linux-kernel - clear_page, copy_page address align question?

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Message-ID: <20170411030823.GB6545@bbox>
Date:   Tue, 11 Apr 2017 12:08:23 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: clear_page, copy_page address align question?

Hello,

When I tested zram in ppc64, I got random corruption.
With investigation, it seems clear_page corrupted the memory.
I passed 64K kmalloced(kmalloc(PAGE_SIZE)) address to clear_page
and turned on slub debug so address is not aligned with PAGE_SIZE.
Is it a valid usecase that non-PAGE_SIZE aligned address is
used for clear_page in ppc64?

As well, copy_page have same rule, too?

Anyway, when I changed clear_page to memset, it seems the problem
is gone.

Thanks.