[PATCH v3 4/6] jbd2: switch to check format version in superblock directly

[Zhihao Cheng]

From: Zhang Yi <yi.zhang@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
---
 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 8ae419152ff6..8d5fe6738cc4 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -2062,10 +2062,12 @@ 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 &
@@ -2227,7 +2229,7 @@ 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;
@@ -2257,11 +2259,7 @@ 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 a91cf9c7a94b..1ffcea5c024e 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1313,11 +1313,22 @@ 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); \
 } \
@@ -1335,7 +1346,7 @@ 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); \
 } \
@@ -1353,7 +1364,7 @@ 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