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>

1 files changed, 32 insertions, 4 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 0a9059eb94db..267d9897ca8c 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -855,6 +855,32 @@ enum {
 
 struct drbd_bitmap; /* opaque for drbd_conf */
 
+/* definition of bits in bm_flags to be used in drbd_bm_lock
+ * and drbd_bitmap_io and friends. */
+enum bm_flag {
+        /* do we need to kfree, or vfree bm_pages? */
+        BM_P_VMALLOCED = 0x10000, /* internal use only, will be masked out */
+
+        /* currently locked for bulk operation */
+        BM_LOCKED_MASK = 0x7,
+
+        /* in detail, that is: */
+        BM_DONT_CLEAR = 0x1,
+        BM_DONT_SET   = 0x2,
+        BM_DONT_TEST  = 0x4,
+
+        /* (test bit, count bit) allowed (common case) */
+        BM_LOCKED_TEST_ALLOWED = 0x3,
+
+        /* testing bits, as well as setting new bits allowed, but clearing bits
+         * would be unexpected.  Used during bitmap receive.  Setting new bits
+         * requires sending of "out-of-sync" information, though. */
+        BM_LOCKED_SET_ALLOWED = 0x1,
+
+        /* clear is not expected while bitmap is locked for bulk operation */
+};
+
+
 /* TODO sort members for performance
  * MAYBE group them further */
 
@@ -920,6 +946,7 @@ struct drbd_md_io {
 struct bm_io_work {
         struct drbd_work w;
         char *why;
+        enum bm_flag flags;
         int (*io_fn)(struct drbd_conf *mdev);
         void (*done)(struct drbd_conf *mdev, int rv);
 };
@@ -1242,7 +1269,6 @@ extern void drbd_free_bc(struct drbd_backing_dev *ldev);
 extern void drbd_mdev_cleanup(struct drbd_conf *mdev);
 void drbd_print_uuids(struct drbd_conf *mdev, const char *text);
 
-/* drbd_meta-data.c (still in drbd_main.c) */
 extern void drbd_md_sync(struct drbd_conf *mdev);
 extern int  drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev);
 extern void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local);
@@ -1263,10 +1289,12 @@ extern void drbd_md_mark_dirty_(struct drbd_conf *mdev,
 extern void drbd_queue_bitmap_io(struct drbd_conf *mdev,
                                  int (*io_fn)(struct drbd_conf *),
                                  void (*done)(struct drbd_conf *, int),
-                                 char *why);
+                                 char *why, enum bm_flag flags);
+extern int drbd_bitmap_io(struct drbd_conf *mdev,
+                int (*io_fn)(struct drbd_conf *),
+                char *why, enum bm_flag flags);
 extern int drbd_bmio_set_n_write(struct drbd_conf *mdev);
 extern int drbd_bmio_clear_n_write(struct drbd_conf *mdev);
-extern int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *), char *why);
 extern void drbd_go_diskless(struct drbd_conf *mdev);
 extern void drbd_ldev_destroy(struct drbd_conf *mdev);
 
@@ -1452,7 +1480,7 @@ extern void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset,
 extern void drbd_bm_get_lel(struct drbd_conf *mdev, size_t offset,
                 size_t number, unsigned long *buffer);
 
-extern void drbd_bm_lock(struct drbd_conf *mdev, char *why);
+extern void drbd_bm_lock(struct drbd_conf *mdev, char *why, enum bm_flag flags);
 extern void drbd_bm_unlock(struct drbd_conf *mdev);
 /* drbd_main.c */