linux-kernel - [PATCH v4 4/8] jbd2: remove unneeded kmap for jh_in->b_frozen_data in jbd2_journal_write_metadata

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Message-Id: <20240801013815.2393869-5-shikemeng@huaweicloud.com>
Date: Thu,  1 Aug 2024 09:38:11 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: tytso@....edu,
	jack@...e.com
Cc: linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v4 4/8] jbd2: remove unneeded kmap for jh_in->b_frozen_data in jbd2_journal_write_metadata_buffer

Remove kmap for page of b_frozen_data from jbd2_alloc() which always
provides an address from the direct kernel mapping.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Reviewed-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/jbd2/journal.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 312c7575b54f..9c1ffb0dc740 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -352,12 +352,13 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
 		done_copy_out = 1;
 		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;
 	} else {
 		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);
 	}
 
-	mapped_data = kmap_local_folio(new_folio, new_offset);
 	/*
 	 * Fire data frozen trigger if data already wasn't frozen.  Do this
 	 * before checking for escaping, as the trigger may modify the magic
@@ -373,7 +374,8 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
 	 */
 	if (*((__be32 *)mapped_data) == cpu_to_be32(JBD2_MAGIC_NUMBER))
 		do_escape = 1;
-	kunmap_local(mapped_data);
+	if (!jh_in->b_frozen_data)
+		kunmap_local(mapped_data);
 
 	/*
 	 * Do we need to do a data copy?
-- 
2.30.0