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Date:	Sun, 4 Oct 2015 23:21:31 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	Nikolay Borisov <kernel@...p.com>
Cc:	Jan Kara <jack@...e.com>, "Theodore Ts'o" <tytso@....edu>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	SiteGround Operations <operations@...eground.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH v2] jbd2: gate checksum calculations on crc driver
 presence, not sb flags

On Mon, Oct 05, 2015 at 08:43:34AM +0300, Nikolay Borisov wrote:
> It is just me or am I not seeing this feature test helper in this patch ?
> 
> On 10/03/2015 06:46 AM, Darrick J. Wong wrote:
> > Change the journal's checksum functions to gate on whether or not the
> > crc32c driver is loaded, and gate the loading on the superblock bits.
> > This prevents a journal crash if someone loads a journal in no-csum
> > mode and then randomizes the superblock, thus flipping on the feature
> > bits.
> > 
> > v2: Create a feature-test helper, use it everywhere.
> > 
> > Tested-By: Nikolay Borisov <kernel@...p.com>
> > Reported-by: Nikolay Borisov <kernel@...p.com>
> > Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> > ---
> >  fs/jbd2/journal.c    |    6 +++---
> >  include/linux/jbd2.h |   13 +++++++++----
> >  2 files changed, 12 insertions(+), 7 deletions(-)
> > 
> > diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> > index 8270fe9..00f7dbd 100644
> > --- a/fs/jbd2/journal.c
> > +++ b/fs/jbd2/journal.c
> > @@ -124,7 +124,7 @@ EXPORT_SYMBOL(__jbd2_debug);
> >  /* Checksumming functions */
> >  static int jbd2_verify_csum_type(journal_t *j, journal_superblock_t *sb)
> >  {
> > -	if (!jbd2_journal_has_csum_v2or3(j))
> > +	if (!jbd2_journal_has_csum_v2or3_feature(j))
> >  		return 1;
> >  
> >  	return sb->s_checksum_type == JBD2_CRC32C_CHKSUM;
> > @@ -1531,7 +1531,7 @@ static int journal_get_superblock(journal_t *journal)
> >  		goto out;
> >  	}
> >  
> > -	if (jbd2_journal_has_csum_v2or3(journal) &&
> > +	if (jbd2_journal_has_csum_v2or3_feature(journal) &&
> >  	    JBD2_HAS_COMPAT_FEATURE(journal, JBD2_FEATURE_COMPAT_CHECKSUM)) {
> >  		/* Can't have checksum v1 and v2 on at the same time! */
> >  		printk(KERN_ERR "JBD2: Can't enable checksumming v1 and v2/3 "
> > @@ -1545,7 +1545,7 @@ static int journal_get_superblock(journal_t *journal)
> >  	}
> >  
> >  	/* Load the checksum driver */
> > -	if (jbd2_journal_has_csum_v2or3(journal)) {
> > +	if (jbd2_journal_has_csum_v2or3_feature(journal)) {
> >  		journal->j_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
> >  		if (IS_ERR(journal->j_chksum_driver)) {
> >  			printk(KERN_ERR "JBD2: Cannot load crc32c driver.\n");
> > diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> > index df07e78..6da6f89 100644
> > --- a/include/linux/jbd2.h
> > +++ b/include/linux/jbd2.h
> > @@ -1338,13 +1338,18 @@ static inline int tid_geq(tid_t x, tid_t y)
> >  extern int jbd2_journal_blocks_per_page(struct inode *inode);
> >  extern size_t journal_tag_bytes(journal_t *journal);
> >  
> > +static inline bool jbd2_journal_has_csum_v2or3_feature(journal_t *j)

Here ^^^^^^^^^^^^^^^

--D

> > +{
> > +	return JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2) ||
> > +	       JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V3);
> > +}
> > +
> >  static inline int jbd2_journal_has_csum_v2or3(journal_t *journal)
> >  {
> > -	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_CSUM_V2) ||
> > -	    JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_CSUM_V3))
> > -		return 1;
> > +	WARN_ON_ONCE(jbd2_journal_has_csum_v2or3_feature(journal) &&
> > +		     journal->j_chksum_driver == NULL);
> >  
> > -	return 0;
> > +	return journal->j_chksum_driver != NULL;
> >  }
> >  
> >  /*
> > 
--
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