diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2b777e5..5939a47 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1407,149 +1407,42 @@
  * Delayed allocation stuff
  */
 
-static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd);
-
-/*
- * mpage_da_submit_io - walks through extent of pages and try to write
- * them with writepage() call back
- *
- * @mpd->inode: inode
- * @mpd->first_page: first page of the extent
- * @mpd->next_page: page after the last page of the extent
- *
- * By the time mpage_da_submit_io() is called we expect all blocks
- * to be allocated. this may be wrong if allocation failed.
- *
- * As pages are already locked by write_cache_pages(), we can't use it
- */
-static int mpage_da_submit_io(struct mpage_da_data *mpd,
-			      struct ext4_map_blocks *map)
-{
-	struct pagevec pvec;
-	unsigned long index, end;
-	int ret = 0, err, nr_pages, i;
-	struct inode *inode = mpd->inode;
-	struct address_space *mapping = inode->i_mapping;
-	loff_t size = i_size_read(inode);
-	unsigned int len, block_start;
-	struct buffer_head *bh, *page_bufs = NULL;
-	sector_t pblock = 0, cur_logical = 0;
-	struct ext4_io_submit io_submit;
-
-	BUG_ON(mpd->next_page <= mpd->first_page);
-	ext4_io_submit_init(&io_submit, mpd->wbc);
-	io_submit.io_end = ext4_init_io_end(inode, GFP_NOFS);
-	if (!io_submit.io_end) {
-		ext4_da_block_invalidatepages(mpd);
-		return -ENOMEM;
-	}
+struct mpage_da_data {
+	struct inode *inode;
+	struct writeback_control *wbc;
+	pgoff_t first_page;	/* The first page to write */
+	pgoff_t next_page;	/* Current page to examine */
+	pgoff_t last_page;	/* Last page to examine */
 	/*
-	 * We need to start from the first_page to the next_page - 1
-	 * to make sure we also write the mapped dirty buffer_heads.
-	 * If we look at mpd->b_blocknr we would only be looking
-	 * at the currently mapped buffer_heads.
+	 * Extent to map - this can be after first_page because that can be
+	 * fully mapped. We somewhat abuse m_flags to store whether the extent
+	 * is delalloc or unwritten.
 	 */
-	index = mpd->first_page;
-	end = mpd->next_page - 1;
+	struct ext4_map_blocks map;
+	struct ext4_io_submit io_submit;	/* IO submission data */
+};
 
-	pagevec_init(&pvec, 0);
-	while (index <= end) {
-		nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
-		if (nr_pages == 0)
-			break;
-		for (i = 0; i < nr_pages; i++) {
-			int skip_page = 0;
-			struct page *page = pvec.pages[i];
-
-			index = page->index;
-			if (index > end)
-				break;
-
-			if (index == size >> PAGE_CACHE_SHIFT)
-				len = size & ~PAGE_CACHE_MASK;
-			else
-				len = PAGE_CACHE_SIZE;
-			if (map) {
-				cur_logical = index << (PAGE_CACHE_SHIFT -
-							inode->i_blkbits);
-				pblock = map->m_pblk + (cur_logical -
-							map->m_lblk);
-			}
-			index++;
-
-			BUG_ON(!PageLocked(page));
-			BUG_ON(PageWriteback(page));
-
-			bh = page_bufs = page_buffers(page);
-			block_start = 0;
-			do {
-				if (map && (cur_logical >= map->m_lblk) &&
-				    (cur_logical <= (map->m_lblk +
-						     (map->m_len - 1)))) {
-					if (buffer_delay(bh)) {
-						clear_buffer_delay(bh);
-						bh->b_blocknr = pblock;
-					}
-					if (buffer_unwritten(bh) ||
-					    buffer_mapped(bh))
-						BUG_ON(bh->b_blocknr != pblock);
-					if (map->m_flags & EXT4_MAP_UNINIT)
-						set_buffer_uninit(bh);
-					clear_buffer_unwritten(bh);
-				}
-
-				/*
-				 * skip page if block allocation undone and
-				 * block is dirty
-				 */
-				if (ext4_bh_delay_or_unwritten(NULL, bh))
-					skip_page = 1;
-				bh = bh->b_this_page;
-				block_start += bh->b_size;
-				cur_logical++;
-				pblock++;
-			} while (bh != page_bufs);
-
-			if (skip_page) {
-				unlock_page(page);
-				continue;
-			}
-
-			clear_page_dirty_for_io(page);
-			err = ext4_bio_write_page(&io_submit, page, len,
-						  mpd->wbc);
-			if (!err)
-				mpd->pages_written++;
-			/*
-			 * In error case, we have to continue because
-			 * remaining pages are still locked
-			 */
-			if (ret == 0)
-				ret = err;
-		}
-		pagevec_release(&pvec);
-	}
-	ext4_io_submit(&io_submit);
-	/* Drop io_end reference we got from init */
-	ext4_put_io_end_defer(io_submit.io_end);
-	return ret;
-}
-
-static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd)
+static void mpage_release_unused_pages(struct mpage_da_data *mpd,
+				       bool invalidate)
 {
 	int nr_pages, i;
 	pgoff_t index, end;
 	struct pagevec pvec;
 	struct inode *inode = mpd->inode;
 	struct address_space *mapping = inode->i_mapping;
-	ext4_lblk_t start, last;
+
+	/* This is necessary when next_page == 0. */
+	if (mpd->first_page >= mpd->next_page)
+		return;
 
 	index = mpd->first_page;
 	end   = mpd->next_page - 1;
-
-	start = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
-	last = end << (PAGE_CACHE_SHIFT - inode->i_blkbits);
-	ext4_es_remove_extent(inode, start, last - start + 1);
+	if (invalidate) {
+		ext4_lblk_t start, last;
+		start = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+		last = end << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+		ext4_es_remove_extent(inode, start, last - start + 1);
+	}
 
 	pagevec_init(&pvec, 0);
 	while (index <= end) {
@@ -1562,14 +1455,15 @@
 				break;
 			BUG_ON(!PageLocked(page));
 			BUG_ON(PageWriteback(page));
-			block_invalidatepage(page, 0, PAGE_CACHE_SIZE);
-			ClearPageUptodate(page);
+			if (invalidate) {
+				block_invalidatepage(page, 0, PAGE_CACHE_SIZE);
+				ClearPageUptodate(page);
+			}
 			unlock_page(page);
 		}
 		index = pvec.pages[nr_pages - 1]->index + 1;
 		pagevec_release(&pvec);
 	}
-	return;
 }
 
 static void ext4_print_free_blocks(struct inode *inode)
@@ -1598,215 +1492,6 @@
 	return;
 }
 
-/*
- * mpage_da_map_and_submit - go through given space, map them
- *       if necessary, and then submit them for I/O
- *
- * @mpd - bh describing space
- *
- * The function skips space we know is already mapped to disk blocks.
- *
- */
-static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
-{
-	int err, blks, get_blocks_flags;
-	struct ext4_map_blocks map, *mapp = NULL;
-	sector_t next = mpd->b_blocknr;
-	unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
-	loff_t disksize = EXT4_I(mpd->inode)->i_disksize;
-	handle_t *handle = NULL;
-
-	/*
-	 * If the blocks are mapped already, or we couldn't accumulate
-	 * any blocks, then proceed immediately to the submission stage.
-	 */
-	if ((mpd->b_size == 0) ||
-	    ((mpd->b_state  & (1 << BH_Mapped)) &&
-	     !(mpd->b_state & (1 << BH_Delay)) &&
-	     !(mpd->b_state & (1 << BH_Unwritten))))
-		goto submit_io;
-
-	handle = ext4_journal_current_handle();
-	BUG_ON(!handle);
-
-	/*
-	 * Call ext4_map_blocks() to allocate any delayed allocation
-	 * blocks, or to convert an uninitialized extent to be
-	 * initialized (in the case where we have written into
-	 * one or more preallocated blocks).
-	 *
-	 * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE to
-	 * indicate that we are on the delayed allocation path.  This
-	 * affects functions in many different parts of the allocation
-	 * call path.  This flag exists primarily because we don't
-	 * want to change *many* call functions, so ext4_map_blocks()
-	 * will set the EXT4_STATE_DELALLOC_RESERVED flag once the
-	 * inode's allocation semaphore is taken.
-	 *
-	 * If the blocks in questions were delalloc blocks, set
-	 * EXT4_GET_BLOCKS_DELALLOC_RESERVE so the delalloc accounting
-	 * variables are updated after the blocks have been allocated.
-	 */
-	map.m_lblk = next;
-	map.m_len = max_blocks;
-	/*
-	 * We're in delalloc path and it is possible that we're going to
-	 * need more metadata blocks than previously reserved. However
-	 * we must not fail because we're in writeback and there is
-	 * nothing we can do about it so it might result in data loss.
-	 * So use reserved blocks to allocate metadata if possible.
-	 */
-	get_blocks_flags = EXT4_GET_BLOCKS_CREATE |
-			   EXT4_GET_BLOCKS_METADATA_NOFAIL;
-	if (ext4_should_dioread_nolock(mpd->inode))
-		get_blocks_flags |= EXT4_GET_BLOCKS_IO_CREATE_EXT;
-	if (mpd->b_state & (1 << BH_Delay))
-		get_blocks_flags |= EXT4_GET_BLOCKS_DELALLOC_RESERVE;
-
-
-	blks = ext4_map_blocks(handle, mpd->inode, &map, get_blocks_flags);
-	if (blks < 0) {
-		struct super_block *sb = mpd->inode->i_sb;
-
-		err = blks;
-		/*
-		 * If get block returns EAGAIN or ENOSPC and there
-		 * appears to be free blocks we will just let
-		 * mpage_da_submit_io() unlock all of the pages.
-		 */
-		if (err == -EAGAIN)
-			goto submit_io;
-
-		if (err == -ENOSPC && ext4_count_free_clusters(sb)) {
-			mpd->retval = err;
-			goto submit_io;
-		}
-
-		/*
-		 * get block failure will cause us to loop in
-		 * writepages, because a_ops->writepage won't be able
-		 * to make progress. The page will be redirtied by
-		 * writepage and writepages will again try to write
-		 * the same.
-		 */
-		if (!(EXT4_SB(sb)->s_mount_flags & EXT4_MF_FS_ABORTED)) {
-			ext4_msg(sb, KERN_CRIT,
-				 "delayed block allocation failed for inode %lu "
-				 "at logical offset %llu with max blocks %zd "
-				 "with error %d", mpd->inode->i_ino,
-				 (unsigned long long) next,
-				 mpd->b_size >> mpd->inode->i_blkbits, err);
-			ext4_msg(sb, KERN_CRIT,
-				"This should not happen!! Data will be lost");
-			if (err == -ENOSPC)
-				ext4_print_free_blocks(mpd->inode);
-		}
-		/* invalidate all the pages */
-		ext4_da_block_invalidatepages(mpd);
-
-		/* Mark this page range as having been completed */
-		mpd->io_done = 1;
-		return;
-	}
-	BUG_ON(blks == 0);
-
-	mapp = &map;
-	if (map.m_flags & EXT4_MAP_NEW) {
-		struct block_device *bdev = mpd->inode->i_sb->s_bdev;
-		int i;
-
-		for (i = 0; i < map.m_len; i++)
-			unmap_underlying_metadata(bdev, map.m_pblk + i);
-	}
-
-	/*
-	 * Update on-disk size along with block allocation.
-	 */
-	disksize = ((loff_t) next + blks) << mpd->inode->i_blkbits;
-	if (disksize > i_size_read(mpd->inode))
-		disksize = i_size_read(mpd->inode);
-	if (disksize > EXT4_I(mpd->inode)->i_disksize) {
-		ext4_update_i_disksize(mpd->inode, disksize);
-		err = ext4_mark_inode_dirty(handle, mpd->inode);
-		if (err)
-			ext4_error(mpd->inode->i_sb,
-				   "Failed to mark inode %lu dirty",
-				   mpd->inode->i_ino);
-	}
-
-submit_io:
-	mpage_da_submit_io(mpd, mapp);
-	mpd->io_done = 1;
-}
-
-#define BH_FLAGS ((1 << BH_Uptodate) | (1 << BH_Mapped) | \
-		(1 << BH_Delay) | (1 << BH_Unwritten))
-
-/*
- * mpage_add_bh_to_extent - try to add one more block to extent of blocks
- *
- * @mpd->lbh - extent of blocks
- * @logical - logical number of the block in the file
- * @b_state - b_state of the buffer head added
- *
- * the function is used to collect contig. blocks in same state
- */
-static void mpage_add_bh_to_extent(struct mpage_da_data *mpd, sector_t logical,
-				   unsigned long b_state)
-{
-	sector_t next;
-	int blkbits = mpd->inode->i_blkbits;
-	int nrblocks = mpd->b_size >> blkbits;
-
-	/*
-	 * XXX Don't go larger than mballoc is willing to allocate
-	 * This is a stopgap solution.  We eventually need to fold
-	 * mpage_da_submit_io() into this function and then call
-	 * ext4_map_blocks() multiple times in a loop
-	 */
-	if (nrblocks >= (8*1024*1024 >> blkbits))
-		goto flush_it;
-
-	/* check if the reserved journal credits might overflow */
-	if (!ext4_test_inode_flag(mpd->inode, EXT4_INODE_EXTENTS)) {
-		if (nrblocks >= EXT4_MAX_TRANS_DATA) {
-			/*
-			 * With non-extent format we are limited by the journal
-			 * credit available.  Total credit needed to insert
-			 * nrblocks contiguous blocks is dependent on the
-			 * nrblocks.  So limit nrblocks.
-			 */
-			goto flush_it;
-		}
-	}
-	/*
-	 * First block in the extent
-	 */
-	if (mpd->b_size == 0) {
-		mpd->b_blocknr = logical;
-		mpd->b_size = 1 << blkbits;
-		mpd->b_state = b_state & BH_FLAGS;
-		return;
-	}
-
-	next = mpd->b_blocknr + nrblocks;
-	/*
-	 * Can we merge the block to our big extent?
-	 */
-	if (logical == next && (b_state & BH_FLAGS) == mpd->b_state) {
-		mpd->b_size += 1 << blkbits;
-		return;
-	}
-
-flush_it:
-	/*
-	 * We couldn't merge the block to our extent, so we
-	 * need to flush current  extent and start new one
-	 */
-	mpage_da_map_and_submit(mpd);
-	return;
-}
-
 static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh)
 {
 	return (buffer_delay(bh) || buffer_unwritten(bh)) && buffer_dirty(bh);
@@ -2204,6 +1889,8 @@
 	return ret;
 }
 
+#define BH_FLAGS ((1 << BH_Unwritten) | (1 << BH_Delay))
+
 /*
  * mballoc gives us at most this number of blocks...
  * XXX: That seems to be only a limitation of ext4_mb_normalize_request().
@@ -2212,6 +1899,315 @@
 #define MAX_WRITEPAGES_EXTENT_LEN 2048
 
 /*
+ * mpage_add_bh_to_extent - try to add bh to extent of blocks to map
+ *
+ * @mpd - extent of blocks
+ * @lblk - logical number of the block in the file
+ * @b_state - b_state of the buffer head added
+ *
+ * the function is used to collect contig. blocks in same state
+ */
+static int mpage_add_bh_to_extent(struct mpage_da_data *mpd, ext4_lblk_t lblk,
+				  unsigned long b_state)
+{
+	struct ext4_map_blocks *map = &mpd->map;
+
+	/* Don't go larger than mballoc is willing to allocate */
+	if (map->m_len >= MAX_WRITEPAGES_EXTENT_LEN)
+		return 0;
+
+	/* First block in the extent? */
+	if (map->m_len == 0) {
+		map->m_lblk = lblk;
+		map->m_len = 1;
+		map->m_flags = b_state & BH_FLAGS;
+		return 1;
+	}
+
+	/* Can we merge the block to our big extent? */
+	if (lblk == map->m_lblk + map->m_len &&
+	    (b_state & BH_FLAGS) == map->m_flags) {
+		map->m_len++;
+		return 1;
+	}
+	return 0;
+}
+
+static bool add_page_bufs_to_extent(struct mpage_da_data *mpd,
+				    struct buffer_head *head,
+				    struct buffer_head *bh,
+				    ext4_lblk_t lblk)
+{
+	struct inode *inode = mpd->inode;
+	ext4_lblk_t blocks = (i_size_read(inode) + (1 << inode->i_blkbits) - 1)
+							>> inode->i_blkbits;
+
+	do {
+		BUG_ON(buffer_locked(bh));
+
+		if (!buffer_dirty(bh) || !buffer_mapped(bh) ||
+		    (!buffer_delay(bh) && !buffer_unwritten(bh)) ||
+		    lblk >= blocks) {
+			/* Found extent to map? */
+			if (mpd->map.m_len)
+				return false;
+			if (lblk >= blocks)
+				return true;
+			continue;
+		}
+		if (!mpage_add_bh_to_extent(mpd, lblk, bh->b_state))
+			return false;
+	} while (lblk++, (bh = bh->b_this_page) != head);
+	return true;
+}
+
+static int mpage_submit_page(struct mpage_da_data *mpd, struct page *page)
+{
+	int len;
+	loff_t size = i_size_read(mpd->inode);
+	int err;
+
+	BUG_ON(page->index != mpd->first_page);
+	if (page->index == size >> PAGE_CACHE_SHIFT)
+		len = size & ~PAGE_CACHE_MASK;
+	else
+		len = PAGE_CACHE_SIZE;
+	clear_page_dirty_for_io(page);
+	err = ext4_bio_write_page(&mpd->io_submit, page, len, mpd->wbc);
+	if (!err)
+		mpd->wbc->nr_to_write--;
+	mpd->first_page++;
+
+	return err;
+}
+
+/*
+ * mpage_map_buffers - update buffers corresponding to changed extent and
+ *		       submit fully mapped pages for IO
+ *
+ * @mpd - description of extent to map, on return next extent to map
+ *
+ * Scan buffers corresponding to changed extent (we expect corresponding pages
+ * to be already locked) and update buffer state according to new extent state.
+ * We map delalloc buffers to their physical location, clear unwritten bits,
+ * and mark buffers as uninit when we perform writes to uninitialized extents
+ * and do extent conversion after IO is finished. If the last page is not fully
+ * mapped, we update @map to the next extent in the last page that needs
+ * mapping. Otherwise we submit the page for IO.
+ */
+static int mpage_map_and_submit_buffers(struct mpage_da_data *mpd)
+{
+	struct pagevec pvec;
+	int nr_pages, i;
+	struct inode *inode = mpd->inode;
+	struct buffer_head *head, *bh;
+	int bpp_bits = PAGE_CACHE_SHIFT - inode->i_blkbits;
+	ext4_lblk_t blocks = (i_size_read(inode) + (1 << inode->i_blkbits) - 1)
+							>> inode->i_blkbits;
+	pgoff_t start, end;
+	ext4_lblk_t lblk;
+	sector_t pblock;
+	int err;
+
+	start = mpd->map.m_lblk >> bpp_bits;
+	end = (mpd->map.m_lblk + mpd->map.m_len - 1) >> bpp_bits;
+	lblk = start << bpp_bits;
+	pblock = mpd->map.m_pblk;
+
+	pagevec_init(&pvec, 0);
+	while (start <= end) {
+		nr_pages = pagevec_lookup(&pvec, inode->i_mapping, start,
+					  PAGEVEC_SIZE);
+		if (nr_pages == 0)
+			break;
+		for (i = 0; i < nr_pages; i++) {
+			struct page *page = pvec.pages[i];
+
+			if (page->index > end)
+				break;
+			/* Upto 'end' pages must be contiguous */
+			BUG_ON(page->index != start);
+			bh = head = page_buffers(page);
+			do {
+				if (lblk < mpd->map.m_lblk)
+					continue;
+				if (lblk >= mpd->map.m_lblk + mpd->map.m_len) {
+					/*
+					 * Buffer after end of mapped extent.
+					 * Find next buffer in the page to map.
+					 */
+					mpd->map.m_len = 0;
+					mpd->map.m_flags = 0;
+					add_page_bufs_to_extent(mpd, head, bh,
+								lblk);
+					pagevec_release(&pvec);
+					return 0;
+				}
+				if (buffer_delay(bh)) {
+					clear_buffer_delay(bh);
+					bh->b_blocknr = pblock++;
+				}
+				if (mpd->map.m_flags & EXT4_MAP_UNINIT)
+					set_buffer_uninit(bh);
+				clear_buffer_unwritten(bh);
+			} while (++lblk < blocks &&
+				 (bh = bh->b_this_page) != head);
+
+			/*
+			 * FIXME: This is going to break if dioread_nolock
+			 * supports blocksize < pagesize as we will try to
+			 * convert potentially unmapped parts of inode.
+			 */
+			mpd->io_submit.io_end->size += PAGE_CACHE_SIZE;
+			/* Page fully mapped - let IO run! */
+			err = mpage_submit_page(mpd, page);
+			if (err < 0) {
+				pagevec_release(&pvec);
+				return err;
+			}
+			start++;
+		}
+		pagevec_release(&pvec);
+	}
+	/* Extent fully mapped and matches with page boundary. We are done. */
+	mpd->map.m_len = 0;
+	mpd->map.m_flags = 0;
+	return 0;
+}
+
+static int mpage_map_one_extent(handle_t *handle, struct mpage_da_data *mpd)
+{
+	struct inode *inode = mpd->inode;
+	struct ext4_map_blocks *map = &mpd->map;
+	int get_blocks_flags;
+	int err;
+
+	trace_ext4_da_write_pages_extent(inode, map);
+	/*
+	 * Call ext4_map_blocks() to allocate any delayed allocation blocks, or
+	 * to convert an uninitialized extent to be initialized (in the case
+	 * where we have written into one or more preallocated blocks).  It is
+	 * possible that we're going to need more metadata blocks than
+	 * previously reserved. However we must not fail because we're in
+	 * writeback and there is nothing we can do about it so it might result
+	 * in data loss.  So use reserved blocks to allocate metadata if
+	 * possible.
+	 *
+	 * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE if the blocks
+	 * in question are delalloc blocks.  This affects functions in many
+	 * different parts of the allocation call path.  This flag exists
+	 * primarily because we don't want to change *many* call functions, so
+	 * ext4_map_blocks() will set the EXT4_STATE_DELALLOC_RESERVED flag
+	 * once the inode's allocation semaphore is taken.
+	 */
+	get_blocks_flags = EXT4_GET_BLOCKS_CREATE |
+			   EXT4_GET_BLOCKS_METADATA_NOFAIL;
+	if (ext4_should_dioread_nolock(inode))
+		get_blocks_flags |= EXT4_GET_BLOCKS_IO_CREATE_EXT;
+	if (map->m_flags & (1 << BH_Delay))
+		get_blocks_flags |= EXT4_GET_BLOCKS_DELALLOC_RESERVE;
+
+	err = ext4_map_blocks(handle, inode, map, get_blocks_flags);
+	if (err < 0)
+		return err;
+
+	BUG_ON(map->m_len == 0);
+	if (map->m_flags & EXT4_MAP_NEW) {
+		struct block_device *bdev = inode->i_sb->s_bdev;
+		int i;
+
+		for (i = 0; i < map->m_len; i++)
+			unmap_underlying_metadata(bdev, map->m_pblk + i);
+	}
+	return 0;
+}
+
+/*
+ * mpage_map_and_submit_extent - map extent starting at mpd->lblk of length
+ *				 mpd->len and submit pages underlying it for IO
+ *
+ * @handle - handle for journal operations
+ * @mpd - extent to map
+ *
+ * The function maps extent starting at mpd->lblk of length mpd->len. If it is
+ * delayed, blocks are allocated, if it is unwritten, we may need to convert
+ * them to initialized or split the described range from larger unwritten
+ * extent. Note that we need not map all the described range since allocation
+ * can return less blocks or the range is covered by more unwritten extents. We
+ * cannot map more because we are limited by reserved transaction credits. On
+ * the other hand we always make sure that the last touched page is fully
+ * mapped so that it can be written out (and thus forward progress is
+ * guaranteed). After mapping we submit all mapped pages for IO.
+ */
+static int mpage_map_and_submit_extent(handle_t *handle,
+				       struct mpage_da_data *mpd)
+{
+	struct inode *inode = mpd->inode;
+	struct ext4_map_blocks *map = &mpd->map;
+	int err;
+	loff_t disksize;
+
+	mpd->io_submit.io_end->offset =
+				((loff_t)map->m_lblk) << inode->i_blkbits;
+	while (map->m_len) {
+		err = mpage_map_one_extent(handle, mpd);
+		if (err < 0) {
+			struct super_block *sb = inode->i_sb;
+
+			/*
+			 * Need to commit transaction to free blocks. Let upper
+			 * layers sort it out.
+			 */
+			if (err == -ENOSPC && ext4_count_free_clusters(sb))
+				return -ENOSPC;
+
+			if (!(EXT4_SB(sb)->s_mount_flags & EXT4_MF_FS_ABORTED)) {
+				ext4_msg(sb, KERN_CRIT,
+					 "Delayed block allocation failed for "
+					 "inode %lu at logical offset %llu with"
+					 " max blocks %u with error %d",
+					 inode->i_ino,
+					 (unsigned long long)map->m_lblk,
+					 (unsigned)map->m_len, err);
+				ext4_msg(sb, KERN_CRIT,
+					 "This should not happen!! Data will "
+					 "be lost\n");
+				if (err == -ENOSPC)
+					ext4_print_free_blocks(inode);
+			}
+			/* invalidate all the pages */
+			mpage_release_unused_pages(mpd, true);
+			return err;
+		}
+		/*
+		 * Update buffer state, submit mapped pages, and get us new
+		 * extent to map
+		 */
+		err = mpage_map_and_submit_buffers(mpd);
+		if (err < 0)
+			return err;
+	}
+
+	/* Update on-disk size after IO is submitted */
+	disksize = ((loff_t)mpd->first_page) << PAGE_CACHE_SHIFT;
+	if (disksize > i_size_read(inode))
+		disksize = i_size_read(inode);
+	if (disksize > EXT4_I(inode)->i_disksize) {
+		int err2;
+
+		ext4_update_i_disksize(inode, disksize);
+		err2 = ext4_mark_inode_dirty(handle, inode);
+		if (err2)
+			ext4_error(inode->i_sb,
+				   "Failed to mark inode %lu dirty",
+				   inode->i_ino);
+		if (!err)
+			err = err2;
+	}
+	return err;
+}
+
+/*
  * Calculate the total number of credits to reserve for one writepages
  * iteration. This is called from ext4_da_writepages(). We map an extent of
  * upto MAX_WRITEPAGES_EXTENT_LEN blocks and then we go on and finish mapping
@@ -2227,44 +2223,49 @@
 }
 
 /*
- * write_cache_pages_da - walk the list of dirty pages of the given
- * address space and accumulate pages that need writing, and call
- * mpage_da_map_and_submit to map a single contiguous memory region
- * and then write them.
+ * mpage_prepare_extent_to_map - find & lock contiguous range of dirty pages
+ * 				 and underlying extent to map
+ *
+ * @mpd - where to look for pages
+ *
+ * Walk dirty pages in the mapping. If they are fully mapped, submit them for
+ * IO immediately. When we find a page which isn't mapped we start accumulating
+ * extent of buffers underlying these pages that needs mapping (formed by
+ * either delayed or unwritten buffers). We also lock the pages containing
+ * these buffers. The extent found is returned in @mpd structure (starting at
+ * mpd->lblk with length mpd->len blocks).
+ *
+ * Note that this function can attach bios to one io_end structure which are
+ * neither logically nor physically contiguous. Although it may seem as an
+ * unnecessary complication, it is actually inevitable in blocksize < pagesize
+ * case as we need to track IO to all buffers underlying a page in one io_end.
  */
-static int write_cache_pages_da(handle_t *handle,
-				struct address_space *mapping,
-				struct writeback_control *wbc,
-				struct mpage_da_data *mpd,
-				pgoff_t *done_index)
+static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
 {
-	struct buffer_head	*bh, *head;
-	struct inode		*inode = mapping->host;
-	struct pagevec		pvec;
-	unsigned int		nr_pages;
-	sector_t		logical;
-	pgoff_t			index, end;
-	long			nr_to_write = wbc->nr_to_write;
-	int			i, tag, ret = 0;
+	struct address_space *mapping = mpd->inode->i_mapping;
+	struct pagevec pvec;
+	unsigned int nr_pages;
+	pgoff_t index = mpd->first_page;
+	pgoff_t end = mpd->last_page;
+	int tag;
+	int i, err = 0;
+	int blkbits = mpd->inode->i_blkbits;
+	ext4_lblk_t lblk;
+	struct buffer_head *head;
 
-	memset(mpd, 0, sizeof(struct mpage_da_data));
-	mpd->wbc = wbc;
-	mpd->inode = inode;
-	pagevec_init(&pvec, 0);
-	index = wbc->range_start >> PAGE_CACHE_SHIFT;
-	end = wbc->range_end >> PAGE_CACHE_SHIFT;
-
-	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
+	if (mpd->wbc->sync_mode == WB_SYNC_ALL || mpd->wbc->tagged_writepages)
 		tag = PAGECACHE_TAG_TOWRITE;
 	else
 		tag = PAGECACHE_TAG_DIRTY;
 
-	*done_index = index;
+	pagevec_init(&pvec, 0);
+	mpd->map.m_len = 0;
+	mpd->next_page = index;
 	while (index <= end) {
 		nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
 			      min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
 		if (nr_pages == 0)
-			return 0;
+			goto out;
 
 		for (i = 0; i < nr_pages; i++) {
 			struct page *page = pvec.pages[i];
@@ -2279,31 +2280,21 @@
 			if (page->index > end)
 				goto out;
 
-			*done_index = page->index + 1;
-
-			/*
-			 * If we can't merge this page, and we have
-			 * accumulated an contiguous region, write it
-			 */
-			if ((mpd->next_page != page->index) &&
-			    (mpd->next_page != mpd->first_page)) {
-				mpage_da_map_and_submit(mpd);
-				goto ret_extent_tail;
-			}
+			/* If we can't merge this page, we are done. */
+			if (mpd->map.m_len > 0 && mpd->next_page != page->index)
+				goto out;
 
 			lock_page(page);
-
 			/*
-			 * If the page is no longer dirty, or its
-			 * mapping no longer corresponds to inode we
-			 * are writing (which means it has been
-			 * truncated or invalidated), or the page is
-			 * already under writeback and we are not
-			 * doing a data integrity writeback, skip the page
+			 * If the page is no longer dirty, or its mapping no
+			 * longer corresponds to inode we are writing (which
+			 * means it has been truncated or invalidated), or the
+			 * page is already under writeback and we are not doing
+			 * a data integrity writeback, skip the page
 			 */
 			if (!PageDirty(page) ||
 			    (PageWriteback(page) &&
-			     (wbc->sync_mode == WB_SYNC_NONE)) ||
+			     (mpd->wbc->sync_mode == WB_SYNC_NONE)) ||
 			    unlikely(page->mapping != mapping)) {
 				unlock_page(page);
 				continue;
@@ -2312,101 +2303,57 @@
 			wait_on_page_writeback(page);
 			BUG_ON(PageWriteback(page));
 
-			/*
-			 * If we have inline data and arrive here, it means that
-			 * we will soon create the block for the 1st page, so
-			 * we'd better clear the inline data here.
-			 */
-			if (ext4_has_inline_data(inode)) {
-				BUG_ON(ext4_test_inode_state(inode,
-						EXT4_STATE_MAY_INLINE_DATA));
-				ext4_destroy_inline_data(handle, inode);
-			}
-
-			if (mpd->next_page != page->index)
+			if (mpd->map.m_len == 0)
 				mpd->first_page = page->index;
 			mpd->next_page = page->index + 1;
-			logical = (sector_t) page->index <<
-				(PAGE_CACHE_SHIFT - inode->i_blkbits);
-
 			/* Add all dirty buffers to mpd */
+			lblk = ((ext4_lblk_t)page->index) <<
+				(PAGE_CACHE_SHIFT - blkbits);
 			head = page_buffers(page);
-			bh = head;
-			do {
-				BUG_ON(buffer_locked(bh));
-				/*
-				 * We need to try to allocate unmapped blocks
-				 * in the same page.  Otherwise we won't make
-				 * progress with the page in ext4_writepage
-				 */
-				if (ext4_bh_delay_or_unwritten(NULL, bh)) {
-					mpage_add_bh_to_extent(mpd, logical,
-							       bh->b_state);
-					if (mpd->io_done)
-						goto ret_extent_tail;
-				} else if (buffer_dirty(bh) &&
-					   buffer_mapped(bh)) {
-					/*
-					 * mapped dirty buffer. We need to
-					 * update the b_state because we look
-					 * at b_state in mpage_da_map_blocks.
-					 * We don't update b_size because if we
-					 * find an unmapped buffer_head later
-					 * we need to use the b_state flag of
-					 * that buffer_head.
-					 */
-					if (mpd->b_size == 0)
-						mpd->b_state =
-							bh->b_state & BH_FLAGS;
-				}
-				logical++;
-			} while ((bh = bh->b_this_page) != head);
-
-			if (nr_to_write > 0) {
-				nr_to_write--;
-				if (nr_to_write == 0 &&
-				    wbc->sync_mode == WB_SYNC_NONE)
-					/*
-					 * We stop writing back only if we are
-					 * not doing integrity sync. In case of
-					 * integrity sync we have to keep going
-					 * because someone may be concurrently
-					 * dirtying pages, and we might have
-					 * synced a lot of newly appeared dirty
-					 * pages, but have not synced all of the
-					 * old dirty pages.
-					 */
+			if (!add_page_bufs_to_extent(mpd, head, head, lblk))
+				goto out;
+			/* So far everything mapped? Submit the page for IO. */
+			if (mpd->map.m_len == 0) {
+				err = mpage_submit_page(mpd, page);
+				if (err < 0)
 					goto out;
 			}
+
+			/*
+			 * Accumulated enough dirty pages? This doesn't apply
+			 * to WB_SYNC_ALL mode. For integrity sync we have to
+			 * keep going because someone may be concurrently
+			 * dirtying pages, and we might have synced a lot of
+			 * newly appeared dirty pages, but have not synced all
+			 * of the old dirty pages.
+			 */
+			if (mpd->wbc->sync_mode == WB_SYNC_NONE &&
+			    mpd->next_page - mpd->first_page >=
+							mpd->wbc->nr_to_write)
+				goto out;
 		}
 		pagevec_release(&pvec);
 		cond_resched();
 	}
 	return 0;
-ret_extent_tail:
-	ret = MPAGE_DA_EXTENT_TAIL;
 out:
 	pagevec_release(&pvec);
-	cond_resched();
-	return ret;
+	return err;
 }
 
-
 static int ext4_da_writepages(struct address_space *mapping,
 			      struct writeback_control *wbc)
 {
-	pgoff_t	index;
+	pgoff_t	writeback_index = 0;
+	long nr_to_write = wbc->nr_to_write;
 	int range_whole = 0;
+	int cycled = 1;
 	handle_t *handle = NULL;
 	struct mpage_da_data mpd;
 	struct inode *inode = mapping->host;
-	int pages_written = 0;
-	int range_cyclic, cycled = 1, io_done = 0;
 	int needed_blocks, ret = 0;
-	loff_t range_start = wbc->range_start;
 	struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
-	pgoff_t done_index = 0;
-	pgoff_t end;
+	bool done;
 	struct blk_plug plug;
 
 	trace_ext4_da_writepages(inode, wbc);
@@ -2432,40 +2379,65 @@
 	if (unlikely(sbi->s_mount_flags & EXT4_MF_FS_ABORTED))
 		return -EROFS;
 
+	/*
+	 * If we have inline data and arrive here, it means that
+	 * we will soon create the block for the 1st page, so
+	 * we'd better clear the inline data here.
+	 */
+	if (ext4_has_inline_data(inode)) {
+		/* Just inode will be modified... */
+		handle = ext4_journal_start(inode, EXT4_HT_INODE, 1);
+		if (IS_ERR(handle)) {
+			ret = PTR_ERR(handle);
+			goto out_writepages;
+		}
+		BUG_ON(ext4_test_inode_state(inode,
+				EXT4_STATE_MAY_INLINE_DATA));
+		ext4_destroy_inline_data(handle, inode);
+		ext4_journal_stop(handle);
+	}
+
 	if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
 		range_whole = 1;
 
-	range_cyclic = wbc->range_cyclic;
 	if (wbc->range_cyclic) {
-		index = mapping->writeback_index;
-		if (index)
+		writeback_index = mapping->writeback_index;
+		if (writeback_index)
 			cycled = 0;
-		wbc->range_start = index << PAGE_CACHE_SHIFT;
-		wbc->range_end  = LLONG_MAX;
-		wbc->range_cyclic = 0;
-		end = -1;
+		mpd.first_page = writeback_index;
+		mpd.last_page = -1;
 	} else {
-		index = wbc->range_start >> PAGE_CACHE_SHIFT;
-		end = wbc->range_end >> PAGE_CACHE_SHIFT;
+		mpd.first_page = wbc->range_start >> PAGE_CACHE_SHIFT;
+		mpd.last_page = wbc->range_end >> PAGE_CACHE_SHIFT;
 	}
 
+	mpd.inode = inode;
+	mpd.wbc = wbc;
+	ext4_io_submit_init(&mpd.io_submit, wbc);
 retry:
 	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
-		tag_pages_for_writeback(mapping, index, end);
-
+		tag_pages_for_writeback(mapping, mpd.first_page, mpd.last_page);
+	done = false;
 	blk_start_plug(&plug);
-	while (!ret && wbc->nr_to_write > 0) {
+	while (!done && mpd.first_page <= mpd.last_page) {
+		/* For each extent of pages we use new io_end */
+		mpd.io_submit.io_end = ext4_init_io_end(inode, GFP_KERNEL);
+		if (!mpd.io_submit.io_end) {
+			ret = -ENOMEM;
+			break;
+		}
 
 		/*
-		 * we  insert one extent at a time. So we need
-		 * credit needed for single extent allocation.
-		 * journalled mode is currently not supported
-		 * by delalloc
+		 * We have two constraints: We find one extent to map and we
+		 * must always write out whole page (makes a difference when
+		 * blocksize < pagesize) so that we don't block on IO when we
+		 * try to write out the rest of the page. Journalled mode is
+		 * not supported by delalloc.
 		 */
 		BUG_ON(ext4_should_journal_data(inode));
 		needed_blocks = ext4_da_writepages_trans_blocks(inode);
 
-		/* start a new transaction*/
+		/* start a new transaction */
 		handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE,
 					    needed_blocks);
 		if (IS_ERR(handle)) {
@@ -2473,76 +2445,67 @@
 			ext4_msg(inode->i_sb, KERN_CRIT, "%s: jbd2_start: "
 			       "%ld pages, ino %lu; err %d", __func__,
 				wbc->nr_to_write, inode->i_ino, ret);
-			blk_finish_plug(&plug);
-			goto out_writepages;
+			/* Release allocated io_end */
+			ext4_put_io_end(mpd.io_submit.io_end);
+			break;
 		}
 
-		/*
-		 * Now call write_cache_pages_da() to find the next
-		 * contiguous region of logical blocks that need
-		 * blocks to be allocated by ext4 and submit them.
-		 */
-		ret = write_cache_pages_da(handle, mapping,
-					   wbc, &mpd, &done_index);
-		/*
-		 * If we have a contiguous extent of pages and we
-		 * haven't done the I/O yet, map the blocks and submit
-		 * them for I/O.
-		 */
-		if (!mpd.io_done && mpd.next_page != mpd.first_page) {
-			mpage_da_map_and_submit(&mpd);
-			ret = MPAGE_DA_EXTENT_TAIL;
+		trace_ext4_da_write_pages(inode, mpd.first_page, mpd.wbc);
+		ret = mpage_prepare_extent_to_map(&mpd);
+		if (!ret) {
+			if (mpd.map.m_len)
+				ret = mpage_map_and_submit_extent(handle, &mpd);
+			else {
+				/*
+				 * We scanned the whole range (or exhausted
+				 * nr_to_write), submitted what was mapped and
+				 * didn't find anything needing mapping. We are
+				 * done.
+				 */
+				done = true;
+			}
 		}
-		trace_ext4_da_write_pages(inode, &mpd);
-		wbc->nr_to_write -= mpd.pages_written;
-
 		ext4_journal_stop(handle);
+		/* Submit prepared bio */
+		ext4_io_submit(&mpd.io_submit);
+		/* Unlock pages we didn't use */
+		mpage_release_unused_pages(&mpd, false);
+		/* Drop our io_end reference we got from init */
+		ext4_put_io_end(mpd.io_submit.io_end);
 
-		if ((mpd.retval == -ENOSPC) && sbi->s_journal) {
-			/* commit the transaction which would
+		if (ret == -ENOSPC && sbi->s_journal) {
+			/*
+			 * Commit the transaction which would
 			 * free blocks released in the transaction
 			 * and try again
 			 */
 			jbd2_journal_force_commit_nested(sbi->s_journal);
 			ret = 0;
-		} else if (ret == MPAGE_DA_EXTENT_TAIL) {
-			/*
-			 * Got one extent now try with rest of the pages.
-			 * If mpd.retval is set -EIO, journal is aborted.
-			 * So we don't need to write any more.
-			 */
-			pages_written += mpd.pages_written;
-			ret = mpd.retval;
-			io_done = 1;
-		} else if (wbc->nr_to_write)
-			/*
-			 * There is no more writeout needed
-			 * or we requested for a noblocking writeout
-			 * and we found the device congested
-			 */
+			continue;
+		}
+		/* Fatal error - ENOMEM, EIO... */
+		if (ret)
 			break;
 	}
 	blk_finish_plug(&plug);
-	if (!io_done && !cycled) {
+	if (!ret && !cycled) {
 		cycled = 1;
-		index = 0;
-		wbc->range_start = index << PAGE_CACHE_SHIFT;
-		wbc->range_end  = mapping->writeback_index - 1;
+		mpd.last_page = writeback_index - 1;
+		mpd.first_page = 0;
 		goto retry;
 	}
 
 	/* Update index */
-	wbc->range_cyclic = range_cyclic;
 	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
 		/*
-		 * set the writeback_index so that range_cyclic
+		 * Set the writeback_index so that range_cyclic
 		 * mode will write it back later
 		 */
-		mapping->writeback_index = done_index;
+		mapping->writeback_index = mpd.first_page;
 
 out_writepages:
-	wbc->range_start = range_start;
-	trace_ext4_da_writepages_result(inode, wbc, ret, pages_written);
+	trace_ext4_da_writepages_result(inode, wbc, ret,
+					nr_to_write - wbc->nr_to_write);
 	return ret;
 }