linux-kernel - [PATCH 02/17] nilfs2: eliminate staggered calls to kunmap in nilfs

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Message-Id: <20231127143036.2425-3-konishi.ryusuke@gmail.com>
Date:   Mon, 27 Nov 2023 23:30:21 +0900
From:   Ryusuke Konishi <konishi.ryusuke@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-nilfs@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 02/17] nilfs2: eliminate staggered calls to kunmap in nilfs_rename

In nilfs_rename(), calls to nilfs_put_page() to release pages obtained
with nilfs_find_entry() or nilfs_dotdot() are alternated in the normal
path.

When replacing the kernel memory mapping method from kmap to
kmap_local_{page,folio}, this violates the constraint on the calling
order of kunmap_local().

Swap the order of nilfs_put_page calls where the kmap sections of
multiple pages overlap so that they are nested, allowing direct
replacement of nilfs_put_page() -> unmap_and_put_page().

Without this reordering, that replacement will cause a kernel WARNING
in kunmap_local_indexed() on architectures with high memory mapping.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@...il.com>
Cc: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 fs/nilfs2/namei.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/nilfs2/namei.c b/fs/nilfs2/namei.c
index 99255694cbe9..d179db8074c2 100644
--- a/fs/nilfs2/namei.c
+++ b/fs/nilfs2/namei.c
@@ -411,13 +411,14 @@ static int nilfs_rename(struct mnt_idmap *idmap,
 	inode_set_ctime_current(old_inode);

 	nilfs_delete_entry(old_de, old_page);
-	nilfs_put_page(old_page);

 	if (dir_de) {
 		nilfs_set_link(old_inode, dir_de, dir_page, new_dir);
 		nilfs_put_page(dir_page);
 		drop_nlink(old_dir);
 	}
+	nilfs_put_page(old_page);
+
 	nilfs_mark_inode_dirty(old_dir);
 	nilfs_mark_inode_dirty(old_inode);

-- 
2.34.1