ext4: fold ext4_alloc_blocks() in ext4_alloc_branch()

The older code was far more complicated than it needed to be because
of how we spliced in the ext4's new multiblock allocator into ext3's
indirect block code.  By folding ext4_alloc_blocks() into
ext4_alloc_branch(), we make the code far more understable, shave off
over 130 lines of code and half a kilobyte of compiled object code.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/indirect.c

@@ -291,131 +291,6 @@ static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
 	return count;
 }
 
-/**
- *	ext4_alloc_blocks: multiple allocate blocks needed for a branch
- *	@handle: handle for this transaction
- *	@inode: inode which needs allocated blocks
- *	@iblock: the logical block to start allocated at
- *	@goal: preferred physical block of allocation
- *	@indirect_blks: the number of blocks need to allocate for indirect
- *			blocks
- *	@blks: number of desired blocks
- *	@new_blocks: on return it will store the new block numbers for
- *	the indirect blocks(if needed) and the first direct block,
- *	@err: on return it will store the error code
- *
- *	This function will return the number of blocks allocated as
- *	requested by the passed-in parameters.
- */
-static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
-			     ext4_lblk_t iblock, ext4_fsblk_t goal,
-			     int indirect_blks, int blks,
-			     ext4_fsblk_t new_blocks[4], int *err)
-{
-	struct ext4_allocation_request ar;
-	int target, i;
-	unsigned long count = 0, blk_allocated = 0;
-	int index = 0;
-	ext4_fsblk_t current_block = 0;
-	int ret = 0;
-
-	/*
-	 * Here we try to allocate the requested multiple blocks at once,
-	 * on a best-effort basis.
-	 * To build a branch, we should allocate blocks for
-	 * the indirect blocks(if not allocated yet), and at least
-	 * the first direct block of this branch.  That's the
-	 * minimum number of blocks need to allocate(required)
-	 */
-	/* first we try to allocate the indirect blocks */
-	target = indirect_blks;
-	while (target > 0) {
-		count = target;
-		/* allocating blocks for indirect blocks and direct blocks */
-		current_block = ext4_new_meta_blocks(handle, inode, goal,
-						     0, &count, err);
-		if (*err)
-			goto failed_out;
-
-		if (unlikely(current_block + count > EXT4_MAX_BLOCK_FILE_PHYS)) {
-			EXT4_ERROR_INODE(inode,
-					 "current_block %llu + count %lu > %d!",
-					 current_block, count,
-					 EXT4_MAX_BLOCK_FILE_PHYS);
-			*err = -EIO;
-			goto failed_out;
-		}
-
-		target -= count;
-		/* allocate blocks for indirect blocks */
-		while (index < indirect_blks && count) {
-			new_blocks[index++] = current_block++;
-			count--;
-		}
-		if (count > 0) {
-			/*
-			 * save the new block number
-			 * for the first direct block
-			 */
-			new_blocks[index] = current_block;
-			WARN(1, KERN_INFO "%s returned more blocks than "
-						"requested\n", __func__);
-			break;
-		}
-	}
-
-	target = blks - count ;
-	blk_allocated = count;
-	if (!target)
-		goto allocated;
-	/* Now allocate data blocks */
-	memset(&ar, 0, sizeof(ar));
-	ar.inode = inode;
-	ar.goal = goal;
-	ar.len = target;
-	ar.logical = iblock;
-	if (S_ISREG(inode->i_mode))
-		/* enable in-core preallocation only for regular files */
-		ar.flags = EXT4_MB_HINT_DATA;
-
-	current_block = ext4_mb_new_blocks(handle, &ar, err);
-	if (unlikely(current_block + ar.len > EXT4_MAX_BLOCK_FILE_PHYS)) {
-		EXT4_ERROR_INODE(inode,
-				 "current_block %llu + ar.len %d > %d!",
-				 current_block, ar.len,
-				 EXT4_MAX_BLOCK_FILE_PHYS);
-		*err = -EIO;
-		goto failed_out;
-	}
-
-	if (*err && (target == blks)) {
-		/*
-		 * if the allocation failed and we didn't allocate
-		 * any blocks before
-		 */
-		goto failed_out;
-	}
-	if (!*err) {
-		if (target == blks) {
-			/*
-			 * save the new block number
-			 * for the first direct block
-			 */
-			new_blocks[index] = current_block;
-		}
-		blk_allocated += ar.len;
-	}
-allocated:
-	/* total number of blocks allocated for direct blocks */
-	ret = blk_allocated;
-	*err = 0;
-	return ret;
-failed_out:
-	for (i = 0; i < index; i++)
-		ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
-	return ret;
-}
-
 /**
  *	ext4_alloc_branch - allocate and set up a chain of blocks.
  *	@handle: handle for this transaction
@@ -448,60 +323,59 @@ static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
 			     int *blks, ext4_fsblk_t goal,
 			     ext4_lblk_t *offsets, Indirect *branch)
 {
-	int blocksize = inode->i_sb->s_blocksize;
-	int i, n = 0;
-	int err = 0;
-	struct buffer_head *bh;
-	int num;
-	ext4_fsblk_t new_blocks[4];
-	ext4_fsblk_t current_block;
+	struct ext4_allocation_request	ar;
+	struct buffer_head *		bh;
+	ext4_fsblk_t			b, new_blocks[4];
+	__le32				*p;
+	int				i, j, err, len = 1;
 
-	num = ext4_alloc_blocks(handle, inode, iblock, goal, indirect_blks,
-				*blks, new_blocks, &err);
-	if (err)
-		return err;
-
-	branch[0].key = cpu_to_le32(new_blocks[0]);
 	/*
-	 * metadata blocks and data blocks are allocated.
+	 * Set up for the direct block allocation
 	 */
-	for (n = 1; n <= indirect_blks;  n++) {
-		/*
-		 * Get buffer_head for parent block, zero it out
-		 * and set the pointer to new one, then send
-		 * parent to disk.
-		 */
-		bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
+	memset(&ar, 0, sizeof(ar));
+	ar.inode = inode;
+	ar.len = *blks;
+	ar.logical = iblock;
+	if (S_ISREG(inode->i_mode))
+		ar.flags = EXT4_MB_HINT_DATA;
+
+	for (i = 0; i <= indirect_blks; i++) {
+		if (i == indirect_blks) {
+			ar.goal = goal;
+			new_blocks[i] = ext4_mb_new_blocks(handle, &ar, &err);
+		} else
+			goal = new_blocks[i] = ext4_new_meta_blocks(handle, inode,
+							goal, 0, NULL, &err);
+		if (err) {
+			i--;
+			goto failed;
+		}
+		branch[i].key = cpu_to_le32(new_blocks[i]);
+		if (i == 0)
+			continue;
+
+		bh = branch[i].bh = sb_getblk(inode->i_sb, new_blocks[i-1]);
 		if (unlikely(!bh)) {
 			err = -ENOMEM;
 			goto failed;
 		}
-
-		branch[n].bh = bh;
 		lock_buffer(bh);
 		BUFFER_TRACE(bh, "call get_create_access");
 		err = ext4_journal_get_create_access(handle, bh);
 		if (err) {
-			/* Don't brelse(bh) here; it's done in
-			 * ext4_journal_forget() below */
 			unlock_buffer(bh);
 			goto failed;
 		}
 
-		memset(bh->b_data, 0, blocksize);
-		branch[n].p = (__le32 *) bh->b_data + offsets[n];
-		branch[n].key = cpu_to_le32(new_blocks[n]);
-		*branch[n].p = branch[n].key;
-		if (n == indirect_blks) {
-			current_block = new_blocks[n];
-			/*
-			 * End of chain, update the last new metablock of
-			 * the chain to point to the new allocated
-			 * data blocks numbers
-			 */
-			for (i = 1; i < num; i++)
-				*(branch[n].p + i) = cpu_to_le32(++current_block);
-		}
+		memset(bh->b_data, 0, bh->b_size);
+		p = branch[i].p = (__le32 *) bh->b_data + offsets[i];
+		b = new_blocks[i];
+
+		if (i == indirect_blks)
+			len = ar.len;
+		for (j = 0; j < len; j++)
+			*p++ = cpu_to_le32(b++);
+
 		BUFFER_TRACE(bh, "marking uptodate");
 		set_buffer_uptodate(bh);
 		unlock_buffer(bh);
@@ -511,25 +385,16 @@ static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
 		if (err)
 			goto failed;
 	}
-	*blks = num;
-	return err;
+	*blks = ar.len;
+	return 0;
 failed:
-	/* Allocation failed, free what we already allocated */
-	ext4_free_blocks(handle, inode, NULL, new_blocks[0], 1, 0);
-	for (i = 1; i <= n ; i++) {
-		/*
-		 * branch[i].bh is newly allocated, so there is no
-		 * need to revoke the block, which is why we don't
-		 * need to set EXT4_FREE_BLOCKS_METADATA.
-		 */
-		ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1,
-				 EXT4_FREE_BLOCKS_FORGET);
+	for (; i >= 0; i--) {
+		if (i != indirect_blks && branch[i].bh)
+			ext4_forget(handle, 1, inode, branch[i].bh,
+				    branch[i].bh->b_blocknr);
+		ext4_free_blocks(handle, inode, NULL, new_blocks[i],
+				 (i == indirect_blks) ? ar.len : 1, 0);
 	}
-	for (i = n+1; i < indirect_blks; i++)
-		ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
-
-	ext4_free_blocks(handle, inode, NULL, new_blocks[i], num, 0);
-
 	return err;
 }