As part of the struct page cleanups underway, we want to remove as much
usage of page->mapping and page->index as possible, as frequently they
are known from context - as they are here in the md bitmap code.

Signed-off-by: Kent Overstreet <redacted>
---
  drivers/md/md-bitmap.c | 44 ++++++++++++++++++++----------------------
  1 file changed, 21 insertions(+), 23 deletions(-)

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index e29c6298ef..dcdb4597c5 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c

@@ -165,10 +165,8 @@ static int read_sb_page(struct mddev *mddev, loff_t offset,
  
  		if (sync_page_io(rdev, target,
  				 roundup(size, bdev_logical_block_size(rdev->bdev)),
-				 page, REQ_OP_READ, 0, true)) {
-			page->index = index;
+				 page, REQ_OP_READ, 0, true))
  			return 0;
-		}
  	}
  	return -EIO;
  }

@@ -209,7 +207,8 @@ static struct md_rdev *next_active_rdev(struct md_rdev *rdev, struct mddev *mdde
  	return NULL;
  }
  
-static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
+static int write_sb_page(struct bitmap *bitmap, struct page *page,
+			 unsigned long index, int wait)
  {
  	struct md_rdev *rdev;
  	struct block_device *bdev;

@@ -224,7 +223,7 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
  
  		bdev = (rdev->meta_bdev) ? rdev->meta_bdev : rdev->bdev;
  
-		if (page->index == store->file_pages-1) {
+		if (index == store->file_pages-1) {
  			int last_page_size = store->bytes & (PAGE_SIZE-1);
  			if (last_page_size == 0)
  				last_page_size = PAGE_SIZE;

@@ -236,8 +235,7 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
  		 */
  		if (mddev->external) {
  			/* Bitmap could be anywhere. */
-			if (rdev->sb_start + offset + (page->index
-						       * (PAGE_SIZE/512))
+			if (rdev->sb_start + offset + index * PAGE_SECTORS
  			    > rdev->data_offset
  			    &&
  			    rdev->sb_start + offset

@@ -247,7 +245,7 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
  		} else if (offset < 0) {
  			/* DATA  BITMAP METADATA  */
  			if (offset
-			    + (long)(page->index * (PAGE_SIZE/512))
+			    + (long)(index * PAGE_SECTORS)
  			    + size/512 > 0)
  				/* bitmap runs in to metadata */
  				goto bad_alignment;

@@ -259,7 +257,7 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
  			/* METADATA BITMAP DATA */
  			if (rdev->sb_start
  			    + offset
-			    + page->index*(PAGE_SIZE/512) + size/512
+			    + index * PAGE_SECTORS + size/512
  			    > rdev->data_offset)
  				/* bitmap runs in to data */
  				goto bad_alignment;

@@ -268,7 +266,7 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
  		}
  		md_super_write(mddev, rdev,
  			       rdev->sb_start + offset
-			       + page->index * (PAGE_SIZE/512),
+			       + index * PAGE_SECTORS,
  			       size,
  			       page);
  	}

@@ -285,12 +283,13 @@ static void md_bitmap_file_kick(struct bitmap *bitmap);
  /*
   * write out a page to a file
   */
-static void write_page(struct bitmap *bitmap, struct page *page, int wait)
+static void write_page(struct bitmap *bitmap, struct page *page,
+		       unsigned long index, int wait)
  {
  	struct buffer_head *bh;
  
  	if (bitmap->storage.file == NULL) {
-		switch (write_sb_page(bitmap, page, wait)) {
+		switch (write_sb_page(bitmap, page, index, wait)) {
  		case -EINVAL:
  			set_bit(BITMAP_WRITE_ERROR, &bitmap->flags);
  		}

@@ -399,7 +398,6 @@ static int read_page(struct file *file, unsigned long index,
  		blk_cur++;
  		bh = bh->b_this_page;
  	}
-	page->index = index;
  
  	wait_event(bitmap->write_wait,
  		   atomic_read(&bitmap->pending_writes)==0);

@@ -472,7 +470,7 @@ void md_bitmap_update_sb(struct bitmap *bitmap)
  	sb->sectors_reserved = cpu_to_le32(bitmap->mddev->
  					   bitmap_info.space);
  	kunmap_atomic(sb);
-	write_page(bitmap, bitmap->storage.sb_page, 1);
+	write_page(bitmap, bitmap->storage.sb_page, 0, 1);
  }
  EXPORT_SYMBOL(md_bitmap_update_sb);
  

@@ -524,7 +522,6 @@ static int md_bitmap_new_disk_sb(struct bitmap *bitmap)
  	bitmap->storage.sb_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
  	if (bitmap->storage.sb_page == NULL)
  		return -ENOMEM;
-	bitmap->storage.sb_page->index = 0;
  
  	sb = kmap_atomic(bitmap->storage.sb_page);
  

@@ -802,7 +799,6 @@ static int md_bitmap_storage_alloc(struct bitmap_storage *store,
  	if (store->sb_page) {
  		store->filemap[0] = store->sb_page;
  		pnum = 1;
-		store->sb_page->index = offset;