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Commit ca215086 authored by David Hildenbrand's avatar David Hildenbrand Committed by Linus Torvalds
Browse files

mm: convert PG_balloon to PG_offline 

PG_balloon was introduced to implement page migration/compaction for
pages inflated in virtio-balloon.  Nowadays, it is only a marker that a
page is part of virtio-balloon and therefore logically offline.

We also want to make use of this flag in other balloon drivers - for
inflated pages or when onlining a section but keeping some pages offline
(e.g.  used right now by XEN and Hyper-V via set_online_page_callback()).

We are going to expose this flag to dump tools like makedumpfile.  But
instead of exposing PG_balloon, let's generalize the concept of marking
pages as logically offline, so it can be reused for other purposes later
on.

Rename PG_balloon to PG_offline.  This is an indicator that the page is
logically offline, the content stale and that it should not be touched
(e.g.  a hypervisor would have to allocate backing storage in order for
the guest to dump an unused page).  We can then e.g.  exclude such pages
from dumps.

We replace and reuse KPF_BALLOON (23), as this shouldn't really harm
(and for now the semantics stay the same).  In following patches, we
will make use of this bit also in other balloon drivers.  While at it,
document PGTABLE.

[akpm@linux-foundation.org: fix comment text, per David]
Link: http://lkml.kernel.org/r/20181119101616.8901-3-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarKonstantin Khlebnikov <koct9i@gmail.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarPankaj gupta <pagupta@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Christian Hansen <chansen3@cisco.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Miles Chen <miles.chen@mediatek.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Julien Freche <jfreche@vmware.com>
Cc: Kairui Song <kasong@redhat.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Lianbo Jiang <lijiang@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Xavier Deguillard <xdeguillard@vmware.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4d3467e1

Documentation/admin-guide/mm/pagemap.rst

+6 −3
Original line number Diff line number Diff line
@@ -75,9 +75,10 @@ number of times a page is mapped. 
    20. NOPAGE

    21. KSM

    22. THP

    23. BALLOON

    23. OFFLINE

    24. ZERO_PAGE

    25. IDLE

    26. PGTABLE



 * ``/proc/kpagecgroup``.  This file contains a 64-bit inode number of the

   memory cgroup each page is charged to, indexed by PFN. Only available when
@@ -118,8 +119,8 @@ Short descriptions to the page flags 
    identical memory pages dynamically shared between one or more processes

22 - THP

    contiguous pages which construct transparent hugepages

23 - BALLOON

    balloon compaction page

23 - OFFLINE

    page is logically offline

24 - ZERO_PAGE

    zero page for pfn_zero or huge_zero page

25 - IDLE
@@ -128,6 +129,8 @@ Short descriptions to the page flags 
    Note that this flag may be stale in case the page was accessed via

    a PTE. To make sure the flag is up-to-date one has to read

    ``/sys/kernel/mm/page_idle/bitmap`` first.

26 - PGTABLE

    page is in use as a page table



IO related page flags

---------------------

fs/proc/page.c

+2 −2
Original line number Diff line number Diff line
@@ -152,8 +152,8 @@ u64 stable_page_flags(struct page *page) 
	else if (page_count(page) == 0 && is_free_buddy_page(page))

		u |= 1 << KPF_BUDDY;



	if (PageBalloon(page))

		u |= 1 << KPF_BALLOON;

	if (PageOffline(page))

		u |= 1 << KPF_OFFLINE;

	if (PageTable(page))

		u |= 1 << KPF_PGTABLE;

include/linux/balloon_compaction.h

+4 −4
Original line number Diff line number Diff line
@@ -95,7 +95,7 @@ extern int balloon_page_migrate(struct address_space *mapping, 
static inline void balloon_page_insert(struct balloon_dev_info *balloon,

				       struct page *page)

{

	__SetPageBalloon(page);

	__SetPageOffline(page);

	__SetPageMovable(page, balloon->inode->i_mapping);

	set_page_private(page, (unsigned long)balloon);

	list_add(&page->lru, &balloon->pages);
@@ -111,7 +111,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon, 
 */

static inline void balloon_page_delete(struct page *page)

{

	__ClearPageBalloon(page);

	__ClearPageOffline(page);

	__ClearPageMovable(page);

	set_page_private(page, 0);

	/*
@@ -141,13 +141,13 @@ static inline gfp_t balloon_mapping_gfp_mask(void) 
static inline void balloon_page_insert(struct balloon_dev_info *balloon,

				       struct page *page)

{

	__SetPageBalloon(page);

	__SetPageOffline(page);

	list_add(&page->lru, &balloon->pages);

}



static inline void balloon_page_delete(struct page *page)

{

	__ClearPageBalloon(page);

	__ClearPageOffline(page);

	list_del(&page->lru);

}

include/linux/page-flags.h

+7 −4
Original line number Diff line number Diff line
@@ -671,7 +671,7 @@ PAGEFLAG_FALSE(DoubleMap) 
/* Reserve		0x0000007f to catch underflows of page_mapcount */

#define PAGE_MAPCOUNT_RESERVE	-128

#define PG_buddy	0x00000080

#define PG_balloon	0x00000100

#define PG_offline	0x00000100

#define PG_kmemcg	0x00000200

#define PG_table	0x00000400
@@ -706,10 +706,13 @@ static __always_inline void __ClearPage##uname(struct page *page) \ 
PAGE_TYPE_OPS(Buddy, buddy)



/*

 * PageBalloon() is true for pages that are on the balloon page list

 * (see mm/balloon_compaction.c).

 * PageOffline() indicates that the page is logically offline although the

 * containing section is online. (e.g. inflated in a balloon driver or

 * not onlined when onlining the section).

 * The content of these pages is effectively stale. Such pages should not

 * be touched (read/write/dump/save) except by their owner.

 */

PAGE_TYPE_OPS(Balloon, balloon)

PAGE_TYPE_OPS(Offline, offline)



/*

 * If kmemcg is enabled, the buddy allocator will set PageKmemcg() on

include/uapi/linux/kernel-page-flags.h

+1 −1
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ 


#define KPF_KSM			21

#define KPF_THP			22

#define KPF_BALLOON		23

#define KPF_OFFLINE		23

#define KPF_ZERO_PAGE		24

#define KPF_IDLE		25

#define KPF_PGTABLE		26