Commit 671384c6 authored by Zhihao Cheng's avatar Zhihao Cheng Committed by Jialin Zhang
Browse files

jbd2: fix data missing when reusing bh which is ready to be checkpointed 

mainline inclusion
from mainline-v6.3-rc1
commit e6b9bd72
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I6C5HV
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e6b9bd7290d334451ce054e98e752abc055e0034

--------------------------------

Following process will make data lost and could lead to a filesystem
corrupted problem:

1. jh(bh) is inserted into T1->t_checkpoint_list, bh is dirty, and
   jh->b_transaction = NULL
2. T1 is added into journal->j_checkpoint_transactions.
3. Get bh prepare to write while doing checkpoing:
           PA				    PB
   do_get_write_access             jbd2_log_do_checkpoint
    spin_lock(&jh->b_state_lock)
     if (buffer_dirty(bh))
      clear_buffer_dirty(bh)   // clear buffer dirty
       set_buffer_jbddirty(bh)
				    transaction =
				    journal->j_checkpoint_transactions
				    jh = transaction->t_checkpoint_list
				    if (!buffer_dirty(bh))
		                      __jbd2_journal_remove_checkpoint(jh)
				      // bh won't be flushed
		                    jbd2_cleanup_journal_tail
    __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved)
4. Aborting journal/Power-cut before writing latest bh on journal area.

In this way we get a corrupted filesystem with bh's data lost.

Fix it by moving the clearing of buffer_dirty bit just before the call
to __jbd2_journal_file_buffer(), both bit clearing and jh->b_transaction
assignment are under journal->j_list_lock locked, so that
jbd2_log_do_checkpoint() will wait until jh's new transaction fininshed
even bh is currently not dirty. And journal_shrink_one_cp_list() won't
remove jh from checkpoint list if the buffer head is reused in
do_get_write_access().

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216898


Cc: <stable@kernel.org>
Signed-off-by: default avatarZhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: default avatarzhanchengbin <zhanchengbin1@huawei.com>
Suggested-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230110015327.1181863-1-chengzhihao1@huawei.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Reviewed-by: default avatarYang Erkun <yangerkun@huawei.com>
Reviewed-by: default avatarZhang Yi <yi.zhang@huawei.com>
Signed-off-by: default avatarJialin Zhang <zhangjialin11@huawei.com>
parent 153d1a86

fs/jbd2/transaction.c

+29 −21
Original line number Diff line number Diff line
@@ -984,36 +984,28 @@ do_get_write_access(handle_t *handle, struct journal_head *jh, 
	 * ie. locked but not dirty) or tune2fs (which may actually have

	 * the buffer dirtied, ugh.)  */



	if (buffer_dirty(bh)) {

		/*

		 * First question: is this buffer already part of the current

		 * transaction or the existing committing transaction?

		 */

		if (jh->b_transaction) {

			J_ASSERT_JH(jh,

				jh->b_transaction == transaction ||

				jh->b_transaction ==

					journal->j_committing_transaction);

			if (jh->b_next_transaction)

				J_ASSERT_JH(jh, jh->b_next_transaction ==

							transaction);

	if (buffer_dirty(bh) && jh->b_transaction) {

		warn_dirty_buffer(bh);

		}

		/*

		 * In any case we need to clean the dirty flag and we must

		 * do it under the buffer lock to be sure we don't race

		 * with running write-out.

		 * We need to clean the dirty flag and we must do it under the

		 * buffer lock to be sure we don't race with running write-out.

		 */

		JBUFFER_TRACE(jh, "Journalling dirty buffer");

		clear_buffer_dirty(bh);

		/*

		 * The buffer is going to be added to BJ_Reserved list now and

		 * nothing guarantees jbd2_journal_dirty_metadata() will be

		 * ever called for it. So we need to set jbddirty bit here to

		 * make sure the buffer is dirtied and written out when the

		 * journaling machinery is done with it.

		 */

		set_buffer_jbddirty(bh);

	}



	unlock_buffer(bh);



	error = -EROFS;

	if (is_handle_aborted(handle)) {

		spin_unlock(&jh->b_state_lock);

		unlock_buffer(bh);

		goto out;

	}

	error = 0;
@@ -1023,8 +1015,10 @@ do_get_write_access(handle_t *handle, struct journal_head *jh, 
	 * b_next_transaction points to it

	 */

	if (jh->b_transaction == transaction ||

	    jh->b_next_transaction == transaction)

	    jh->b_next_transaction == transaction) {

		unlock_buffer(bh);

		goto done;

	}



	/*

	 * this is the first time this transaction is touching this buffer,
@@ -1048,10 +1042,24 @@ do_get_write_access(handle_t *handle, struct journal_head *jh, 
		 */

		smp_wmb();

		spin_lock(&journal->j_list_lock);

		if (test_clear_buffer_dirty(bh)) {

			/*

			 * Execute buffer dirty clearing and jh->b_transaction

			 * assignment under journal->j_list_lock locked to

			 * prevent bh being removed from checkpoint list if

			 * the buffer is in an intermediate state (not dirty

			 * and jh->b_transaction is NULL).

			 */

			JBUFFER_TRACE(jh, "Journalling dirty buffer");

			set_buffer_jbddirty(bh);

		}

		__jbd2_journal_file_buffer(jh, transaction, BJ_Reserved);

		spin_unlock(&journal->j_list_lock);

		unlock_buffer(bh);

		goto done;

	}

	unlock_buffer(bh);



	/*

	 * If there is already a copy-out version of this buffer, then we don't

	 * need to make another one