2 files changed, 118 insertions, 102 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 17e2b47..c7784a9 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -883,6 +883,8 @@ void bitmap_unplug(struct bitmap *bitmap)
 		need_write = test_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
 		clear_page_attr(bitmap, page, BITMAP_PAGE_DIRTY);
 		clear_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
+		if (dirty || need_write)
+			clear_page_attr(bitmap, page, BITMAP_PAGE_PENDING);
 		if (dirty)
 			wait = 1;
 		spin_unlock_irqrestore(&bitmap->lock, flags);
@@ -1086,6 +1088,17 @@ static void bitmap_count_page(struct bitmap *bitmap, sector_t offset, int inc)
 	bitmap->bp[page].count += inc;
 	bitmap_checkfree(bitmap, page);
 }
+
+static void bitmap_set_pending(struct bitmap *bitmap, sector_t offset)
+{
+	sector_t chunk = offset >> bitmap->chunkshift;
+	unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
+	struct bitmap_page *bp = &bitmap->bp[page];
+
+	if (!bp->pending)
+		bp->pending = 1;
+}
+
 static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
 					    sector_t offset, sector_t *blocks,
 					    int create);
@@ -1099,8 +1112,8 @@ void bitmap_daemon_work(struct mddev *mddev)
 {
 	struct bitmap *bitmap;
 	unsigned long j;
+	unsigned long nextpage;
 	unsigned long flags;
-	struct page *page = NULL, *lastpage = NULL;
 	sector_t blocks;
 	void *paddr;
 
@@ -1124,114 +1137,120 @@ void bitmap_daemon_work(struct mddev *mddev)
 	}
 	bitmap->allclean = 1;
 
+	/* Any file-page which is PENDING now needs to be written.
+	 * So set NEEDWRITE now, then after we make any last-minute changes
+	 * we will write it.
+	 */
 	spin_lock_irqsave(&bitmap->lock, flags);
+	if (!bitmap->filemap)
+		/* error or shutdown */
+		goto out;
+
+	for (j = 0; j < bitmap->file_pages; j++)
+		if (test_page_attr(bitmap, bitmap->filemap[j],
+				   BITMAP_PAGE_PENDING)) {
+			set_page_attr(bitmap, bitmap->filemap[j],
+				      BITMAP_PAGE_NEEDWRITE);
+			clear_page_attr(bitmap, bitmap->filemap[j],
+					BITMAP_PAGE_PENDING);
+		}
+
+	if (bitmap->need_sync &&
+	    mddev->bitmap_info.external == 0) {
+		/* Arrange for superblock update as well as
+		 * other changes */
+		bitmap_super_t *sb;
+		bitmap->need_sync = 0;
+		sb = kmap_atomic(bitmap->sb_page);
+		sb->events_cleared =
+			cpu_to_le64(bitmap->events_cleared);
+		kunmap_atomic(sb);
+		set_page_attr(bitmap, bitmap->sb_page, BITMAP_PAGE_NEEDWRITE);
+	}
+	/* Now look at the bitmap counters and if any are '2' or '1',
+	 * decrement and handle accordingly.
+	 */
+	nextpage = 0;
 	for (j = 0; j < bitmap->chunks; j++) {
 		bitmap_counter_t *bmc;
-		if (!bitmap->filemap)
-			/* error or shutdown */
-			break;
 
-		page = filemap_get_page(bitmap, j);
-
-		if (page != lastpage) {
-			/* skip this page unless it's marked as needing cleaning */
-			if (!test_page_attr(bitmap, page, BITMAP_PAGE_PENDING)) {
-				int need_write = test_page_attr(bitmap, page,
-								BITMAP_PAGE_NEEDWRITE);
-				if (need_write)
-					clear_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
-
-				spin_unlock_irqrestore(&bitmap->lock, flags);
-				if (need_write)
-					write_page(bitmap, page, 0);
-				spin_lock_irqsave(&bitmap->lock, flags);
-				j |= (PAGE_BITS - 1);
+		if (j == nextpage) {
+			nextpage += PAGE_COUNTER_RATIO;
+			if (!bitmap->bp[j >> PAGE_COUNTER_SHIFT].pending) {
+				j |= PAGE_COUNTER_MASK;
 				continue;
 			}
-
-			/* grab the new page, sync and release the old */
-			if (lastpage != NULL) {
-				if (test_page_attr(bitmap, lastpage,
-						   BITMAP_PAGE_NEEDWRITE)) {
-					clear_page_attr(bitmap, lastpage,
-							BITMAP_PAGE_NEEDWRITE);
-					spin_unlock_irqrestore(&bitmap->lock, flags);
-					write_page(bitmap, lastpage, 0);
-				} else {
-					set_page_attr(bitmap, lastpage,
-						      BITMAP_PAGE_NEEDWRITE);
-					bitmap->allclean = 0;
-					spin_unlock_irqrestore(&bitmap->lock, flags);
-				}
-			} else
-				spin_unlock_irqrestore(&bitmap->lock, flags);
-			lastpage = page;
-
-			/* We are possibly going to clear some bits, so make
-			 * sure that events_cleared is up-to-date.
-			 */
-			if (bitmap->need_sync &&
-			    mddev->bitmap_info.external == 0) {
-				bitmap_super_t *sb;
-				bitmap->need_sync = 0;
-				sb = kmap_atomic(bitmap->sb_page);
-				sb->events_cleared =
-					cpu_to_le64(bitmap->events_cleared);
-				kunmap_atomic(sb);
-				write_page(bitmap, bitmap->sb_page, 1);
-			}
-			spin_lock_irqsave(&bitmap->lock, flags);
-			if (!bitmap->need_sync)
-				clear_page_attr(bitmap, page, BITMAP_PAGE_PENDING);
-			else
-				bitmap->allclean = 0;
+			bitmap->bp[j >> PAGE_COUNTER_SHIFT].pending = 0;
 		}
 		bmc = bitmap_get_counter(bitmap,
 					 (sector_t)j << bitmap->chunkshift,
 					 &blocks, 0);
-		if (!bmc)
+
+		if (!bmc) {
 			j |= PAGE_COUNTER_MASK;
-		else if (*bmc) {
-			if (*bmc == 1 && !bitmap->need_sync) {
-				/* we can clear the bit */
-				*bmc = 0;
-				bitmap_count_page(bitmap,
-						  (sector_t)j << bitmap->chunkshift,
-						  -1);
-
-				/* clear the bit */
-				paddr = kmap_atomic(page);
-				if (bitmap->flags & BITMAP_HOSTENDIAN)
-					clear_bit(file_page_offset(bitmap, j),
-						  paddr);
-				else
-					__clear_bit_le(
-						file_page_offset(bitmap,
-								 j),
-						paddr);
-				kunmap_atomic(paddr);
-			} else if (*bmc <= 2) {
-				*bmc = 1; /* maybe clear the bit next time */
-				set_page_attr(bitmap, page, BITMAP_PAGE_PENDING);
+			continue;
+		}
+		if (*bmc == 1 && !bitmap->need_sync) {
+			/* We can clear the bit */
+			struct page *page;
+			*bmc = 0;
+			bitmap_count_page(
+				bitmap,
+				(sector_t)j << bitmap->chunkshift,
+				-1);
+
+			page = filemap_get_page(bitmap, j);
+			paddr = kmap_atomic(page);
+			if (bitmap->flags & BITMAP_HOSTENDIAN)
+				clear_bit(file_page_offset(bitmap, j),
+					  paddr);
+			else
+				__clear_bit_le(file_page_offset(bitmap, j),
+					       paddr);
+			kunmap_atomic(paddr);
+			if (!test_page_attr(bitmap, page,
+					    BITMAP_PAGE_NEEDWRITE)) {
+				set_page_attr(bitmap, page,
+					      BITMAP_PAGE_PENDING);
 				bitmap->allclean = 0;
 			}
+		} else if (*bmc && *bmc <= 2) {
+			*bmc = 1;
+			bitmap_set_pending(
+				bitmap,
+				(sector_t)j << bitmap->chunkshift);
+			bitmap->allclean = 0;
 		}
 	}
-	spin_unlock_irqrestore(&bitmap->lock, flags);
 
-	/* now sync the final page */
-	if (lastpage != NULL) {
-		spin_lock_irqsave(&bitmap->lock, flags);
-		if (test_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE)) {
-			clear_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
-			spin_unlock_irqrestore(&bitmap->lock, flags);
-			write_page(bitmap, lastpage, 0);
-		} else {
-			set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
-			bitmap->allclean = 0;
+	/* Now start writeout on any page in NEEDWRITE that isn't DIRTY.
+	 * DIRTY pages need to be written by bitmap_unplug so it can wait
+	 * for them.
+	 * If we find any DIRTY page we stop there and let bitmap_unplug
+	 * handle all the rest.  This is important in the case where
+	 * the first blocking holds the superblock and it has been updated.
+	 * We mustn't write any other blocks before the superblock.
+	 */
+	for (j = 0; j < bitmap->file_pages; j++) {
+		struct page *page = bitmap->filemap[j];
+
+		if (test_page_attr(bitmap, page,
+				   BITMAP_PAGE_DIRTY))
+			/* bitmap_unplug will handle the rest */
+			break;
+		if (test_page_attr(bitmap, page,
+				   BITMAP_PAGE_NEEDWRITE)) {
+			clear_page_attr(bitmap, page,
+					BITMAP_PAGE_NEEDWRITE);
 			spin_unlock_irqrestore(&bitmap->lock, flags);
+			write_page(bitmap, page, 0);
+			spin_lock_irqsave(&bitmap->lock, flags);
+			if (!bitmap->filemap)
+				break;
 		}
 	}
+out:
+	spin_unlock_irqrestore(&bitmap->lock, flags);
 
  done:
 	if (bitmap->allclean == 0)
@@ -1386,11 +1405,7 @@ void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long secto
 
 		(*bmc)--;
 		if (*bmc <= 2) {
-			set_page_attr(bitmap,
-				      filemap_get_page(
-					      bitmap,
-					      offset >> bitmap->chunkshift),
-				      BITMAP_PAGE_PENDING);
+			bitmap_set_pending(bitmap, offset);
 			bitmap->allclean = 0;
 		}
 		spin_unlock_irqrestore(&bitmap->lock, flags);
@@ -1476,9 +1491,7 @@ void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, i
 			*bmc |= NEEDED_MASK;
 		else {
 			if (*bmc <= 2) {
-				set_page_attr(bitmap,
-					      filemap_get_page(bitmap, offset >> bitmap->chunkshift),
-					      BITMAP_PAGE_PENDING);
+				bitmap_set_pending(bitmap, offset);
 				bitmap->allclean = 0;
 			}
 		}
@@ -1551,11 +1564,9 @@ static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int n
 		return;
 	}
 	if (!*bmc) {
-		struct page *page;
 		*bmc = 2 | (needed ? NEEDED_MASK : 0);
 		bitmap_count_page(bitmap, offset, 1);
-		page = filemap_get_page(bitmap, offset >> bitmap->chunkshift);
-		set_page_attr(bitmap, page, BITMAP_PAGE_PENDING);
+		bitmap_set_pending(bitmap, offset);
 		bitmap->allclean = 0;
 	}
 	spin_unlock_irq(&bitmap->lock);
diff --git a/drivers/md/bitmap.h b/drivers/md/bitmap.h
index b44b0aba..79e1798 100644
--- a/drivers/md/bitmap.h
+++ b/drivers/md/bitmap.h
@@ -160,9 +160,14 @@ struct bitmap_page {
 	 */
 	unsigned int hijacked:1;
 	/*
+	 * If any counter in this page is '1' or '2' - and so could be
+	 * cleared then that page is marked as 'pending'
+	 */
+	unsigned int pending:1;
+	/*
 	 * count of dirty bits on the page
 	 */
-	unsigned int  count:31;
+	unsigned int  count:30;
 };
 
 /* the main bitmap structure - one per mddev */