linux-kernel - Re: [PATCH v2] jbd2: gate checksum calculations on crc driver presence, not sb flags

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Date:	Mon, 5 Oct 2015 09:28:41 +0300
From:	Nikolay Borisov <kernel@...p.com>
To:	"Darrick J. Wong" <darrick.wong@...cle.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 10/05/2015 09:21 AM, Darrick J. Wong wrote:
> 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 ^^^^^^^^^^^^^^^
> 

But you had this function in v1 as well? I thought you had integrated
Andreas' suggestion?

> --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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