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From: William Kucharski <william.kucharski@oracle.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
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 05:21:26 -0600	[thread overview]
Message-ID: <A935F599-BB18-40C3-90DD-47B7700743D6@oracle.com> (raw)
In-Reply-To: <20191001104558.rdcqhjdz7frfuhca@box>



> 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?

    -- Bill

  reply	other threads:[~2019-10-01 11:21 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 [this message]
2019-10-01 11:32       ` Kirill A. Shutemov
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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