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, 9 insertions, 5 deletions

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 365d800ff8c1..3f5c67bf13a2 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1503,6 +1503,10 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
         if (err)
                 goto out;
 
+        err = ext4_alloc_flex_bg_array(sb, input->group + 1);
+        if (err)
+                return err;
+
         flex_gd.count = 1;
         flex_gd.groups = input;
         flex_gd.bg_flags = &bg_flags;
@@ -1662,7 +1666,7 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
         unsigned long n_desc_blocks;
         unsigned long o_desc_blocks;
         unsigned long desc_blocks;
-        int err = 0, flexbg_size = 1;
+        int err = 0, flexbg_size = 1 << sbi->s_log_groups_per_flex;
 
         o_blocks_count = ext4_blocks_count(es);
 
@@ -1721,13 +1725,13 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
                         goto out;
         }
 
-        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
-            es->s_log_groups_per_flex)
-                flexbg_size = 1 << es->s_log_groups_per_flex;
-
         if (ext4_blocks_count(es) == n_blocks_count)
                 goto out;
 
+        err = ext4_alloc_flex_bg_array(sb, n_group + 1);
+        if (err)
+                return err;
+
         flex_gd = alloc_flex_gd(flexbg_size);
         if (flex_gd == NULL) {
                 err = -ENOMEM;