diff mbox series

[02/17] nilfs2: eliminate staggered calls to kunmap in nilfs_rename

Message ID 20231127143036.2425-3-konishi.ryusuke@gmail.com
State New
Headers
Series nilfs2: Folio conversions for directory paths |

Commit Message

Ryusuke Konishi Nov. 27, 2023, 2:30 p.m. UTC 
  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@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/nilfs2/namei.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Matthew Wilcox Nov. 27, 2023, 5:08 p.m. UTC | #1 
On Mon, Nov 27, 2023 at 11:30:21PM +0900, Ryusuke Konishi wrote:
> 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@gmail.com>
> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>

Thanks for catching this!

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
diff mbox series

Patch

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);