ext4: Use EXT4_GROUP_INFO_NEED_INIT_BIT during resize

The new groups added during resize are flagged as
need_init group. Make sure we properly initialize these
groups. When we have block size < page size and we are adding
new groups the page may still be marked uptodate even though
we haven't initialized the group. While forcing the init
of buddy cache we need to make sure other groups part of the
same page of buddy cache is not using the cache.
group_info->alloc_sem is added to ensure the same.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
cc: stable@kernel.org

1 files changed, 13 insertions, 8 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index c54192e2384e..404d81cc9157 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -381,6 +381,7 @@ void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,
         ext4_debug("Adding block(s) %llu-%llu\n", block, block + count - 1);
 
         ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
+        grp = ext4_get_group_info(sb, block_group);
         /*
          * Check to see if we are freeing blocks across a group
          * boundary.
@@ -425,7 +426,11 @@ void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,
         err = ext4_journal_get_write_access(handle, gd_bh);
         if (err)
                 goto error_return;
-
+        /*
+         * make sure we don't allow a parallel init on other groups in the
+         * same buddy cache
+         */
+        down_write(&grp->alloc_sem);
         for (i = 0, blocks_freed = 0; i < count; i++) {
                 BUFFER_TRACE(bitmap_bh, "clear bit");
                 if (!ext4_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
@@ -450,6 +455,13 @@ void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,
                 sbi->s_flex_groups[flex_group].free_blocks += blocks_freed;
                 spin_unlock(sb_bgl_lock(sbi, flex_group));
         }
+        /*
+         * request to reload the buddy with the
+         * new bitmap information
+         */
+        set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));
+        ext4_mb_update_group_info(grp, blocks_freed);
+        up_write(&grp->alloc_sem);
 
         /* We dirtied the bitmap block */
         BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
@@ -461,13 +473,6 @@ void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,
         if (!err)
                 err = ret;
         sb->s_dirt = 1;
-        /*
-         * request to reload the buddy with the
-         * new bitmap information
-         */
-        grp = ext4_get_group_info(sb, block_group);
-        set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));
-        ext4_mb_update_group_info(grp, blocks_freed);
 
 error_return:
         brelse(bitmap_bh);