md: raid5: check stripe cache is large enough in start_reshape

In reshape cases that do not change the number of devices,
start_reshape is called without first calling check_reshape.

Currently, the check that the stripe_cache is large enough is
only done in check_reshape.  It should be in start_reshape too.

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

1 files changed, 27 insertions, 17 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 009344156751..b84766e347c3 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4845,6 +4845,29 @@ static int raid5_resize(mddev_t *mddev, sector_t sectors)
         return 0;
 }
 
+static int check_stripe_cache(mddev_t *mddev)
+{
+        /* Can only proceed if there are plenty of stripe_heads.
+         * We need a minimum of one full stripe,, and for sensible progress
+         * it is best to have about 4 times that.
+         * If we require 4 times, then the default 256 4K stripe_heads will
+         * allow for chunk sizes up to 256K, which is probably OK.
+         * If the chunk size is greater, user-space should request more
+         * stripe_heads first.
+         */
+        raid5_conf_t *conf = mddev->private;
+        if (((mddev->chunk_sectors << 9) / STRIPE_SIZE) * 4
+            > conf->max_nr_stripes ||
+            ((mddev->new_chunk_sectors << 9) / STRIPE_SIZE) * 4
+            > conf->max_nr_stripes) {
+                printk(KERN_WARNING "raid5: reshape: not enough stripes.  Needed %lu\n",
+                       ((max(mddev->chunk_sectors, mddev->new_chunk_sectors) << 9)
+                        / STRIPE_SIZE)*4);
+                return 0;
+        }
+        return 1;
+}
+
 static int raid5_check_reshape(mddev_t *mddev)
 {
         raid5_conf_t *conf = mddev->private;
@@ -4871,24 +4894,8 @@ static int raid5_check_reshape(mddev_t *mddev)
                         return -EINVAL;
         }
 
-        /* Can only proceed if there are plenty of stripe_heads.
-         * We need a minimum of one full stripe,, and for sensible progress
-         * it is best to have about 4 times that.
-         * If we require 4 times, then the default 256 4K stripe_heads will
-         * allow for chunk sizes up to 256K, which is probably OK.
-         * If the chunk size is greater, user-space should request more
-         * stripe_heads first.
-         */
-        if (((mddev->chunk_sectors << 9) / STRIPE_SIZE) * 4
-                > conf->max_nr_stripes ||
-            ((mddev->new_chunk_sectors << 9) / STRIPE_SIZE) * 4
-                > conf->max_nr_stripes) {
-                printk(KERN_WARNING "raid5: reshape: not enough stripes.  Needed %lu\n",
-                       (max(mddev->chunk_sectors << 9,
-                        mddev->new_chunk_sectors << 9)
-                        / STRIPE_SIZE)*4);
+        if (!check_stripe_cache(mddev))
                 return -ENOSPC;
-        }
 
         return resize_stripes(conf, conf->raid_disks + mddev->delta_disks);
 }
@@ -4904,6 +4911,9 @@ static int raid5_start_reshape(mddev_t *mddev)
         if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
                 return -EBUSY;
 
+        if (!check_stripe_cache(mddev))
+                return -ENOSPC;
+
         list_for_each_entry(rdev, &mddev->disks, same_set)
                 if (rdev->raid_disk < 0 &&
                     !test_bit(Faulty, &rdev->flags))