drbd: describe bitmap locking for bulk operation in finer detail

Now that we do no longer in-place endian-swap the bitmap, we allow
selected bitmap operations (testing bits, sometimes even settting bits)
during some bulk operations.

This caused us to hit a lot of FIXME asserts similar to
	FIXME asender in drbd_bm_count_bits,
	bitmap locked for 'write from resync_finished' by worker
Which now is nonsense: looking at the bitmap is perfectly legal
as long as it is not being resized.

This cosmetic patch defines some flags to describe expectations in finer
detail, so the asserts in e.g. bm_change_bits_to() can be skipped if
appropriate.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index ce6f2fe..bc0bcb9 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -648,7 +648,9 @@
 		dev_info(DEV, "Writing the whole bitmap, %s\n",
 			 la_size_changed && md_moved ? "size changed and md moved" :
 			 la_size_changed ? "size changed" : "md moved");
-		err = drbd_bitmap_io(mdev, &drbd_bm_write, "size changed"); /* does drbd_resume_io() ! */
+		/* next line implicitly does drbd_suspend_io()+drbd_resume_io() */
+		err = drbd_bitmap_io(mdev, &drbd_bm_write,
+				"size changed", BM_LOCKED_MASK);
 		if (err) {
 			rv = dev_size_error;
 			goto out;
@@ -1160,12 +1162,14 @@
 	if (drbd_md_test_flag(mdev->ldev, MDF_FULL_SYNC)) {
 		dev_info(DEV, "Assuming that all blocks are out of sync "
 		     "(aka FullSync)\n");
-		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from attaching")) {
+		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write,
+			"set_n_write from attaching", BM_LOCKED_MASK)) {
 			retcode = ERR_IO_MD_DISK;
 			goto force_diskless_dec;
 		}
 	} else {
-		if (drbd_bitmap_io(mdev, &drbd_bm_read, "read from attaching") < 0) {
+		if (drbd_bitmap_io(mdev, &drbd_bm_read,
+			"read from attaching", BM_LOCKED_MASK) < 0) {
 			retcode = ERR_IO_MD_DISK;
 			goto force_diskless_dec;
 		}
@@ -1173,7 +1177,8 @@
 
 	if (cp_discovered) {
 		drbd_al_apply_to_bm(mdev);
-		if (drbd_bitmap_io(mdev, &drbd_bm_write, "crashed primary apply AL")) {
+		if (drbd_bitmap_io(mdev, &drbd_bm_write,
+			"crashed primary apply AL", BM_LOCKED_MASK)) {
 			retcode = ERR_IO_MD_DISK;
 			goto force_diskless_dec;
 		}
@@ -1925,7 +1930,8 @@
 			retcode = drbd_request_state(mdev, NS(pdsk, D_INCONSISTENT));
 			if (retcode >= SS_SUCCESS) {
 				if (drbd_bitmap_io(mdev, &drbd_bmio_set_susp_al,
-						   "set_n_write from invalidate_peer"))
+					"set_n_write from invalidate_peer",
+					BM_LOCKED_SET_ALLOWED))
 					retcode = ERR_IO_MD_DISK;
 			}
 		} else
@@ -2143,7 +2149,8 @@
 	drbd_uuid_new_current(mdev); /* New current, previous to UI_BITMAP */
 
 	if (args.clear_bm) {
-		err = drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write, "clear_n_write from new_c_uuid");
+		err = drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write,
+			"clear_n_write from new_c_uuid", BM_LOCKED_MASK);
 		if (err) {
 			dev_err(DEV, "Writing bitmap failed with %d\n",err);
 			retcode = ERR_IO_MD_DISK;