Date:   Mon, 13 Mar 2023 11:57:05 +0100
From:   Jan Kara <jack@suse.cz>
To:     Zhihao Cheng <chengzhihao1@huawei.com>
Cc:     tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.com,
        linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        yi.zhang@huawei.com
Subject: Re: [PATCH 3/5] jbd2: switch to check format version in superblock
 directly
Message-ID: <20230313105705.5t2huh3hjgqm2ovf@quack3>
References: <20230310125206.2867822-1-chengzhihao1@huawei.com>
 <20230310125206.2867822-4-chengzhihao1@huawei.com>
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On Fri 10-03-23 20:52:04, Zhihao Cheng wrote:
> From: Zhang Yi <yi.zhang@huawei.com>
> 
> We should only check and set extented features if journal format version
> is 2, and now we check the in memory copy of the superblock
> 'journal->j_format_version', which relys on the parameter initialization
> sequence, switch to use the h_blocktype in superblock cloud be more
> clear.
> 
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>

Looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/jbd2/journal.c    | 16 +++++++---------
>  include/linux/jbd2.h | 17 ++++++++++++++---
>  2 files changed, 21 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index e80c781731f8..b991d5c21d16 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -2059,10 +2059,12 @@ int jbd2_journal_load(journal_t *journal)
>  		return err;
>  
>  	sb = journal->j_superblock;
> -	/* If this is a V2 superblock, then we have to check the
> -	 * features flags on it. */
>  
> -	if (journal->j_format_version >= 2) {
> +	/*
> +	 * If this is a V2 superblock, then we have to check the
> +	 * features flags on it.
> +	 */
> +	if (jbd2_format_support_feature(journal)) {
>  		if ((sb->s_feature_ro_compat &
>  		     ~cpu_to_be32(JBD2_KNOWN_ROCOMPAT_FEATURES)) ||
>  		    (sb->s_feature_incompat &
> @@ -2224,7 +2226,7 @@ int jbd2_journal_check_used_features(journal_t *journal, unsigned long compat,
>  	if (journal->j_format_version == 0 &&
>  	    journal_get_superblock(journal) != 0)
>  		return 0;
> -	if (journal->j_format_version == 1)
> +	if (!jbd2_format_support_feature(journal))
>  		return 0;
>  
>  	sb = journal->j_superblock;
> @@ -2254,11 +2256,7 @@ int jbd2_journal_check_available_features(journal_t *journal, unsigned long comp
>  	if (!compat && !ro && !incompat)
>  		return 1;
>  
> -	/* We can support any known requested features iff the
> -	 * superblock is in version 2.  Otherwise we fail to support any
> -	 * extended sb features. */
> -
> -	if (journal->j_format_version != 2)
> +	if (!jbd2_format_support_feature(journal))
>  		return 0;
>  
>  	if ((compat   & JBD2_KNOWN_COMPAT_FEATURES) == compat &&
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index ad7bb6861143..7095c0f17ad0 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -1305,11 +1305,22 @@ struct journal_s
>  		rwsem_release(&j->j_trans_commit_map, _THIS_IP_); \
>  	} while (0)
>  
> +/*
> + * We can support any known requested features iff the
> + * superblock is not in version 1.  Otherwise we fail to support any
> + * extended sb features.
> + */
> +static inline bool jbd2_format_support_feature(journal_t *j)
> +{
> +	return j->j_superblock->s_header.h_blocktype !=
> +					cpu_to_be32(JBD2_SUPERBLOCK_V1);
> +}
> +
>  /* journal feature predicate functions */
>  #define JBD2_FEATURE_COMPAT_FUNCS(name, flagname) \
>  static inline bool jbd2_has_feature_##name(journal_t *j) \
>  { \
> -	return ((j)->j_format_version >= 2 && \
> +	return (jbd2_format_support_feature(j) && \
>  		((j)->j_superblock->s_feature_compat & \
>  		 cpu_to_be32(JBD2_FEATURE_COMPAT_##flagname)) != 0); \
>  } \
> @@ -1327,7 +1338,7 @@ static inline void jbd2_clear_feature_##name(journal_t *j) \
>  #define JBD2_FEATURE_RO_COMPAT_FUNCS(name, flagname) \
>  static inline bool jbd2_has_feature_##name(journal_t *j) \
>  { \
> -	return ((j)->j_format_version >= 2 && \
> +	return (jbd2_format_support_feature(j) && \
>  		((j)->j_superblock->s_feature_ro_compat & \
>  		 cpu_to_be32(JBD2_FEATURE_RO_COMPAT_##flagname)) != 0); \
>  } \
> @@ -1345,7 +1356,7 @@ static inline void jbd2_clear_feature_##name(journal_t *j) \
>  #define JBD2_FEATURE_INCOMPAT_FUNCS(name, flagname) \
>  static inline bool jbd2_has_feature_##name(journal_t *j) \
>  { \
> -	return ((j)->j_format_version >= 2 && \
> +	return (jbd2_format_support_feature(j) && \
>  		((j)->j_superblock->s_feature_incompat & \
>  		 cpu_to_be32(JBD2_FEATURE_INCOMPAT_##flagname)) != 0); \
>  } \
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR