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Date:   Wed, 14 Apr 2021 21:47:32 +0800
From:   Zhang Yi <yi.zhang@...wei.com>
To:     <linux-ext4@...r.kernel.org>
CC:     <linux-fsdevel@...r.kernel.org>, <tytso@....edu>,
        <adilger.kernel@...ger.ca>, <jack@...e.cz>, <yi.zhang@...wei.com>,
        <yukuai3@...wei.com>
Subject: [RFC PATCH v2 2/7] jbd2: ensure abort the journal if detect IO error when writing original buffer back

Althourh we merged <c044f3d8360> ("jbd2: abort journal if free a async
write error metadata buffer"), there is a race between
jbd2_journal_try_to_free_buffers() and jbd2_journal_destroy(), so the
jbd2_log_do_checkpoint() may still missing to detect the buffer write
io error flag and will end up leading to filesystem inconsistency.

jbd2_journal_try_to_free_buffers()     ext4_put_super()
                                        jbd2_journal_destroy()
  __jbd2_journal_remove_checkpoint()
  detect buffer write error              jbd2_log_do_checkpoint()
                                         jbd2_cleanup_journal_tail()
                                           <--- lead to inconsistency
  jbd2_journal_abort()

Fix this issue by introduce a new mark j_checkpoint_io_error and set it
in __jbd2_journal_remove_checkpoint() when freeing a checkpoint buffer
has write_io_error flag. Then jbd2_journal_destroy() will detect this
mark and abort the journal to prevent updating log tail.

Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/jbd2/checkpoint.c | 32 +++++++++++++++++++-------------
 fs/jbd2/journal.c    |  9 +++++++++
 include/linux/jbd2.h |  7 +++++++
 3 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index bf5511d19ac5..ff3d38ad3a1e 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -221,14 +221,15 @@ int jbd2_log_do_checkpoint(journal_t *journal)
 	result = jbd2_cleanup_journal_tail(journal);
 	trace_jbd2_checkpoint(journal, result);
 	jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
-	if (result <= 0)
+	if (result == 0)
 		return result;
+	if (result < 0)
+		goto error;
 
 	/*
 	 * OK, we need to start writing disk blocks.  Take one transaction
 	 * and write it.
 	 */
-	result = 0;
 	spin_lock(&journal->j_list_lock);
 	if (!journal->j_checkpoint_transactions)
 		goto out;
@@ -295,8 +296,6 @@ int jbd2_log_do_checkpoint(journal_t *journal)
 			goto restart;
 		}
 		if (!buffer_dirty(bh)) {
-			if (unlikely(buffer_write_io_error(bh)) && !result)
-				result = -EIO;
 			BUFFER_TRACE(bh, "remove from checkpoint");
 			if (__jbd2_journal_remove_checkpoint(jh))
 				/* The transaction was released; we're done */
@@ -356,9 +355,6 @@ int jbd2_log_do_checkpoint(journal_t *journal)
 			spin_lock(&journal->j_list_lock);
 			goto restart2;
 		}
-		if (unlikely(buffer_write_io_error(bh)) && !result)
-			result = -EIO;
-
 		/*
 		 * Now in whatever state the buffer currently is, we
 		 * know that it has been written out and so we can
@@ -369,12 +365,13 @@ int jbd2_log_do_checkpoint(journal_t *journal)
 	}
 out:
 	spin_unlock(&journal->j_list_lock);
-	if (result < 0)
+	result = jbd2_cleanup_journal_tail(journal);
+	if (result >= 0)
+		return 0;
+error:
+	if (!is_journal_aborted(journal))
 		jbd2_journal_abort(journal, result);
-	else
-		result = jbd2_cleanup_journal_tail(journal);
-
-	return (result < 0) ? result : 0;
+	return result;
 }
 
 /*
@@ -400,7 +397,7 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
 	tid_t		first_tid;
 	unsigned long	blocknr;
 
-	if (is_journal_aborted(journal))
+	if (is_journal_aborted(journal) || journal->j_checkpoint_io_error)
 		return -EIO;
 
 	if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
@@ -564,6 +561,7 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 	struct transaction_chp_stats_s *stats;
 	transaction_t *transaction;
 	journal_t *journal;
+	struct buffer_head *bh = jh2bh(jh);
 
 	JBUFFER_TRACE(jh, "entry");
 
@@ -575,6 +573,14 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 	journal = transaction->t_journal;
 
 	JBUFFER_TRACE(jh, "removing from transaction");
+	/*
+	 * If the buffer has been failed to write out to disk, it may probably
+	 * lead to filesystem inconsistency after remove it from the log, so
+	 * mark the journal checkpoint write back IO error.
+	 */
+	if (buffer_write_io_error(bh))
+		journal->j_checkpoint_io_error = true;
+
 	__buffer_unlink(jh);
 	jh->b_cp_transaction = NULL;
 	jbd2_journal_put_journal_head(jh);
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 2dc944442802..6dbeab8b9feb 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1995,6 +1995,15 @@ int jbd2_journal_destroy(journal_t *journal)
 	J_ASSERT(journal->j_checkpoint_transactions == NULL);
 	spin_unlock(&journal->j_list_lock);
 
+	/*
+	 * OK, all checkpoint transactions have been checked, now check the
+	 * write out io error flag and abort the journal if some buffer failed
+	 * to write back to the original location, otherwise the filesystem
+	 * may probably becomes inconsistency.
+	 */
+	if (!is_journal_aborted(journal) && journal->j_checkpoint_io_error)
+		jbd2_journal_abort(journal, -EIO);
+
 	if (journal->j_sb_buffer) {
 		if (!is_journal_aborted(journal)) {
 			mutex_lock_io(&journal->j_checkpoint_mutex);
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 99d3cd051ac3..53ca70f80ad8 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -841,6 +841,13 @@ struct journal_s
 	 */
 	transaction_t		*j_checkpoint_transactions;
 
+	/**
+	 * @j_checkpoint_io_error:
+	 *
+	 * Detect io error while writing back original buffer to disk.
+	 */
+	bool			j_checkpoint_io_error;
+
 	/**
 	 * @j_wait_transaction_locked:
 	 *
-- 
2.25.4

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