From: Mateusz Guzik <mjguzik@gmail.com>
Date: Sat, 30 Nov 2024 05:17:11 +0000 (+0100)
Subject: fs: use a consume fence in mnt_idmap()
X-Git-Tag: v6.14-rc1~216^2~10
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3212a8f34021a16d13ace91d3ac5f451ef8d0103;p=thirdparty%2Flinux.git

fs: use a consume fence in mnt_idmap()

The routine is used in link_path_walk() for every path component.

To my reading the entire point of the fence was to grab a fully
populated mnt_idmap, but that's already going to happen with mere
consume fence.

Eliminates an actual fence on arm64.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20241130051712.1036527-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
---

diff --git a/include/linux/mount.h b/include/linux/mount.h
index c34c18b4e8f36..33f17b6e87323 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -76,7 +76,7 @@ struct vfsmount {
 static inline struct mnt_idmap *mnt_idmap(const struct vfsmount *mnt)
 {
 	/* Pairs with smp_store_release() in do_idmap_mount(). */
-	return smp_load_acquire(&mnt->mnt_idmap);
+	return READ_ONCE(mnt->mnt_idmap);
 }
 
 extern int mnt_want_write(struct vfsmount *mnt);