ext4: Convert callers of ext4_get_blocks() to use ext4_map_blocks()
authorTheodore Ts'o <tytso@mit.edu>
Mon, 17 May 2010 00:00:00 +0000 (20:00 -0400)
committerTheodore Ts'o <tytso@mit.edu>
Mon, 17 May 2010 00:00:00 +0000 (20:00 -0400)
This saves a huge amount of stack space by avoiding unnecesary struct
buffer_head's from being allocated on the stack.

In addition, to make the code easier to understand, collapse and
refactor ext4_get_block(), ext4_get_block_write(),
noalloc_get_block_write(), into a single function.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
fs/ext4/dir.c
fs/ext4/extents.c
fs/ext4/inode.c

index 86cb6d8..e3f2700 100644 (file)
@@ -128,14 +128,14 @@ static int ext4_readdir(struct file *filp,
        offset = filp->f_pos & (sb->s_blocksize - 1);
 
        while (!error && !stored && filp->f_pos < inode->i_size) {
-               ext4_lblk_t blk = filp->f_pos >> EXT4_BLOCK_SIZE_BITS(sb);
-               struct buffer_head map_bh;
+               struct ext4_map_blocks map;
                struct buffer_head *bh = NULL;
 
-               map_bh.b_state = 0;
-               err = ext4_get_blocks(NULL, inode, blk, 1, &map_bh, 0);
+               map.m_lblk = filp->f_pos >> EXT4_BLOCK_SIZE_BITS(sb);
+               map.m_len = 1;
+               err = ext4_map_blocks(NULL, inode, &map, 0);
                if (err > 0) {
-                       pgoff_t index = map_bh.b_blocknr >>
+                       pgoff_t index = map.m_pblk >>
                                        (PAGE_CACHE_SHIFT - inode->i_blkbits);
                        if (!ra_has_index(&filp->f_ra, index))
                                page_cache_sync_readahead(
@@ -143,7 +143,7 @@ static int ext4_readdir(struct file *filp,
                                        &filp->f_ra, filp,
                                        index, 1);
                        filp->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
-                       bh = ext4_bread(NULL, inode, blk, 0, &err);
+                       bh = ext4_bread(NULL, inode, map.m_lblk, 0, &err);
                }
 
                /*
index 37f9387..d6801eb 100644 (file)
@@ -3667,13 +3667,12 @@ static void ext4_falloc_update_inode(struct inode *inode,
 long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
 {
        handle_t *handle;
-       ext4_lblk_t block;
        loff_t new_size;
        unsigned int max_blocks;
        int ret = 0;
        int ret2 = 0;
        int retries = 0;
-       struct buffer_head map_bh;
+       struct ext4_map_blocks map;
        unsigned int credits, blkbits = inode->i_blkbits;
 
        /*
@@ -3687,13 +3686,13 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
        if (S_ISDIR(inode->i_mode))
                return -ENODEV;
 
-       block = offset >> blkbits;
+       map.m_lblk = offset >> blkbits;
        /*
         * We can't just convert len to max_blocks because
         * If blocksize = 4096 offset = 3072 and len = 2048
         */
        max_blocks = (EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits)
-                                                       - block;
+               - map.m_lblk;
        /*
         * credits to insert 1 extent into extent tree
         */
@@ -3706,16 +3705,14 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
        }
 retry:
        while (ret >= 0 && ret < max_blocks) {
-               block = block + ret;
-               max_blocks = max_blocks - ret;
+               map.m_lblk = map.m_lblk + ret;
+               map.m_len = max_blocks = max_blocks - ret;
                handle = ext4_journal_start(inode, credits);
                if (IS_ERR(handle)) {
                        ret = PTR_ERR(handle);
                        break;
                }
-               map_bh.b_state = 0;
-               ret = ext4_get_blocks(handle, inode, block,
-                                     max_blocks, &map_bh,
+               ret = ext4_map_blocks(handle, inode, &map,
                                      EXT4_GET_BLOCKS_CREATE_UNINIT_EXT);
                if (ret <= 0) {
 #ifdef EXT4FS_DEBUG
@@ -3729,14 +3726,14 @@ retry:
                        ret2 = ext4_journal_stop(handle);
                        break;
                }
-               if ((block + ret) >= (EXT4_BLOCK_ALIGN(offset + len,
+               if ((map.m_lblk + ret) >= (EXT4_BLOCK_ALIGN(offset + len,
                                                blkbits) >> blkbits))
                        new_size = offset + len;
                else
-                       new_size = (block + ret) << blkbits;
+                       new_size = (map.m_lblk + ret) << blkbits;
 
                ext4_falloc_update_inode(inode, mode, new_size,
-                                               buffer_new(&map_bh));
+                                        (map.m_flags & EXT4_MAP_NEW));
                ext4_mark_inode_dirty(handle, inode);
                ret2 = ext4_journal_stop(handle);
                if (ret2)
@@ -3765,42 +3762,39 @@ int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
                                    ssize_t len)
 {
        handle_t *handle;
-       ext4_lblk_t block;
        unsigned int max_blocks;
        int ret = 0;
        int ret2 = 0;
-       struct buffer_head map_bh;
+       struct ext4_map_blocks map;
        unsigned int credits, blkbits = inode->i_blkbits;
 
-       block = offset >> blkbits;
+       map.m_lblk = offset >> blkbits;
        /*
         * We can't just convert len to max_blocks because
         * If blocksize = 4096 offset = 3072 and len = 2048
         */
-       max_blocks = (EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits)
-                                                       - block;
+       max_blocks = ((EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits) -
+                     map.m_lblk);
        /*
         * credits to insert 1 extent into extent tree
         */
        credits = ext4_chunk_trans_blocks(inode, max_blocks);
        while (ret >= 0 && ret < max_blocks) {
-               block = block + ret;
-               max_blocks = max_blocks - ret;
+               map.m_lblk += ret;
+               map.m_len = (max_blocks -= ret);
                handle = ext4_journal_start(inode, credits);
                if (IS_ERR(handle)) {
                        ret = PTR_ERR(handle);
                        break;
                }
-               map_bh.b_state = 0;
-               ret = ext4_get_blocks(handle, inode, block,
-                                     max_blocks, &map_bh,
+               ret = ext4_map_blocks(handle, inode, &map,
                                      EXT4_GET_BLOCKS_IO_CONVERT_EXT);
                if (ret <= 0) {
                        WARN_ON(ret <= 0);
                        printk(KERN_ERR "%s: ext4_ext_map_blocks "
                                    "returned error inode#%lu, block=%u, "
                                    "max_blocks=%u", __func__,
-                                   inode->i_ino, block, max_blocks);
+                                   inode->i_ino, map.m_lblk, map.m_len);
                }
                ext4_mark_inode_dirty(handle, inode);
                ret2 = ext4_journal_stop(handle);
index ff2f5fd..0b1d7c8 100644 (file)
@@ -1336,133 +1336,112 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
        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
 
-int ext4_get_block(struct inode *inode, sector_t iblock,
-                  struct buffer_head *bh_result, int create)
+static int _ext4_get_block(struct inode *inode, sector_t iblock,
+                          struct buffer_head *bh, int flags)
 {
        handle_t *handle = ext4_journal_current_handle();
+       struct ext4_map_blocks map;
        int ret = 0, started = 0;
-       unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
        int dio_credits;
 
-       if (create && !handle) {
+       map.m_lblk = iblock;
+       map.m_len = bh->b_size >> inode->i_blkbits;
+
+       if (flags && !handle) {
                /* Direct IO write... */
-               if (max_blocks > DIO_MAX_BLOCKS)
-                       max_blocks = DIO_MAX_BLOCKS;
-               dio_credits = ext4_chunk_trans_blocks(inode, max_blocks);
+               if (map.m_len > DIO_MAX_BLOCKS)
+                       map.m_len = DIO_MAX_BLOCKS;
+               dio_credits = ext4_chunk_trans_blocks(inode, map.m_len);
                handle = ext4_journal_start(inode, dio_credits);
                if (IS_ERR(handle)) {
                        ret = PTR_ERR(handle);
-                       goto out;
+                       return ret;
                }
                started = 1;
        }
 
-       ret = ext4_get_blocks(handle, inode, iblock, max_blocks, bh_result,
-                             create ? EXT4_GET_BLOCKS_CREATE : 0);
+       ret = ext4_map_blocks(handle, inode, &map, flags);
        if (ret > 0) {
-               bh_result->b_size = (ret << inode->i_blkbits);
+               map_bh(bh, inode->i_sb, map.m_pblk);
+               bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
+               bh->b_size = inode->i_sb->s_blocksize * map.m_len;
                ret = 0;
        }
        if (started)
                ext4_journal_stop(handle);
-out:
        return ret;
 }
 
+int ext4_get_block(struct inode *inode, sector_t iblock,
+                  struct buffer_head *bh, int create)
+{
+       return _ext4_get_block(inode, iblock, bh,
+                              create ? EXT4_GET_BLOCKS_CREATE : 0);
+}
+
 /*
  * `handle' can be NULL if create is zero
  */
 struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
                                ext4_lblk_t block, int create, int *errp)
 {
-       struct buffer_head dummy;
+       struct ext4_map_blocks map;
+       struct buffer_head *bh;
        int fatal = 0, err;
-       int flags = 0;
 
        J_ASSERT(handle != NULL || create == 0);
 
-       dummy.b_state = 0;
-       dummy.b_blocknr = -1000;
-       buffer_trace_init(&dummy.b_history);
-       if (create)
-               flags |= EXT4_GET_BLOCKS_CREATE;
-       err = ext4_get_blocks(handle, inode, block, 1, &dummy, flags);
-       /*
-        * ext4_get_blocks() returns number of blocks mapped. 0 in
-        * case of a HOLE.
-        */
-       if (err > 0) {
-               if (err > 1)
-                       WARN_ON(1);
-               err = 0;
+       map.m_lblk = block;
+       map.m_len = 1;
+       err = ext4_map_blocks(handle, inode, &map,
+                             create ? EXT4_GET_BLOCKS_CREATE : 0);
+
+       if (err < 0)
+               *errp = err;
+       if (err <= 0)
+               return NULL;
+       *errp = 0;
+
+       bh = sb_getblk(inode->i_sb, map.m_pblk);
+       if (!bh) {
+               *errp = -EIO;
+               return NULL;
        }
-       *errp = err;
-       if (!err && buffer_mapped(&dummy)) {
-               struct buffer_head *bh;
-               bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
-               if (!bh) {
-                       *errp = -EIO;
-                       goto err;
-               }
-               if (buffer_new(&dummy)) {
-                       J_ASSERT(create != 0);
-                       J_ASSERT(handle != NULL);
+       if (map.m_flags & EXT4_MAP_NEW) {
+               J_ASSERT(create != 0);
+               J_ASSERT(handle != NULL);
 
-                       /*
-                        * Now that we do not always journal data, we should
-                        * keep in mind whether this should always journal the
-                        * new buffer as metadata.  For now, regular file
-                        * writes use ext4_get_block instead, so it's not a
-                        * problem.
-                        */
-                       lock_buffer(bh);
-                       BUFFER_TRACE(bh, "call get_create_access");
-                       fatal = ext4_journal_get_create_access(handle, bh);
-                       if (!fatal && !buffer_uptodate(bh)) {
-                               memset(bh->b_data, 0, inode->i_sb->s_blocksize);
-                               set_buffer_uptodate(bh);
-                       }
-                       unlock_buffer(bh);
-                       BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
-                       err = ext4_handle_dirty_metadata(handle, inode, bh);
-                       if (!fatal)
-                               fatal = err;
-               } else {
-                       BUFFER_TRACE(bh, "not a new buffer");
-               }
-               if (fatal) {
-                       *errp = fatal;
-                       brelse(bh);
-                       bh = NULL;
+               /*
+                * Now that we do not always journal data, we should
+                * keep in mind whether this should always journal the
+                * new buffer as metadata.  For now, regular file
+                * writes use ext4_get_block instead, so it's not a
+                * problem.
+                */
+               lock_buffer(bh);
+               BUFFER_TRACE(bh, "call get_create_access");
+               fatal = ext4_journal_get_create_access(handle, bh);
+               if (!fatal && !buffer_uptodate(bh)) {
+                       memset(bh->b_data, 0, inode->i_sb->s_blocksize);
+                       set_buffer_uptodate(bh);
                }
-               return bh;
+               unlock_buffer(bh);
+               BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
+               err = ext4_handle_dirty_metadata(handle, inode, bh);
+               if (!fatal)
+                       fatal = err;
+       } else {
+               BUFFER_TRACE(bh, "not a new buffer");
        }
-err:
-       return NULL;
+       if (fatal) {
+               *errp = fatal;
+               brelse(bh);
+               bh = NULL;
+       }
+       return bh;
 }
 
 struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
@@ -2050,28 +2029,23 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
 /*
  * mpage_put_bnr_to_bhs - walk blocks and assign them actual numbers
  *
- * @mpd->inode - inode to walk through
- * @exbh->b_blocknr - first block on a disk
- * @exbh->b_size - amount of space in bytes
- * @logical - first logical block to start assignment with
- *
  * the function goes through all passed space and put actual disk
  * block numbers into buffer heads, dropping BH_Delay and BH_Unwritten
  */
-static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
-                                struct buffer_head *exbh)
+static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd,
+                                struct ext4_map_blocks *map)
 {
        struct inode *inode = mpd->inode;
        struct address_space *mapping = inode->i_mapping;
-       int blocks = exbh->b_size >> inode->i_blkbits;
-       sector_t pblock = exbh->b_blocknr, cur_logical;
+       int blocks = map->m_len;
+       sector_t pblock = map->m_pblk, cur_logical;
        struct buffer_head *head, *bh;
        pgoff_t index, end;
        struct pagevec pvec;
        int nr_pages, i;
 
-       index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
-       end = (logical + blocks - 1) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
+       index = map->m_lblk >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
+       end = (map->m_lblk + blocks - 1) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
        cur_logical = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
 
        pagevec_init(&pvec, 0);
@@ -2098,17 +2072,16 @@ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
 
                        /* skip blocks out of the range */
                        do {
-                               if (cur_logical >= logical)
+                               if (cur_logical >= map->m_lblk)
                                        break;
                                cur_logical++;
                        } while ((bh = bh->b_this_page) != head);
 
                        do {
-                               if (cur_logical >= logical + blocks)
+                               if (cur_logical >= map->m_lblk + blocks)
                                        break;
 
-                               if (buffer_delay(bh) ||
-                                               buffer_unwritten(bh)) {
+                               if (buffer_delay(bh) || buffer_unwritten(bh)) {
 
                                        BUG_ON(bh->b_bdev != inode->i_sb->s_bdev);
 
@@ -2127,7 +2100,7 @@ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
                                } else if (buffer_mapped(bh))
                                        BUG_ON(bh->b_blocknr != pblock);
 
-                               if (buffer_uninit(exbh))
+                               if (map->m_flags & EXT4_MAP_UNINIT)
                                        set_buffer_uninit(bh);
                                cur_logical++;
                                pblock++;
@@ -2138,21 +2111,6 @@ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
 }
 
 
-/*
- * __unmap_underlying_blocks - just a helper function to unmap
- * set of blocks described by @bh
- */
-static inline void __unmap_underlying_blocks(struct inode *inode,
-                                            struct buffer_head *bh)
-{
-       struct block_device *bdev = inode->i_sb->s_bdev;
-       int blocks, i;
-
-       blocks = bh->b_size >> inode->i_blkbits;
-       for (i = 0; i < blocks; i++)
-               unmap_underlying_metadata(bdev, bh->b_blocknr + i);
-}
-
 static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
                                        sector_t logical, long blk_cnt)
 {
@@ -2214,7 +2172,7 @@ static void ext4_print_free_blocks(struct inode *inode)
 static int mpage_da_map_blocks(struct mpage_da_data *mpd)
 {
        int err, blks, get_blocks_flags;
-       struct buffer_head new;
+       struct ext4_map_blocks map;
        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;
@@ -2255,15 +2213,15 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
         * EXT4_GET_BLOCKS_DELALLOC_RESERVE so the delalloc accounting
         * variables are updated after the blocks have been allocated.
         */
-       new.b_state = 0;
+       map.m_lblk = next;
+       map.m_len = max_blocks;
        get_blocks_flags = EXT4_GET_BLOCKS_CREATE;
        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_get_blocks(handle, mpd->inode, next, max_blocks,
-                              &new, get_blocks_flags);
+       blks = ext4_map_blocks(handle, mpd->inode, &map, get_blocks_flags);
        if (blks < 0) {
                err = blks;
                /*
@@ -2305,10 +2263,13 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
        }
        BUG_ON(blks == 0);
 
-       new.b_size = (blks << mpd->inode->i_blkbits);
+       if (map.m_flags & EXT4_MAP_NEW) {
+               struct block_device *bdev = mpd->inode->i_sb->s_bdev;
+               int i;
 
-       if (buffer_new(&new))
-               __unmap_underlying_blocks(mpd->inode, &new);
+               for (i = 0; i < map.m_len; i++)
+                       unmap_underlying_metadata(bdev, map.m_pblk + i);
+       }
 
        /*
         * If blocks are delayed marked, we need to
@@ -2316,7 +2277,7 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
         */
        if ((mpd->b_state & (1 << BH_Delay)) ||
            (mpd->b_state & (1 << BH_Unwritten)))
-               mpage_put_bnr_to_bhs(mpd, next, &new);
+               mpage_put_bnr_to_bhs(mpd, &map);
 
        if (ext4_should_order_data(mpd->inode)) {
                err = ext4_jbd2_file_inode(handle, mpd->inode);
@@ -2534,8 +2495,9 @@ static int __mpage_da_writepage(struct page *page,
  * initialized properly.
  */
 static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
-                                 struct buffer_head *bh_result, int create)
+                                 struct buffer_head *bh, int create)
 {
+       struct ext4_map_blocks map;
        int ret = 0;
        sector_t invalid_block = ~((sector_t) 0xffff);
 
@@ -2543,16 +2505,22 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
                invalid_block = ~0;
 
        BUG_ON(create == 0);
-       BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
+       BUG_ON(bh->b_size != inode->i_sb->s_blocksize);
+
+       map.m_lblk = iblock;
+       map.m_len = 1;
 
        /*
         * first, we need to know whether the block is allocated already
         * preallocated blocks are unmapped but should treated
         * the same as allocated blocks.
         */
-       ret = ext4_get_blocks(NULL, inode, iblock, 1,  bh_result, 0);
-       if ((ret == 0) && !buffer_delay(bh_result)) {
-               /* the block isn't (pre)allocated yet, let's reserve space */
+       ret = ext4_map_blocks(NULL, inode, &map, 0);
+       if (ret < 0)
+               return ret;
+       if (ret == 0) {
+               if (buffer_delay(bh))
+                       return 0; /* Not sure this could or should happen */
                /*
                 * XXX: __block_prepare_write() unmaps passed block,
                 * is it OK?
@@ -2562,26 +2530,26 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
                        /* not enough space to reserve */
                        return ret;
 
-               map_bh(bh_result, inode->i_sb, invalid_block);
-               set_buffer_new(bh_result);
-               set_buffer_delay(bh_result);
-       } else if (ret > 0) {
-               bh_result->b_size = (ret << inode->i_blkbits);
-               if (buffer_unwritten(bh_result)) {
-                       /* A delayed write to unwritten bh should
-                        * be marked new and mapped.  Mapped ensures
-                        * that we don't do get_block multiple times
-                        * when we write to the same offset and new
-                        * ensures that we do proper zero out for
-                        * partial write.
-                        */
-                       set_buffer_new(bh_result);
-                       set_buffer_mapped(bh_result);
-               }
-               ret = 0;
+               map_bh(bh, inode->i_sb, invalid_block);
+               set_buffer_new(bh);
+               set_buffer_delay(bh);
+               return 0;
        }
 
-       return ret;
+       map_bh(bh, inode->i_sb, map.m_pblk);
+       bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
+
+       if (buffer_unwritten(bh)) {
+               /* A delayed write to unwritten bh should be marked
+                * new and mapped.  Mapped ensures that we don't do
+                * get_block multiple times when we write to the same
+                * offset and new ensures that we do proper zero out
+                * for partial write.
+                */
+               set_buffer_new(bh);
+               set_buffer_mapped(bh);
+       }
+       return 0;
 }
 
 /*
@@ -2603,21 +2571,8 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
                                   struct buffer_head *bh_result, int create)
 {
-       int ret = 0;
-       unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
-
        BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
-
-       /*
-        * we don't want to do block allocation in writepage
-        * so call get_block_wrap with create = 0
-        */
-       ret = ext4_get_blocks(NULL, inode, iblock, max_blocks, bh_result, 0);
-       if (ret > 0) {
-               bh_result->b_size = (ret << inode->i_blkbits);
-               ret = 0;
-       }
-       return ret;
+       return _ext4_get_block(inode, iblock, bh_result, 0);
 }
 
 static int bget_one(handle_t *handle, struct buffer_head *bh)
@@ -3644,46 +3599,18 @@ out:
        return ret;
 }
 
+/*
+ * ext4_get_block used when preparing for a DIO write or buffer write.
+ * We allocate an uinitialized extent if blocks haven't been allocated.
+ * The extent will be converted to initialized after the IO is complete.
+ */
 static int ext4_get_block_write(struct inode *inode, sector_t iblock,
                   struct buffer_head *bh_result, int create)
 {
-       handle_t *handle = ext4_journal_current_handle();
-       int ret = 0;
-       unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
-       int dio_credits;
-       int started = 0;
-
        ext4_debug("ext4_get_block_write: inode %lu, create flag %d\n",
                   inode->i_ino, create);
-       /*
-        * ext4_get_block in prepare for a DIO write or buffer write.
-        * We allocate an uinitialized extent if blocks haven't been allocated.
-        * The extent will be converted to initialized after IO complete.
-        */
-       create = EXT4_GET_BLOCKS_IO_CREATE_EXT;
-
-       if (!handle) {
-               if (max_blocks > DIO_MAX_BLOCKS)
-                       max_blocks = DIO_MAX_BLOCKS;
-               dio_credits = ext4_chunk_trans_blocks(inode, max_blocks);
-               handle = ext4_journal_start(inode, dio_credits);
-               if (IS_ERR(handle)) {
-                       ret = PTR_ERR(handle);
-                       goto out;
-               }
-               started = 1;
-       }
-
-       ret = ext4_get_blocks(handle, inode, iblock, max_blocks, bh_result,
-                             create);
-       if (ret > 0) {
-               bh_result->b_size = (ret << inode->i_blkbits);
-               ret = 0;
-       }
-       if (started)
-               ext4_journal_stop(handle);
-out:
-       return ret;
+       return _ext4_get_block(inode, iblock, bh_result,
+                              EXT4_GET_BLOCKS_IO_CREATE_EXT);
 }
 
 static void dump_completed_IO(struct inode * inode)