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Commit 7234ab2a authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: Fix and simplify s_dirt handling 



The s_dirt flag wasn't completely handled correctly, but it didn't
really matter when journalling was enabled.  It turns out that when
ext4 runs without a journal, we don't clear s_dirt in places where we
should have, with the result that the high-level write_super()
function was writing the superblock when it wasn't necessary.

So we fix this by making ext4_commit_super() clear the s_dirt flag,
and removing many of the other places where s_dirt is manipulated.
When journalling is enabled, the s_dirt flag might be left set more
often, but s_dirt really doesn't matter when journalling is enabled.

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent e2d67052

fs/ext4/super.c

+3 −11
Original line number Diff line number Diff line
@@ -3128,7 +3128,6 @@ static int ext4_load_journal(struct super_block *sb, 
	if (journal_devnum &&

	    journal_devnum != le32_to_cpu(es->s_journal_dev)) {

		es->s_journal_dev = cpu_to_le32(journal_devnum);

		sb->s_dirt = 1;



		/* Make sure we flush the recovery flag to disk. */

		ext4_commit_super(sb, 1);
@@ -3168,7 +3167,7 @@ static int ext4_commit_super(struct super_block *sb, int sync) 
					&EXT4_SB(sb)->s_freeblocks_counter));

	es->s_free_inodes_count = cpu_to_le32(percpu_counter_sum_positive(

					&EXT4_SB(sb)->s_freeinodes_counter));



	sb->s_dirt = 0;

	BUFFER_TRACE(sbh, "marking dirty");

	mark_buffer_dirty(sbh);

	if (sync) {
@@ -3210,7 +3209,6 @@ static void ext4_mark_recovery_complete(struct super_block *sb, 
	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER) &&

	    sb->s_flags & MS_RDONLY) {

		EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);

		sb->s_dirt = 0;

		ext4_commit_super(sb, 1);

	}

	unlock_super(sb);
@@ -3271,10 +3269,8 @@ int ext4_force_commit(struct super_block *sb) 
		return 0;



	journal = EXT4_SB(sb)->s_journal;

	if (journal) {

		sb->s_dirt = 0;

	if (journal)

		ret = ext4_journal_force_commit(journal);

	}



	return ret;

}
@@ -3282,15 +3278,13 @@ int ext4_force_commit(struct super_block *sb) 
/*

 * 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.  (We can probably nuke this function altogether, and remove

 * any mention to sb->s_dirt in all of fs/ext4; eventual cleanup...)

 * 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();

		sb->s_dirt = 0;

	} else {

		ext4_commit_super(sb, 1);

	}
@@ -3302,7 +3296,6 @@ 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);

	sb->s_dirt = 0;

	if (EXT4_SB(sb)->s_journal) {

		if (jbd2_journal_start_commit(EXT4_SB(sb)->s_journal,

					      &target)) {
@@ -3324,7 +3317,6 @@ static int ext4_freeze(struct super_block *sb) 
{

	int error = 0;

	journal_t *journal;

	sb->s_dirt = 0;



	if (!(sb->s_flags & MS_RDONLY)) {

		journal = EXT4_SB(sb)->s_journal;