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Commit e6c9f5c1 authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds
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[PATCH] Fix JBD race in t_forget list handling 



Fix race between journal_commit_transaction() and other places as
journal_unmap_buffer() that are adding buffers to transaction's t_forget list.
 We have to protect against such places by holding j_list_lock even when
traversing the t_forget list.  The fact that other places can only add buffers
to the list makes the locking easier.  OTOH the lock ranking complicates the
stuff...

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent cbf0d27a

fs/jbd/commit.c

+24 −10
Original line number Diff line number Diff line
@@ -720,11 +720,17 @@ void journal_commit_transaction(journal_t *journal) 
	J_ASSERT(commit_transaction->t_log_list == NULL);



restart_loop:

	/*

	 * As there are other places (journal_unmap_buffer()) adding buffers

	 * to this list we have to be careful and hold the j_list_lock.

	 */

	spin_lock(&journal->j_list_lock);

	while (commit_transaction->t_forget) {

		transaction_t *cp_transaction;

		struct buffer_head *bh;



		jh = commit_transaction->t_forget;

		spin_unlock(&journal->j_list_lock);

		bh = jh2bh(jh);

		jbd_lock_bh_state(bh);

		J_ASSERT_JH(jh,	jh->b_transaction == commit_transaction ||
@@ -792,8 +798,24 @@ void journal_commit_transaction(journal_t *journal) 
			journal_remove_journal_head(bh);  /* needs a brelse */

			release_buffer_page(bh);

		}

		cond_resched_lock(&journal->j_list_lock);

	}

	spin_unlock(&journal->j_list_lock);

		if (cond_resched())

	/*

	 * This is a bit sleazy.  We borrow j_list_lock to protect

	 * journal->j_committing_transaction in __journal_remove_checkpoint.

	 * Really, __journal_remove_checkpoint should be using j_state_lock but

	 * it's a bit hassle to hold that across __journal_remove_checkpoint

	 */

	spin_lock(&journal->j_state_lock);

	spin_lock(&journal->j_list_lock);

	/*

	 * Now recheck if some buffers did not get attached to the transaction

	 * while the lock was dropped...

	 */

	if (commit_transaction->t_forget) {

		spin_unlock(&journal->j_list_lock);

		spin_unlock(&journal->j_state_lock);

		goto restart_loop;

	}
@@ -803,14 +825,6 @@ void journal_commit_transaction(journal_t *journal) 


	J_ASSERT(commit_transaction->t_state == T_COMMIT);



	/*

	 * This is a bit sleazy.  We borrow j_list_lock to protect

	 * journal->j_committing_transaction in __journal_remove_checkpoint.

	 * Really, __jornal_remove_checkpoint should be using j_state_lock but

	 * it's a bit hassle to hold that across __journal_remove_checkpoint

	 */

	spin_lock(&journal->j_state_lock);

	spin_lock(&journal->j_list_lock);

	commit_transaction->t_state = T_FINISHED;

	J_ASSERT(commit_transaction == journal->j_committing_transaction);

	journal->j_commit_sequence = commit_transaction->t_tid;