Allow setting start point for requested check/repair

This makes it possible to just resync a small part of an array.
e.g. if a drive reports that it has questionable sectors,
a 'repair' of just the region covering those sectors will
cause them to be read and, if there is an error, re-written
with correct data.

Signed-off-by: Neil Brown <neilb@suse.de>

2 files changed, 44 insertions, 5 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 2580ac1b9b0f..261322722c19 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -278,6 +278,7 @@ static mddev_t * mddev_find(dev_t unit)
         init_waitqueue_head(&new->sb_wait);
         init_waitqueue_head(&new->recovery_wait);
         new->reshape_position = MaxSector;
+        new->resync_min = 0;
         new->resync_max = MaxSector;
         new->level = LEVEL_NONE;
 
@@ -3075,6 +3076,36 @@ sync_completed_show(mddev_t *mddev, char *page)
 static struct md_sysfs_entry md_sync_completed = __ATTR_RO(sync_completed);
 
 static ssize_t
+min_sync_show(mddev_t *mddev, char *page)
+{
+        return sprintf(page, "%llu\n",
+                       (unsigned long long)mddev->resync_min);
+}
+static ssize_t
+min_sync_store(mddev_t *mddev, const char *buf, size_t len)
+{
+        unsigned long long min;
+        if (strict_strtoull(buf, 10, &min))
+                return -EINVAL;
+        if (min > mddev->resync_max)
+                return -EINVAL;
+        if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
+                return -EBUSY;
+
+        /* Must be a multiple of chunk_size */
+        if (mddev->chunk_size) {
+                if (min & (sector_t)((mddev->chunk_size>>9)-1))
+                        return -EINVAL;
+        }
+        mddev->resync_min = min;
+
+        return len;
+}
+
+static struct md_sysfs_entry md_min_sync =
+__ATTR(sync_min, S_IRUGO|S_IWUSR, min_sync_show, min_sync_store);
+
+static ssize_t
 max_sync_show(mddev_t *mddev, char *page)
 {
         if (mddev->resync_max == MaxSector)
@@ -3089,9 +3120,10 @@ max_sync_store(mddev_t *mddev, const char *buf, size_t len)
         if (strncmp(buf, "max", 3) == 0)
                 mddev->resync_max = MaxSector;
         else {
-                char *ep;
-                unsigned long long max = simple_strtoull(buf, &ep, 10);
-                if (ep == buf || (*ep != 0 && *ep != '\n'))
+                unsigned long long max;
+                if (strict_strtoull(buf, 10, &max))
+                        return -EINVAL;
+                if (max < mddev->resync_min)
                         return -EINVAL;
                 if (max < mddev->resync_max &&
                     test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
@@ -3222,6 +3254,7 @@ static struct attribute *md_redundancy_attrs[] = {
         &md_sync_speed.attr,
         &md_sync_force_parallel.attr,
         &md_sync_completed.attr,
+        &md_min_sync.attr,
         &md_max_sync.attr,
         &md_suspend_lo.attr,
         &md_suspend_hi.attr,
@@ -3777,6 +3810,7 @@ static int do_md_stop(mddev_t * mddev, int mode)
                 mddev->size = 0;
                 mddev->raid_disks = 0;
                 mddev->recovery_cp = 0;
+                mddev->resync_min = 0;
                 mddev->resync_max = MaxSector;
                 mddev->reshape_position = MaxSector;
                 mddev->external = 0;
@@ -5625,9 +5659,11 @@ void md_do_sync(mddev_t *mddev)
                 max_sectors = mddev->resync_max_sectors;
                 mddev->resync_mismatches = 0;
                 /* we don't use the checkpoint if there's a bitmap */
-                if (!mddev->bitmap &&
-                    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+                if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+                        j = mddev->resync_min;
+                else if (!mddev->bitmap)
                         j = mddev->recovery_cp;
+
         } else if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
                 max_sectors = mddev->size << 1;
         else {
@@ -5796,6 +5832,7 @@ void md_do_sync(mddev_t *mddev)
 
  skip:
         mddev->curr_resync = 0;
+        mddev->resync_min = 0;
         mddev->resync_max = MaxSector;
         sysfs_notify(&mddev->kobj, NULL, "sync_completed");
         wake_up(&resync_wait);
diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 3dea9f545c8f..780e0613e6d5 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -227,6 +227,8 @@ struct mddev_s
         atomic_t                        recovery_active; /* blocks scheduled, but not written */
         wait_queue_head_t               recovery_wait;
         sector_t                        recovery_cp;
+        sector_t                        resync_min;     /* user requested sync
+                                                         * starts here */
         sector_t                        resync_max;     /* resync should pause
                                                          * when it gets here */