fs: spell out fenced ->i_state accesses with explicit smp_wmb/smp_rmb

The incomming helpers don't ship with _release/_acquire variants, for
the time being anyway.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 2b35e80037feed4c711d55199a4e73eb0fc3ff26..9cda19a40ca2ed7567f8b13c2513fa8a5e41fd8a 100644 (file)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -476,10 +476,11 @@ static bool inode_do_switch_wbs(struct inode *inode,
        switched = true;
 skip_switch:
        /*
-        * Paired with load_acquire in unlocked_inode_to_wb_begin() and
+        * Paired with an acquire fence in unlocked_inode_to_wb_begin() and
         * ensures that the new wb is visible if they see !I_WB_SWITCH.
         */
-       smp_store_release(&inode->i_state, inode->i_state & ~I_WB_SWITCH);
+       smp_wmb();
+       inode->i_state &= ~I_WB_SWITCH;
 
        xa_unlock_irq(&mapping->i_pages);
        spin_unlock(&inode->i_lock);

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 3e64f14739dd2d08a9fb5153ac1ebc5374a308aa..065cba5dc111be196c6a3a0b1411d232a5661082 100644 (file)
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -277,10 +277,11 @@ unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
        rcu_read_lock();
 
        /*
-        * Paired with store_release in inode_switch_wbs_work_fn() and
+        * Paired with a release fence in inode_do_switch_wbs() and
         * ensures that we see the new wb if we see cleared I_WB_SWITCH.
         */
-       cookie->locked = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;
+       cookie->locked = inode->i_state & I_WB_SWITCH;
+       smp_rmb();
 
        if (unlikely(cookie->locked))
                xa_lock_irqsave(&inode->i_mapping->i_pages, cookie->flags);