writeback: fix false warning in inode_to_wb()

commit 9e888998ea4d22257b07ce911576509486fa0667 upstream.

inode_to_wb() is used also for filesystems that don't support cgroup
writeback.  For these filesystems inode->i_wb is stable during the
lifetime of the inode (it points to bdi->wb) and there's no need to hold
locks protecting the inode->i_wb dereference.  Improve the warning in
inode_to_wb() to not trigger for these filesystems.

Link: https://lkml.kernel.org/r/20250412163914.3773459-3-agruenba@redhat.com
Fixes: aaa2cacf8184 ("writeback: add lockdep annotation to inode_to_wb()")
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 1a97277f99b1b82de9e96eb8b9ca5544f9aa6e3a..ae8c46ad92222e6efc5c69bf9ce3b3c5488a5cb8 100644 (file)
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -250,6 +250,7 @@ static inline struct bdi_writeback *inode_to_wb(const struct inode *inode)
 {
 #ifdef CONFIG_LOCKDEP
        WARN_ON_ONCE(debug_locks &&
+                    (inode->i_sb->s_iflags & SB_I_CGROUPWB) &&
                     (!lockdep_is_held(&inode->i_lock) &&
                      !lockdep_is_held(&inode->i_mapping->i_pages.xa_lock) &&
                      !lockdep_is_held(&inode->i_wb->list_lock)));