ext4: Use separate super_operations structure for no_journal filesystems

By using a separate super_operations structure for filesystems that
have and don't have journals, we can simply ext4_write_super() ---
which is only needed when no journal is present --- and ext4_freeze(),
ext4_unfreeze(), and ext4_sync_fs(), which are only needed when the
journal is present.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7c7a08af1200878517bdda4ce2757f90ceb7c15c..68c3a44c4a970e5da4fcdddcc04028b32dac1bed 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -995,7 +995,6 @@ static const struct super_operations ext4_sops = {
        .dirty_inode    = ext4_dirty_inode,
        .delete_inode   = ext4_delete_inode,
        .put_super      = ext4_put_super,
-       .write_super    = ext4_write_super,
        .sync_fs        = ext4_sync_fs,
        .freeze_fs      = ext4_freeze,
        .unfreeze_fs    = ext4_unfreeze,
@@ -1010,6 +1009,25 @@ static const struct super_operations ext4_sops = {
        .bdev_try_to_free_page = bdev_try_to_free_page,
 };
 
+static const struct super_operations ext4_nojournal_sops = {
+       .alloc_inode    = ext4_alloc_inode,
+       .destroy_inode  = ext4_destroy_inode,
+       .write_inode    = ext4_write_inode,
+       .dirty_inode    = ext4_dirty_inode,
+       .delete_inode   = ext4_delete_inode,
+       .write_super    = ext4_write_super,
+       .put_super      = ext4_put_super,
+       .statfs         = ext4_statfs,
+       .remount_fs     = ext4_remount,
+       .clear_inode    = ext4_clear_inode,
+       .show_options   = ext4_show_options,
+#ifdef CONFIG_QUOTA
+       .quota_read     = ext4_quota_read,
+       .quota_write    = ext4_quota_write,
+#endif
+       .bdev_try_to_free_page = bdev_try_to_free_page,
+};
+
 static const struct export_operations ext4_export_ops = {
        .fh_to_dentry = ext4_fh_to_dentry,
        .fh_to_parent = ext4_fh_to_parent,
@@ -2615,7 +2633,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
        /*
         * set up enough so that it can read an inode
         */
-       sb->s_op = &ext4_sops;
+       if (!test_opt(sb, NOLOAD) &&
+           EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL))
+               sb->s_op = &ext4_sops;
+       else
+               sb->s_op = &ext4_nojournal_sops;
        sb->s_export_op = &ext4_export_ops;
        sb->s_xattr = ext4_xattr_handlers;
 #ifdef CONFIG_QUOTA
@@ -3275,19 +3297,9 @@ int ext4_force_commit(struct super_block *sb)
        return ret;
 }
 
-/*
- * Ext4 always journals updates to the superblock itself, so we don't
- * have to propagate any other updates to the superblock on disk at this
- * point if the journalling is enabled.
- */
 static void ext4_write_super(struct super_block *sb)
 {
-       if (EXT4_SB(sb)->s_journal) {
-               if (mutex_trylock(&sb->s_lock) != 0)
-                       BUG();
-       } else {
-               ext4_commit_super(sb, 1);
-       }
+       ext4_commit_super(sb, 1);
 }
 
 static int ext4_sync_fs(struct super_block *sb, int wait)
@@ -3296,15 +3308,9 @@ static int ext4_sync_fs(struct super_block *sb, int wait)
        tid_t target;
 
        trace_mark(ext4_sync_fs, "dev %s wait %d", sb->s_id, wait);
-       if (EXT4_SB(sb)->s_journal) {
-               if (jbd2_journal_start_commit(EXT4_SB(sb)->s_journal,
-                                             &target)) {
-                       if (wait)
-                               jbd2_log_wait_commit(EXT4_SB(sb)->s_journal,
-                                                    target);
-               }
-       } else {
-               ext4_commit_super(sb, wait);
+       if (jbd2_journal_start_commit(EXT4_SB(sb)->s_journal, &target)) {
+               if (wait)
+                       jbd2_log_wait_commit(EXT4_SB(sb)->s_journal, target);
        }
        return ret;
 }
@@ -3318,32 +3324,31 @@ static int ext4_freeze(struct super_block *sb)
        int error = 0;
        journal_t *journal;
 
-       if (!(sb->s_flags & MS_RDONLY)) {
-               journal = EXT4_SB(sb)->s_journal;
+       if (sb->s_flags & MS_RDONLY)
+               return 0;
 
-               if (journal) {
-                       /* Now we set up the journal barrier. */
-                       jbd2_journal_lock_updates(journal);
+       journal = EXT4_SB(sb)->s_journal;
 
-                       /*
-                        * We don't want to clear needs_recovery flag when we
-                        * failed to flush the journal.
-                        */
-                       error = jbd2_journal_flush(journal);
-                       if (error < 0)
-                               goto out;
-               }
+       /* Now we set up the journal barrier. */
+       jbd2_journal_lock_updates(journal);
 
-               /* Journal blocked and flushed, clear needs_recovery flag. */
-               EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
-               error = ext4_commit_super(sb, 1);
-               if (error)
-                       goto out;
+       /*
+        * Don't clear the needs_recovery flag if we failed to flush
+        * the journal.
+        */
+       error = jbd2_journal_flush(journal);
+       if (error < 0) {
+       out:
+               jbd2_journal_unlock_updates(journal);
+               return error;
        }
+
+       /* Journal blocked and flushed, clear needs_recovery flag. */
+       EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
+       error = ext4_commit_super(sb, 1);
+       if (error)
+               goto out;
        return 0;
-out:
-       jbd2_journal_unlock_updates(journal);
-       return error;
 }
 
 /*
@@ -3352,14 +3357,15 @@ out:
  */
 static int ext4_unfreeze(struct super_block *sb)
 {
-       if (EXT4_SB(sb)->s_journal && !(sb->s_flags & MS_RDONLY)) {
-               lock_super(sb);
-               /* Reser the needs_recovery flag before the fs is unlocked. */
-               EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
-               ext4_commit_super(sb, 1);
-               unlock_super(sb);
-               jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
-       }
+       if (sb->s_flags & MS_RDONLY)
+               return 0;
+
+       lock_super(sb);
+       /* Reset the needs_recovery flag before the fs is unlocked. */
+       EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
+       ext4_commit_super(sb, 1);
+       unlock_super(sb);
+       jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
        return 0;
 }