kernel/git/stable/linux.git/mm/rmap.c, branch linux-2.6.33.y

memcg: make memcg's file mapped consistent with global VM

2009-12-16T15:20:07+00:00

In global VM, FILE_MAPPED is used but memcg uses MAPPED_FILE. This makes grep difficult. Replace memcg's MAPPED_FILE with FILE_MAPPED And in global VM, mapped shared memory is accounted into FILE_MAPPED. But memcg doesn't. fix it. Note: page_is_file_cache() just checks SwapBacked or not. So, we need to check PageAnon. Cc: Balbir Singh Reviewed-by: Daisuke Nishimura Signed-off-by: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: simplify try_to_unmap_one()

2009-12-15T16:53:20+00:00

SWAP_MLOCK mean "We marked the page as PG_MLOCK, please move it to unevictable-lru". So, following code is easy confusable. if (vma->vm_flags & VM_LOCKED) { ret = SWAP_MLOCK; goto out_unmap; } Plus, if the VMA doesn't have VM_LOCKED, We don't need to check the needed of calling mlock_vma_page(). Also, add some commentary to try_to_unmap_one(). Acked-by: Hugh Dickins Signed-off-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ksm: rmap_walk to remove_migation_ptes

2009-12-15T16:53:20+00:00

A side-effect of making ksm pages swappable is that they have to be placed on the LRUs: which then exposes them to isolate_lru_page() and hence to page migration. Add rmap_walk() for remove_migration_ptes() to use: rmap_walk_anon() and rmap_walk_file() in rmap.c, but rmap_walk_ksm() in ksm.c. Perhaps some consolidation with existing code is possible, but don't attempt that yet (try_to_unmap needs to handle nonlinears, but migration pte removal does not). rmap_walk() is sadly less general than it appears: rmap_walk_anon(), like remove_anon_migration_ptes() which it replaces, avoids calling page_lock_anon_vma(), because that includes a page_mapped() test which fails when all migration ptes are in place. That was valid when NUMA page migration was introduced (holding mmap_sem provided the missing guarantee that anon_vma's slab had not already been destroyed), but I believe not valid in the memory hotremove case added since. For now do the same as before, and consider the best way to fix that unlikely race later on. When fixed, we can probably use rmap_walk() on hwpoisoned ksm pages too: for now, they remain among hwpoison's various exceptions (its PageKsm test comes before the page is locked, but its page_lock_anon_vma fails safely if an anon gets upgraded). Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Chris Wright Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ksm: share anon page without allocating

2009-12-15T16:53:19+00:00

When ksm pages were unswappable, it made no sense to include them in mem cgroup accounting; but now that they are swappable (although I see no strict logical connection) the principle of least surprise implies that they should be accounted (with the usual dissatisfaction, that a shared page is accounted to only one of the cgroups using it). This patch was intended to add mem cgroup accounting where necessary; but turned inside out, it now avoids allocating a ksm page, instead upgrading an anon page to ksm - which brings its existing mem cgroup accounting with it. Thus mem cgroups don't appear in the patch at all. This upgrade from PageAnon to PageKsm takes place under page lock (via a somewhat hacky NULL kpage interface), and audit showed only one place which needed to cope with the race - page_referenced() is sometimes used without page lock, so page_lock_anon_vma() needs an ACCESS_ONCE() to be sure of getting anon_vma and flags together (no problem if the page goes ksm an instant after, the integrity of that anon_vma list is unaffected). Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Chris Wright Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ksm: hold anon_vma in rmap_item

2009-12-15T16:53:19+00:00

For full functionality, page_referenced_one() and try_to_unmap_one() need to know the vma: to pass vma down to arch-dependent flushes, or to observe VM_LOCKED or VM_EXEC. But KSM keeps no record of vma: nor can it, since vmas get split and merged without its knowledge. Instead, note page's anon_vma in its rmap_item when adding to stable tree: all the vmas which might map that page are listed by its anon_vma. page_referenced_ksm() and try_to_unmap_ksm() then traverse the anon_vma, first to find the probable vma, that which matches rmap_item's mm; but if that is not enough to locate all instances, traverse again to try the others. This catches those occasions when fork has duplicated a pte of a ksm page, but ksmd has not yet come around to assign it an rmap_item. But each rmap_item in the stable tree which refers to an anon_vma needs to take a reference to it. Andrea's anon_vma design cleverly avoided a reference count (an anon_vma was free when its list of vmas was empty), but KSM now needs to add that. Is a 32-bit count sufficient? I believe so - the anon_vma is only free when both count is 0 and list is empty. Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Chris Wright Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ksm: let shared pages be swappable

2009-12-15T16:53:19+00:00

Initial implementation for swapping out KSM's shared pages: add page_referenced_ksm() and try_to_unmap_ksm(), which rmap.c calls when faced with a PageKsm page. Most of what's needed can be got from the rmap_items listed from the stable_node of the ksm page, without discovering the actual vma: so in this patch just fake up a struct vma for page_referenced_one() or try_to_unmap_one(), then refine that in the next patch. Add VM_NONLINEAR to ksm_madvise()'s list of exclusions: it has always been implicit there (being only set with VM_SHARED, already excluded), but let's make it explicit, to help justify the lack of nonlinear unmap. Rely on the page lock to protect against concurrent modifications to that page's node of the stable tree. The awkward part is not swapout but swapin: do_swap_page() and page_add_anon_rmap() now have to allow for new possibilities - perhaps a ksm page still in swapcache, perhaps a swapcache page associated with one location in one anon_vma now needed for another location or anon_vma. (And the vma might even be no longer VM_MERGEABLE when that happens.) ksm_might_need_to_copy() checks for that case, and supplies a duplicate page when necessary, simply leaving it to a subsequent pass of ksmd to rediscover the identity and merge them back into one ksm page. Disappointingly primitive: but the alternative would have to accumulate unswappable info about the swapped out ksm pages, limiting swappability. Remove page_add_ksm_rmap(): page_add_anon_rmap() now has to allow for the particular case it was handling, so just use it instead. Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Chris Wright Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: pass address down to rmap ones

2009-12-15T16:53:17+00:00

KSM swapping will know where page_referenced_one() and try_to_unmap_one() should look. It could hack page->index to get them to do what it wants, but it seems cleaner now to pass the address down to them. Make the same change to page_mkclean_one(), since it follows the same pattern; but there's no real need in its case. Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Nick Piggin Cc: KOSAKI Motohiro Cc: Rik van Riel Cc: Lee Schermerhorn Cc: Andi Kleen Cc: KAMEZAWA Hiroyuki Cc: Wu Fengguang Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: CONFIG_MMU for PG_mlocked

2009-12-15T16:53:17+00:00

Remove three degrees of obfuscation, left over from when we had CONFIG_UNEVICTABLE_LRU. MLOCK_PAGES is CONFIG_HAVE_MLOCKED_PAGE_BIT is CONFIG_HAVE_MLOCK is CONFIG_MMU. rmap.o (and memory-failure.o) are only built when CONFIG_MMU, so don't need such conditions at all. Somehow, I feel no compulsion to remove the CONFIG_HAVE_MLOCK* lines from 169 defconfigs: leave those to evolve in due course. Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Nick Piggin Reviewed-by: KOSAKI Motohiro Cc: Rik van Riel Cc: Lee Schermerhorn Cc: Andi Kleen Cc: KAMEZAWA Hiroyuki Cc: Wu Fengguang Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: mlocking in try_to_unmap_one

2009-12-15T16:53:17+00:00

There's contorted mlock/munlock handling in try_to_unmap_anon() and try_to_unmap_file(), which we'd prefer not to repeat for KSM swapping. Simplify it by moving it all down into try_to_unmap_one(). One thing is then lost, try_to_munlock()'s distinction between when no vma holds the page mlocked, and when a vma does mlock it, but we could not get mmap_sem to set the page flag. But its only caller takes no interest in that distinction (and is better testing SWAP_MLOCK anyway), so let's keep the code simple and return SWAP_AGAIN for both cases. try_to_unmap_file()'s TTU_MUNLOCK nonlinear handling was particularly amusing: once unravelled, it turns out to have been choosing between two different ways of doing the same nothing. Ah, no, one way was actually returning SWAP_FAIL when it meant to return SWAP_SUCCESS. [kosaki.motohiro@jp.fujitsu.com: comment adding to mlocking in try_to_unmap_one] [akpm@linux-foundation.org: remove test of MLOCK_PAGES] Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Nick Piggin Cc: Rik van Riel Cc: Lee Schermerhorn Cc: Andi Kleen Cc: KAMEZAWA Hiroyuki Cc: Wu Fengguang Cc: Minchan Kim Signed-off-by: KOSAKI Motohiro Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: define PAGE_MAPPING_FLAGS

2009-12-15T16:53:17+00:00

At present we define PageAnon(page) by the low PAGE_MAPPING_ANON bit set in page->mapping, with the higher bits a pointer to the anon_vma; and have defined PageKsm(page) as that with NULL anon_vma. But KSM swapping will need to store a pointer there: so in preparation for that, now define PAGE_MAPPING_FLAGS as the low two bits, including PAGE_MAPPING_KSM (always set along with PAGE_MAPPING_ANON, until some other use for the bit emerges). Declare page_rmapping(page) to return the pointer part of page->mapping, and page_anon_vma(page) to return the anon_vma pointer when that's what it is. Use these in a few appropriate places: notably, unuse_vma() has been testing page->mapping, but is better to be testing page_anon_vma() (cases may be added in which flag bits are set without any pointer). Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Nick Piggin Cc: KOSAKI Motohiro Reviewed-by: Rik van Riel Cc: Lee Schermerhorn Cc: Andi Kleen Cc: KAMEZAWA Hiroyuki Cc: Wu Fengguang Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds