jbd2: move escape handle to futher improve jbd2_journal_write_metadata_buffer

Move escape handle to futher improve code readability and remove some
repeat check.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20240801013815.2393869-7-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: Kemeng Shi

fs/jbd2/journal.c

@@ -281,6 +281,16 @@ static void journal_kill_thread(journal_t *journal)
 	write_unlock(&journal->j_state_lock);
 }
 
+static inline bool jbd2_data_needs_escaping(char *data)
+{
+	return *((__be32 *)data) == cpu_to_be32(JBD2_MAGIC_NUMBER);
+}
+
+static inline void jbd2_data_do_escape(char *data)
+{
+	*((unsigned int *)data) = 0;
+}
+
 /*
  * jbd2_journal_write_metadata_buffer: write a metadata buffer to the journal.
  *
@@ -319,7 +329,6 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
 				  sector_t blocknr)
 {
 	int do_escape = 0;
-	char *mapped_data;
 	struct buffer_head *new_bh;
 	struct folio *new_folio;
 	unsigned int new_offset;
@@ -350,8 +359,13 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
 	if (jh_in->b_frozen_data) {
 		new_folio = virt_to_folio(jh_in->b_frozen_data);
 		new_offset = offset_in_folio(new_folio, jh_in->b_frozen_data);
-		mapped_data = jh_in->b_frozen_data;
+		do_escape = jbd2_data_needs_escaping(jh_in->b_frozen_data);
+		if (do_escape)
+			jbd2_data_do_escape(jh_in->b_frozen_data);
 	} else {
+		char *tmp;
+		char *mapped_data;
+
 		new_folio = bh_in->b_folio;
 		new_offset = offset_in_folio(new_folio, bh_in->b_data);
 		mapped_data = kmap_local_folio(new_folio, new_offset);
@@ -363,21 +377,13 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
 		 */
 		jbd2_buffer_frozen_trigger(jh_in, mapped_data,
 					   jh_in->b_triggers);
-	}
-
-	/*
-	 * Check for escaping
-	 */
-	if (*((__be32 *)mapped_data) == cpu_to_be32(JBD2_MAGIC_NUMBER))
-		do_escape = 1;
-	if (!jh_in->b_frozen_data)
+		do_escape = jbd2_data_needs_escaping(mapped_data);
 		kunmap_local(mapped_data);
-
-	/*
-	 * Do we need to do a data copy?
-	 */
-	if (do_escape && !jh_in->b_frozen_data) {
-		char *tmp;
+		/*
+		 * Do we need to do a data copy?
+		 */
+		if (!do_escape)
+			goto escape_done;
 
 		spin_unlock(&jh_in->b_state_lock);
 		tmp = jbd2_alloc(bh_in->b_size, GFP_NOFS);
@@ -404,17 +410,10 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
 copy_done:
 		new_folio = virt_to_folio(jh_in->b_frozen_data);
 		new_offset = offset_in_folio(new_folio, jh_in->b_frozen_data);
+		jbd2_data_do_escape(jh_in->b_frozen_data);
 	}
 
-	/*
-	 * Did we need to do an escaping?  Now we've done all the
-	 * copying, we can finally do so.
-	 * b_frozen_data is from jbd2_alloc() which always provides an
-	 * address from the direct kernels mapping.
-	 */
-	if (do_escape)
-		*((unsigned int *)jh_in->b_frozen_data) = 0;
-
+escape_done:
 	folio_set_bh(new_bh, new_folio, new_offset);
 	new_bh->b_size = bh_in->b_size;
 	new_bh->b_bdev = journal->j_dev;