if (last_check + window > io_sectors || j == max_sectors)
                         continue;
@@ -4262,6 +4331,7 @@ void md_check_recovery(mddev_t *mddev)
                         mddev->recovery = 0;
                         /* flag recovery needed just to double check */
                         set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+                        md_new_event(mddev);
                         goto unlock;
                 }
                 /* Clear some bits that don't mean anything, but
@@ -4299,6 +4369,7 @@ void md_check_recovery(mddev_t *mddev)
                                                 sprintf(nm, "rd%d", rdev->raid_disk);
                                                 sysfs_create_link(&mddev->kobj, &rdev->kobj, nm);
                                                 spares++;
+                                                md_new_event(mddev);
                                         } else
                                                 break;
                                 }
@@ -4331,9 +4402,9 @@ void md_check_recovery(mddev_t *mddev)
                                         mdname(mddev));
                                 /* leave the spares where they are, it shouldn't hurt */
                                 mddev->recovery = 0;
-                        } else {
+                        } else
                                 md_wakeup_thread(mddev->sync_thread);
-                        }
+                        md_new_event(mddev);
                 }
         unlock:
                 mddev_unlock(mddev);