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-rw-r--r--mm/rmap.c862
1 files changed, 862 insertions, 0 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
new file mode 100644
index 00000000000..884d6d1928b
--- /dev/null
+++ b/mm/rmap.c
@@ -0,0 +1,862 @@
+/*
+ * mm/rmap.c - physical to virtual reverse mappings
+ *
+ * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
+ * Released under the General Public License (GPL).
+ *
+ * Simple, low overhead reverse mapping scheme.
+ * Please try to keep this thing as modular as possible.
+ *
+ * Provides methods for unmapping each kind of mapped page:
+ * the anon methods track anonymous pages, and
+ * the file methods track pages belonging to an inode.
+ *
+ * Original design by Rik van Riel <riel@conectiva.com.br> 2001
+ * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
+ * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
+ * Contributions by Hugh Dickins <hugh@veritas.com> 2003, 2004
+ */
+
+/*
+ * 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)
+ * mmlist_lock (in mmput, drain_mmlist and others)
+ * 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/pagemap.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/rmap.h>
+#include <linux/rcupdate.h>
+
+#include <asm/tlbflush.h>
+
+//#define RMAP_DEBUG /* can be enabled only for debugging */
+
+kmem_cache_t *anon_vma_cachep;
+
+static inline void validate_anon_vma(struct vm_area_struct *find_vma)
+{
+#ifdef RMAP_DEBUG
+ struct anon_vma *anon_vma = find_vma->anon_vma;
+ struct vm_area_struct *vma;
+ unsigned int mapcount = 0;
+ int found = 0;
+
+ list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
+ mapcount++;
+ BUG_ON(mapcount > 100000);
+ if (vma == find_vma)
+ found = 1;
+ }
+ BUG_ON(!found);
+#endif
+}
+
+/* This must be called under the mmap_sem. */
+int anon_vma_prepare(struct vm_area_struct *vma)
+{
+ struct anon_vma *anon_vma = vma->anon_vma;
+
+ might_sleep();
+ if (unlikely(!anon_vma)) {
+ struct mm_struct *mm = vma->vm_mm;
+ struct anon_vma *allocated, *locked;
+
+ anon_vma = find_mergeable_anon_vma(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)) {
+ vma->anon_vma = anon_vma;
+ list_add(&vma->anon_vma_node, &anon_vma->head);
+ allocated = NULL;
+ }
+ spin_unlock(&mm->page_table_lock);
+
+ if (locked)
+ spin_unlock(&locked->lock);
+ if (unlikely(allocated))
+ anon_vma_free(allocated);
+ }
+ return 0;
+}
+
+void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
+{
+ BUG_ON(vma->anon_vma != next->anon_vma);
+ list_del(&next->anon_vma_node);
+}
+
+void __anon_vma_link(struct vm_area_struct *vma)
+{
+ struct anon_vma *anon_vma = vma->anon_vma;
+
+ if (anon_vma) {
+ list_add(&vma->anon_vma_node, &anon_vma->head);
+ validate_anon_vma(vma);
+ }
+}
+
+void anon_vma_link(struct vm_area_struct *vma)
+{
+ struct anon_vma *anon_vma = vma->anon_vma;
+
+ if (anon_vma) {
+ spin_lock(&anon_vma->lock);
+ list_add(&vma->anon_vma_node, &anon_vma->head);
+ validate_anon_vma(vma);
+ spin_unlock(&anon_vma->lock);
+ }
+}
+
+void anon_vma_unlink(struct vm_area_struct *vma)
+{
+ struct anon_vma *anon_vma = vma->anon_vma;
+ int empty;
+
+ if (!anon_vma)
+ return;
+
+ spin_lock(&anon_vma->lock);
+ validate_anon_vma(vma);
+ list_del(&vma->anon_vma_node);
+
+ /* We must garbage collect the anon_vma if it's empty */
+ empty = list_empty(&anon_vma->head);
+ spin_unlock(&anon_vma->lock);
+
+ if (empty)
+ anon_vma_free(anon_vma);
+}
+
+static void anon_vma_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
+{
+ if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
+ SLAB_CTOR_CONSTRUCTOR) {
+ struct anon_vma *anon_vma = data;
+
+ spin_lock_init(&anon_vma->lock);
+ INIT_LIST_HEAD(&anon_vma->head);
+ }
+}
+
+void __init anon_vma_init(void)
+{
+ anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
+ 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL);
+}
+
+/*
+ * 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)
+{
+ 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;
+}
+
+/*
+ * At what user virtual address is page expected in vma?
+ */
+static inline unsigned long
+vma_address(struct page *page, struct vm_area_struct *vma)
+{
+ pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+ unsigned long address;
+
+ address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+ if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
+ /* page should be within any vma from prio_tree_next */
+ BUG_ON(!PageAnon(page));
+ return -EFAULT;
+ }
+ 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.
+ */
+static int page_referenced_one(struct page *page,
+ struct vm_area_struct *vma, unsigned int *mapcount, int ignore_token)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long address;
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+ int referenced = 0;
+
+ if (!get_mm_counter(mm, rss))
+ goto out;
+ address = vma_address(page, vma);
+ if (address == -EFAULT)
+ goto out;
+
+ spin_lock(&mm->page_table_lock);
+
+ pgd = pgd_offset(mm, address);
+ if (!pgd_present(*pgd))
+ goto out_unlock;
+
+ pud = pud_offset(pgd, address);
+ if (!pud_present(*pud))
+ goto out_unlock;
+
+ pmd = pmd_offset(pud, address);
+ if (!pmd_present(*pmd))
+ goto out_unlock;
+
+ pte = pte_offset_map(pmd, address);
+ if (!pte_present(*pte))
+ goto out_unmap;
+
+ if (page_to_pfn(page) != pte_pfn(*pte))
+ goto out_unmap;
+
+ if (ptep_clear_flush_young(vma, address, pte))
+ referenced++;
+
+ if (mm != current->mm && !ignore_token && has_swap_token(mm))
+ referenced++;
+
+ (*mapcount)--;
+
+out_unmap:
+ pte_unmap(pte);
+out_unlock:
+ spin_unlock(&mm->page_table_lock);
+out:
+ return referenced;
+}
+
+static int page_referenced_anon(struct page *page, int ignore_token)
+{
+ unsigned int mapcount;
+ struct anon_vma *anon_vma;
+ struct vm_area_struct *vma;
+ int referenced = 0;
+
+ 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,
+ ignore_token);
+ if (!mapcount)
+ break;
+ }
+ spin_unlock(&anon_vma->lock);
+ return referenced;
+}
+
+/**
+ * page_referenced_file - referenced check for object-based rmap
+ * @page: the page we're checking references on.
+ *
+ * For an object-based mapped page, find all the places it is mapped and
+ * check/clear the referenced flag. This is done by following the page->mapping
+ * pointer, then walking the chain of vmas it holds. It returns the number
+ * of references it found.
+ *
+ * This function is only called from page_referenced for object-based pages.
+ */
+static int page_referenced_file(struct page *page, int ignore_token)
+{
+ unsigned int mapcount;
+ struct address_space *mapping = page->mapping;
+ pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+ struct vm_area_struct *vma;
+ struct prio_tree_iter iter;
+ int referenced = 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));
+
+ 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++;
+ break;
+ }
+ referenced += page_referenced_one(page, vma, &mapcount,
+ ignore_token);
+ if (!mapcount)
+ break;
+ }
+
+ spin_unlock(&mapping->i_mmap_lock);
+ return 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.
+ */
+int page_referenced(struct page *page, int is_locked, int ignore_token)
+{
+ int referenced = 0;
+
+ if (!swap_token_default_timeout)
+ ignore_token = 1;
+
+ if (page_test_and_clear_young(page))
+ referenced++;
+
+ if (TestClearPageReferenced(page))
+ referenced++;
+
+ if (page_mapped(page) && page->mapping) {
+ if (PageAnon(page))
+ referenced += page_referenced_anon(page, ignore_token);
+ else if (is_locked)
+ referenced += page_referenced_file(page, ignore_token);
+ else if (TestSetPageLocked(page))
+ referenced++;
+ else {
+ if (page->mapping)
+ referenced += page_referenced_file(page,
+ ignore_token);
+ unlock_page(page);
+ }
+ }
+ return referenced;
+}
+
+/**
+ * page_add_anon_rmap - add pte mapping to an anonymous page
+ * @page: the page to add the mapping to
+ * @vma: the vm area in which the mapping is added
+ * @address: the user virtual address mapped
+ *
+ * The caller needs to hold the mm->page_table_lock.
+ */
+void page_add_anon_rmap(struct page *page,
+ struct vm_area_struct *vma, unsigned long address)
+{
+ struct anon_vma *anon_vma = vma->anon_vma;
+ pgoff_t index;
+
+ BUG_ON(PageReserved(page));
+ BUG_ON(!anon_vma);
+
+ inc_mm_counter(vma->vm_mm, anon_rss);
+
+ 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;
+
+ if (atomic_inc_and_test(&page->_mapcount)) {
+ page->index = index;
+ page->mapping = (struct address_space *) anon_vma;
+ inc_page_state(nr_mapped);
+ }
+ /* else checking page index and mapping is racy */
+}
+
+/**
+ * page_add_file_rmap - add pte mapping to a file page
+ * @page: the page to add the mapping to
+ *
+ * The caller needs to hold the mm->page_table_lock.
+ */
+void page_add_file_rmap(struct page *page)
+{
+ BUG_ON(PageAnon(page));
+ if (!pfn_valid(page_to_pfn(page)) || PageReserved(page))
+ return;
+
+ if (atomic_inc_and_test(&page->_mapcount))
+ inc_page_state(nr_mapped);
+}
+
+/**
+ * page_remove_rmap - take down pte mapping from a page
+ * @page: page to remove mapping from
+ *
+ * Caller needs to hold the mm->page_table_lock.
+ */
+void page_remove_rmap(struct page *page)
+{
+ BUG_ON(PageReserved(page));
+
+ 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);
+ dec_page_state(nr_mapped);
+ }
+}
+
+/*
+ * Subfunctions of try_to_unmap: try_to_unmap_one called
+ * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
+ */
+static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long address;
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+ pte_t pteval;
+ int ret = SWAP_AGAIN;
+
+ if (!get_mm_counter(mm, rss))
+ goto out;
+ address = vma_address(page, vma);
+ if (address == -EFAULT)
+ goto out;
+
+ /*
+ * We need the page_table_lock to protect us from page faults,
+ * munmap, fork, etc...
+ */
+ spin_lock(&mm->page_table_lock);
+
+ pgd = pgd_offset(mm, address);
+ if (!pgd_present(*pgd))
+ goto out_unlock;
+
+ pud = pud_offset(pgd, address);
+ if (!pud_present(*pud))
+ goto out_unlock;
+
+ pmd = pmd_offset(pud, address);
+ if (!pmd_present(*pmd))
+ goto out_unlock;
+
+ pte = pte_offset_map(pmd, address);
+ if (!pte_present(*pte))
+ goto out_unmap;
+
+ if (page_to_pfn(page) != pte_pfn(*pte))
+ goto out_unmap;
+
+ /*
+ * If the page is mlock()d, we cannot swap it out.
+ * If it's recently referenced (perhaps page_referenced
+ * skipped over this mm) then we should reactivate it.
+ */
+ if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) ||
+ ptep_clear_flush_young(vma, address, pte)) {
+ ret = SWAP_FAIL;
+ goto out_unmap;
+ }
+
+ /*
+ * Don't pull an anonymous page out from under get_user_pages.
+ * GUP carefully breaks COW and raises page count (while holding
+ * page_table_lock, as we have here) to make sure that the page
+ * cannot be freed. If we unmap that page here, a user write
+ * access to the virtual address will bring back the page, but
+ * its raised count will (ironically) be taken to mean it's not
+ * an exclusive swap page, do_wp_page will replace it by a copy
+ * page, and the user never get to see the data GUP was holding
+ * the original page for.
+ *
+ * This test is also useful for when swapoff (unuse_process) has
+ * to drop page lock: its reference to the page stops existing
+ * ptes from being unmapped, so swapoff can make progress.
+ */
+ if (PageSwapCache(page) &&
+ page_count(page) != page_mapcount(page) + 2) {
+ ret = SWAP_FAIL;
+ goto out_unmap;
+ }
+
+ /* Nuke the page table entry. */
+ flush_cache_page(vma, address, page_to_pfn(page));
+ pteval = ptep_clear_flush(vma, address, pte);
+
+ /* Move the dirty bit to the physical page now the pte is gone. */
+ if (pte_dirty(pteval))
+ set_page_dirty(page);
+
+ if (PageAnon(page)) {
+ swp_entry_t entry = { .val = page->private };
+ /*
+ * Store the swap location in the pte.
+ * See handle_pte_fault() ...
+ */
+ BUG_ON(!PageSwapCache(page));
+ swap_duplicate(entry);
+ if (list_empty(&mm->mmlist)) {
+ spin_lock(&mmlist_lock);
+ list_add(&mm->mmlist, &init_mm.mmlist);
+ spin_unlock(&mmlist_lock);
+ }
+ set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
+ BUG_ON(pte_file(*pte));
+ dec_mm_counter(mm, anon_rss);
+ }
+
+ inc_mm_counter(mm, rss);
+ page_remove_rmap(page);
+ page_cache_release(page);
+
+out_unmap:
+ pte_unmap(pte);
+out_unlock:
+ spin_unlock(&mm->page_table_lock);
+out:
+ return ret;
+}
+
+/*
+ * objrmap doesn't work for nonlinear VMAs because the assumption that
+ * offset-into-file correlates with offset-into-virtual-addresses does not hold.
+ * Consequently, given a particular page and its ->index, we cannot locate the
+ * ptes which are mapping that page without an exhaustive linear search.
+ *
+ * So what this code does is a mini "virtual scan" of each nonlinear VMA which
+ * maps the file to which the target page belongs. The ->vm_private_data field
+ * holds the current cursor into that scan. Successive searches will circulate
+ * around the vma's virtual address space.
+ *
+ * So as more replacement pressure is applied to the pages in a nonlinear VMA,
+ * more scanning pressure is placed against them as well. Eventually pages
+ * will become fully unmapped and are eligible for eviction.
+ *
+ * For very sparsely populated VMAs this is a little inefficient - chances are
+ * there there won't be many ptes located within the scan cluster. In this case
+ * maybe we could scan further - to the end of the pte page, perhaps.
+ */
+#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
+#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
+
+static void try_to_unmap_cluster(unsigned long cursor,
+ unsigned int *mapcount, struct vm_area_struct *vma)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+ pte_t pteval;
+ struct page *page;
+ unsigned long address;
+ unsigned long end;
+ unsigned long pfn;
+
+ /*
+ * We need the page_table_lock to protect us from page faults,
+ * munmap, fork, etc...
+ */
+ spin_lock(&mm->page_table_lock);
+
+ address = (vma->vm_start + cursor) & CLUSTER_MASK;
+ end = address + CLUSTER_SIZE;
+ if (address < vma->vm_start)
+ address = vma->vm_start;
+ if (end > vma->vm_end)
+ end = vma->vm_end;
+
+ pgd = pgd_offset(mm, address);
+ if (!pgd_present(*pgd))
+ goto out_unlock;
+
+ pud = pud_offset(pgd, address);
+ if (!pud_present(*pud))
+ goto out_unlock;
+
+ pmd = pmd_offset(pud, address);
+ if (!pmd_present(*pmd))
+ goto out_unlock;
+
+ for (pte = pte_offset_map(pmd, address);
+ address < end; pte++, address += PAGE_SIZE) {
+
+ if (!pte_present(*pte))
+ continue;
+
+ pfn = pte_pfn(*pte);
+ if (!pfn_valid(pfn))
+ continue;
+
+ page = pfn_to_page(pfn);
+ BUG_ON(PageAnon(page));
+ if (PageReserved(page))
+ continue;
+
+ if (ptep_clear_flush_young(vma, address, pte))
+ continue;
+
+ /* Nuke the page table entry. */
+ flush_cache_page(vma, address, pfn);
+ pteval = ptep_clear_flush(vma, address, pte);
+
+ /* If nonlinear, store the file page offset in the pte. */
+ if (page->index != linear_page_index(vma, address))
+ set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
+
+ /* Move the dirty bit to the physical page now the pte is gone. */
+ if (pte_dirty(pteval))
+ set_page_dirty(page);
+
+ page_remove_rmap(page);
+ page_cache_release(page);
+ dec_mm_counter(mm, rss);
+ (*mapcount)--;
+ }
+
+ pte_unmap(pte);
+
+out_unlock:
+ spin_unlock(&mm->page_table_lock);
+}
+
+static int try_to_unmap_anon(struct page *page)
+{
+ struct anon_vma *anon_vma;
+ struct vm_area_struct *vma;
+ int ret = SWAP_AGAIN;
+
+ 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_mapped(page))
+ break;
+ }
+ spin_unlock(&anon_vma->lock);
+ return ret;
+}
+
+/**
+ * try_to_unmap_file - unmap file page using the object-based rmap method
+ * @page: the page to unmap
+ *
+ * Find all the mappings of a page using the mapping pointer and the vma chains
+ * contained in the address_space struct it points to.
+ *
+ * This function is only called from try_to_unmap for object-based pages.
+ */
+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;
+ struct prio_tree_iter iter;
+ int ret = SWAP_AGAIN;
+ unsigned long cursor;
+ unsigned long max_nl_cursor = 0;
+ unsigned long max_nl_size = 0;
+ unsigned int mapcount;
+
+ 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_mapped(page))
+ goto out;
+ }
+
+ if (list_empty(&mapping->i_mmap_nonlinear))
+ goto out;
+
+ list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
+ shared.vm_set.list) {
+ if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
+ continue;
+ cursor = (unsigned long) vma->vm_private_data;
+ if (cursor > max_nl_cursor)
+ max_nl_cursor = cursor;
+ cursor = vma->vm_end - vma->vm_start;
+ if (cursor > max_nl_size)
+ max_nl_size = cursor;
+ }
+
+ 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,
+ * and page_referenced wouldn't have found it anyway. Instead
+ * just walk the nonlinear vmas trying to age and unmap some.
+ * 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);
+ if (!mapcount)
+ goto out;
+ cond_resched_lock(&mapping->i_mmap_lock);
+
+ max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
+ if (max_nl_cursor == 0)
+ max_nl_cursor = CLUSTER_SIZE;
+
+ do {
+ list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
+ shared.vm_set.list) {
+ if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
+ continue;
+ cursor = (unsigned long) vma->vm_private_data;
+ while (get_mm_counter(vma->vm_mm, rss) &&
+ cursor < max_nl_cursor &&
+ cursor < vma->vm_end - vma->vm_start) {
+ try_to_unmap_cluster(cursor, &mapcount, vma);
+ cursor += CLUSTER_SIZE;
+ vma->vm_private_data = (void *) cursor;
+ if ((int)mapcount <= 0)
+ goto out;
+ }
+ vma->vm_private_data = (void *) max_nl_cursor;
+ }
+ cond_resched_lock(&mapping->i_mmap_lock);
+ max_nl_cursor += CLUSTER_SIZE;
+ } while (max_nl_cursor <= max_nl_size);
+
+ /*
+ * Don't loop forever (perhaps all the remaining pages are
+ * in locked vmas). Reset cursor on all unreserved nonlinear
+ * vmas, now forgetting on which ones it had fallen behind.
+ */
+ list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
+ shared.vm_set.list) {
+ if (!(vma->vm_flags & VM_RESERVED))
+ vma->vm_private_data = NULL;
+ }
+out:
+ spin_unlock(&mapping->i_mmap_lock);
+ return ret;
+}
+
+/**
+ * try_to_unmap - try to remove all page table mappings to a page
+ * @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.
+ * Return values are:
+ *
+ * SWAP_SUCCESS - we succeeded in removing all mappings
+ * SWAP_AGAIN - we missed a mapping, try again later
+ * SWAP_FAIL - the page is unswappable
+ */
+int try_to_unmap(struct page *page)
+{
+ int ret;
+
+ BUG_ON(PageReserved(page));
+ BUG_ON(!PageLocked(page));
+
+ if (PageAnon(page))
+ ret = try_to_unmap_anon(page);
+ else
+ ret = try_to_unmap_file(page);
+
+ if (!page_mapped(page))
+ ret = SWAP_SUCCESS;
+ return ret;
+}
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-12-05 00:10:52 +0000