jbd: Delay discarding buffers in journal_unmap_buffer (86963918) · Commits · 戴 / test

fs/jbd/commit.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -862,12 +862,12 @@ restart_loop:
		/* A buffer which has been freed while still being
		* journaled by a previous transaction may end up still
		* being dirty here, but we want to avoid writing back
		* that buffer in the future now that the last use has
		* been committed. That's not only a performance gain,
		* it also stops aliasing problems if the buffer is left
		* behind for writeback and gets reallocated for another
		* that buffer in the future after the "add to orphan"
		* operation been committed, That's not only a performance
		* gain, it also stops aliasing problems if the buffer is
		* left behind for writeback and gets reallocated for another
		* use in a different page. */
		if (buffer_freed(bh)) {
		if (buffer_freed(bh) && !jh->b_next_transaction) {
		clear_buffer_freed(bh);
		clear_buffer_jbddirty(bh);
		}

fs/jbd/transaction.c

+31 −12

Original line number	Diff line number	Diff line
		@@ -1864,6 +1864,21 @@ static int journal_unmap_buffer(journal_t journal, struct buffer_head bh)
		if (!jh)
		goto zap_buffer_no_jh;

		/*
		* We cannot remove the buffer from checkpoint lists until the
		* transaction adding inode to orphan list (let's call it T)
		* is committed. Otherwise if the transaction changing the
		* buffer would be cleaned from the journal before T is
		* committed, a crash will cause that the correct contents of
		* the buffer will be lost. On the other hand we have to
		* clear the buffer dirty bit at latest at the moment when the
		* transaction marking the buffer as freed in the filesystem
		* structures is committed because from that moment on the
		* buffer can be reallocated and used by a different page.
		* Since the block hasn't been freed yet but the inode has
		* already been added to orphan list, it is safe for us to add
		* the buffer to BJ_Forget list of the newest transaction.
		*/
		transaction = jh->b_transaction;
		if (transaction == NULL) {
		/* First case: not on any transaction. If it
		@@ -1929,16 +1944,15 @@ static int journal_unmap_buffer(journal_t journal, struct buffer_head bh)
		goto zap_buffer;
		}
		/*
		* If it is committing, we simply cannot touch it. We
		* can remove it's next_transaction pointer from the
		* running transaction if that is set, but nothing
		* else. */
		* The buffer is committing, we simply cannot touch
		* it. So we just set j_next_transaction to the
		* running transaction (if there is one) and mark
		* buffer as freed so that commit code knows it should
		* clear dirty bits when it is done with the buffer.
		*/
		set_buffer_freed(bh);
		if (jh->b_next_transaction) {
		J_ASSERT(jh->b_next_transaction ==
		journal->j_running_transaction);
		jh->b_next_transaction = NULL;
		}
		if (journal->j_running_transaction && buffer_jbddirty(bh))
		jh->b_next_transaction = journal->j_running_transaction;
		journal_put_journal_head(jh);
		spin_unlock(&journal->j_list_lock);
		jbd_unlock_bh_state(bh);
		@@ -2120,7 +2134,7 @@ void journal_file_buffer(struct journal_head *jh,
		*/
		void __journal_refile_buffer(struct journal_head *jh)
		{
		int was_dirty;
		int was_dirty, jlist;
		struct buffer_head *bh = jh2bh(jh);

		J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
		@@ -2142,8 +2156,13 @@ void __journal_refile_buffer(struct journal_head *jh)
		__journal_temp_unlink_buffer(jh);
		jh->b_transaction = jh->b_next_transaction;
		jh->b_next_transaction = NULL;
		__journal_file_buffer(jh, jh->b_transaction,
		jh->b_modified ? BJ_Metadata : BJ_Reserved);
		if (buffer_freed(bh))
		jlist = BJ_Forget;
		else if (jh->b_modified)
		jlist = BJ_Metadata;
		else
		jlist = BJ_Reserved;
		__journal_file_buffer(jh, jh->b_transaction, jlist);
		J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING);

		if (was_dirty)

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