From: Matthew Wilcox <willy@infradead.org>
To: Mike Rapoport <rppt@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Borislav Petkov <bp@alien8.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Christopher Lameter <cl@linux.com>,
Dan Williams <dan.j.williams@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
David Hildenbrand <david@redhat.com>,
Elena Reshetova <elena.reshetova@intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
James Bottomley <jejb@linux.ibm.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Matthew Garrett <mjg59@srcf.ucam.org>,
Mark Rutland <mark.rutland@arm.com>,
Michal Hocko <mhocko@suse.com>,
Mike Rapoport <rppt@linux.ibm.com>,
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Shuah Khan <shuah@kernel.org>,
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linux-arm-kernel@lists.infradead.org,
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x86@kernel.org, kernel test robot <oliver.sang@intel.com>
Subject: Re: [PATCH] secretmem: optimize page_is_secretmem()
Date: Mon, 19 Apr 2021 12:23:02 +0100 [thread overview]
Message-ID: <20210419112302.GX2531743@casper.infradead.org> (raw)
In-Reply-To: <20210419084218.7466-1-rppt@kernel.org>
On Mon, Apr 19, 2021 at 11:42:18AM +0300, Mike Rapoport wrote:
> The perf profile of the test indicated that the regression is caused by
> page_is_secretmem() called from gup_pte_range() (inlined by gup_pgd_range):
Uhh ... you're calling it in the wrong place!
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
page = pte_page(pte);
if (page_is_secretmem(page))
goto pte_unmap;
head = try_grab_compound_head(page, 1, flags);
if (!head)
goto pte_unmap;
So you're calling page_is_secretmem() on a struct page without having
a refcount on it. That is definitely not allowed. secretmem seems to
be full of these kinds of races; I know this isn't the first one I've
seen in it. I don't think this patchset is ready for this merge window.
With that fixed, you'll have a head page that you can use for testing,
which means you don't need to test PageCompound() (because you know the
page isn't PageTail), you can just test PageHead().
next prev parent reply other threads:[~2021-04-19 11:27 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-19 8:42 [PATCH] secretmem: optimize page_is_secretmem() Mike Rapoport
2021-04-19 9:15 ` David Hildenbrand
2021-04-19 9:36 ` Mike Rapoport
2021-04-19 9:38 ` David Hildenbrand
2021-04-19 9:40 ` David Hildenbrand
2021-04-19 10:14 ` Mike Rapoport
2021-04-19 10:21 ` David Hildenbrand
2021-04-19 11:43 ` Matthew Wilcox
2021-04-19 11:23 ` Matthew Wilcox [this message]
2021-04-19 11:56 ` Mike Rapoport
2021-04-19 12:21 ` Matthew Wilcox
2021-04-19 18:24 ` Mike Rapoport
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