ext4: Add new abstraction ext4_map_blocks() underneath ext4_get_blocks()

Jack up ext4_get_blocks() and add a new function, ext4_map_blocks()
which uses a much smaller structure, struct ext4_map_blocks which is
20 bytes, as opposed to a struct buffer_head, which nearly 5 times
bigger on an x86_64 machine.  By switching things to use
ext4_map_blocks(), we can save stack space by using ext4_map_blocks()
since we can avoid allocating a struct buffer_head on the stack.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

3 files changed, 199 insertions, 170 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index d266003..57fc0e5 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -126,6 +126,29 @@ struct ext4_allocation_request {
 };
 
 /*
+ * Logical to physical block mapping, used by ext4_map_blocks()
+ *
+ * This structure is used to pass requests into ext4_map_blocks() as
+ * well as to store the information returned by ext4_map_blocks().  It
+ * takes less room on the stack than a struct buffer_head.
+ */
+#define EXT4_MAP_NEW		(1 << BH_New)
+#define EXT4_MAP_MAPPED		(1 << BH_Mapped)
+#define EXT4_MAP_UNWRITTEN	(1 << BH_Unwritten)
+#define EXT4_MAP_BOUNDARY	(1 << BH_Boundary)
+#define EXT4_MAP_UNINIT		(1 << BH_Uninit)
+#define EXT4_MAP_FLAGS		(EXT4_MAP_NEW | EXT4_MAP_MAPPED |\
+				 EXT4_MAP_UNWRITTEN | EXT4_MAP_BOUNDARY |\
+				 EXT4_MAP_UNINIT)
+
+struct ext4_map_blocks {
+	ext4_fsblk_t m_pblk;
+	ext4_lblk_t m_lblk;
+	unsigned int m_len;
+	unsigned int m_flags;
+};
+
+/*
  * For delayed allocation tracking
  */
 struct mpage_da_data {
@@ -1773,9 +1796,8 @@ extern int ext4_ext_tree_init(handle_t *handle, struct inode *);
 extern int ext4_ext_writepage_trans_blocks(struct inode *, int);
 extern int ext4_ext_index_trans_blocks(struct inode *inode, int nrblocks,
 				       int chunk);
-extern int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
-			       ext4_lblk_t iblock, unsigned int max_blocks,
-			       struct buffer_head *bh_result, int flags);
+extern int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
+			       struct ext4_map_blocks *map, int flags);
 extern void ext4_ext_truncate(struct inode *);
 extern void ext4_ext_init(struct super_block *);
 extern void ext4_ext_release(struct super_block *);
@@ -1783,6 +1805,8 @@ extern long ext4_fallocate(struct inode *inode, int mode, loff_t offset,
 			  loff_t len);
 extern int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
 			  ssize_t len);
+extern int ext4_map_blocks(handle_t *handle, struct inode *inode,
+			   struct ext4_map_blocks *map, int flags);
 extern int ext4_get_blocks(handle_t *handle, struct inode *inode,
 			   sector_t block, unsigned int max_blocks,
 			   struct buffer_head *bh, int flags);
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 8a8f9f0..37f9387 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2611,7 +2611,7 @@ static int ext4_ext_zeroout(struct inode *inode, struct ext4_extent *ex)
 
 #define EXT4_EXT_ZERO_LEN 7
 /*
- * This function is called by ext4_ext_get_blocks() if someone tries to write
+ * This function is called by ext4_ext_map_blocks() if someone tries to write
  * to an uninitialized extent. It may result in splitting the uninitialized
  * extent into multiple extents (upto three - one initialized and two
  * uninitialized).
@@ -2621,10 +2621,9 @@ static int ext4_ext_zeroout(struct inode *inode, struct ext4_extent *ex)
  *   c> Splits in three extents: Somone is writing in middle of the extent
  */
 static int ext4_ext_convert_to_initialized(handle_t *handle,
-						struct inode *inode,
-						struct ext4_ext_path *path,
-						ext4_lblk_t iblock,
-						unsigned int max_blocks)
+					   struct inode *inode,
+					   struct ext4_map_blocks *map,
+					   struct ext4_ext_path *path)
 {
 	struct ext4_extent *ex, newex, orig_ex;
 	struct ext4_extent *ex1 = NULL;
@@ -2640,20 +2639,20 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 
 	ext_debug("ext4_ext_convert_to_initialized: inode %lu, logical"
 		"block %llu, max_blocks %u\n", inode->i_ino,
-		(unsigned long long)iblock, max_blocks);
+		(unsigned long long)map->m_lblk, map->m_len);
 
 	eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
 		inode->i_sb->s_blocksize_bits;
-	if (eof_block < iblock + max_blocks)
-		eof_block = iblock + max_blocks;
+	if (eof_block < map->m_lblk + map->m_len)
+		eof_block = map->m_lblk + map->m_len;
 
 	depth = ext_depth(inode);
 	eh = path[depth].p_hdr;
 	ex = path[depth].p_ext;
 	ee_block = le32_to_cpu(ex->ee_block);
 	ee_len = ext4_ext_get_actual_len(ex);
-	allocated = ee_len - (iblock - ee_block);
-	newblock = iblock - ee_block + ext_pblock(ex);
+	allocated = ee_len - (map->m_lblk - ee_block);
+	newblock = map->m_lblk - ee_block + ext_pblock(ex);
 
 	ex2 = ex;
 	orig_ex.ee_block = ex->ee_block;
@@ -2683,10 +2682,10 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 		return allocated;
 	}
 
-	/* ex1: ee_block to iblock - 1 : uninitialized */
-	if (iblock > ee_block) {
+	/* ex1: ee_block to map->m_lblk - 1 : uninitialized */
+	if (map->m_lblk > ee_block) {
 		ex1 = ex;
-		ex1->ee_len = cpu_to_le16(iblock - ee_block);
+		ex1->ee_len = cpu_to_le16(map->m_lblk - ee_block);
 		ext4_ext_mark_uninitialized(ex1);
 		ex2 = &newex;
 	}
@@ -2695,15 +2694,15 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 	 * we insert ex3, if ex1 is NULL. This is to avoid temporary
 	 * overlap of blocks.
 	 */
-	if (!ex1 && allocated > max_blocks)
-		ex2->ee_len = cpu_to_le16(max_blocks);
+	if (!ex1 && allocated > map->m_len)
+		ex2->ee_len = cpu_to_le16(map->m_len);
 	/* ex3: to ee_block + ee_len : uninitialised */
-	if (allocated > max_blocks) {
+	if (allocated > map->m_len) {
 		unsigned int newdepth;
 		/* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */
 		if (allocated <= EXT4_EXT_ZERO_LEN && may_zeroout) {
 			/*
-			 * iblock == ee_block is handled by the zerouout
+			 * map->m_lblk == ee_block is handled by the zerouout
 			 * at the beginning.
 			 * Mark first half uninitialized.
 			 * Mark second half initialized and zero out the
@@ -2716,7 +2715,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 			ext4_ext_dirty(handle, inode, path + depth);
 
 			ex3 = &newex;
-			ex3->ee_block = cpu_to_le32(iblock);
+			ex3->ee_block = cpu_to_le32(map->m_lblk);
 			ext4_ext_store_pblock(ex3, newblock);
 			ex3->ee_len = cpu_to_le16(allocated);
 			err = ext4_ext_insert_extent(handle, inode, path,
@@ -2729,7 +2728,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 				ex->ee_len   = orig_ex.ee_len;
 				ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
 				ext4_ext_dirty(handle, inode, path + depth);
-				/* blocks available from iblock */
+				/* blocks available from map->m_lblk */
 				return allocated;
 
 			} else if (err)
@@ -2751,8 +2750,8 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 				 */
 				depth = ext_depth(inode);
 				ext4_ext_drop_refs(path);
-				path = ext4_ext_find_extent(inode,
-								iblock, path);
+				path = ext4_ext_find_extent(inode, map->m_lblk,
+							    path);
 				if (IS_ERR(path)) {
 					err = PTR_ERR(path);
 					return err;
@@ -2772,9 +2771,9 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 			return allocated;
 		}
 		ex3 = &newex;
-		ex3->ee_block = cpu_to_le32(iblock + max_blocks);
-		ext4_ext_store_pblock(ex3, newblock + max_blocks);
-		ex3->ee_len = cpu_to_le16(allocated - max_blocks);
+		ex3->ee_block = cpu_to_le32(map->m_lblk + map->m_len);
+		ext4_ext_store_pblock(ex3, newblock + map->m_len);
+		ex3->ee_len = cpu_to_le16(allocated - map->m_len);
 		ext4_ext_mark_uninitialized(ex3);
 		err = ext4_ext_insert_extent(handle, inode, path, ex3, 0);
 		if (err == -ENOSPC && may_zeroout) {
@@ -2787,7 +2786,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
 			ext4_ext_dirty(handle, inode, path + depth);
 			/* zeroed the full extent */
-			/* blocks available from iblock */
+			/* blocks available from map->m_lblk */
 			return allocated;
 
 		} else if (err)
@@ -2807,7 +2806,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 
 		depth = newdepth;
 		ext4_ext_drop_refs(path);
-		path = ext4_ext_find_extent(inode, iblock, path);
+		path = ext4_ext_find_extent(inode, map->m_lblk, path);
 		if (IS_ERR(path)) {
 			err = PTR_ERR(path);
 			goto out;
@@ -2821,14 +2820,14 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 		if (err)
 			goto out;
 
-		allocated = max_blocks;
+		allocated = map->m_len;
 
 		/* If extent has less than EXT4_EXT_ZERO_LEN and we are trying
 		 * to insert a extent in the middle zerout directly
 		 * otherwise give the extent a chance to merge to left
 		 */
 		if (le16_to_cpu(orig_ex.ee_len) <= EXT4_EXT_ZERO_LEN &&
-			iblock != ee_block && may_zeroout) {
+			map->m_lblk != ee_block && may_zeroout) {
 			err =  ext4_ext_zeroout(inode, &orig_ex);
 			if (err)
 				goto fix_extent_len;
@@ -2838,7 +2837,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
 			ext4_ext_dirty(handle, inode, path + depth);
 			/* zero out the first half */
-			/* blocks available from iblock */
+			/* blocks available from map->m_lblk */
 			return allocated;
 		}
 	}
@@ -2849,12 +2848,12 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 	 */
 	if (ex1 && ex1 != ex) {
 		ex1 = ex;
-		ex1->ee_len = cpu_to_le16(iblock - ee_block);
+		ex1->ee_len = cpu_to_le16(map->m_lblk - ee_block);
 		ext4_ext_mark_uninitialized(ex1);
 		ex2 = &newex;
 	}
-	/* ex2: iblock to iblock + maxblocks-1 : initialised */
-	ex2->ee_block = cpu_to_le32(iblock);
+	/* ex2: map->m_lblk to map->m_lblk + maxblocks-1 : initialised */
+	ex2->ee_block = cpu_to_le32(map->m_lblk);
 	ext4_ext_store_pblock(ex2, newblock);
 	ex2->ee_len = cpu_to_le16(allocated);
 	if (ex2 != ex)
@@ -2924,7 +2923,7 @@ fix_extent_len:
 }
 
 /*
- * This function is called by ext4_ext_get_blocks() from
+ * This function is called by ext4_ext_map_blocks() from
  * ext4_get_blocks_dio_write() when DIO to write
  * to an uninitialized extent.
  *
@@ -2947,9 +2946,8 @@ fix_extent_len:
  */
 static int ext4_split_unwritten_extents(handle_t *handle,
 					struct inode *inode,
+					struct ext4_map_blocks *map,
 					struct ext4_ext_path *path,
-					ext4_lblk_t iblock,
-					unsigned int max_blocks,
 					int flags)
 {
 	struct ext4_extent *ex, newex, orig_ex;
@@ -2965,20 +2963,20 @@ static int ext4_split_unwritten_extents(handle_t *handle,
 
 	ext_debug("ext4_split_unwritten_extents: inode %lu, logical"
 		"block %llu, max_blocks %u\n", inode->i_ino,
-		(unsigned long long)iblock, max_blocks);
+		(unsigned long long)map->m_lblk, map->m_len);
 
 	eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
 		inode->i_sb->s_blocksize_bits;
-	if (eof_block < iblock + max_blocks)
-		eof_block = iblock + max_blocks;
+	if (eof_block < map->m_lblk + map->m_len)
+		eof_block = map->m_lblk + map->m_len;
 
 	depth = ext_depth(inode);
 	eh = path[depth].p_hdr;
 	ex = path[depth].p_ext;
 	ee_block = le32_to_cpu(ex->ee_block);
 	ee_len = ext4_ext_get_actual_len(ex);
-	allocated = ee_len - (iblock - ee_block);
-	newblock = iblock - ee_block + ext_pblock(ex);
+	allocated = ee_len - (map->m_lblk - ee_block);
+	newblock = map->m_lblk - ee_block + ext_pblock(ex);
 
 	ex2 = ex;
 	orig_ex.ee_block = ex->ee_block;
@@ -2996,16 +2994,16 @@ static int ext4_split_unwritten_extents(handle_t *handle,
  	 * block where the write begins, and the write completely
  	 * covers the extent, then we don't need to split it.
  	 */
-	if ((iblock == ee_block) && (allocated <= max_blocks))
+	if ((map->m_lblk == ee_block) && (allocated <= map->m_len))
 		return allocated;
 
 	err = ext4_ext_get_access(handle, inode, path + depth);
 	if (err)
 		goto out;
-	/* ex1: ee_block to iblock - 1 : uninitialized */
-	if (iblock > ee_block) {
+	/* ex1: ee_block to map->m_lblk - 1 : uninitialized */
+	if (map->m_lblk > ee_block) {
 		ex1 = ex;
-		ex1->ee_len = cpu_to_le16(iblock - ee_block);
+		ex1->ee_len = cpu_to_le16(map->m_lblk - ee_block);
 		ext4_ext_mark_uninitialized(ex1);
 		ex2 = &newex;
 	}
@@ -3014,15 +3012,15 @@ static int ext4_split_unwritten_extents(handle_t *handle,
 	 * we insert ex3, if ex1 is NULL. This is to avoid temporary
 	 * overlap of blocks.
 	 */
-	if (!ex1 && allocated > max_blocks)
-		ex2->ee_len = cpu_to_le16(max_blocks);
+	if (!ex1 && allocated > map->m_len)
+		ex2->ee_len = cpu_to_le16(map->m_len);
 	/* ex3: to ee_block + ee_len : uninitialised */
-	if (allocated > max_blocks) {
+	if (allocated > map->m_len) {
 		unsigned int newdepth;
 		ex3 = &newex;
-		ex3->ee_block = cpu_to_le32(iblock + max_blocks);
-		ext4_ext_store_pblock(ex3, newblock + max_blocks);
-		ex3->ee_len = cpu_to_le16(allocated - max_blocks);
+		ex3->ee_block = cpu_to_le32(map->m_lblk + map->m_len);
+		ext4_ext_store_pblock(ex3, newblock + map->m_len);
+		ex3->ee_len = cpu_to_le16(allocated - map->m_len);
 		ext4_ext_mark_uninitialized(ex3);
 		err = ext4_ext_insert_extent(handle, inode, path, ex3, flags);
 		if (err == -ENOSPC && may_zeroout) {
@@ -3035,7 +3033,7 @@ static int ext4_split_unwritten_extents(handle_t *handle,
 			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
 			ext4_ext_dirty(handle, inode, path + depth);
 			/* zeroed the full extent */
-			/* blocks available from iblock */
+			/* blocks available from map->m_lblk */
 			return allocated;
 
 		} else if (err)
@@ -3055,7 +3053,7 @@ static int ext4_split_unwritten_extents(handle_t *handle,
 
 		depth = newdepth;
 		ext4_ext_drop_refs(path);
-		path = ext4_ext_find_extent(inode, iblock, path);
+		path = ext4_ext_find_extent(inode, map->m_lblk, path);
 		if (IS_ERR(path)) {
 			err = PTR_ERR(path);
 			goto out;
@@ -3069,7 +3067,7 @@ static int ext4_split_unwritten_extents(handle_t *handle,
 		if (err)
 			goto out;
 
-		allocated = max_blocks;
+		allocated = map->m_len;
 	}
 	/*
 	 * If there was a change of depth as part of the
@@ -3078,15 +3076,15 @@ static int ext4_split_unwritten_extents(handle_t *handle,
 	 */
 	if (ex1 && ex1 != ex) {
 		ex1 = ex;
-		ex1->ee_len = cpu_to_le16(iblock - ee_block);
+		ex1->ee_len = cpu_to_le16(map->m_lblk - ee_block);
 		ext4_ext_mark_uninitialized(ex1);
 		ex2 = &newex;
 	}
 	/*
-	 * ex2: iblock to iblock + maxblocks-1 : to be direct IO written,
-	 * uninitialised still.
+	 * ex2: map->m_lblk to map->m_lblk + map->m_len-1 : to be written
+	 * using direct I/O, uninitialised still.
 	 */
-	ex2->ee_block = cpu_to_le32(iblock);
+	ex2->ee_block = cpu_to_le32(map->m_lblk);
 	ext4_ext_store_pblock(ex2, newblock);
 	ex2->ee_len = cpu_to_le16(allocated);
 	ext4_ext_mark_uninitialized(ex2);
@@ -3188,10 +3186,9 @@ static void unmap_underlying_metadata_blocks(struct block_device *bdev,
 
 static int
 ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
-			ext4_lblk_t iblock, unsigned int max_blocks,
+			struct ext4_map_blocks *map,
 			struct ext4_ext_path *path, int flags,
-			unsigned int allocated, struct buffer_head *bh_result,
-			ext4_fsblk_t newblock)
+			unsigned int allocated, ext4_fsblk_t newblock)
 {
 	int ret = 0;
 	int err = 0;
@@ -3199,15 +3196,14 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
 
 	ext_debug("ext4_ext_handle_uninitialized_extents: inode %lu, logical"
 		  "block %llu, max_blocks %u, flags %d, allocated %u",
-		  inode->i_ino, (unsigned long long)iblock, max_blocks,
+		  inode->i_ino, (unsigned long long)map->m_lblk, map->m_len,
 		  flags, allocated);
 	ext4_ext_show_leaf(inode, path);
 
 	/* get_block() before submit the IO, split the extent */
 	if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
-		ret = ext4_split_unwritten_extents(handle,
-						inode, path, iblock,
-						max_blocks, flags);
+		ret = ext4_split_unwritten_extents(handle, inode, map,
+						   path, flags);
 		/*
 		 * Flag the inode(non aio case) or end_io struct (aio case)
 		 * that this IO needs to convertion to written when IO is
@@ -3218,7 +3214,7 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
 		else
 			ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
 		if (ext4_should_dioread_nolock(inode))
-			set_buffer_uninit(bh_result);
+			map->m_flags |= EXT4_MAP_UNINIT;
 		goto out;
 	}
 	/* IO end_io complete, convert the filled extent to written */
@@ -3246,14 +3242,12 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
 		 * the buffer head will be unmapped so that
 		 * a read from the block returns 0s.
 		 */
-		set_buffer_unwritten(bh_result);
+		map->m_flags |= EXT4_MAP_UNWRITTEN;
 		goto out1;
 	}
 
 	/* buffered write, writepage time, convert*/
-	ret = ext4_ext_convert_to_initialized(handle, inode,
-						path, iblock,
-						max_blocks);
+	ret = ext4_ext_convert_to_initialized(handle, inode, map, path);
 	if (ret >= 0)
 		ext4_update_inode_fsync_trans(handle, inode, 1);
 out:
@@ -3262,7 +3256,7 @@ out:
 		goto out2;
 	} else
 		allocated = ret;
-	set_buffer_new(bh_result);
+	map->m_flags |= EXT4_MAP_NEW;
 	/*
 	 * if we allocated more blocks than requested
 	 * we need to make sure we unmap the extra block
@@ -3270,11 +3264,11 @@ out:
 	 * unmapped later when we find the buffer_head marked
 	 * new.
 	 */
-	if (allocated > max_blocks) {
+	if (allocated > map->m_len) {
 		unmap_underlying_metadata_blocks(inode->i_sb->s_bdev,
-					newblock + max_blocks,
-					allocated - max_blocks);
-		allocated = max_blocks;
+					newblock + map->m_len,
+					allocated - map->m_len);
+		allocated = map->m_len;
 	}
 
 	/*
@@ -3288,13 +3282,13 @@ out:
 		ext4_da_update_reserve_space(inode, allocated, 0);
 
 map_out:
-	set_buffer_mapped(bh_result);
+	map->m_flags |= EXT4_MAP_MAPPED;
 out1:
-	if (allocated > max_blocks)
-		allocated = max_blocks;
+	if (allocated > map->m_len)
+		allocated = map->m_len;
 	ext4_ext_show_leaf(inode, path);
-	bh_result->b_bdev = inode->i_sb->s_bdev;
-	bh_result->b_blocknr = newblock;
+	map->m_pblk = newblock;
+	map->m_len = allocated;
 out2:
 	if (path) {
 		ext4_ext_drop_refs(path);
@@ -3320,10 +3314,8 @@ out2:
  *
  * return < 0, error case.
  */
-int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
-			ext4_lblk_t iblock,
-			unsigned int max_blocks, struct buffer_head *bh_result,
-			int flags)
+int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
+			struct ext4_map_blocks *map, int flags)
 {
 	struct ext4_ext_path *path = NULL;
 	struct ext4_extent_header *eh;
@@ -3334,12 +3326,11 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 	struct ext4_allocation_request ar;
 	ext4_io_end_t *io = EXT4_I(inode)->cur_aio_dio;
 
-	__clear_bit(BH_New, &bh_result->b_state);
 	ext_debug("blocks %u/%u requested for inode %lu\n",
-			iblock, max_blocks, inode->i_ino);
+		  map->m_lblk, map->m_len, inode->i_ino);
 
 	/* check in cache */
-	cache_type = ext4_ext_in_cache(inode, iblock, &newex);
+	cache_type = ext4_ext_in_cache(inode, map->m_lblk, &newex);
 	if (cache_type) {
 		if (cache_type == EXT4_EXT_CACHE_GAP) {
 			if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
@@ -3352,12 +3343,12 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 			/* we should allocate requested block */
 		} else if (cache_type == EXT4_EXT_CACHE_EXTENT) {
 			/* block is already allocated */
-			newblock = iblock
+			newblock = map->m_lblk
 				   - le32_to_cpu(newex.ee_block)
 				   + ext_pblock(&newex);
 			/* number of remaining blocks in the extent */
 			allocated = ext4_ext_get_actual_len(&newex) -
-					(iblock - le32_to_cpu(newex.ee_block));
+				(map->m_lblk - le32_to_cpu(newex.ee_block));
 			goto out;
 		} else {
 			BUG();
@@ -3365,7 +3356,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 	}
 
 	/* find extent for this block */
-	path = ext4_ext_find_extent(inode, iblock, NULL);
+	path = ext4_ext_find_extent(inode, map->m_lblk, NULL);
 	if (IS_ERR(path)) {
 		err = PTR_ERR(path);
 		path = NULL;
@@ -3382,7 +3373,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 	if (unlikely(path[depth].p_ext == NULL && depth != 0)) {
 		EXT4_ERROR_INODE(inode, "bad extent address "
 				 "iblock: %d, depth: %d pblock %lld",
-				 iblock, depth, path[depth].p_block);
+				 map->m_lblk, depth, path[depth].p_block);
 		err = -EIO;
 		goto out2;
 	}
@@ -3400,12 +3391,12 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 		 */
 		ee_len = ext4_ext_get_actual_len(ex);
 		/* if found extent covers block, simply return it */
-		if (in_range(iblock, ee_block, ee_len)) {
-			newblock = iblock - ee_block + ee_start;
+		if (in_range(map->m_lblk, ee_block, ee_len)) {
+			newblock = map->m_lblk - ee_block + ee_start;
 			/* number of remaining blocks in the extent */
-			allocated = ee_len - (iblock - ee_block);
-			ext_debug("%u fit into %u:%d -> %llu\n", iblock,
-					ee_block, ee_len, newblock);
+			allocated = ee_len - (map->m_lblk - ee_block);
+			ext_debug("%u fit into %u:%d -> %llu\n", map->m_lblk,
+				  ee_block, ee_len, newblock);
 
 			/* Do not put uninitialized extent in the cache */
 			if (!ext4_ext_is_uninitialized(ex)) {
@@ -3415,8 +3406,8 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 				goto out;
 			}
 			ret = ext4_ext_handle_uninitialized_extents(handle,
-					inode, iblock, max_blocks, path,
-					flags, allocated, bh_result, newblock);
+					inode, map, path, flags, allocated,
+					newblock);
 			return ret;
 		}
 	}
@@ -3430,7 +3421,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 		 * put just found gap into cache to speed up
 		 * subsequent requests
 		 */
-		ext4_ext_put_gap_in_cache(inode, path, iblock);
+		ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
 		goto out2;
 	}
 	/*
@@ -3438,11 +3429,11 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 	 */
 
 	/* find neighbour allocated blocks */
-	ar.lleft = iblock;
+	ar.lleft = map->m_lblk;
 	err = ext4_ext_search_left(inode, path, &ar.lleft, &ar.pleft);
 	if (err)
 		goto out2;
-	ar.lright = iblock;
+	ar.lright = map->m_lblk;
 	err = ext4_ext_search_right(inode, path, &ar.lright, &ar.pright);
 	if (err)
 		goto out2;
@@ -3453,26 +3444,26 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 	 * EXT_INIT_MAX_LEN and for an uninitialized extent this limit is
 	 * EXT_UNINIT_MAX_LEN.
 	 */
-	if (max_blocks > EXT_INIT_MAX_LEN &&
+	if (map->m_len > EXT_INIT_MAX_LEN &&
 	    !(flags & EXT4_GET_BLOCKS_UNINIT_EXT))
-		max_blocks = EXT_INIT_MAX_LEN;
-	else if (max_blocks > EXT_UNINIT_MAX_LEN &&
+		map->m_len = EXT_INIT_MAX_LEN;
+	else if (map->m_len > EXT_UNINIT_MAX_LEN &&
 		 (flags & EXT4_GET_BLOCKS_UNINIT_EXT))
-		max_blocks = EXT_UNINIT_MAX_LEN;
+		map->m_len = EXT_UNINIT_MAX_LEN;
 
-	/* Check if we can really insert (iblock)::(iblock+max_blocks) extent */
-	newex.ee_block = cpu_to_le32(iblock);
-	newex.ee_len = cpu_to_le16(max_blocks);
+	/* Check if we can really insert (m_lblk)::(m_lblk + m_len) extent */
+	newex.ee_block = cpu_to_le32(map->m_lblk);
+	newex.ee_len = cpu_to_le16(map->m_len);
 	err = ext4_ext_check_overlap(inode, &newex, path);
 	if (err)
 		allocated = ext4_ext_get_actual_len(&newex);
 	else
-		allocated = max_blocks;
+		allocated = map->m_len;
 
 	/* allocate new block */
 	ar.inode = inode;
-	ar.goal = ext4_ext_find_goal(inode, path, iblock);
-	ar.logical = iblock;
+	ar.goal = ext4_ext_find_goal(inode, path, map->m_lblk);
+	ar.logical = map->m_lblk;
 	ar.len = allocated;
 	if (S_ISREG(inode->i_mode))
 		ar.flags = EXT4_MB_HINT_DATA;
@@ -3506,7 +3497,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 						     EXT4_STATE_DIO_UNWRITTEN);
 		}
 		if (ext4_should_dioread_nolock(inode))
-			set_buffer_uninit(bh_result);
+			map->m_flags |= EXT4_MAP_UNINIT;
 	}
 
 	if (unlikely(EXT4_I(inode)->i_flags & EXT4_EOFBLOCKS_FL)) {
@@ -3518,7 +3509,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 			goto out2;
 		}
 		last_ex = EXT_LAST_EXTENT(eh);
-		if (iblock + ar.len > le32_to_cpu(last_ex->ee_block)
+		if (map->m_lblk + ar.len > le32_to_cpu(last_ex->ee_block)
 		    + ext4_ext_get_actual_len(last_ex))
 			EXT4_I(inode)->i_flags &= ~EXT4_EOFBLOCKS_FL;
 	}
@@ -3536,9 +3527,9 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 	/* previous routine could use block we allocated */
 	newblock = ext_pblock(&newex);
 	allocated = ext4_ext_get_actual_len(&newex);
-	if (allocated > max_blocks)
-		allocated = max_blocks;
-	set_buffer_new(bh_result);
+	if (allocated > map->m_len)
+		allocated = map->m_len;
+	map->m_flags |= EXT4_MAP_NEW;
 
 	/*
 	 * Update reserved blocks/metadata blocks after successful
@@ -3552,18 +3543,18 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 	 * when it is _not_ an uninitialized extent.
 	 */
 	if ((flags & EXT4_GET_BLOCKS_UNINIT_EXT) == 0) {
-		ext4_ext_put_in_cache(inode, iblock, allocated, newblock,
+		ext4_ext_put_in_cache(inode, map->m_lblk, allocated, newblock,
 						EXT4_EXT_CACHE_EXTENT);
 		ext4_update_inode_fsync_trans(handle, inode, 1);
 	} else
 		ext4_update_inode_fsync_trans(handle, inode, 0);
 out:
-	if (allocated > max_blocks)
-		allocated = max_blocks;
+	if (allocated > map->m_len)
+		allocated = map->m_len;
 	ext4_ext_show_leaf(inode, path);
-	set_buffer_mapped(bh_result);
-	bh_result->b_bdev = inode->i_sb->s_bdev;
-	bh_result->b_blocknr = newblock;
+	map->m_flags |= EXT4_MAP_MAPPED;
+	map->m_pblk = newblock;
+	map->m_len = allocated;
 out2:
 	if (path) {
 		ext4_ext_drop_refs(path);
@@ -3729,7 +3720,7 @@ retry:
 		if (ret <= 0) {
 #ifdef EXT4FS_DEBUG
 			WARN_ON(ret <= 0);
-			printk(KERN_ERR "%s: ext4_ext_get_blocks "
+			printk(KERN_ERR "%s: ext4_ext_map_blocks "
 				    "returned error inode#%lu, block=%u, "
 				    "max_blocks=%u", __func__,
 				    inode->i_ino, block, max_blocks);
@@ -3806,7 +3797,7 @@ int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
 				      EXT4_GET_BLOCKS_IO_CONVERT_EXT);
 		if (ret <= 0) {
 			WARN_ON(ret <= 0);
-			printk(KERN_ERR "%s: ext4_ext_get_blocks "
+			printk(KERN_ERR "%s: ext4_ext_map_blocks "
 				    "returned error inode#%lu, block=%u, "
 				    "max_blocks=%u", __func__,
 				    inode->i_ino, block, max_blocks);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 830336d..ff2f5fd 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -149,7 +149,7 @@ int ext4_truncate_restart_trans(handle_t *handle, struct inode *inode,
 	int ret;
 
 	/*
-	 * Drop i_data_sem to avoid deadlock with ext4_get_blocks At this
+	 * Drop i_data_sem to avoid deadlock with ext4_map_blocks.  At this
 	 * moment, get_block can be called only for blocks inside i_size since
 	 * page cache has been already dropped and writes are blocked by
 	 * i_mutex. So we can safely drop the i_data_sem here.
@@ -890,9 +890,9 @@ err_out:
 }
 
 /*
- * The ext4_ind_get_blocks() function handles non-extents inodes
+ * The ext4_ind_map_blocks() function handles non-extents inodes
  * (i.e., using the traditional indirect/double-indirect i_blocks
- * scheme) for ext4_get_blocks().
+ * scheme) for ext4_map_blocks().
  *
  * Allocation strategy is simple: if we have to allocate something, we will
  * have to go the whole way to leaf. So let's do it before attaching anything
@@ -917,9 +917,8 @@ err_out:
  * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
  * blocks.
  */
-static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
-			       ext4_lblk_t iblock, unsigned int maxblocks,
-			       struct buffer_head *bh_result,
+static int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
+			       struct ext4_map_blocks *map,
 			       int flags)
 {
 	int err = -EIO;
@@ -935,7 +934,7 @@ static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
 
 	J_ASSERT(!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL));
 	J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
-	depth = ext4_block_to_path(inode, iblock, offsets,
+	depth = ext4_block_to_path(inode, map->m_lblk, offsets,
 				   &blocks_to_boundary);
 
 	if (depth == 0)
@@ -946,10 +945,9 @@ static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
 	/* Simplest case - block found, no allocation needed */
 	if (!partial) {
 		first_block = le32_to_cpu(chain[depth - 1].key);
-		clear_buffer_new(bh_result);
 		count++;
 		/*map more blocks*/
-		while (count < maxblocks && count <= blocks_to_boundary) {
+		while (count < map->m_len && count <= blocks_to_boundary) {
 			ext4_fsblk_t blk;
 
 			blk = le32_to_cpu(*(chain[depth-1].p + count));
@@ -969,7 +967,7 @@ static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
 	/*
 	 * Okay, we need to do block allocation.
 	*/
-	goal = ext4_find_goal(inode, iblock, partial);
+	goal = ext4_find_goal(inode, map->m_lblk, partial);
 
 	/* the number of blocks need to allocate for [d,t]indirect blocks */
 	indirect_blks = (chain + depth) - partial - 1;
@@ -979,11 +977,11 @@ static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
 	 * direct blocks to allocate for this branch.
 	 */
 	count = ext4_blks_to_allocate(partial, indirect_blks,
-					maxblocks, blocks_to_boundary);
+				      map->m_len, blocks_to_boundary);
 	/*
 	 * Block out ext4_truncate while we alter the tree
 	 */
-	err = ext4_alloc_branch(handle, inode, iblock, indirect_blks,
+	err = ext4_alloc_branch(handle, inode, map->m_lblk, indirect_blks,
 				&count, goal,
 				offsets + (partial - chain), partial);
 
@@ -995,18 +993,20 @@ static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
 	 * may need to return -EAGAIN upwards in the worst case.  --sct
 	 */
 	if (!err)
-		err = ext4_splice_branch(handle, inode, iblock,
+		err = ext4_splice_branch(handle, inode, map->m_lblk,
 					 partial, indirect_blks, count);
 	if (err)
 		goto cleanup;
 
-	set_buffer_new(bh_result);
+	map->m_flags |= EXT4_MAP_NEW;
 
 	ext4_update_inode_fsync_trans(handle, inode, 1);
 got_it:
-	map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
+	map->m_flags |= EXT4_MAP_MAPPED;
+	map->m_pblk = le32_to_cpu(chain[depth-1].key);
+	map->m_len = count;
 	if (count > blocks_to_boundary)
-		set_buffer_boundary(bh_result);
+		map->m_flags |= EXT4_MAP_BOUNDARY;
 	err = count;
 	/* Clean up and exit */
 	partial = chain + depth - 1;	/* the whole chain */
@@ -1016,7 +1016,6 @@ cleanup:
 		brelse(partial->bh);
 		partial--;
 	}
-	BUFFER_TRACE(bh_result, "returned");
 out:
 	return err;
 }
@@ -1203,15 +1202,15 @@ static pgoff_t ext4_num_dirty_pages(struct inode *inode, pgoff_t idx,
 }
 
 /*
- * The ext4_get_blocks() function tries to look up the requested blocks,
+ * The ext4_map_blocks() function tries to look up the requested blocks,
  * and returns if the blocks are already mapped.
  *
  * Otherwise it takes the write lock of the i_data_sem and allocate blocks
  * and store the allocated blocks in the result buffer head and mark it
  * mapped.
  *
- * If file type is extents based, it will call ext4_ext_get_blocks(),
- * Otherwise, call with ext4_ind_get_blocks() to handle indirect mapping
+ * If file type is extents based, it will call ext4_ext_map_blocks(),
+ * Otherwise, call with ext4_ind_map_blocks() to handle indirect mapping
  * based files
  *
  * On success, it returns the number of blocks being mapped or allocate.
@@ -1224,35 +1223,30 @@ static pgoff_t ext4_num_dirty_pages(struct inode *inode, pgoff_t idx,
  *
  * It returns the error in case of allocation failure.
  */
-int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
-		    unsigned int max_blocks, struct buffer_head *bh,
-		    int flags)
+int ext4_map_blocks(handle_t *handle, struct inode *inode,
+		    struct ext4_map_blocks *map, int flags)
 {
 	int retval;
 
-	clear_buffer_mapped(bh);
-	clear_buffer_unwritten(bh);
-
-	ext_debug("ext4_get_blocks(): inode %lu, flag %d, max_blocks %u,"
-		  "logical block %lu\n", inode->i_ino, flags, max_blocks,
-		  (unsigned long)block);
+	map->m_flags = 0;
+	ext_debug("ext4_map_blocks(): inode %lu, flag %d, max_blocks %u,"
+		  "logical block %lu\n", inode->i_ino, flags, map->m_len,
+		  (unsigned long) map->m_lblk);
 	/*
 	 * Try to see if we can get the block without requesting a new
 	 * file system block.
 	 */
 	down_read((&EXT4_I(inode)->i_data_sem));
 	if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
-		retval =  ext4_ext_get_blocks(handle, inode, block, max_blocks,
-				bh, 0);
+		retval = ext4_ext_map_blocks(handle, inode, map, 0);
 	} else {
-		retval = ext4_ind_get_blocks(handle, inode, block, max_blocks,
-					     bh, 0);
+		retval = ext4_ind_map_blocks(handle, inode, map, 0);
 	}
 	up_read((&EXT4_I(inode)->i_data_sem));
 
-	if (retval > 0 && buffer_mapped(bh)) {
+	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
 		int ret = check_block_validity(inode, "file system corruption",
-					       block, bh->b_blocknr, retval);
+					map->m_lblk, map->m_pblk, retval);
 		if (ret != 0)
 			return ret;
 	}
@@ -1268,7 +1262,7 @@ int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
 	 * ext4_ext_get_block() returns th create = 0
 	 * with buffer head unmapped.
 	 */
-	if (retval > 0 && buffer_mapped(bh))
+	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED)
 		return retval;
 
 	/*
@@ -1281,7 +1275,7 @@ int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
 	 * of BH_Unwritten and BH_Mapped flags being simultaneously
 	 * set on the buffer_head.
 	 */
-	clear_buffer_unwritten(bh);
+	map->m_flags &= ~EXT4_MAP_UNWRITTEN;
 
 	/*
 	 * New blocks allocate and/or writing to uninitialized extent
@@ -1304,13 +1298,11 @@ int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
 	 * could have changed the inode type in between
 	 */
 	if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
-		retval =  ext4_ext_get_blocks(handle, inode, block, max_blocks,
-					      bh, flags);
+		retval = ext4_ext_map_blocks(handle, inode, map, flags);
 	} else {
-		retval = ext4_ind_get_blocks(handle, inode, block,
-					     max_blocks, bh, flags);
+		retval = ext4_ind_map_blocks(handle, inode, map, flags);
 
-		if (retval > 0 && buffer_new(bh)) {
+		if (retval > 0 && map->m_flags & EXT4_MAP_NEW) {
 			/*
 			 * We allocated new blocks which will result in
 			 * i_data's format changing.  Force the migrate
@@ -1333,16 +1325,38 @@ int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
 		EXT4_I(inode)->i_delalloc_reserved_flag = 0;
 
 	up_write((&EXT4_I(inode)->i_data_sem));
-	if (retval > 0 && buffer_mapped(bh)) {
+	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
 		int ret = check_block_validity(inode, "file system "
 					       "corruption after allocation",
-					       block, bh->b_blocknr, retval);
+					       map->m_lblk, map->m_pblk,
+					       retval);
 		if (ret != 0)
 			return ret;
 	}
 	return retval;
 }
 
+int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
+		    unsigned int max_blocks, struct buffer_head *bh,
+		    int flags)
+{
+	struct ext4_map_blocks map;
+	int ret;
+
+	map.m_lblk = block;
+	map.m_len = max_blocks;
+
+	ret = ext4_map_blocks(handle, inode, &map, flags);
+	if (ret < 0)
+		return ret;
+
+	bh->b_blocknr = map.m_pblk;
+	bh->b_size = inode->i_sb->s_blocksize * map.m_len;
+	bh->b_bdev = inode->i_sb->s_bdev;
+	bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
+	return ret;
+}
+
 /* Maximum number of blocks we map for direct IO at once. */
 #define DIO_MAX_BLOCKS 4096