Message-ID: <20200923122435.GG6719@quack2.suse.cz>
Date:   Wed, 23 Sep 2020 14:24:35 +0200
From:   Jan Kara <jack@...e.cz>
To:     常凤楠 <changfengnan@...vision.com>
Cc:     Jan Kara <jack@...e.cz>, changfengnan <changfengnan@...com>,
        "adilger@...ger.ca" <adilger@...ger.ca>,
        "darrick.wong@...cle.com" <darrick.wong@...cle.com>,
        "jack@...e.com" <jack@...e.com>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "tytso@....edu" <tytso@....edu>
Subject: Re: 答复: 答复: 答复: [PATCH] jbd2: avoid transaction reuse after reformatting

On Wed 23-09-20 06:29:12, 常凤楠 wrote:
> The attachment is new patch.

Thanks!

> I have fix the logic in JBD2_REVOKE_BLOCK and JBD2_COMMIT_BLOCK case.
> If the revoke block is the first block after valid transaction, I set the
> flag like descriptor block ,and check it in commit block.  If the commit
> block is the first block after valid transaction, I use ri_commit_block
> to judge whether this commit block is next to another commit block, if so
> it is illegal. I did't use time to judge commit block, because of the
> possibility of time calibration, I think use ri_commit_block is more
> reliable.

If the time is unreliable, your logic with ri_commit_block will detect only
a small minority of the cases. The majority of cases will fail with
checksum error. So I still don't think the ri_commit_block logic is really
worth the additional code. Other than that the current version looks OK to
me. So please do next submission with full changelog, Signed-off-by line,
and the coding style issues fixed (you can use scripts/checkpatch.pl for
patch verification). Thanks!

								Honza

> 
> -----邮件原件-----
> 发件人: Jan Kara <jack@...e.cz>
> 发送时间: 2020年9月18日 21:03
> 收件人: 常凤楠 <changfengnan@...vision.com>
> 抄送: Jan Kara <jack@...e.cz>; changfengnan <changfengnan@...com>; adilger@...ger.ca; darrick.wong@...cle.com; jack@...e.com; linux-ext4@...r.kernel.org; tytso@....edu
> 主题: Re: 答复: 答复: [PATCH] jbd2: avoid transaction reuse after reformatting
> 
> Hello,
> 
> On Fri 18-09-20 01:49:09, 常凤楠 wrote:
> > Sorry about my mailer, the patch is in the attachment.
> 
> Thanks for the patch. Functionally the patch looks mostly OK now. The only concern I have is that it handles checksum failures only in JBD2_DESCRIPTOR_BLOCK. This is the most likely case but it could also happen that JBD2_REVOKE_BLOCK or JBD2_COMMIT_BLOCK is the first one you see with mismatching checksum. So I think you need to handle these cases as well. I think your ri_commit_block logic below is an attempt to deal with these cases (but it's difficult to be sure because of complete lack of
> comments) but it is not reliable. A valid transaction can begin both with a descriptor or with a revoke block.
> 
> A few other comments mostly about coding style below:
> 
> diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c index a4967b27ffb6..f7702e14077f 100644
> --- a/fs/jbd2/recovery.c
> +++ b/fs/jbd2/recovery.c
> @@ -417,7 +417,7 @@ static int do_one_pass(journal_t *journal,
>  struct recovery_info *info, enum passtype pass)  {
>  unsigned intfirst_commit_ID, next_commit_ID;
> -unsigned longnext_log_block;
> +unsigned longnext_log_block, ri_commit_block = 0;
>  interr, success = 0;
>  journal_superblock_t *sb;
>  journal_header_t *tmp;
> @@ -428,7 +428,9 @@ 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;
> +__be64last_trans_commit_time;
> 
> All variable names in this function seem to be indented by one more column. Please keep the indentation.
> 
> +
> 
> This empty line has whitespace on it. Please delete.
> 
>  /*
>   * First thing is to establish what we expect to find in the log
>   * (in terms of transaction IDs), and where (in terms of log @@ -514,18 +516,18 @@ static int do_one_pass(journal_t *journal,
>  switch(blocktype) {
>  case JBD2_DESCRIPTOR_BLOCK:
>  /* Verify checksum first */
> +if(pass == PASS_SCAN)
>   ^ Coding style requires space before opening (.
> You have this problem at multiple places.
> 
> +ri_commit_block = 0;
> +
>  if (jbd2_journal_has_csum_v2or3(journal))
>  descr_csum_size =
>  sizeof(struct jbd2_journal_block_tail);
>  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;
> +need_check_commit_time = true;
> +jbd_debug(1, "invalid descriptor block found in %lu, continue
> +recovery first.\n",next_log_block);
> +
>  }
> 
>  /* If it is a valid descriptor block, replay it @@ -535,6 +537,7 @@ 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,
> @@ -688,6 +691,36 @@ static int do_one_pass(journal_t *journal,
>   * are present verify them in PASS_SCAN; else not
>   * much to do other than move on to the next sequence
>   * number. */
> +if(pass == PASS_SCAN) {
> +struct commit_header *cbh =
> +(struct commit_header *)bh->b_data;
> +if(need_check_commit_time) {
> +__be64 commit_time = be64_to_cpu(cbh->h_commit_sec);
> +if(commit_time >= last_trans_commit_time) {
> +printk(KERN_ERR "JBD2: Invalid checksum found in log, %d\n",
> +next_commit_ID);
> +err = -EFSBADCRC;
> +brelse(bh);
> +goto failed;
> +}
> +else
> +{
>   Coding style requires to put opening { on the same line as 'else'. Like:
> else {
> +/*it's not belong to same journal, just end this recovery with success*/
> +jbd_debug(1, "JBD2: Invalid checksum found in block in log, but not same journal %d\n",
> +next_commit_ID);
> +err = 0;
> +brelse(bh);
> +goto done;
> +}
> +}
> +if(ri_commit_block) {
> +jbd_debug(1, "invalid commit block found in %lu, stop here.\n",next_log_block);
> +brelse(bh);
> +goto done;
> +}
> +ri_commit_block = next_log_block;
> 
> Why does the ri_commit_block logic exist? I don't see it bringing any benefit...
> 
> +last_trans_commit_time = be64_to_cpu(cbh->h_commit_sec);
> +}
>  if (pass == PASS_SCAN &&
>      jbd2_has_feature_checksum(journal)) {
>  int chksum_err, chksum_seen;
> @@ -755,6 +788,12 @@ static int do_one_pass(journal_t *journal,
>  continue;
> 
>  case JBD2_REVOKE_BLOCK:
> +if (pass == PASS_SCAN &&
> +ri_commit_block) {
> +jbd_debug(1, "invalid revoke block found in %lu, stop here.\n",next_log_block);
> +brelse(bh);
> +goto done;
> +}
> 
> This is wrong. A valid transaction can start with a revoke block...
> 
>  /* If we aren't in the REVOKE pass, then we can
>   * just skip over this block. */
>  if (pass != PASS_REVOKE) {
> 
> Honza
> --
> Jan Kara <jack@...e.com>
> SUSE Labs, CR
> 
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-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

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