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Subject[PATCH 10/49] ext4: Use separate super_operations structure for no_journal filesystems
Date
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>
---
fs/ext4/super.c | 108 +++++++++++++++++++++++++++++--------------------------
1 files changed, 57 insertions(+), 51 deletions(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7c7a08a..68c3a44 100644
--- 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;
}

--
1.6.3.2.1.gb9f7d.dirty


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