From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: William Kucharski <william.kucharski@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 14/15] mm: Align THP mappings for non-DAX
Date: Tue, 1 Oct 2019 14:32:16 +0300 [thread overview]
Message-ID: <20191001113216.3qbrkqmb2b2xtwkd@box> (raw)
In-Reply-To: <A935F599-BB18-40C3-90DD-47B7700743D6@oracle.com>
On Tue, Oct 01, 2019 at 05:21:26AM -0600, William Kucharski wrote:
>
>
> > On Oct 1, 2019, at 4:45 AM, Kirill A. Shutemov <kirill@shutemov.name> wrote:
> >
> > On Tue, Sep 24, 2019 at 05:52:13PM -0700, Matthew Wilcox wrote:
> >>
> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> >> index cbe7d0619439..670a1780bd2f 100644
> >> --- a/mm/huge_memory.c
> >> +++ b/mm/huge_memory.c
> >> @@ -563,8 +563,6 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
> >>
> >> if (addr)
> >> goto out;
> >> - if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
> >> - goto out;
> >>
> >> addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
> >> if (addr)
> >
> > I think you reducing ASLR without any real indication that THP is relevant
> > for the VMA. We need to know if any huge page allocation will be
> > *attempted* for the VMA or the file.
>
> Without a properly aligned address the code will never even attempt allocating
> a THP.
>
> I don't think rounding an address to one that would be properly aligned to map
> to a THP if possible is all that detrimental to ASLR and without the ability to
> pick an aligned address it's rather unlikely anyone would ever map anything to
> a THP unless they explicitly designate an address with MAP_FIXED.
>
> If you do object to the slight reduction of the ASLR address space, what
> alternative would you prefer to see?
We need to know by the time if THP is allowed for this
file/VMA/process/whatever. Meaning that we do not give up ASLR entropy for
nothing.
For instance, if THP is disabled globally, there is no reason to align the
VMA to the THP requirements.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2019-10-01 11:32 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-25 0:51 [RFC 00/15] Large pages in the page-cache Matthew Wilcox
2019-09-25 0:52 ` [PATCH 01/15] mm: Use vm_fault error code directly Matthew Wilcox
2019-09-26 13:55 ` Kirill A. Shutemov
2019-09-25 0:52 ` [PATCH 02/15] fs: Introduce i_blocks_per_page Matthew Wilcox
2019-09-25 8:36 ` Dave Chinner
2019-10-04 19:28 ` Matthew Wilcox
2019-10-08 3:53 ` Dave Chinner
2019-09-25 0:52 ` [PATCH 03/15] mm: Add file_offset_of_ helpers Matthew Wilcox
2019-09-26 14:02 ` Kirill A. Shutemov
2019-10-04 19:39 ` Matthew Wilcox
2019-09-25 0:52 ` [PATCH 04/15] iomap: Support large pages Matthew Wilcox
2019-09-25 0:52 ` [PATCH 05/15] xfs: " Matthew Wilcox
2019-09-25 0:52 ` [PATCH 06/15] xfs: Pass a page to xfs_finish_page_writeback Matthew Wilcox
2019-09-25 0:52 ` [PATCH 07/15] mm: Make prep_transhuge_page tail-callable Matthew Wilcox
2019-09-26 14:13 ` Kirill A. Shutemov
2019-09-25 0:52 ` [PATCH 08/15] mm: Add __page_cache_alloc_order Matthew Wilcox
2019-09-26 14:15 ` Kirill A. Shutemov
2019-09-25 0:52 ` [PATCH 09/15] mm: Allow large pages to be added to the page cache Matthew Wilcox
2019-09-26 14:22 ` Kirill A. Shutemov
2019-09-25 0:52 ` [PATCH 10/15] mm: Allow find_get_page to be used for large pages Matthew Wilcox
2019-10-01 10:32 ` Kirill A. Shutemov
2019-09-25 0:52 ` [PATCH 11/15] mm: Remove hpage_nr_pages Matthew Wilcox
2019-10-01 10:35 ` Kirill A. Shutemov
2019-09-25 0:52 ` [PATCH 12/15] mm: Support removing arbitrary sized pages from mapping Matthew Wilcox
2019-10-01 10:39 ` Kirill A. Shutemov
2019-09-25 0:52 ` [PATCH 13/15] mm: Add a huge page fault handler for files Matthew Wilcox
2019-10-01 10:42 ` Kirill A. Shutemov
2019-09-25 0:52 ` [PATCH 14/15] mm: Align THP mappings for non-DAX Matthew Wilcox
2019-10-01 10:45 ` Kirill A. Shutemov
2019-10-01 11:21 ` William Kucharski
2019-10-01 11:32 ` Kirill A. Shutemov [this message]
2019-10-01 12:18 ` William Kucharski
2019-10-01 14:20 ` Kirill A. Shutemov
2019-10-01 16:08 ` William Kucharski
2019-10-02 0:15 ` Kirill A. Shutemov
2019-09-25 0:52 ` [PATCH 15/15] xfs: Use filemap_huge_fault Matthew Wilcox
[not found] ` <20191002130753.7680-1-hdanton@sina.com>
2019-10-04 19:33 ` [PATCH 03/15] mm: Add file_offset_of_ helpers Matthew Wilcox
[not found] ` <20191002133211.15696-1-hdanton@sina.com>
2019-10-04 19:34 ` [PATCH 04/15] iomap: Support large pages Matthew Wilcox
[not found] ` <20191003040846.17604-1-hdanton@sina.com>
2019-10-04 19:35 ` [PATCH 06/15] xfs: Pass a page to xfs_finish_page_writeback Matthew Wilcox
[not found] ` <20191003050859.18140-1-hdanton@sina.com>
2019-10-04 19:36 ` [PATCH 11/15] mm: Remove hpage_nr_pages Matthew Wilcox
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