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author | Hugh Dickins <hugh.dickins@tiscali.co.uk> | 2009-12-14 17:59:25 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-15 08:53:19 -0800 |
commit | db114b83ab6064d9b1d6ec5650e096c89bd95e25 (patch) | |
tree | 15e289b25fec011238f6838c6aafa1ff5e293224 /include/linux/rmap.h | |
parent | 5ad6468801d28c4d4ac9f48ec19297817c915f6a (diff) | |
download | linux-stable-db114b83ab6064d9b1d6ec5650e096c89bd95e25.tar.gz linux-stable-db114b83ab6064d9b1d6ec5650e096c89bd95e25.tar.bz2 linux-stable-db114b83ab6064d9b1d6ec5650e096c89bd95e25.zip |
ksm: hold anon_vma in rmap_item
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 <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wright <chrisw@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/rmap.h')
-rw-r--r-- | include/linux/rmap.h | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 0b4913a4a344..980094a527ee 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -26,6 +26,9 @@ */ struct anon_vma { spinlock_t lock; /* Serialize access to vma list */ +#ifdef CONFIG_KSM + atomic_t ksm_refcount; +#endif /* * NOTE: the LSB of the head.next is set by * mm_take_all_locks() _after_ taking the above lock. So the @@ -38,6 +41,26 @@ struct anon_vma { }; #ifdef CONFIG_MMU +#ifdef CONFIG_KSM +static inline void ksm_refcount_init(struct anon_vma *anon_vma) +{ + atomic_set(&anon_vma->ksm_refcount, 0); +} + +static inline int ksm_refcount(struct anon_vma *anon_vma) +{ + return atomic_read(&anon_vma->ksm_refcount); +} +#else +static inline void ksm_refcount_init(struct anon_vma *anon_vma) +{ +} + +static inline int ksm_refcount(struct anon_vma *anon_vma) +{ + return 0; +} +#endif /* CONFIG_KSM */ static inline struct anon_vma *page_anon_vma(struct page *page) { @@ -70,6 +93,7 @@ void __anon_vma_merge(struct vm_area_struct *, struct vm_area_struct *); void anon_vma_unlink(struct vm_area_struct *); void anon_vma_link(struct vm_area_struct *); void __anon_vma_link(struct vm_area_struct *); +void anon_vma_free(struct anon_vma *); /* * rmap interfaces called when adding or removing pte of page |