use-journal-inode-to-determine-journal-overhead

   1 ext4: use journal inode to determine journal overhead
   2
   3 From: Eric Whitney <enwlinux@gmail.com>
   4
   5 When a file system contains an internal journal that has not been
   6 loaded, use the journal inode's i_size field to determine its
   7 contribution to the file system's overhead.  (The journal's j_maxlen
   8 field is normally used to determine its size, but it's unavailable when
   9 the journal has not been loaded.)
  10
  11 Signed-off-by: Eric Whitney <enwlinux@gmail.com>
  12 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  13 ---
  14  fs/ext4/super.c | 19 +++++++++++++++++--
  15  1 file changed, 17 insertions(+), 2 deletions(-)
  16
  17 diff --git a/fs/ext4/super.c b/fs/ext4/super.c
  18 index 4b0ca25..1a7b6fd 100644
  19 --- a/fs/ext4/super.c
  20 +++ b/fs/ext4/super.c
  21 @@ -3210,6 +3210,8 @@ int ext4_calculate_overhead(struct super_block *sb)
  22  {
  23         struct ext4_sb_info *sbi = EXT4_SB(sb);
  24         struct ext4_super_block *es = sbi->s_es;
  25 +       struct inode *j_inode;
  26 +       unsigned int j_blocks, j_inum = le32_to_cpu(es->s_journal_inum);
  27         ext4_group_t i, ngroups = ext4_get_groups_count(sb);
  28         ext4_fsblk_t overhead = 0;
  29         char *buf = (char *) get_zeroed_page(GFP_NOFS);
  30 @@ -3240,10 +3242,23 @@ int ext4_calculate_overhead(struct super_block *sb)
  31                         memset(buf, 0, PAGE_SIZE);
  32                 cond_resched();
  33         }
  34 -       /* Add the internal journal blocks as well */
  35 +
  36 +       /*
  37 +        * Add the internal journal blocks whether the journal has been
  38 +        * loaded or not
  39 +        */
  40         if (sbi->s_journal && !sbi->journal_bdev)
  41                 overhead += EXT4_NUM_B2C(sbi, sbi->s_journal->j_maxlen);
  42 -
  43 +       else if (ext4_has_feature_journal(sb) && !sbi->s_journal) {
  44 +               j_inode = ext4_get_journal_inode(sb, j_inum);
  45 +               if (j_inode) {
  46 +                       j_blocks = j_inode->i_size >> sb->s_blocksize_bits;
  47 +                       overhead += EXT4_NUM_B2C(sbi, j_blocks);
  48 +                       iput(j_inode);
  49 +               } else {
  50 +                       ext4_msg(sb, KERN_ERR, "can't get journal size");
  51 +               }
  52 +       }
  53         sbi->s_overhead = overhead;
  54         smp_wmb();
  55         free_page((unsigned long) buf);
  56 --
  57 2.1.4
  58
  59