ldiskfs/kernel_patches/patches/rhel8/ext4-mballoc-skip-uninit-groups-cr0.patch

   1 --- linux-4.18/fs/ext4/mballoc.c        2019-11-28 14:55:26.500545920 +0300
   2 +++ linux-4.18/fs/ext4/mballoc.c        2019-11-28 14:53:18.600086008 +0300
   3 @@ -1885,6 +1885,21 @@ void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,
   4
   5         return 0;
   6  }
   7 +
   8 +static inline int ext4_mb_uninit_on_disk(struct super_block *sb,
   9 +                                   ext4_group_t group)
  10 +{
  11 +       struct ext4_group_desc *desc;
  12 +
  13 +       if (!ext4_has_group_desc_csum(sb))
  14 +               return 0;
  15 +
  16 +       desc = ext4_get_group_desc(sb, group, NULL);
  17 +       if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))
  18 +               return 1;
  19 +
  20 +       return 0;
  21 +}
  22
  23  /*
  24   * The routine scans buddy structures (not bitmap!) from given order
  25 @@ -2060,7 +2060,15 @@ static int ext4_mb_good_group(struct
  26
  27         /* We only do this if the grp has never been initialized */
  28         if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
  29 -               int ret = ext4_mb_init_group(ac->ac_sb, group, GFP_NOFS);
  30 +               int ret;
  31 +
  32 +               /* cr=0/1 is a very optimistic search to find large
  33 +                * good chunks almost for free. if buddy data is
  34 +                * not ready, then this optimization makes no sense */
  35 +
  36 +               if (cr < 2 && !ext4_mb_uninit_on_disk(ac->ac_sb, group))
  37 +                       return 0;
  38 +               ret = ext4_mb_init_group(ac->ac_sb, group, GFP_NOFS);
  39                 if (ret)
  40                         return ret;
  41         }