Date:   Tue, 13 Oct 2020 05:42:07 +0000
From:   常凤楠 <changfengnan@...vision.com>
To:     Jan Kara <jack@...e.cz>, Ted Tso <tytso@....edu>
CC:     "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "adilger@...ger.ca" <adilger@...ger.ca>,
        changfengnan <fengnanchang@...mail.com>
Subject: 答复: [PATCH v6] jbd2: avoid transaction reuse after reformatting

This version is good for my test cases.


-----邮件原件-----
发件人: Jan Kara <jack@...e.cz>
发送时间: 2020年10月13日 0:49
收件人: Ted Tso <tytso@....edu>
抄送: linux-ext4@...r.kernel.org; 常凤楠 <changfengnan@...vision.com>; adilger@...ger.ca; changfengnan <fengnanchang@...mail.com>; Jan Kara <jack@...e.cz>
主题: [PATCH v6] jbd2: avoid transaction reuse after reformatting

From: changfengnan <fengnanchang@...mail.com>

When ext4 is formatted with lazy_journal_init=1 and transactions from the previous filesystem are still on disk, it is possible that they are considered during a recovery after a crash. Because the checksum seed has changed, the CRC check will fail, and the journal recovery fails with checksum error although the journal is otherwise perfectly valid.
Fix the problem by checking commit block time stamps to determine whether the data in the journal block is just stale or whether it is indeed corrupt.

Reported-by: kernel test robot <lkp@...el.com>
Reviewed-by: Andreas Dilger <adilger@...ger.ca>
Signed-off-by: Fengnan Chang <changfengnan@...vision.com>
Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/jbd2/recovery.c | 78 +++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 66 insertions(+), 12 deletions(-)

Changes since v5:
- rebase on current upstream kernel
- reduced some code duplication and indentation level

Changes since v4:
- fix logic to handle also v2/v3 journal checksum mismatch in the commit block

diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c index faa97d748474..fb134c7a12c8 100644
--- a/fs/jbd2/recovery.c
+++ b/fs/jbd2/recovery.c
@@ -428,6 +428,8 @@ static int do_one_pass(journal_t *journal,
 __u32crc32_sum = ~0; /* Transactional Checksums */
 intdescr_csum_size = 0;
 intblock_error = 0;
+boolneed_check_commit_time = false;
+__u64last_trans_commit_time = 0, commit_time;

 /*
  * First thing is to establish what we expect to find in the log @@ -520,12 +522,21 @@ static int do_one_pass(journal_t *journal,
 if (descr_csum_size > 0 &&
     !jbd2_descriptor_block_csum_verify(journal,
        bh->b_data)) {
-printk(KERN_ERR "JBD2: Invalid checksum "
-       "recovering block %lu in log\n",
-       next_log_block);
-err = -EFSBADCRC;
-brelse(bh);
-goto failed;
+/*
+ * PASS_SCAN can see stale blocks due to lazy
+ * journal init. Don't error out on those yet.
+ */
+if (pass != PASS_SCAN) {
+pr_err("JBD2: Invalid checksum recovering block %lu in log\n",
+       next_log_block);
+err = -EFSBADCRC;
+brelse(bh);
+goto failed;
+}
+need_check_commit_time = true;
+jbd_debug(1,
+"invalid descriptor block found in %lu\n",
+next_log_block);
 }

 /* If it is a valid descriptor block, replay it @@ -535,6 +546,7 @@ static int do_one_pass(journal_t *journal,
 if (pass != PASS_REPLAY) {
 if (pass == PASS_SCAN &&
     jbd2_has_feature_checksum(journal) &&
+    !need_check_commit_time &&
     !info->end_transaction) {
 if (calc_chksums(journal, bh,
 &next_log_block,
@@ -683,11 +695,41 @@ static int do_one_pass(journal_t *journal,
  * mentioned conditions. Hence assume
  * "Interrupted Commit".)
  */
+commit_time = be64_to_cpu(
+((struct commit_header *)bh->b_data)->h_commit_sec);
+/*
+ * If need_check_commit_time is set, it means we are in
+ * PASS_SCAN and csum verify failed before. If
+ * commit_time is increasing, it's the same journal,
+ * otherwise it is stale journal block, just end this
+ * recovery.
+ */
+if (need_check_commit_time) {
+if (commit_time >= last_trans_commit_time) {
+pr_err("JBD2: Invalid checksum found in transaction %u\n",
+       next_commit_ID);
+err = -EFSBADCRC;
+brelse(bh);
+goto failed;
+}
+ignore_crc_mismatch:
+/*
+ * It likely does not belong to same journal,
+ * just end this recovery with success.
+ */
+jbd_debug(1, "JBD2: Invalid checksum ignored in transaction %u, likely stale data\n",
+  next_commit_ID);
+err = 0;
+brelse(bh);
+goto done;
+}

-/* Found an expected commit block: if checksums
- * are present verify them in PASS_SCAN; else not
+/*
+ * Found an expected commit block: if checksums
+ * are present, verify them in PASS_SCAN; else not
  * much to do other than move on to the next sequence
- * number. */
+ * number.
+ */
 if (pass == PASS_SCAN &&
     jbd2_has_feature_checksum(journal)) {
 struct commit_header *cbh =
@@ -719,6 +761,8 @@ static int do_one_pass(journal_t *journal,
     !jbd2_commit_block_csum_verify(journal,
    bh->b_data)) {
 chksum_error:
+if (commit_time < last_trans_commit_time)
+goto ignore_crc_mismatch;
 info->end_transaction = next_commit_ID;

 if (!jbd2_has_feature_async_commit(journal)) { @@ -728,11 +772,24 @@ static int do_one_pass(journal_t *journal,
 break;
 }
 }
+if (pass == PASS_SCAN)
+last_trans_commit_time = commit_time;
 brelse(bh);
 next_commit_ID++;
 continue;

 case JBD2_REVOKE_BLOCK:
+/*
+ * Check revoke block crc in pass_scan, if csum verify
+ * failed, check commit block time later.
+ */
+if (pass == PASS_SCAN &&
+    !jbd2_descriptor_block_csum_verify(journal,
+       bh->b_data)) {
+jbd_debug(1, "JBD2: invalid revoke block found in %lu\n",
+  next_log_block);
+need_check_commit_time = true;
+}
 /* If we aren't in the REVOKE pass, then we can
  * just skip over this block. */
 if (pass != PASS_REVOKE) {
@@ -800,9 +857,6 @@ static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 offset = sizeof(jbd2_journal_revoke_header_t);
 rcount = be32_to_cpu(header->r_count);

-if (!jbd2_descriptor_block_csum_verify(journal, header))
-return -EFSBADCRC;
-
 if (jbd2_journal_has_csum_v2or3(journal))
 csum_size = sizeof(struct jbd2_journal_block_tail);
 if (rcount > journal->j_blocksize - csum_size)
--
2.16.4


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