X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=mm%2Frmap.c;h=10993942d6c989314477291520c6bb6980a0439d;hb=bc9c4068388eea01d3b5da31016879f2341ecec5;hp=0383acfcb0681a877f15f59d4d712980c37e1811;hpb=7e392f8c29ee045c6a29d50193d2fb10712eceb0;p=linux-2.6-omap-h63xx.git diff --git a/mm/rmap.c b/mm/rmap.c index 0383acfcb06..10993942d6c 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -53,9 +53,47 @@ #include -struct kmem_cache *anon_vma_cachep; +#include "internal.h" -/* This must be called under the mmap_sem. */ +static struct kmem_cache *anon_vma_cachep; + +static inline struct anon_vma *anon_vma_alloc(void) +{ + return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); +} + +static inline void anon_vma_free(struct anon_vma *anon_vma) +{ + kmem_cache_free(anon_vma_cachep, anon_vma); +} + +/** + * anon_vma_prepare - attach an anon_vma to a memory region + * @vma: the memory region in question + * + * This makes sure the memory mapping described by 'vma' has + * an 'anon_vma' attached to it, so that we can associate the + * anonymous pages mapped into it with that anon_vma. + * + * The common case will be that we already have one, but if + * if not we either need to find an adjacent mapping that we + * can re-use the anon_vma from (very common when the only + * reason for splitting a vma has been mprotect()), or we + * allocate a new one. + * + * Anon-vma allocations are very subtle, because we may have + * optimistically looked up an anon_vma in page_lock_anon_vma() + * and that may actually touch the spinlock even in the newly + * allocated vma (it depends on RCU to make sure that the + * anon_vma isn't actually destroyed). + * + * As a result, we need to do proper anon_vma locking even + * for the new allocation. At the same time, we do not want + * to do any locking for the common case of already having + * an anon_vma. + * + * This must be called with the mmap_sem held for reading. + */ int anon_vma_prepare(struct vm_area_struct *vma) { struct anon_vma *anon_vma = vma->anon_vma; @@ -63,20 +101,17 @@ int anon_vma_prepare(struct vm_area_struct *vma) might_sleep(); if (unlikely(!anon_vma)) { struct mm_struct *mm = vma->vm_mm; - struct anon_vma *allocated, *locked; + struct anon_vma *allocated; anon_vma = find_mergeable_anon_vma(vma); - if (anon_vma) { - allocated = NULL; - locked = anon_vma; - spin_lock(&locked->lock); - } else { + allocated = NULL; + if (!anon_vma) { anon_vma = anon_vma_alloc(); if (unlikely(!anon_vma)) return -ENOMEM; allocated = anon_vma; - locked = NULL; } + spin_lock(&anon_vma->lock); /* page_table_lock to protect against threads */ spin_lock(&mm->page_table_lock); @@ -87,8 +122,7 @@ int anon_vma_prepare(struct vm_area_struct *vma) } spin_unlock(&mm->page_table_lock); - if (locked) - spin_unlock(&locked->lock); + spin_unlock(&anon_vma->lock); if (unlikely(allocated)) anon_vma_free(allocated); } @@ -157,7 +191,7 @@ void __init anon_vma_init(void) * 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 *page_lock_anon_vma(struct page *page) { struct anon_vma *anon_vma; unsigned long anon_mapping; @@ -177,7 +211,7 @@ out: return NULL; } -static void page_unlock_anon_vma(struct anon_vma *anon_vma) +void page_unlock_anon_vma(struct anon_vma *anon_vma) { spin_unlock(&anon_vma->lock); rcu_read_unlock(); @@ -268,6 +302,32 @@ pte_t *page_check_address(struct page *page, struct mm_struct *mm, return NULL; } +/** + * page_mapped_in_vma - check whether a page is really mapped in a VMA + * @page: the page to test + * @vma: the VMA to test + * + * Returns 1 if the page is mapped into the page tables of the VMA, 0 + * if the page is not mapped into the page tables of this VMA. Only + * valid for normal file or anonymous VMAs. + */ +static int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) +{ + unsigned long address; + pte_t *pte; + spinlock_t *ptl; + + address = vma_address(page, vma); + if (address == -EFAULT) /* out of vma range */ + return 0; + pte = page_check_address(page, vma->vm_mm, address, &ptl, 1); + if (!pte) /* the page is not in this mm */ + return 0; + pte_unmap_unlock(pte, ptl); + + return 1; +} + /* * Subfunctions of page_referenced: page_referenced_one called * repeatedly from either page_referenced_anon or page_referenced_file. @@ -289,10 +349,17 @@ static int page_referenced_one(struct page *page, if (!pte) goto out; + /* + * Don't want to elevate referenced for mlocked page that gets this far, + * in order that it progresses to try_to_unmap and is moved to the + * unevictable list. + */ if (vma->vm_flags & VM_LOCKED) { - referenced++; *mapcount = 1; /* break early from loop */ - } else if (ptep_clear_flush_young_notify(vma, address, pte)) + goto out_unmap; + } + + if (ptep_clear_flush_young_notify(vma, address, pte)) referenced++; /* Pretend the page is referenced if the task has the @@ -301,6 +368,7 @@ static int page_referenced_one(struct page *page, rwsem_is_locked(&mm->mmap_sem)) referenced++; +out_unmap: (*mapcount)--; pte_unmap_unlock(pte, ptl); out: @@ -390,11 +458,6 @@ static int page_referenced_file(struct page *page, */ if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) continue; - if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE)) - == (VM_LOCKED|VM_MAYSHARE)) { - referenced++; - break; - } referenced += page_referenced_one(page, vma, &mapcount); if (!mapcount) break; @@ -674,8 +737,8 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma) page_clear_dirty(page); set_page_dirty(page); } - - mem_cgroup_uncharge_page(page); + if (PageAnon(page)) + mem_cgroup_uncharge_page(page); __dec_zone_page_state(page, PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED); /* @@ -717,11 +780,16 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, * If it's recently referenced (perhaps page_referenced * skipped over this mm) then we should reactivate it. */ - if (!migration && ((vma->vm_flags & VM_LOCKED) || - (ptep_clear_flush_young_notify(vma, address, pte)))) { - ret = SWAP_FAIL; - goto out_unmap; - } + if (!migration) { + if (vma->vm_flags & VM_LOCKED) { + ret = SWAP_MLOCK; + goto out_unmap; + } + if (ptep_clear_flush_young_notify(vma, address, pte)) { + ret = SWAP_FAIL; + goto out_unmap; + } + } /* Nuke the page table entry. */ flush_cache_page(vma, address, page_to_pfn(page)); @@ -802,12 +870,17 @@ out: * 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. + * + * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can + * acquire it without blocking. If vma locked, mlock the pages in the cluster, + * rather than unmapping them. If we encounter the "check_page" that vmscan is + * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN. */ #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) +static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, + struct vm_area_struct *vma, struct page *check_page) { struct mm_struct *mm = vma->vm_mm; pgd_t *pgd; @@ -819,6 +892,8 @@ static void try_to_unmap_cluster(unsigned long cursor, struct page *page; unsigned long address; unsigned long end; + int ret = SWAP_AGAIN; + int locked_vma = 0; address = (vma->vm_start + cursor) & CLUSTER_MASK; end = address + CLUSTER_SIZE; @@ -829,15 +904,26 @@ static void try_to_unmap_cluster(unsigned long cursor, pgd = pgd_offset(mm, address); if (!pgd_present(*pgd)) - return; + return ret; pud = pud_offset(pgd, address); if (!pud_present(*pud)) - return; + return ret; pmd = pmd_offset(pud, address); if (!pmd_present(*pmd)) - return; + return ret; + + /* + * MLOCK_PAGES => feature is configured. + * if we can acquire the mmap_sem for read, and vma is VM_LOCKED, + * keep the sem while scanning the cluster for mlocking pages. + */ + if (MLOCK_PAGES && down_read_trylock(&vma->vm_mm->mmap_sem)) { + locked_vma = (vma->vm_flags & VM_LOCKED); + if (!locked_vma) + up_read(&vma->vm_mm->mmap_sem); /* don't need it */ + } pte = pte_offset_map_lock(mm, pmd, address, &ptl); @@ -850,6 +936,13 @@ static void try_to_unmap_cluster(unsigned long cursor, page = vm_normal_page(vma, address, *pte); BUG_ON(!page || PageAnon(page)); + if (locked_vma) { + mlock_vma_page(page); /* no-op if already mlocked */ + if (page == check_page) + ret = SWAP_MLOCK; + continue; /* don't unmap */ + } + if (ptep_clear_flush_young_notify(vma, address, pte)) continue; @@ -871,39 +964,104 @@ static void try_to_unmap_cluster(unsigned long cursor, (*mapcount)--; } pte_unmap_unlock(pte - 1, ptl); + if (locked_vma) + up_read(&vma->vm_mm->mmap_sem); + return ret; } -static int try_to_unmap_anon(struct page *page, int migration) +/* + * common handling for pages mapped in VM_LOCKED vmas + */ +static int try_to_mlock_page(struct page *page, struct vm_area_struct *vma) +{ + int mlocked = 0; + + if (down_read_trylock(&vma->vm_mm->mmap_sem)) { + if (vma->vm_flags & VM_LOCKED) { + mlock_vma_page(page); + mlocked++; /* really mlocked the page */ + } + up_read(&vma->vm_mm->mmap_sem); + } + return mlocked; +} + +/** + * try_to_unmap_anon - unmap or unlock anonymous page using the object-based + * rmap method + * @page: the page to unmap/unlock + * @unlock: request for unlock rather than unmap [unlikely] + * @migration: unmapping for migration - ignored if @unlock + * + * Find all the mappings of a page using the mapping pointer and the vma chains + * contained in the anon_vma struct it points to. + * + * This function is only called from try_to_unmap/try_to_munlock for + * anonymous pages. + * When called from try_to_munlock(), the mmap_sem of the mm containing the vma + * where the page was found will be held for write. So, we won't recheck + * vm_flags for that VMA. That should be OK, because that vma shouldn't be + * 'LOCKED. + */ +static int try_to_unmap_anon(struct page *page, int unlock, int migration) { struct anon_vma *anon_vma; struct vm_area_struct *vma; + unsigned int mlocked = 0; int ret = SWAP_AGAIN; + if (MLOCK_PAGES && unlikely(unlock)) + ret = SWAP_SUCCESS; /* default for try_to_munlock() */ + 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, migration); - if (ret == SWAP_FAIL || !page_mapped(page)) - break; + if (MLOCK_PAGES && unlikely(unlock)) { + if (!((vma->vm_flags & VM_LOCKED) && + page_mapped_in_vma(page, vma))) + continue; /* must visit all unlocked vmas */ + ret = SWAP_MLOCK; /* saw at least one mlocked vma */ + } else { + ret = try_to_unmap_one(page, vma, migration); + if (ret == SWAP_FAIL || !page_mapped(page)) + break; + } + if (ret == SWAP_MLOCK) { + mlocked = try_to_mlock_page(page, vma); + if (mlocked) + break; /* stop if actually mlocked page */ + } } page_unlock_anon_vma(anon_vma); + + if (mlocked) + ret = SWAP_MLOCK; /* actually mlocked the page */ + else if (ret == SWAP_MLOCK) + ret = SWAP_AGAIN; /* saw VM_LOCKED vma */ + return ret; } /** - * try_to_unmap_file - unmap file page using the object-based rmap method - * @page: the page to unmap - * @migration: migration flag + * try_to_unmap_file - unmap/unlock file page using the object-based rmap method + * @page: the page to unmap/unlock + * @unlock: request for unlock rather than unmap [unlikely] + * @migration: unmapping for migration - ignored if @unlock * * 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. + * This function is only called from try_to_unmap/try_to_munlock for + * object-based pages. + * When called from try_to_munlock(), the mmap_sem of the mm containing the vma + * where the page was found will be held for write. So, we won't recheck + * vm_flags for that VMA. That should be OK, because that vma shouldn't be + * 'LOCKED. */ -static int try_to_unmap_file(struct page *page, int migration) +static int try_to_unmap_file(struct page *page, int unlock, int migration) { struct address_space *mapping = page->mapping; pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); @@ -914,20 +1072,44 @@ static int try_to_unmap_file(struct page *page, int migration) unsigned long max_nl_cursor = 0; unsigned long max_nl_size = 0; unsigned int mapcount; + unsigned int mlocked = 0; + + if (MLOCK_PAGES && unlikely(unlock)) + ret = SWAP_SUCCESS; /* default for try_to_munlock() */ spin_lock(&mapping->i_mmap_lock); vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { - ret = try_to_unmap_one(page, vma, migration); - if (ret == SWAP_FAIL || !page_mapped(page)) - goto out; + if (MLOCK_PAGES && unlikely(unlock)) { + if (!(vma->vm_flags & VM_LOCKED)) + continue; /* must visit all vmas */ + ret = SWAP_MLOCK; + } else { + ret = try_to_unmap_one(page, vma, migration); + if (ret == SWAP_FAIL || !page_mapped(page)) + goto out; + } + if (ret == SWAP_MLOCK) { + mlocked = try_to_mlock_page(page, vma); + if (mlocked) + break; /* stop if actually mlocked page */ + } } + if (mlocked) + 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) && !migration) + if (MLOCK_PAGES && unlikely(unlock)) { + if (!(vma->vm_flags & VM_LOCKED)) + continue; /* must visit all vmas */ + ret = SWAP_MLOCK; /* leave mlocked == 0 */ + goto out; /* no need to look further */ + } + if (!MLOCK_PAGES && !migration && (vma->vm_flags & VM_LOCKED)) continue; cursor = (unsigned long) vma->vm_private_data; if (cursor > max_nl_cursor) @@ -937,7 +1119,7 @@ static int try_to_unmap_file(struct page *page, int migration) max_nl_size = cursor; } - if (max_nl_size == 0) { /* any nonlinears locked or reserved */ + if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */ ret = SWAP_FAIL; goto out; } @@ -961,12 +1143,16 @@ static int try_to_unmap_file(struct page *page, int migration) do { list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) { - if ((vma->vm_flags & VM_LOCKED) && !migration) + if (!MLOCK_PAGES && !migration && + (vma->vm_flags & VM_LOCKED)) continue; cursor = (unsigned long) vma->vm_private_data; while ( cursor < max_nl_cursor && cursor < vma->vm_end - vma->vm_start) { - try_to_unmap_cluster(cursor, &mapcount, vma); + ret = try_to_unmap_cluster(cursor, &mapcount, + vma, page); + if (ret == SWAP_MLOCK) + mlocked = 2; /* to return below */ cursor += CLUSTER_SIZE; vma->vm_private_data = (void *) cursor; if ((int)mapcount <= 0) @@ -987,6 +1173,10 @@ static int try_to_unmap_file(struct page *page, int migration) vma->vm_private_data = NULL; out: spin_unlock(&mapping->i_mmap_lock); + if (mlocked) + ret = SWAP_MLOCK; /* actually mlocked the page */ + else if (ret == SWAP_MLOCK) + ret = SWAP_AGAIN; /* saw VM_LOCKED vma */ return ret; } @@ -1002,6 +1192,7 @@ out: * SWAP_SUCCESS - we succeeded in removing all mappings * SWAP_AGAIN - we missed a mapping, try again later * SWAP_FAIL - the page is unswappable + * SWAP_MLOCK - page is mlocked. */ int try_to_unmap(struct page *page, int migration) { @@ -1010,12 +1201,36 @@ int try_to_unmap(struct page *page, int migration) BUG_ON(!PageLocked(page)); if (PageAnon(page)) - ret = try_to_unmap_anon(page, migration); + ret = try_to_unmap_anon(page, 0, migration); else - ret = try_to_unmap_file(page, migration); - - if (!page_mapped(page)) + ret = try_to_unmap_file(page, 0, migration); + if (ret != SWAP_MLOCK && !page_mapped(page)) ret = SWAP_SUCCESS; return ret; } +#ifdef CONFIG_UNEVICTABLE_LRU +/** + * try_to_munlock - try to munlock a page + * @page: the page to be munlocked + * + * Called from munlock code. Checks all of the VMAs mapping the page + * to make sure nobody else has this page mlocked. The page will be + * returned with PG_mlocked cleared if no other vmas have it mlocked. + * + * Return values are: + * + * SWAP_SUCCESS - no vma's holding page mlocked. + * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem + * SWAP_MLOCK - page is now mlocked. + */ +int try_to_munlock(struct page *page) +{ + VM_BUG_ON(!PageLocked(page) || PageLRU(page)); + + if (PageAnon(page)) + return try_to_unmap_anon(page, 1, 0); + else + return try_to_unmap_file(page, 1, 0); +} +#endif