kernel.git/fs/proc/page.c, branch linux-3.12.y

mm: close PageTail race

2014-04-03T08:32:30Z

commit 668f9abbd4334e6c29fa8acd71635c4f9101caa7 upstream. Commit bf6bddf1924e ("mm: introduce compaction and migration for ballooned pages") introduces page_count(page) into memory compaction which dereferences page->first_page if PageTail(page). This results in a very rare NULL pointer dereference on the aforementioned page_count(page). Indeed, anything that does compound_head(), including page_count() is susceptible to racing with prep_compound_page() and seeing a NULL or dangling page->first_page pointer. This patch uses Andrea's implementation of compound_trans_head() that deals with such a race and makes it the default compound_head() implementation. This includes a read memory barrier that ensures that if PageTail(head) is true that we return a head page that is neither NULL nor dangling. The patch then adds a store memory barrier to prep_compound_page() to ensure page->first_page is set. This is the safest way to ensure we see the head page that we are expecting, PageTail(page) is already in the unlikely() path and the memory barriers are unfortunately required. Hugetlbfs is the exception, we don't enforce a store memory barrier during init since no race is possible. Signed-off-by: David Rientjes Cc: Holger Kiehl Cc: Christoph Lameter Cc: Rafael Aquini Cc: Vlastimil Babka Cc: Michal Hocko Cc: Mel Gorman Cc: Andrea Arcangeli Cc: Rik van Riel Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby

kpageflags: fix wrong KPF_THP on non-huge compound pages

2012-10-09T07:23:00Z

KPF_THP can be set on non-huge compound pages (like slab pages or pages allocated by drivers with __GFP_COMP) because PageTransCompound only checks PG_head and PG_tail. Obviously this is a bug and breaks user space applications which look for thp via /proc/kpageflags. This patch rules out setting KPF_THP wrongly by additionally checking PageLRU on the head pages. Signed-off-by: Naoya Horiguchi Acked-by: KOSAKI Motohiro Acked-by: David Rientjes Reviewed-by: Fengguang Wu Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

pagemap: export KPF_THP

2012-03-22T00:54:57Z

This flag shows that a given page is a subpage of a transparent hugepage. It helps us debug and test the kernel by showing physical address of thp. Signed-off-by: Naoya Horiguchi Reviewed-by: Wu Fengguang Reviewed-by: KAMEZAWA Hiroyuki Acked-by: KOSAKI Motohiro Cc: David Rientjes Cc: Andi Kleen Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

thp: remove PG_buddy

2011-01-14T01:32:43Z

PG_buddy can be converted to _mapcount == -2. So the PG_compound_lock can be added to page->flags without overflowing (because of the sparse section bits increasing) with CONFIG_X86_PAE=y and CONFIG_X86_PAT=y. This also has to move the memory hotplug code from _mapcount to lru.next to avoid any risk of clashes. We can't use lru.next for PG_buddy removal, but memory hotplug can use lru.next even more easily than the mapcount instead. Signed-off-by: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kpagecount: add slab page checking because _mapcount is in a union

2011-01-13T16:03:17Z

Add a PageSlab() check before adding the _mapcount value to /kpagecount. page->_mapcount is in a union with the SLAB structure so for pages controlled by SLAB, page_mapcount() returns nonsense. Signed-off-by: Petr Holasek Cc: Wu Fengguang Cc: Matt Mackall Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc: export uncached bit properly in /proc/kpageflags

2010-09-10T01:57:23Z

Fix the left-over old ifdef for PG_uncached in /proc/kpageflags. Now it's used by x86, too. Signed-off-by: Takashi Iwai Cc: Wu Fengguang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: export stable page flags

2009-12-16T11:19:59Z

Rename get_uflags() to stable_page_flags() and make it a global function for use in the hwpoison page flags filter, which need to compare user page flags with the value provided by user space. Also move KPF_* to kernel-page-flags.h for use by user space tools. Acked-by: Matt Mackall Signed-off-by: Andi Kleen CC: Nick Piggin CC: Christoph Lameter Signed-off-by: Wu Fengguang Signed-off-by: Andi Kleen

pagemap: export KPF_HWPOISON

2009-10-08T14:36:39Z

This flag indicates a hardware detected memory corruption on the page. Any future access of the page data may bring down the machine. Signed-off-by: Wu Fengguang Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ksm: identify PageKsm pages

2009-09-22T14:17:31Z

KSM will need to identify its kernel merged pages unambiguously, and /proc/kpageflags will probably like to do so too. Since KSM will only be substituting anonymous pages, statistics are best preserved by making a PageKsm page a special PageAnon page: one with no anon_vma. But KSM then needs its own page_add_ksm_rmap() - keep it in ksm.h near PageKsm; and do_wp_page() must COW them, unlike singly mapped PageAnons. Signed-off-by: Hugh Dickins Signed-off-by: Chris Wright Signed-off-by: Izik Eidus Cc: Wu Fengguang Cc: Andrea Arcangeli Cc: Rik van Riel Cc: Wu Fengguang Cc: Balbir Singh Cc: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Lee Schermerhorn Cc: Avi Kivity Cc: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: remove CONFIG_UNEVICTABLE_LRU config option

2009-06-17T02:47:42Z

Currently, nobody wants to turn UNEVICTABLE_LRU off. Thus this configurability is unnecessary. Signed-off-by: KOSAKI Motohiro Cc: Johannes Weiner Cc: Andi Kleen Acked-by: Minchan Kim Cc: David Woodhouse Cc: Matt Mackall Cc: Rik van Riel Cc: Lee Schermerhorn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds