[PATCH] md: always honour md bitmap being read from disk

The code currently will ignore the bitmap if the array seem to be in-sync.
This is wrong if the array is degraded, and probably wrong anyway.  If the
bitmap says some chunks are not in in-sync, and the superblock says everything
IS in sync, then something is clearly wrong, and it is safer to trust the
bitmap.
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/bitmap.c

@@ -818,8 +818,7 @@ int bitmap_unplug(struct bitmap *bitmap)
 	return 0;
 }
 
-static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset,
-	unsigned long sectors, int in_sync);
+static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset);
 /* * bitmap_init_from_disk -- called at bitmap_create time to initialize
  * the in-memory bitmap from the on-disk bitmap -- also, sets up the
  * memory mapping of the bitmap file
@@ -828,7 +827,7 @@ static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset,
  *   previously kicked from the array, we mark all the bits as
  *   1's in order to cause a full resync.
  */
-static int bitmap_init_from_disk(struct bitmap *bitmap, int in_sync)
+static int bitmap_init_from_disk(struct bitmap *bitmap)
 {
 	unsigned long i, chunks, index, oldindex, bit;
 	struct page *page = NULL, *oldpage = NULL;
@@ -929,8 +928,7 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, int in_sync)
 		}
 		if (test_bit(bit, page_address(page))) {
 			/* if the disk bit is set, set the memory bit */
-			bitmap_set_memory_bits(bitmap,
-					i << CHUNK_BLOCK_SHIFT(bitmap), 1, in_sync);
+			bitmap_set_memory_bits(bitmap, i << CHUNK_BLOCK_SHIFT(bitmap));
 			bit_cnt++;
 		}
 	}
@@ -1426,35 +1424,30 @@ void bitmap_close_sync(struct bitmap *bitmap)
 	}
 }
 
-static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset,
-				   unsigned long sectors, int in_sync)
+static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset)
 {
 	/* For each chunk covered by any of these sectors, set the
-	 * counter to 1 and set resync_needed unless in_sync.  They should all
+	 * counter to 1 and set resync_needed.  They should all
 	 * be 0 at this point
 	 */
-	while (sectors) {
-		int secs;
-		bitmap_counter_t *bmc;
-		spin_lock_irq(&bitmap->lock);
-		bmc = bitmap_get_counter(bitmap, offset, &secs, 1);
-		if (!bmc) {
-			spin_unlock_irq(&bitmap->lock);
-			return;
-		}
-		if (! *bmc) {
-			struct page *page;
-			*bmc = 1 | (in_sync? 0 : NEEDED_MASK);
-			bitmap_count_page(bitmap, offset, 1);
-			page = filemap_get_page(bitmap, offset >> CHUNK_BLOCK_SHIFT(bitmap));
-			set_page_attr(bitmap, page, BITMAP_PAGE_CLEAN);
-		}
+
+	int secs;
+	bitmap_counter_t *bmc;
+	spin_lock_irq(&bitmap->lock);
+	bmc = bitmap_get_counter(bitmap, offset, &secs, 1);
+	if (!bmc) {
 		spin_unlock_irq(&bitmap->lock);
-		if (sectors > secs)
-			sectors -= secs;
-		else
-			sectors = 0;
+		return;
 	}
+	if (! *bmc) {
+		struct page *page;
+		*bmc = 1 | NEEDED_MASK;
+		bitmap_count_page(bitmap, offset, 1);
+		page = filemap_get_page(bitmap, offset >> CHUNK_BLOCK_SHIFT(bitmap));
+		set_page_attr(bitmap, page, BITMAP_PAGE_CLEAN);
+	}
+	spin_unlock_irq(&bitmap->lock);
+
 }
 
 /*
@@ -1565,7 +1558,8 @@ int bitmap_create(mddev_t *mddev)
 
 	/* now that we have some pages available, initialize the in-memory
 	 * bitmap from the on-disk bitmap */
-	err = bitmap_init_from_disk(bitmap, mddev->recovery_cp == MaxSector);
+	err = bitmap_init_from_disk(bitmap);
+
 	if (err)
 		return err;