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Date:   Mon, 21 Nov 2022 09:00:02 +0100 (CET)
From:   Richard Weinberger <richard@nod.at>
To:     Lihua <hucool.lihua@huawei.com>
Cc:     Sascha Hauer <s.hauer@pengutronix.de>,
        linux-mtd <linux-mtd@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Wei Yongjun <weiyongjun1@huawei.com>,
        yusongping <yusongping@huawei.com>
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Subject: Re: [PATCH] ubifs: Fix build errors as symbol undefined
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Thread-Topic: ubifs: Fix build errors as symbol undefined
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----- Ursprüngliche Mail -----
> Von: "Lihua" <hucool.lihua@huawei.com>
> An: "richard" <richard@nod.at>
> CC: "Sascha Hauer" <s.hauer@pengutronix.de>, "linux-mtd" <linux-mtd@lists.infradead.org>, "linux-kernel"
> <linux-kernel@vger.kernel.org>, "Wei Yongjun" <weiyongjun1@huawei.com>, "yusongping" <yusongping@huawei.com>
> Gesendet: Montag, 21. November 2022 02:54:53
> Betreff: Re: [PATCH] ubifs: Fix build errors as symbol undefined

> You can verify it with the config in the attachment. TKS :D

Thanks for your .config, I was able to identify the problem.
When CONFIG_CC_OPTIMIZE_FOR_SIZE is set the compiler does not optimize this construct:

        err = ubifs_node_check_hash(c, buf, zbr->hash);
        if (err) {
                ubifs_bad_hash(c, buf, zbr->hash, lnum, offs);
                return 0;
        }

With CONFIG_UBIFS_FS_AUTHENTICATION not set, the compiler can assume that
ubifs_node_check_hash() is never true and drops the call to ubifs_bad_hash().
Is CONFIG_CC_OPTIMIZE_FOR_SIZE enabled this optimization does not happen anymore.

So we need a no-op ubifs_bad_hash() for the CONFIG_UBIFS_FS_AUTHENTICATION=n case.

Thanks,
//richard