linux-ext4 - Re: [PATCH] ext4: fix race conditions in ->d_compare() and ->d

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Message-ID: <20200124053415.GC31271@hsiangkao-HP-ZHAN-66-Pro-G1>
Date:   Fri, 24 Jan 2020 13:34:23 +0800
From:   Gao Xiang <hsiangkao@....com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Daniel Rosenberg <drosen@...gle.com>,
        Gabriel Krisman Bertazi <krisman@...labora.com>
Subject: Re: [PATCH] ext4: fix race conditions in ->d_compare() and ->d_hash()

On Thu, Jan 23, 2020 at 09:16:01PM -0800, Eric Biggers wrote:

[]

> So we need READ_ONCE() to ensure that a consistent value is used.

By the way, my understanding is all pointer could be accessed
atomicly guaranteed by compiler. In my opinion, we generally
use READ_ONCE() on pointers for other uses (such as, avoid
accessing a variable twice due to compiler optimization and
it will break some logic potentially or need some data
dependency barrier...)

Thanks,
Gao Xiang