drbd: fix NULL pointer dereference on 4k hard sect size

we still don't support 4k 'physical' sectors 'natively',
but use a read-modify-write workaround.
And we even tried to use the extra page before we allocated it :(

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 19 insertions, 19 deletions

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 4df3b40b1057..d53d36cd0e57 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -941,6 +941,25 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
 
         drbd_md_set_sector_offsets(mdev, nbc);
 
+        /* allocate a second IO page if logical_block_size != 512 */
+        logical_block_size = bdev_logical_block_size(nbc->md_bdev);
+        if (logical_block_size == 0)
+                logical_block_size = MD_SECTOR_SIZE;
+
+        if (logical_block_size != MD_SECTOR_SIZE) {
+                if (!mdev->md_io_tmpp) {
+                        struct page *page = alloc_page(GFP_NOIO);
+                        if (!page)
+                                goto force_diskless_dec;
+
+                        dev_warn(DEV, "Meta data's bdev logical_block_size = %d != %d\n",
+                             logical_block_size, MD_SECTOR_SIZE);
+                        dev_warn(DEV, "Workaround engaged (has performance impact).\n");
+
+                        mdev->md_io_tmpp = page;
+                }
+        }
+
         if (!mdev->bitmap) {
                 if (drbd_bm_init(mdev)) {
                         retcode = ERR_NOMEM;
@@ -980,25 +999,6 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
                 goto force_diskless_dec;
         }
 
-        /* allocate a second IO page if logical_block_size != 512 */
-        logical_block_size = bdev_logical_block_size(nbc->md_bdev);
-        if (logical_block_size == 0)
-                logical_block_size = MD_SECTOR_SIZE;
-
-        if (logical_block_size != MD_SECTOR_SIZE) {
-                if (!mdev->md_io_tmpp) {
-                        struct page *page = alloc_page(GFP_NOIO);
-                        if (!page)
-                                goto force_diskless_dec;
-
-                        dev_warn(DEV, "Meta data's bdev logical_block_size = %d != %d\n",
-                             logical_block_size, MD_SECTOR_SIZE);
-                        dev_warn(DEV, "Workaround engaged (has performance impact).\n");
-
-                        mdev->md_io_tmpp = page;
-                }
-        }
-
         /* Reset the "barriers don't work" bits here, then force meta data to
          * be written, to ensure we determine if barriers are supported. */
         if (nbc->dc.no_md_flush)