vfs, freeze: use ACCESS_ONCE() to guard access to ->mnt_flags

The compiler may optimize the while loop and make the check just be done once,
so we should use ACCESS_ONCE() to guard access to ->mnt_flags

Signed-off-by: Miao Xie <[email protected]>
Signed-off-by: Al Viro <[email protected]>
This commit is contained in:
Miao Xie 2012-11-16 17:23:50 +08:00 • committed by Al Viro
commit 1e75529e3c

View file

@ -313,7 +313,7 @@ int __mnt_want_write(struct vfsmount *m)
* incremented count after it has set MNT_WRITE_HOLD.
*/
smp_mb();
while (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
cpu_relax();
/*
* After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will