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Message-ID: <20230109134545.2234414-1-chengzhihao1@huawei.com>
Date: Mon, 9 Jan 2023 21:45:45 +0800
From: Zhihao Cheng <chengzhihao1@...wei.com>
To: <tytso@....edu>, <jack@...e.com>
CC: <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<chengzhihao1@...wei.com>, <yi.zhang@...wei.com>,
<libaokun1@...wei.com>, <zhanchengbin1@...wei.com>
Subject: [PATCH -next v3] jbd2: Fix data missing when reusing bh which is ready to be checkpointed
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@...nel.org>
Signed-off-by: Zhihao Cheng <chengzhihao1@...wei.com>
Signed-off-by: zhanchengbin <zhanchengbin1@...wei.com>
Suggested-by: Jan Kara <jack@...e.cz>
---
v1->v2: Adopt Jan's suggestion, move the clearing of buffer_dirty bit
and __jbd2_journal_file_buffer() inside journal->j_list_lock
locking area.
v2->v3: Remove redundant assertions in in branch 'if (jh->b_transaction)'
Add reproducer link in commit message.
fs/jbd2/transaction.c | 51 +++++++++++++++++++++++++------------------
1 file changed, 30 insertions(+), 21 deletions(-)
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 6a404ac1c178..2fbe0f201b29 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1010,36 +1010,29 @@ 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)) {
+ if (buffer_dirty(bh) && jh->b_transaction) {
+ warn_dirty_buffer(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);
- 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);
+ /*
+ * Setting jbddirty after clearing buffer dirty is necessary.
+ * Function jbd2_journal_restart() could keep buffer on
+ * BJ_Reserved list until the transaction committing, then the
+ * buffer won't be dirtied by jbd2_journal_refile_buffer()
+ * after committing, the buffer couldn't fall on disk even
+ * last checkpoint finished, which may corrupt filesystem.
+ */
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;
@@ -1049,8 +1042,10 @@ 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,
@@ -1074,10 +1069,24 @@ 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
--
2.31.1
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