add-ext4-journal-lazy-mount-option

   1 ext4: add journal_lazy mount option
   2
   3 This option turns out the lazy journalling option, as described in the
   4 FAST 2017 paper, "Evolving Ext4 for Shingled Disks"[1].
   5
   6 [1] https://www.usenix.org/conference/fast17/technical-sessions/presentation/aghayev
   7
   8 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   9 ---
  10  fs/ext4/ext4.h  |  1 +
  11  fs/ext4/inode.c |  2 +-
  12  fs/ext4/ioctl.c | 42 ++++++++++++++++++++++++++++++++----------
  13  fs/ext4/super.c | 56 ++++++++++++++++++++++++++++++++++++++++++++------------
  14  4 files changed, 78 insertions(+), 23 deletions(-)
  15
  16 diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
  17 index fc2bdaa71c44..e19b6bac2d91 100644
  18 --- a/fs/ext4/ext4.h
  19 +++ b/fs/ext4/ext4.h
  20 @@ -1079,6 +1079,7 @@ struct ext4_inode_info {
  21   * Mount flags set via mount options or defaults
  22   */
  23  #define EXT4_MOUNT_NO_MBCACHE          0x00001 /* Do not use mbcache */
  24 +#define EXT4_MOUNT_JOURNAL_LAZY                0x00002 /* Do lazy writeback of journalled metadata */
  25  #define EXT4_MOUNT_GRPID               0x00004 /* Create files with directory's group */
  26  #define EXT4_MOUNT_DEBUG               0x00008 /* Some debugging messages */
  27  #define EXT4_MOUNT_ERRORS_CONT         0x00010 /* Continue on errors */
  28 diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
  29 index 3969d0278469..d43c326f4048 100644
  30 --- a/fs/ext4/inode.c
  31 +++ b/fs/ext4/inode.c
  32 @@ -3287,7 +3287,7 @@ static sector_t ext4_bmap(struct address_space *mapping, sector_t block)
  33                 filemap_write_and_wait(mapping);
  34         }
  35
  36 -       if (EXT4_JOURNAL(inode) &&
  37 +       if (EXT4_JOURNAL(inode) && !test_opt(inode->i_sb, JOURNAL_LAZY) &&
  38             ext4_test_inode_state(inode, EXT4_STATE_JDATA)) {
  39                 /*
  40                  * This is a REALLY heavyweight approach, but the use of
  41 diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
  42 index a7074115d6f6..8556d6003d15 100644
  43 --- a/fs/ext4/ioctl.c
  44 +++ b/fs/ext4/ioctl.c
  45 @@ -239,6 +239,20 @@ static int ext4_ioctl_setflags(struct inode *inode,
  46                 if (!capable(CAP_SYS_RESOURCE))
  47                         goto flags_out;
  48         }
  49 +
  50 +       /*
  51 +        * Clearing the JOURNAL_DATA flag is *hard* with lazy
  52 +        * journalling.  We can't use jbd2_journal_flush(); instead,
  53 +        * we would have to make sure all blocks belonging to the file
  54 +        * are evacuated from the journal and saved to their final
  55 +        * location on disk.  Punt for now.
  56 +        */
  57 +       if ((oldflags & EXT4_JOURNAL_DATA_FL) && !jflag &&
  58 +           test_opt(inode->i_sb, JOURNAL_LAZY)) {
  59 +               err = -EOPNOTSUPP;
  60 +               goto flags_out;
  61 +       }
  62 +
  63         if ((flags ^ oldflags) & EXT4_EXTENTS_FL)
  64                 migrate = 1;
  65
  66 @@ -626,6 +640,22 @@ static long ext4_ioctl_group_add(struct file *file,
  67         return err;
  68  }
  69
  70 +/*
  71 + * If we are using journalling (excepting JBD2 lazy mode), make sure
  72 + * the block group descriptors are written out immediately
  73 + */
  74 +static int flush_fs_group_descriptors(struct super_block *sb)
  75 +{
  76 +       int err = 0;
  77 +
  78 +       if (EXT4_SB(sb)->s_journal && !test_opt(sb, JOURNAL_LAZY)) {
  79 +               jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
  80 +               err = jbd2_journal_flush(EXT4_SB(sb)->s_journal);
  81 +               jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
  82 +       }
  83 +       return err;
  84 +}
  85 +
  86  long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
  87  {
  88         struct inode *inode = file_inode(filp);
  89 @@ -744,11 +774,7 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
  90                         goto group_extend_out;
  91
  92                 err = ext4_group_extend(sb, EXT4_SB(sb)->s_es, n_blocks_count);
  93 -               if (EXT4_SB(sb)->s_journal) {
  94 -                       jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
  95 -                       err2 = jbd2_journal_flush(EXT4_SB(sb)->s_journal);
  96 -                       jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
  97 -               }
  98 +               err2 = flush_fs_group_descriptors(sb);
  99                 if (err == 0)
 100                         err = err2;
 101                 mnt_drop_write_file(filp);
 102 @@ -886,11 +912,7 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 103                         goto resizefs_out;
 104
 105                 err = ext4_resize_fs(sb, n_blocks_count);
 106 -               if (EXT4_SB(sb)->s_journal) {
 107 -                       jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
 108 -                       err2 = jbd2_journal_flush(EXT4_SB(sb)->s_journal);
 109 -                       jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
 110 -               }
 111 +               err2 = flush_fs_group_descriptors(sb);
 112                 if (err == 0)
 113                         err = err2;
 114                 mnt_drop_write_file(filp);
 115 diff --git a/fs/ext4/super.c b/fs/ext4/super.c
 116 index 9339717b85c8..406e4d4ffae0 100644
 117 --- a/fs/ext4/super.c
 118 +++ b/fs/ext4/super.c
 119 @@ -928,7 +928,8 @@ static void ext4_put_super(struct super_block *sb)
 120         ext4_mb_release(sb);
 121         ext4_ext_release(sb);
 122
 123 -       if (!sb_rdonly(sb) && !aborted && !test_opt(sb, JOURNAL_NOCLEANUP)) {
 124 +       if (!sb_rdonly(sb) && !aborted && !test_opt(sb, JOURNAL_NOCLEANUP) &&
 125 +           !test_opt(sb, JOURNAL_LAZY)) {
 126                 ext4_clear_feature_journal_needs_recovery(sb);
 127                 es->s_state = cpu_to_le16(sbi->s_mount_state);
 128         }
 129 @@ -1384,6 +1385,7 @@ enum {
 130         Opt_inode_readahead_blks, Opt_journal_ioprio,
 131         Opt_dioread_nolock, Opt_dioread_lock,
 132         Opt_journal_nocleanup, Opt_journal_cleanup,
 133 +       Opt_journal_nolazy, Opt_journal_lazy,
 134         Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
 135         Opt_max_dir_size_kb, Opt_nojournal_checksum, Opt_nombcache,
 136  };
 137 @@ -1474,6 +1476,8 @@ static const match_table_t tokens = {
 138         {Opt_nombcache, "no_mbcache"},  /* for backward compatibility */
 139         {Opt_journal_nocleanup, "journal_nocleanup"},
 140         {Opt_journal_cleanup, "journal_cleanup"},
 141 +       {Opt_journal_lazy, "journal_lazy"},
 142 +       {Opt_journal_nolazy, "journal_nolazy"},
 143         {Opt_removed, "check=none"},    /* mount option from ext2/3 */
 144         {Opt_removed, "nocheck"},       /* mount option from ext2/3 */
 145         {Opt_removed, "reservation"},   /* mount option from ext2/3 */
 146 @@ -1686,6 +1690,8 @@ static const struct mount_opts {
 147         {Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET},
 148         {Opt_journal_nocleanup, EXT4_MOUNT_JOURNAL_NOCLEANUP, MOPT_SET},
 149         {Opt_journal_cleanup, EXT4_MOUNT_JOURNAL_NOCLEANUP, MOPT_CLEAR},
 150 +       {Opt_journal_lazy, EXT4_MOUNT_JOURNAL_LAZY, MOPT_SET},
 151 +       {Opt_journal_nolazy, EXT4_MOUNT_JOURNAL_LAZY, MOPT_CLEAR},
 152         {Opt_err, 0, 0}
 153  };
 154
 155 @@ -4570,6 +4576,10 @@ static void ext4_init_journal_params(struct super_block *sb, journal_t *journal)
 156                 journal->j_flags |= JBD2_NO_CLEANUP;
 157         else
 158                 journal->j_flags &= ~JBD2_NO_CLEANUP;
 159 +       if (test_opt(sb, JOURNAL_LAZY))
 160 +               journal->j_flags |= JBD2_LAZY;
 161 +       else
 162 +               journal->j_flags &= ~JBD2_LAZY;
 163         write_unlock(&journal->j_state_lock);
 164  }
 165
 166 @@ -4804,6 +4814,24 @@ static int ext4_load_journal(struct super_block *sb,
 167
 168         EXT4_SB(sb)->s_journal = journal;
 169         ext4_clear_journal_err(sb, es);
 170 +
 171 +       if (test_opt(sb, JOURNAL_LAZY)) {
 172 +               struct buffer_head *sbh = EXT4_SB(sb)->s_sbh;
 173 +
 174 +               /* Read the latest version of the superblock from the journal */
 175 +               lock_buffer(sbh);
 176 +               clear_buffer_uptodate(sbh);
 177 +               err = jbd2_bh_submit_read(journal, sbh, __func__);
 178 +               if (err) {
 179 +                       ext4_msg(sb, KERN_ERR, "error rereading superblock %d",
 180 +                               err);
 181 +                       set_buffer_uptodate(sbh);
 182 +               }
 183 +               if (!ext4_superblock_csum_verify(sb, es))
 184 +                       ext4_msg(sb, KERN_ERR,
 185 +                                "superblock csum doesn't verify"
 186 +                                "after journal replay!");
 187 +       }
 188         return 0;
 189  }
 190
 191 @@ -4894,6 +4922,9 @@ static void ext4_mark_recovery_complete(struct super_block *sb,
 192  {
 193         journal_t *journal = EXT4_SB(sb)->s_journal;
 194
 195 +       if (test_opt(sb, JOURNAL_LAZY))
 196 +               return;
 197 +
 198         if (!ext4_has_feature_journal(sb)) {
 199                 BUG_ON(journal != NULL);
 200                 return;
 201 @@ -5029,21 +5060,20 @@ static int ext4_freeze(struct super_block *sb)
 202         journal = EXT4_SB(sb)->s_journal;
 203
 204         if (journal) {
 205 -               /* Now we set up the journal barrier. */
 206 -               jbd2_journal_lock_updates(journal);
 207 -
 208                 /*
 209 -                * Don't clear the needs_recovery flag if we failed to
 210 -                * flush the journal.
 211 +                * Set the journal barrier, then flush the journal and
 212 +                * clear the needs_recovery flag if we are not in
 213 +                * JBD2_LAZY mode.
 214                  */
 215 -               error = jbd2_journal_flush(journal);
 216 -               if (error < 0)
 217 -                       goto out;
 218 +               jbd2_journal_lock_updates(journal);
 219
 220 -               /* Journal blocked and flushed, clear needs_recovery flag. */
 221 +               if (!test_opt(sb, JOURNAL_LAZY)) {
 222 +                       error = jbd2_journal_flush(journal);
 223 +                       if (error < 0)
 224 +                               goto out;
 225 +               }
 226                 ext4_clear_feature_journal_needs_recovery(sb);
 227         }
 228 -
 229         error = ext4_commit_super(sb, 1);
 230  out:
 231         if (journal)
 232 @@ -5061,7 +5091,7 @@ static int ext4_unfreeze(struct super_block *sb)
 233         if (sb_rdonly(sb) || ext4_forced_shutdown(EXT4_SB(sb)))
 234                 return 0;
 235
 236 -       if (EXT4_SB(sb)->s_journal) {
 237 +       if (EXT4_SB(sb)->s_journal && !test_opt(sb, JOURNAL_LAZY)) {
 238                 /* Reset the needs_recovery flag before the fs is unlocked. */
 239                 ext4_set_feature_journal_needs_recovery(sb);
 240         }
 241 @@ -5595,6 +5625,8 @@ static int ext4_quota_on(struct super_block *sb, int type, int format_id,
 242                  * We don't need to lock updates but journal_flush() could
 243                  * otherwise be livelocked...
 244                  */
 245 +               if (test_opt(sb, JOURNAL_LAZY))
 246 +                       return -EOPNOTSUPP;
 247                 jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
 248                 err = jbd2_journal_flush(EXT4_SB(sb)->s_journal);
 249                 jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);