md: fix 'safemode' handling for external metadata.

'safemode' relates to marking an array as 'clean' if there has been no write
traffic for a while (a couple of seconds), to reduce the chance of the array
being found dirty on reboot.

->safemode is set to '1' when there have been no write for a while, and it
gets set to '0' when the superblock is updates with the 'clean' flag set.

This requires a few fixes for 'external' metadata:
 - When an array is set to 'clean' via sysfs, 'safemode' must be cleared.
 - when we write to an array that has 'safemode' set (there must have been
        some delay in updating the metadata), we need to clear safemode.
 - Don't try to update external metadata in md_check_recovery for safemode
        transitions - it won't work.

Also, don't try to support "immediate safe mode" (safemode==2) for external
metadata, it cannot really work (the safemode timeout can be set very low if
this is really needed).

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 11 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 7a44c81ae3cd..ff9fef389608 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2615,6 +2615,8 @@ array_state_store(mddev_t *mddev, const char *buf, size_t len)
                         if (atomic_read(&mddev->writes_pending) == 0) {
                                 if (mddev->in_sync == 0) {
                                         mddev->in_sync = 1;
+                                        if (mddev->safemode == 1)
+                                                mddev->safemode = 0;
                                         if (mddev->persistent)
                                                 set_bit(MD_CHANGE_CLEAN,
                                                         &mddev->flags);
@@ -5392,6 +5394,8 @@ void md_write_start(mddev_t *mddev, struct bio *bi)
                 md_wakeup_thread(mddev->sync_thread);
         }
         atomic_inc(&mddev->writes_pending);
+        if (mddev->safemode == 1)
+                mddev->safemode = 0;
         if (mddev->in_sync) {
                 spin_lock_irq(&mddev->write_lock);
                 if (mddev->in_sync) {
@@ -5816,7 +5820,7 @@ void md_check_recovery(mddev_t *mddev)
                 return;
 
         if (signal_pending(current)) {
-                if (mddev->pers->sync_request) {
+                if (mddev->pers->sync_request && !mddev->external) {
                         printk(KERN_INFO "md: %s in immediate safe mode\n",
                                mdname(mddev));
                         mddev->safemode = 2;
@@ -5828,7 +5832,7 @@ void md_check_recovery(mddev_t *mddev)
                 (mddev->flags && !mddev->external) ||
                 test_bit(MD_RECOVERY_NEEDED, &mddev->recovery) ||
                 test_bit(MD_RECOVERY_DONE, &mddev->recovery) ||
-                (mddev->safemode == 1) ||
+                (mddev->external == 0 && mddev->safemode == 1) ||
                 (mddev->safemode == 2 && ! atomic_read(&mddev->writes_pending)
                  && !mddev->in_sync && mddev->recovery_cp == MaxSector)
                 ))
@@ -5837,16 +5841,20 @@ void md_check_recovery(mddev_t *mddev)
         if (mddev_trylock(mddev)) {
                 int spares = 0;
 
-                spin_lock_irq(&mddev->write_lock);
-                if (mddev->safemode && !atomic_read(&mddev->writes_pending) &&
-                    !mddev->in_sync && mddev->recovery_cp == MaxSector) {
-                        mddev->in_sync = 1;
-                        if (mddev->persistent)
-                                set_bit(MD_CHANGE_CLEAN, &mddev->flags);
+                if (!mddev->external) {
+                        spin_lock_irq(&mddev->write_lock);
+                        if (mddev->safemode &&
+                            !atomic_read(&mddev->writes_pending) &&
+                            !mddev->in_sync &&
+                            mddev->recovery_cp == MaxSector) {
+                                mddev->in_sync = 1;
+                                if (mddev->persistent)
+                                        set_bit(MD_CHANGE_CLEAN, &mddev->flags);
+                        }
+                        if (mddev->safemode == 1)
+                                mddev->safemode = 0;
+                        spin_unlock_irq(&mddev->write_lock);
                 }
-                if (mddev->safemode == 1)
-                        mddev->safemode = 0;
-                spin_unlock_irq(&mddev->write_lock);
 
                 if (mddev->flags)
                         md_update_sb(mddev, 0);