ext4: grow the s_flex_groups array as needed when resizing

Previously, we allocated the s_flex_groups array to the maximum size
that the file system could be resized.  There was two problems with
this approach.  First, it wasted memory in the common case where the
file system was not resized.  Secondly, once we start allowing online
resizing using the meta_bg scheme, there is no maximum size that the
file system can be resized.  So instead, we need to grow the
s_flex_groups at inline resize time.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0df5ee102b61..464cff711ed6 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1276,6 +1276,7 @@ struct ext4_sb_info {
 
         unsigned int s_log_groups_per_flex;
         struct flex_groups *s_flex_groups;
+        ext4_group_t s_flex_groups_allocated;
 
         /* workqueue for dio unwritten */
         struct workqueue_struct *dio_unwritten_wq;
@@ -2055,6 +2056,8 @@ extern void ext4_superblock_csum_set(struct super_block *sb,
 extern void *ext4_kvmalloc(size_t size, gfp_t flags);
 extern void *ext4_kvzalloc(size_t size, gfp_t flags);
 extern void ext4_kvfree(void *ptr);
+extern int ext4_alloc_flex_bg_array(struct super_block *sb,
+                                    ext4_group_t ngroup);
 extern __printf(4, 5)
 void __ext4_error(struct super_block *, const char *, unsigned int,
                   const char *, ...);