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    Subject[RFC][PATCH 3/5] overlayfs: Remove smp_mb__before_spinlock() usage
    While we could replace the smp_mb__before_spinlock() with the new
    smp_mb__after_spinlock(), the normal pattern is to use
    smp_store_release() to publish an object that is used for
    lockless_dereference() -- and mirrors the regular rcu_assign_pointer()
    / rcu_dereference() patterns.

    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    ---
    fs/overlayfs/readdir.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/fs/overlayfs/readdir.c
    +++ b/fs/overlayfs/readdir.c
    @@ -446,14 +446,14 @@ static int ovl_dir_fsync(struct file *fi

    ovl_path_upper(dentry, &upperpath);
    realfile = ovl_path_open(&upperpath, O_RDONLY);
    - smp_mb__before_spinlock();
    +
    inode_lock(inode);
    if (!od->upperfile) {
    if (IS_ERR(realfile)) {
    inode_unlock(inode);
    return PTR_ERR(realfile);
    }
    - od->upperfile = realfile;
    + smp_store_release(&od->upperfile, realfile);
    } else {
    /* somebody has beaten us to it */
    if (!IS_ERR(realfile))

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