mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-24 17:59:32 +00:00
![Michel Lespinasse](/assets/img/avatar_default.png)
When a large VMA (anon or private file mapping) is first touched, which will populate its anon_vma field, and then split into many regions through the use of mprotect(), the original anon_vma ends up linking all of the vmas on a linked list. This can cause rmap to become inefficient, as we have to walk potentially thousands of irrelevent vmas before finding the one a given anon page might fall into. By replacing the same_anon_vma linked list with an interval tree (where each avc's interval is determined by its vma's start and last pgoffs), we can make rmap efficient for this use case again. While the change is large, all of its pieces are fairly simple. Most places that were walking the same_anon_vma list were looking for a known pgoff, so they can just use the anon_vma_interval_tree_foreach() interval tree iterator instead. The exception here is ksm, where the page's index is not known. It would probably be possible to rework ksm so that the index would be known, but for now I have decided to keep things simple and just walk the entirety of the interval tree there. When updating vma's that already have an anon_vma assigned, we must take care to re-index the corresponding avc's on their interval tree. This is done through the use of anon_vma_interval_tree_pre_update_vma() and anon_vma_interval_tree_post_update_vma(), which remove the avc's from their interval tree before the update and re-insert them after the update. The anon_vma stays locked during the update, so there is no chance that rmap would miss the vmas that are being updated. Signed-off-by: Michel Lespinasse <walken@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Daniel Santos <daniel.santos@pobox.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
261 lines
7.6 KiB
C
261 lines
7.6 KiB
C
#ifndef _LINUX_RMAP_H
|
|
#define _LINUX_RMAP_H
|
|
/*
|
|
* Declarations for Reverse Mapping functions in mm/rmap.c
|
|
*/
|
|
|
|
#include <linux/list.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/memcontrol.h>
|
|
|
|
/*
|
|
* The anon_vma heads a list of private "related" vmas, to scan if
|
|
* an anonymous page pointing to this anon_vma needs to be unmapped:
|
|
* the vmas on the list will be related by forking, or by splitting.
|
|
*
|
|
* Since vmas come and go as they are split and merged (particularly
|
|
* in mprotect), the mapping field of an anonymous page cannot point
|
|
* directly to a vma: instead it points to an anon_vma, on whose list
|
|
* the related vmas can be easily linked or unlinked.
|
|
*
|
|
* After unlinking the last vma on the list, we must garbage collect
|
|
* the anon_vma object itself: we're guaranteed no page can be
|
|
* pointing to this anon_vma once its vma list is empty.
|
|
*/
|
|
struct anon_vma {
|
|
struct anon_vma *root; /* Root of this anon_vma tree */
|
|
struct mutex mutex; /* Serialize access to vma list */
|
|
/*
|
|
* The refcount is taken on an anon_vma when there is no
|
|
* guarantee that the vma of page tables will exist for
|
|
* the duration of the operation. A caller that takes
|
|
* the reference is responsible for clearing up the
|
|
* anon_vma if they are the last user on release
|
|
*/
|
|
atomic_t refcount;
|
|
|
|
/*
|
|
* NOTE: the LSB of the rb_root.rb_node is set by
|
|
* mm_take_all_locks() _after_ taking the above lock. So the
|
|
* rb_root must only be read/written after taking the above lock
|
|
* to be sure to see a valid next pointer. The LSB bit itself
|
|
* is serialized by a system wide lock only visible to
|
|
* mm_take_all_locks() (mm_all_locks_mutex).
|
|
*/
|
|
struct rb_root rb_root; /* Interval tree of private "related" vmas */
|
|
};
|
|
|
|
/*
|
|
* The copy-on-write semantics of fork mean that an anon_vma
|
|
* can become associated with multiple processes. Furthermore,
|
|
* each child process will have its own anon_vma, where new
|
|
* pages for that process are instantiated.
|
|
*
|
|
* This structure allows us to find the anon_vmas associated
|
|
* with a VMA, or the VMAs associated with an anon_vma.
|
|
* The "same_vma" list contains the anon_vma_chains linking
|
|
* all the anon_vmas associated with this VMA.
|
|
* The "rb" field indexes on an interval tree the anon_vma_chains
|
|
* which link all the VMAs associated with this anon_vma.
|
|
*/
|
|
struct anon_vma_chain {
|
|
struct vm_area_struct *vma;
|
|
struct anon_vma *anon_vma;
|
|
struct list_head same_vma; /* locked by mmap_sem & page_table_lock */
|
|
struct rb_node rb; /* locked by anon_vma->mutex */
|
|
unsigned long rb_subtree_last;
|
|
};
|
|
|
|
#ifdef CONFIG_MMU
|
|
static inline void get_anon_vma(struct anon_vma *anon_vma)
|
|
{
|
|
atomic_inc(&anon_vma->refcount);
|
|
}
|
|
|
|
void __put_anon_vma(struct anon_vma *anon_vma);
|
|
|
|
static inline void put_anon_vma(struct anon_vma *anon_vma)
|
|
{
|
|
if (atomic_dec_and_test(&anon_vma->refcount))
|
|
__put_anon_vma(anon_vma);
|
|
}
|
|
|
|
static inline struct anon_vma *page_anon_vma(struct page *page)
|
|
{
|
|
if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
|
|
PAGE_MAPPING_ANON)
|
|
return NULL;
|
|
return page_rmapping(page);
|
|
}
|
|
|
|
static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
|
|
{
|
|
struct anon_vma *anon_vma = vma->anon_vma;
|
|
if (anon_vma)
|
|
mutex_lock(&anon_vma->root->mutex);
|
|
}
|
|
|
|
static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
|
|
{
|
|
struct anon_vma *anon_vma = vma->anon_vma;
|
|
if (anon_vma)
|
|
mutex_unlock(&anon_vma->root->mutex);
|
|
}
|
|
|
|
static inline void anon_vma_lock(struct anon_vma *anon_vma)
|
|
{
|
|
mutex_lock(&anon_vma->root->mutex);
|
|
}
|
|
|
|
static inline void anon_vma_unlock(struct anon_vma *anon_vma)
|
|
{
|
|
mutex_unlock(&anon_vma->root->mutex);
|
|
}
|
|
|
|
/*
|
|
* anon_vma helper functions.
|
|
*/
|
|
void anon_vma_init(void); /* create anon_vma_cachep */
|
|
int anon_vma_prepare(struct vm_area_struct *);
|
|
void unlink_anon_vmas(struct vm_area_struct *);
|
|
int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
|
|
int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
|
|
|
|
static inline void anon_vma_merge(struct vm_area_struct *vma,
|
|
struct vm_area_struct *next)
|
|
{
|
|
VM_BUG_ON(vma->anon_vma != next->anon_vma);
|
|
unlink_anon_vmas(next);
|
|
}
|
|
|
|
struct anon_vma *page_get_anon_vma(struct page *page);
|
|
|
|
/*
|
|
* rmap interfaces called when adding or removing pte of page
|
|
*/
|
|
void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
|
|
void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
|
|
void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
|
|
unsigned long, int);
|
|
void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
|
|
void page_add_file_rmap(struct page *);
|
|
void page_remove_rmap(struct page *);
|
|
|
|
void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
|
|
unsigned long);
|
|
void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
|
|
unsigned long);
|
|
|
|
static inline void page_dup_rmap(struct page *page)
|
|
{
|
|
atomic_inc(&page->_mapcount);
|
|
}
|
|
|
|
/*
|
|
* Called from mm/vmscan.c to handle paging out
|
|
*/
|
|
int page_referenced(struct page *, int is_locked,
|
|
struct mem_cgroup *memcg, unsigned long *vm_flags);
|
|
int page_referenced_one(struct page *, struct vm_area_struct *,
|
|
unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
|
|
|
|
enum ttu_flags {
|
|
TTU_UNMAP = 0, /* unmap mode */
|
|
TTU_MIGRATION = 1, /* migration mode */
|
|
TTU_MUNLOCK = 2, /* munlock mode */
|
|
TTU_ACTION_MASK = 0xff,
|
|
|
|
TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */
|
|
TTU_IGNORE_ACCESS = (1 << 9), /* don't age */
|
|
TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
|
|
};
|
|
#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
|
|
|
|
int try_to_unmap(struct page *, enum ttu_flags flags);
|
|
int try_to_unmap_one(struct page *, struct vm_area_struct *,
|
|
unsigned long address, enum ttu_flags flags);
|
|
|
|
/*
|
|
* Called from mm/filemap_xip.c to unmap empty zero page
|
|
*/
|
|
pte_t *__page_check_address(struct page *, struct mm_struct *,
|
|
unsigned long, spinlock_t **, int);
|
|
|
|
static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
|
|
unsigned long address,
|
|
spinlock_t **ptlp, int sync)
|
|
{
|
|
pte_t *ptep;
|
|
|
|
__cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
|
|
ptlp, sync));
|
|
return ptep;
|
|
}
|
|
|
|
/*
|
|
* Used by swapoff to help locate where page is expected in vma.
|
|
*/
|
|
unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
|
|
|
|
/*
|
|
* Cleans the PTEs of shared mappings.
|
|
* (and since clean PTEs should also be readonly, write protects them too)
|
|
*
|
|
* returns the number of cleaned PTEs.
|
|
*/
|
|
int page_mkclean(struct page *);
|
|
|
|
/*
|
|
* called in munlock()/munmap() path to check for other vmas holding
|
|
* the page mlocked.
|
|
*/
|
|
int try_to_munlock(struct page *);
|
|
|
|
/*
|
|
* Called by memory-failure.c to kill processes.
|
|
*/
|
|
struct anon_vma *page_lock_anon_vma(struct page *page);
|
|
void page_unlock_anon_vma(struct anon_vma *anon_vma);
|
|
int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
|
|
|
|
/*
|
|
* Called by migrate.c to remove migration ptes, but might be used more later.
|
|
*/
|
|
int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
|
|
struct vm_area_struct *, unsigned long, void *), void *arg);
|
|
|
|
#else /* !CONFIG_MMU */
|
|
|
|
#define anon_vma_init() do {} while (0)
|
|
#define anon_vma_prepare(vma) (0)
|
|
#define anon_vma_link(vma) do {} while (0)
|
|
|
|
static inline int page_referenced(struct page *page, int is_locked,
|
|
struct mem_cgroup *memcg,
|
|
unsigned long *vm_flags)
|
|
{
|
|
*vm_flags = 0;
|
|
return 0;
|
|
}
|
|
|
|
#define try_to_unmap(page, refs) SWAP_FAIL
|
|
|
|
static inline int page_mkclean(struct page *page)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
|
|
#endif /* CONFIG_MMU */
|
|
|
|
/*
|
|
* Return values of try_to_unmap
|
|
*/
|
|
#define SWAP_SUCCESS 0
|
|
#define SWAP_AGAIN 1
|
|
#define SWAP_FAIL 2
|
|
#define SWAP_MLOCK 3
|
|
|
|
#endif /* _LINUX_RMAP_H */
|