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From: Matthew Wilcox <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Andrey Ryabinin" <aryabinin@virtuozzo.com>,
	linux-mm@kvack.org, "Matthew Wilcox" <mawilcox@microsoft.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	"Christoph Lameter" <cl@linux.com>,
	"Lai Jiangshan" <jiangshanlai@gmail.com>,
	"Pekka Enberg" <penberg@kernel.org>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Jérôme Glisse" <jglisse@redhat.com>
Subject: Re: [PATCH v6 17/17] mm: Distinguish VMalloc pages
Date: Tue, 22 May 2018 14:45:17 -0700
Message-ID: <20180522214517.GA30913@bombadil.infradead.org> (raw)
In-Reply-To: <20180522134838.fe59b6e4a405fa9af9fc0487@linux-foundation.org>

On Tue, May 22, 2018 at 01:48:38PM -0700, Andrew Morton wrote:
> -ENOCOMMENT ;)
> 
> --- a/mm/util.c~mm-distinguish-vmalloc-pages-fix-fix
> +++ a/mm/util.c
> @@ -512,6 +512,8 @@ struct address_space *page_mapping(struc
>  	mapping = page->mapping;
>  	if ((unsigned long)mapping & PAGE_MAPPING_ANON)
>  		return NULL;
> +
> +	/* Don't trip over a vmalloc page's MAPPING_VMalloc cookie */
>  	if ((unsigned long)mapping < PAGE_SIZE)
>  		return NULL;
>  
> It's a bit sad to put even more stuff into page_mapping() just for
> page_types diddling.  Is this really justified?  How many people will
> use it, and get significant benefit from it?

We could leave page->mapping NULL for vmalloc pages.  We just need to
find a spot where we can put a unique identifier.  The first word of
the union looks like a string candidate; bit 0 is already reserved for
PageTail.  The other users are list_head.prev, a struct page *, and
struct dev_pagemap *, so that should work out OK.

If you want to just drop this patch, I'd be OK with that.  I can always
submit it to you again next merge window.

  reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-18 19:45 [PATCH v6 00/17] Rearrange struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 01/17] s390: Use _refcount for pgtables Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 02/17] mm: Split page_type out from _mapcount Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 03/17] mm: Mark pages in use for page tables Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 04/17] mm: Switch s_mem and slab_cache in struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 05/17] mm: Move 'private' union within " Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 06/17] mm: Move _refcount out of struct page union Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 07/17] mm: Combine first three unions in struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 08/17] mm: Use page->deferred_list Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 09/17] mm: Move lru union within struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 10/17] mm: Combine LRU and main union in " Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 11/17] mm: Improve struct page documentation Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 12/17] mm: Add pt_mm to struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 13/17] mm: Add hmm_data " Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 14/17] slab,slub: Remove rcu_head size checks Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 15/17] slub: Remove kmem_cache->reserved Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 16/17] slub: Remove 'reserved' file from sysfs Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 17/17] mm: Distinguish VMalloc pages Matthew Wilcox
2018-05-22 16:10   ` Andrey Ryabinin
2018-05-22 17:58     ` Matthew Wilcox
2018-05-22 19:49       ` Andrew Morton
2018-05-22 19:57       ` Andrey Ryabinin
2018-05-22 20:19         ` Matthew Wilcox
2018-05-22 20:48           ` Andrew Morton
2018-05-22 21:45             ` Matthew Wilcox [this message]
2018-05-22 23:02               ` Andrew Morton
2018-05-23  6:36           ` Michal Hocko
2018-05-23  6:34         ` Michal Hocko
2018-05-23  9:14           ` Andrey Ryabinin
2018-05-23  9:25             ` Michal Hocko
2018-05-23  9:28               ` Andrey Ryabinin
2018-05-23  9:52                 ` Michal Hocko

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