*/
/*
- * Locking: see "Lock ordering" summary in filemap.c.
- * In swapout, page_map_lock is held on entry to page_referenced and
- * try_to_unmap, so they trylock for i_mmap_lock and page_table_lock.
+ * Lock ordering in mm:
+ *
+ * inode->i_sem (while writing or truncating, not reading or faulting)
+ * inode->i_alloc_sem
+ *
+ * When a page fault occurs in writing from user to file, down_read
+ * of mmap_sem nests within i_sem; in sys_msync, i_sem nests within
+ * down_read of mmap_sem; i_sem and down_write of mmap_sem are never
+ * taken together; in truncation, i_sem is taken outermost.
+ *
+ * mm->mmap_sem
+ * page->flags PG_locked (lock_page)
+ * mapping->i_mmap_lock
+ * anon_vma->lock
+ * mm->page_table_lock
+ * zone->lru_lock (in mark_page_accessed)
+ * swap_list_lock (in swap_free etc's swap_info_get)
+ * swap_device_lock (in swap_duplicate, swap_info_get)
+ * mapping->private_lock (in __set_page_dirty_buffers)
+ * inode_lock (in set_page_dirty's __mark_inode_dirty)
+ * sb_lock (within inode_lock in fs/fs-writeback.c)
+ * mapping->tree_lock (widely used, in set_page_dirty,
+ * in arch-dependent flush_dcache_mmap_lock,
+ * within inode_lock in __sync_single_inode)
*/
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/rmap.h>
+#include <linux/rcupdate.h>
#include <linux/vs_memory.h>
#include <asm/tlbflush.h>
might_sleep();
if (unlikely(!anon_vma)) {
struct mm_struct *mm = vma->vm_mm;
- struct anon_vma *allocated = NULL;
+ struct anon_vma *allocated, *locked;
anon_vma = find_mergeable_anon_vma(vma);
- if (!anon_vma) {
+ if (anon_vma) {
+ allocated = NULL;
+ locked = anon_vma;
+ spin_lock(&locked->lock);
+ } else {
anon_vma = anon_vma_alloc();
if (unlikely(!anon_vma))
return -ENOMEM;
allocated = anon_vma;
+ locked = NULL;
}
/* page_table_lock to protect against threads */
spin_lock(&mm->page_table_lock);
if (likely(!vma->anon_vma)) {
- if (!allocated)
- spin_lock(&anon_vma->lock);
vma->anon_vma = anon_vma;
list_add(&vma->anon_vma_node, &anon_vma->head);
- if (!allocated)
- spin_unlock(&anon_vma->lock);
allocated = NULL;
}
spin_unlock(&mm->page_table_lock);
+
+ if (locked)
+ spin_unlock(&locked->lock);
if (unlikely(allocated))
anon_vma_free(allocated);
}
void __init anon_vma_init(void)
{
- anon_vma_cachep = kmem_cache_create("anon_vma",
- sizeof(struct anon_vma), 0, SLAB_PANIC, anon_vma_ctor, NULL);
+ anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
+ 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL);
}
-/* this needs the page->flags PG_maplock held */
-static inline void clear_page_anon(struct page *page)
+/*
+ * Getting a lock on a stable anon_vma from a page off the LRU is
+ * tricky: page_lock_anon_vma rely on RCU to guard against the races.
+ */
+static struct anon_vma *page_lock_anon_vma(struct page *page)
{
- BUG_ON(!page->mapping);
- page->mapping = NULL;
- ClearPageAnon(page);
+ struct anon_vma *anon_vma = NULL;
+ unsigned long anon_mapping;
+
+ rcu_read_lock();
+ anon_mapping = (unsigned long) page->mapping;
+ if (!(anon_mapping & PAGE_MAPPING_ANON))
+ goto out;
+ if (!page_mapped(page))
+ goto out;
+
+ anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
+ spin_lock(&anon_vma->lock);
+out:
+ rcu_read_unlock();
+ return anon_vma;
}
/*
return address;
}
+/*
+ * At what user virtual address is page expected in vma? checking that the
+ * page matches the vma: currently only used by unuse_process, on anon pages.
+ */
+unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
+{
+ if (PageAnon(page)) {
+ if ((void *)vma->anon_vma !=
+ (void *)page->mapping - PAGE_MAPPING_ANON)
+ return -EFAULT;
+ } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
+ if (vma->vm_file->f_mapping != page->mapping)
+ return -EFAULT;
+ } else
+ return -EFAULT;
+ return vma_address(page, vma);
+}
+
/*
* Subfunctions of page_referenced: page_referenced_one called
* repeatedly from either page_referenced_anon or page_referenced_file.
if (address == -EFAULT)
goto out;
- if (!spin_trylock(&mm->page_table_lock))
- goto out;
+ spin_lock(&mm->page_table_lock);
pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
if (ptep_clear_flush_young(vma, address, pte))
referenced++;
+ if (mm != current->mm && has_swap_token(mm))
+ referenced++;
+
(*mapcount)--;
out_unmap:
return referenced;
}
-static inline int page_referenced_anon(struct page *page)
+static int page_referenced_anon(struct page *page)
{
- unsigned int mapcount = page->mapcount;
- struct anon_vma *anon_vma = (struct anon_vma *) page->mapping;
+ unsigned int mapcount;
+ struct anon_vma *anon_vma;
struct vm_area_struct *vma;
int referenced = 0;
- spin_lock(&anon_vma->lock);
- BUG_ON(list_empty(&anon_vma->head));
+ anon_vma = page_lock_anon_vma(page);
+ if (!anon_vma)
+ return referenced;
+
+ mapcount = page_mapcount(page);
list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
referenced += page_referenced_one(page, vma, &mapcount);
if (!mapcount)
* of references it found.
*
* This function is only called from page_referenced for object-based pages.
- *
- * The spinlock address_space->i_mmap_lock is tried. If it can't be gotten,
- * assume a reference count of 0, so try_to_unmap will then have a go.
*/
-static inline int page_referenced_file(struct page *page)
+static int page_referenced_file(struct page *page)
{
- unsigned int mapcount = page->mapcount;
+ unsigned int mapcount;
struct address_space *mapping = page->mapping;
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
- struct vm_area_struct *vma = NULL;
+ struct vm_area_struct *vma;
struct prio_tree_iter iter;
int referenced = 0;
- if (!spin_trylock(&mapping->i_mmap_lock))
- return 0;
+ /*
+ * The caller's checks on page->mapping and !PageAnon have made
+ * sure that this is a file page: the check for page->mapping
+ * excludes the case just before it gets set on an anon page.
+ */
+ BUG_ON(PageAnon(page));
+
+ /*
+ * The page lock not only makes sure that page->mapping cannot
+ * suddenly be NULLified by truncation, it makes sure that the
+ * structure at mapping cannot be freed and reused yet,
+ * so we can safely take mapping->i_mmap_lock.
+ */
+ BUG_ON(!PageLocked(page));
- while ((vma = vma_prio_tree_next(vma, &mapping->i_mmap,
- &iter, pgoff, pgoff)) != NULL) {
+ spin_lock(&mapping->i_mmap_lock);
+
+ /*
+ * i_mmap_lock does not stabilize mapcount at all, but mapcount
+ * is more likely to be accurate if we note it after spinning.
+ */
+ mapcount = page_mapcount(page);
+
+ vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
== (VM_LOCKED|VM_MAYSHARE)) {
referenced++;
/**
* page_referenced - test if the page was referenced
* @page: the page to test
+ * @is_locked: caller holds lock on the page
*
* Quick test_and_clear_referenced for all mappings to a page,
* returns the number of ptes which referenced the page.
- * Caller needs to hold the rmap lock.
*/
-int page_referenced(struct page *page)
+int page_referenced(struct page *page, int is_locked)
{
int referenced = 0;
if (TestClearPageReferenced(page))
referenced++;
- if (page->mapcount && page->mapping) {
+ if (page_mapped(page) && page->mapping) {
if (PageAnon(page))
referenced += page_referenced_anon(page);
- else
+ else if (is_locked)
referenced += page_referenced_file(page);
+ else if (TestSetPageLocked(page))
+ referenced++;
+ else {
+ if (page->mapping)
+ referenced += page_referenced_file(page);
+ unlock_page(page);
+ }
}
return referenced;
}
BUG_ON(PageReserved(page));
BUG_ON(!anon_vma);
+ anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
index = (address - vma->vm_start) >> PAGE_SHIFT;
index += vma->vm_pgoff;
index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
- /*
- * Setting and clearing PG_anon must always happen inside
- * page_map_lock to avoid races between mapping and
- * unmapping on different processes of the same
- * shared cow swapcache page. And while we take the
- * page_map_lock PG_anon cannot change from under us.
- * Actually PG_anon cannot change under fork either
- * since fork holds a reference on the page so it cannot
- * be unmapped under fork and in turn copy_page_range is
- * allowed to read PG_anon outside the page_map_lock.
- */
- page_map_lock(page);
- if (!page->mapcount) {
- BUG_ON(PageAnon(page));
- BUG_ON(page->mapping);
- SetPageAnon(page);
+ if (atomic_inc_and_test(&page->_mapcount)) {
page->index = index;
page->mapping = (struct address_space *) anon_vma;
inc_page_state(nr_mapped);
- } else {
- BUG_ON(!PageAnon(page));
- BUG_ON(page->index != index);
- BUG_ON(page->mapping != (struct address_space *) anon_vma);
}
- page->mapcount++;
- page_map_unlock(page);
+ /* else checking page index and mapping is racy */
}
/**
if (!pfn_valid(page_to_pfn(page)) || PageReserved(page))
return;
- page_map_lock(page);
- if (!page->mapcount)
+ if (atomic_inc_and_test(&page->_mapcount))
inc_page_state(nr_mapped);
- page->mapcount++;
- page_map_unlock(page);
}
/**
void page_remove_rmap(struct page *page)
{
BUG_ON(PageReserved(page));
- BUG_ON(!page->mapcount);
- page_map_lock(page);
- page->mapcount--;
- if (!page->mapcount) {
+ if (atomic_add_negative(-1, &page->_mapcount)) {
+ BUG_ON(page_mapcount(page) < 0);
+ /*
+ * It would be tidy to reset the PageAnon mapping here,
+ * but that might overwrite a racing page_add_anon_rmap
+ * which increments mapcount after us but sets mapping
+ * before us: so leave the reset to free_hot_cold_page,
+ * and remember that it's only reliable while mapped.
+ * Leaving it set also helps swapoff to reinstate ptes
+ * faster for those pages still in swapcache.
+ */
if (page_test_and_clear_dirty(page))
set_page_dirty(page);
- if (PageAnon(page))
- clear_page_anon(page);
dec_page_state(nr_mapped);
}
- page_map_unlock(page);
}
/*
* We need the page_table_lock to protect us from page faults,
* munmap, fork, etc...
*/
- if (!spin_trylock(&mm->page_table_lock))
- goto out;
+ spin_lock(&mm->page_table_lock);
pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
* ptes from being unmapped, so swapoff can make progress.
*/
if (PageSwapCache(page) &&
- page_count(page) != page->mapcount + 2) {
+ page_count(page) != page_mapcount(page) + 2) {
ret = SWAP_FAIL;
goto out_unmap;
}
// mm->rss--;
vx_rsspages_dec(mm);
- BUG_ON(!page->mapcount);
- page->mapcount--;
+ page_remove_rmap(page);
page_cache_release(page);
out_unmap:
#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
-static int try_to_unmap_cluster(unsigned long cursor,
+static void try_to_unmap_cluster(unsigned long cursor,
unsigned int *mapcount, struct vm_area_struct *vma)
{
struct mm_struct *mm = vma->vm_mm;
* We need the page_table_lock to protect us from page faults,
* munmap, fork, etc...
*/
- if (!spin_trylock(&mm->page_table_lock))
- return SWAP_FAIL;
+ spin_lock(&mm->page_table_lock);
address = (vma->vm_start + cursor) & CLUSTER_MASK;
end = address + CLUSTER_SIZE;
out_unlock:
spin_unlock(&mm->page_table_lock);
- return SWAP_AGAIN;
}
-static inline int try_to_unmap_anon(struct page *page)
+static int try_to_unmap_anon(struct page *page)
{
- struct anon_vma *anon_vma = (struct anon_vma *) page->mapping;
+ struct anon_vma *anon_vma;
struct vm_area_struct *vma;
int ret = SWAP_AGAIN;
- spin_lock(&anon_vma->lock);
- BUG_ON(list_empty(&anon_vma->head));
+ anon_vma = page_lock_anon_vma(page);
+ if (!anon_vma)
+ return ret;
+
list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
ret = try_to_unmap_one(page, vma);
- if (ret == SWAP_FAIL || !page->mapcount)
+ if (ret == SWAP_FAIL || !page_mapped(page))
break;
}
spin_unlock(&anon_vma->lock);
* contained in the address_space struct it points to.
*
* This function is only called from try_to_unmap for object-based pages.
- *
- * The spinlock address_space->i_mmap_lock is tried. If it can't be gotten,
- * return a temporary error.
*/
-static inline int try_to_unmap_file(struct page *page)
+static int try_to_unmap_file(struct page *page)
{
struct address_space *mapping = page->mapping;
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
- struct vm_area_struct *vma = NULL;
+ struct vm_area_struct *vma;
struct prio_tree_iter iter;
int ret = SWAP_AGAIN;
unsigned long cursor;
unsigned long max_nl_size = 0;
unsigned int mapcount;
- if (!spin_trylock(&mapping->i_mmap_lock))
- return ret;
-
- while ((vma = vma_prio_tree_next(vma, &mapping->i_mmap,
- &iter, pgoff, pgoff)) != NULL) {
+ spin_lock(&mapping->i_mmap_lock);
+ vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
ret = try_to_unmap_one(page, vma);
- if (ret == SWAP_FAIL || !page->mapcount)
+ if (ret == SWAP_FAIL || !page_mapped(page))
goto out;
}
max_nl_size = cursor;
}
- if (max_nl_size == 0) /* any nonlinears locked or reserved */
+ if (max_nl_size == 0) { /* any nonlinears locked or reserved */
+ ret = SWAP_FAIL;
goto out;
+ }
/*
* We don't try to search for this page in the nonlinear vmas,
* The mapcount of the page we came in with is irrelevant,
* but even so use it as a guide to how hard we should try?
*/
- mapcount = page->mapcount;
- page_map_unlock(page);
+ mapcount = page_mapcount(page);
+ if (!mapcount)
+ goto out;
cond_resched_lock(&mapping->i_mmap_lock);
max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
while (vma->vm_mm->rss &&
cursor < max_nl_cursor &&
cursor < vma->vm_end - vma->vm_start) {
- ret = try_to_unmap_cluster(
- cursor, &mapcount, vma);
- if (ret == SWAP_FAIL)
- break;
+ try_to_unmap_cluster(cursor, &mapcount, vma);
cursor += CLUSTER_SIZE;
vma->vm_private_data = (void *) cursor;
if ((int)mapcount <= 0)
- goto relock;
+ goto out;
}
- if (ret != SWAP_FAIL)
- vma->vm_private_data =
- (void *) max_nl_cursor;
- ret = SWAP_AGAIN;
+ vma->vm_private_data = (void *) max_nl_cursor;
}
cond_resched_lock(&mapping->i_mmap_lock);
max_nl_cursor += CLUSTER_SIZE;
if (!(vma->vm_flags & VM_RESERVED))
vma->vm_private_data = NULL;
}
-relock:
- page_map_lock(page);
out:
spin_unlock(&mapping->i_mmap_lock);
return ret;
* @page: the page to get unmapped
*
* Tries to remove all the page table entries which are mapping this
- * page, used in the pageout path. Caller must hold the page lock
- * and its rmap lock. Return values are:
+ * page, used in the pageout path. Caller must hold the page lock.
+ * Return values are:
*
* SWAP_SUCCESS - we succeeded in removing all mappings
- * SWAP_AGAIN - we missed a trylock, try again later
+ * SWAP_AGAIN - we missed a mapping, try again later
* SWAP_FAIL - the page is unswappable
*/
int try_to_unmap(struct page *page)
BUG_ON(PageReserved(page));
BUG_ON(!PageLocked(page));
- BUG_ON(!page->mapcount);
if (PageAnon(page))
ret = try_to_unmap_anon(page);
else
ret = try_to_unmap_file(page);
- if (!page->mapcount) {
- if (page_test_and_clear_dirty(page))
- set_page_dirty(page);
- if (PageAnon(page))
- clear_page_anon(page);
- dec_page_state(nr_mapped);
+ if (!page_mapped(page))
ret = SWAP_SUCCESS;
- }
return ret;
}
git://git.onelab.eu / linux-2.6.git / blobdiff