1 files changed, 48 insertions, 11 deletions

diff --git a/ext4_utils/extent.c b/ext4_utils/extent.c
index 1900b104..42ddd97d 100644
--- a/ext4_utils/extent.c
+++ b/ext4_utils/extent.c
@@ -5,7 +5,7 @@
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
- *      http://www.apache.org/licenses/LICENSE-2.0
+ *	  http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
@@ -72,23 +72,43 @@ static void extent_create_backing_file(struct block_allocation *alloc,
 }
 
 static struct block_allocation *do_inode_allocate_extents(
-	struct ext4_inode *inode, u64 len)
+	struct ext4_inode *inode, u64 len, struct block_allocation *prealloc)
 {
-	u32 block_len = DIV_ROUND_UP(len, info.block_size);
-	struct block_allocation *alloc = allocate_blocks(block_len + 1);
+	u32 block_len = DIV_ROUND_UP(len, info.block_size), prealloc_block_len;
+	struct block_allocation *alloc;
 	u32 extent_block = 0;
 	u32 file_block = 0;
 	struct ext4_extent *extent;
 	u64 blocks;
 
-	if (alloc == NULL) {
-		error("Failed to allocate %d blocks\n", block_len + 1);
-		return NULL;
+	if (!prealloc) {
+		alloc = allocate_blocks(block_len + 1);
+		if (alloc == NULL) {
+			error("Failed to allocate %d blocks\n", block_len + 1);
+			return NULL;
+		}
+	} else {
+		prealloc_block_len = block_allocation_len(prealloc);
+		if (block_len + 1 > prealloc_block_len) {
+			alloc = allocate_blocks(block_len + 1 - prealloc_block_len);
+			if (alloc == NULL) {
+				error("Failed to allocate %d blocks\n",
+						block_len + 1 - prealloc_block_len);
+				return NULL;
+			}
+			region_list_append(&prealloc->list, alloc->list.first);
+			free(alloc);
+		}
+		alloc = prealloc;
 	}
 
 	int allocation_len = block_allocation_num_regions(alloc);
 	if (allocation_len <= 3) {
 		reduce_allocation(alloc, 1);
+		// IMPORTANT: reduce_allocation may have changed allocation
+		// length, otherwise file corruption happens when fs thinks
+		// a block is missing from extent header.
+		allocation_len = block_allocation_num_regions(alloc);
 	} else {
 		reserve_oob_blocks(alloc, 1);
 		extent_block = get_oob_block(alloc, 0);
@@ -183,7 +203,7 @@ u8 *inode_allocate_data_extents(struct ext4_inode *inode, u64 len,
 	struct block_allocation *alloc;
 	u8 *data = NULL;
 
-	alloc = do_inode_allocate_extents(inode, len);
+	alloc = do_inode_allocate_extents(inode, len, NULL);
 	if (alloc == NULL) {
 		error("failed to allocate extents for %"PRIu64" bytes", len);
 		return NULL;
@@ -205,9 +225,26 @@ u8 *inode_allocate_data_extents(struct ext4_inode *inode, u64 len,
 struct block_allocation* inode_allocate_file_extents(struct ext4_inode *inode, u64 len,
 	const char *filename)
 {
-	struct block_allocation *alloc;
+	struct block_allocation *alloc, *prealloc = base_fs_allocations, *prev_prealloc = NULL;
+	// TODO(mkayyash): base_fs_allocations is sorted by filename, consider
+	// storing it in an array and then binary searching for a filename match instead
+	while (prealloc && prealloc->filename != NULL) {
+		if (!strcmp(filename, prealloc->filename)) {
+			break;
+		}
+		prev_prealloc = prealloc;
+		prealloc = prealloc->next;
+	}
+	if (prealloc) {
+		if (!prev_prealloc) {
+			base_fs_allocations = base_fs_allocations->next;
+		} else {
+			prev_prealloc->next = prealloc->next;
+		}
+		prealloc->next = NULL;
+	}
 
-	alloc = do_inode_allocate_extents(inode, len);
+	alloc = do_inode_allocate_extents(inode, len, prealloc);
 	if (alloc == NULL) {
 		error("failed to allocate extents for %"PRIu64" bytes", len);
 		return NULL;
@@ -222,7 +259,7 @@ void inode_allocate_extents(struct ext4_inode *inode, u64 len)
 {
 	struct block_allocation *alloc;
 
-	alloc = do_inode_allocate_extents(inode, len);
+	alloc = do_inode_allocate_extents(inode, len, NULL);
 	if (alloc == NULL) {
 		error("failed to allocate extents for %"PRIu64" bytes", len);
 		return;