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>

1 files changed, 114 insertions, 123 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 8a8f9f0be911..37f938789344 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);