1 files changed, 64 insertions, 9 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index af99b78b288..5edcee3a617 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -414,11 +414,29 @@ static noinline int remove_from_bitmap(struct btrfs_block_group_cache *block_gro
 			      u64 *offset, u64 *bytes)
 {
 	u64 end;
+	u64 search_start, search_bytes;
+	int ret;
 
 again:
 	end = bitmap_info->offset +
 		(u64)(BITS_PER_BITMAP * block_group->sectorsize) - 1;
 
+	/*
+	 * XXX - this can go away after a few releases.
+	 *
+	 * since the only user of btrfs_remove_free_space is the tree logging
+	 * stuff, and the only way to test that is under crash conditions, we
+	 * want to have this debug stuff here just in case somethings not
+	 * working.  Search the bitmap for the space we are trying to use to
+	 * make sure its actually there.  If its not there then we need to stop
+	 * because something has gone wrong.
+	 */
+	search_start = *offset;
+	search_bytes = *bytes;
+	ret = search_bitmap(block_group, bitmap_info, &search_start,
+			    &search_bytes);
+	BUG_ON(ret < 0 || search_start != *offset);
+
 	if (*offset > bitmap_info->offset && *offset + *bytes > end) {
 		bitmap_clear_bits(block_group, bitmap_info, *offset,
 				  end - *offset + 1);
@@ -430,6 +448,7 @@ again:
 	}
 
 	if (*bytes) {
+		struct rb_node *next = rb_next(&bitmap_info->offset_index);
 		if (!bitmap_info->bytes) {
 			unlink_free_space(block_group, bitmap_info);
 			kfree(bitmap_info->bitmap);
@@ -438,16 +457,36 @@ again:
 			recalculate_thresholds(block_group);
 		}
 
-		bitmap_info = tree_search_offset(block_group,
-						 offset_to_bitmap(block_group,
-								  *offset),
-						 1, 0);
-		if (!bitmap_info)
+		/*
+		 * no entry after this bitmap, but we still have bytes to
+		 * remove, so something has gone wrong.
+		 */
+		if (!next)
 			return -EINVAL;
 
+		bitmap_info = rb_entry(next, struct btrfs_free_space,
+				       offset_index);
+
+		/*
+		 * if the next entry isn't a bitmap we need to return to let the
+		 * extent stuff do its work.
+		 */
 		if (!bitmap_info->bitmap)
 			return -EAGAIN;
 
+		/*
+		 * Ok the next item is a bitmap, but it may not actually hold
+		 * the information for the rest of this free space stuff, so
+		 * look for it, and if we don't find it return so we can try
+		 * everything over again.
+		 */
+		search_start = *offset;
+		search_bytes = *bytes;
+		ret = search_bitmap(block_group, bitmap_info, &search_start,
+				    &search_bytes);
+		if (ret < 0 || search_start != *offset)
+			return -EAGAIN;
+
 		goto again;
 	} else if (!bitmap_info->bytes) {
 		unlink_free_space(block_group, bitmap_info);
@@ -644,8 +683,17 @@ int btrfs_remove_free_space(struct btrfs_block_group_cache *block_group,
 again:
 	info = tree_search_offset(block_group, offset, 0, 0);
 	if (!info) {
-		WARN_ON(1);
-		goto out_lock;
+		/*
+		 * oops didn't find an extent that matched the space we wanted
+		 * to remove, look for a bitmap instead
+		 */
+		info = tree_search_offset(block_group,
+					  offset_to_bitmap(block_group, offset),
+					  1, 0);
+		if (!info) {
+			WARN_ON(1);
+			goto out_lock;
+		}
 	}
 
 	if (info->bytes < bytes && rb_next(&info->offset_index)) {
@@ -957,8 +1005,15 @@ static u64 btrfs_alloc_from_bitmap(struct btrfs_block_group_cache *block_group,
 	if (cluster->block_group != block_group)
 		goto out;
 
-	entry = tree_search_offset(block_group, search_start, 0, 0);
-
+	/*
+	 * search_start is the beginning of the bitmap, but at some point it may
+	 * be a good idea to point to the actual start of the free area in the
+	 * bitmap, so do the offset_to_bitmap trick anyway, and set bitmap_only
+	 * to 1 to make sure we get the bitmap entry
+	 */
+	entry = tree_search_offset(block_group,
+				   offset_to_bitmap(block_group, search_start),
+				   1, 0);
 	if (!entry || !entry->bitmap)
 		goto out;