btrfs: set max_extent_size properly

We can't use entry->bytes if our entry is a bitmap entry, we need to use
entry->max_extent_size in that case.  Fix up all the logic to make this
consistent.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/free-space-cache.c

@@ -1772,6 +1772,13 @@ static int search_bitmap(struct btrfs_free_space_ctl *ctl,
 	return -1;
 }
 
+static inline u64 get_max_extent_size(struct btrfs_free_space *entry)
+{
+	if (entry->bitmap)
+		return entry->max_extent_size;
+	return entry->bytes;
+}
+
 /* Cache the size of the max extent in bytes */
 static struct btrfs_free_space *
 find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
@@ -1793,8 +1800,8 @@ find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
 	for (node = &entry->offset_index; node; node = rb_next(node)) {
 		entry = rb_entry(node, struct btrfs_free_space, offset_index);
 		if (entry->bytes < *bytes) {
-			if (entry->bytes > *max_extent_size)
-				*max_extent_size = entry->bytes;
+			*max_extent_size = max(get_max_extent_size(entry),
+					       *max_extent_size);
 			continue;
 		}
 
@@ -1812,8 +1819,8 @@ find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
 		}
 
 		if (entry->bytes < *bytes + align_off) {
-			if (entry->bytes > *max_extent_size)
-				*max_extent_size = entry->bytes;
+			*max_extent_size = max(get_max_extent_size(entry),
+					       *max_extent_size);
 			continue;
 		}
 
@@ -1825,8 +1832,10 @@ find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
 				*offset = tmp;
 				*bytes = size;
 				return entry;
-			} else if (size > *max_extent_size) {
-				*max_extent_size = size;
+			} else {
+				*max_extent_size =
+					max(get_max_extent_size(entry),
+					    *max_extent_size);
 			}
 			continue;
 		}
@@ -2685,8 +2694,8 @@ static u64 btrfs_alloc_from_bitmap(struct btrfs_block_group_cache *block_group,
 
 	err = search_bitmap(ctl, entry, &search_start, &search_bytes, true);
 	if (err) {
-		if (search_bytes > *max_extent_size)
-			*max_extent_size = search_bytes;
+		*max_extent_size = max(get_max_extent_size(entry),
+				       *max_extent_size);
 		return 0;
 	}
 
@@ -2723,8 +2732,9 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group_cache *block_group,
 
 	entry = rb_entry(node, struct btrfs_free_space, offset_index);
 	while (1) {
-		if (entry->bytes < bytes && entry->bytes > *max_extent_size)
-			*max_extent_size = entry->bytes;
+		if (entry->bytes < bytes)
+			*max_extent_size = max(get_max_extent_size(entry),
+					       *max_extent_size);
 
 		if (entry->bytes < bytes ||
 		    (!entry->bitmap && entry->offset < min_start)) {