/* * linux/mm/memory.c * * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds */ /* * demand-loading started 01.12.91 - seems it is high on the list of * things wanted, and it should be easy to implement. - Linus */ /* * Ok, demand-loading was easy, shared pages a little bit tricker. Shared * pages started 02.12.91, seems to work. - Linus. * * Tested sharing by executing about 30 /bin/sh: under the old kernel it * would have taken more than the 6M I have free, but it worked well as * far as I could see. * * Also corrected some "invalidate()"s - I wasn't doing enough of them. */ /* * Real VM (paging to/from disk) started 18.12.91. Much more work and * thought has to go into this. Oh, well.. * 19.12.91 - works, somewhat. Sometimes I get faults, don't know why. * Found it. Everything seems to work now. * 20.12.91 - Ok, making the swap-device changeable like the root. */ /* * 05.04.94 - Multi-page memory management added for v1.1. * Idea by Alex Bligh (alex@cconcepts.co.uk) * * 16.07.99 - Support of BIGMEM added by Gerhard Wichert, Siemens AG * (Gerhard.Wichert@pdb.siemens.de) */ #include #include #include #include #include #include #include #include #include #include unsigned long max_mapnr; unsigned long num_physpages; void * high_memory; struct page *highmem_start_page; /* * We special-case the C-O-W ZERO_PAGE, because it's such * a common occurrence (no need to read the page to know * that it's zero - better for the cache and memory subsystem). */ static inline void copy_cow_page(struct page * from, struct page * to, unsigned long address) { if (from == ZERO_PAGE(address)) { clear_user_highpage(to, address); return; } copy_user_highpage(to, from, address); } mem_map_t * mem_map = NULL; /* * Note: this doesn't free the actual pages themselves. That * has been handled earlier when unmapping all the memory regions. */ static inline void free_one_pmd(pmd_t * dir) { pte_t * pte; if (pmd_none(*dir)) return; if (pmd_bad(*dir)) { pmd_ERROR(*dir); pmd_clear(dir); return; } pte = pte_offset(dir, 0); pmd_clear(dir); pte_free(pte); } static inline void free_one_pgd(pgd_t * dir) { int j; pmd_t * pmd; if (pgd_none(*dir)) return; if (pgd_bad(*dir)) { pgd_ERROR(*dir); pgd_clear(dir); return; } pmd = pmd_offset(dir, 0); pgd_clear(dir); for (j = 0; j < PTRS_PER_PMD ; j++) free_one_pmd(pmd+j); pmd_free(pmd); } /* Low and high watermarks for page table cache. The system should try to have pgt_water[0] <= cache elements <= pgt_water[1] */ int pgt_cache_water[2] = { 25, 50 }; /* Returns the number of pages freed */ int check_pgt_cache(void) { return do_check_pgt_cache(pgt_cache_water[0], pgt_cache_water[1]); } /* * This function clears all user-level page tables of a process - this * is needed by execve(), so that old pages aren't in the way. */ void clear_page_tables(struct mm_struct *mm, unsigned long first, int nr) { pgd_t * page_dir = mm->pgd; page_dir += first; do { free_one_pgd(page_dir); page_dir++; } while (--nr); /* keep the page table cache within bounds */ check_pgt_cache(); } #define PTE_TABLE_MASK ((PTRS_PER_PTE-1) * sizeof(pte_t)) #define PMD_TABLE_MASK ((PTRS_PER_PMD-1) * sizeof(pmd_t)) /* * copy one vm_area from one task to the other. Assumes the page tables * already present in the new task to be cleared in the whole range * covered by this vma. * * 08Jan98 Merged into one routine from several inline routines to reduce * variable count and make things faster. -jj */ int copy_page_range(struct mm_struct *dst, struct mm_struct *src, struct vm_area_struct *vma) { pgd_t * src_pgd, * dst_pgd; unsigned long address = vma->vm_start; unsigned long end = vma->vm_end; unsigned long cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; src_pgd = pgd_offset(src, address)-1; dst_pgd = pgd_offset(dst, address)-1; for (;;) { pmd_t * src_pmd, * dst_pmd; src_pgd++; dst_pgd++; /* copy_pmd_range */ if (pgd_none(*src_pgd)) goto skip_copy_pmd_range; if (pgd_bad(*src_pgd)) { pgd_ERROR(*src_pgd); pgd_clear(src_pgd); skip_copy_pmd_range: address = (address + PGDIR_SIZE) & PGDIR_MASK; if (!address || (address >= end)) goto out; continue; } if (pgd_none(*dst_pgd)) { if (!pmd_alloc(dst_pgd, 0)) goto nomem; } src_pmd = pmd_offset(src_pgd, address); dst_pmd = pmd_offset(dst_pgd, address); do { pte_t * src_pte, * dst_pte; /* copy_pte_range */ if (pmd_none(*src_pmd)) goto skip_copy_pte_range; if (pmd_bad(*src_pmd)) { pmd_ERROR(*src_pmd); pmd_clear(src_pmd); skip_copy_pte_range: address = (address + PMD_SIZE) & PMD_MASK; if (address >= end) goto out; goto cont_copy_pmd_range; } if (pmd_none(*dst_pmd)) { if (!pte_alloc(dst_pmd, 0)) goto nomem; } src_pte = pte_offset(src_pmd, address); dst_pte = pte_offset(dst_pmd, address); do { pte_t pte = *src_pte; struct page *ptepage; /* copy_one_pte */ if (pte_none(pte)) goto cont_copy_pte_range; if (!pte_present(pte)) { swap_duplicate(pte_to_swp_entry(pte)); set_pte(dst_pte, pte); goto cont_copy_pte_range; } ptepage = pte_page(pte); if ((!VALID_PAGE(ptepage)) || PageReserved(ptepage)) { set_pte(dst_pte, pte); goto cont_copy_pte_range; } /* If it's a COW mapping, write protect it both in the parent and the child */ if (cow) { pte = pte_wrprotect(pte); set_pte(src_pte, pte); } /* If it's a shared mapping, mark it clean in the child */ if (vma->vm_flags & VM_SHARED) pte = pte_mkclean(pte); set_pte(dst_pte, pte_mkold(pte)); get_page(ptepage); cont_copy_pte_range: address += PAGE_SIZE; if (address >= end) goto out; src_pte++; dst_pte++; } while ((unsigned long)src_pte & PTE_TABLE_MASK); cont_copy_pmd_range: src_pmd++; dst_pmd++; } while ((unsigned long)src_pmd & PMD_TABLE_MASK); } out: return 0; nomem: return -ENOMEM; } /* * Return indicates whether a page was freed so caller can adjust rss */ static inline int free_pte(pte_t page) { if (pte_present(page)) { struct page *ptpage = pte_page(page); if ((!VALID_PAGE(ptpage)) || PageReserved(ptpage)) return 0; /* * free_page() used to be able to clear swap cache * entries. We may now have to do it manually. */ free_page_and_swap_cache(ptpage); return 1; } swap_free(pte_to_swp_entry(page)); return 0; } static inline void forget_pte(pte_t page) { if (!pte_none(page)) { printk("forget_pte: old mapping existed!\n"); free_pte(page); } } static inline int zap_pte_range(struct mm_struct *mm, pmd_t * pmd, unsigned long address, unsigned long size) { pte_t * pte; int freed; if (pmd_none(*pmd)) return 0; if (pmd_bad(*pmd)) { pmd_ERROR(*pmd); pmd_clear(pmd); return 0; } pte = pte_offset(pmd, address); address &= ~PMD_MASK; if (address + size > PMD_SIZE) size = PMD_SIZE - address; size >>= PAGE_SHIFT; freed = 0; for (;;) { pte_t page; if (!size) break; page = *pte; pte++; size--; pte_clear(pte-1); if (pte_none(page)) continue; freed += free_pte(page); } return freed; } static inline int zap_pmd_range(struct mm_struct *mm, pgd_t * dir, unsigned long address, unsigned long size) { pmd_t * pmd; unsigned long end; int freed; if (pgd_none(*dir)) return 0; if (pgd_bad(*dir)) { pgd_ERROR(*dir); pgd_clear(dir); return 0; } pmd = pmd_offset(dir, address); address &= ~PGDIR_MASK; end = address + size; if (end > PGDIR_SIZE) end = PGDIR_SIZE; freed = 0; do { freed += zap_pte_range(mm, pmd, address, end - address); address = (address + PMD_SIZE) & PMD_MASK; pmd++; } while (address < end); return freed; } /* * remove user pages in a given range. */ void zap_page_range(struct mm_struct *mm, unsigned long address, unsigned long size) { pgd_t * dir; unsigned long end = address + size; int freed = 0; dir = pgd_offset(mm, address); /* * This is a long-lived spinlock. That's fine. * There's no contention, because the page table * lock only protects against kswapd anyway, and * even if kswapd happened to be looking at this * process we _want_ it to get stuck. */ if (address >= end) BUG(); spin_lock(&mm->page_table_lock); do { freed += zap_pmd_range(mm, dir, address, end - address); address = (address + PGDIR_SIZE) & PGDIR_MASK; dir++; } while (address && (address < end)); spin_unlock(&mm->page_table_lock); /* * Update rss for the mm_struct (not necessarily current->mm) * Notice that rss is an unsigned long. */ if (mm->rss > freed) mm->rss -= freed; else mm->rss = 0; } /* * Do a quick page-table lookup for a single page. */ static struct page * follow_page(unsigned long address) { pgd_t *pgd; pmd_t *pmd; pgd = pgd_offset(current->mm, address); pmd = pmd_offset(pgd, address); if (pmd) { pte_t * pte = pte_offset(pmd, address); if (pte && pte_present(*pte)) return pte_page(*pte); } return NULL; } /* * Given a physical address, is there a useful struct page pointing to * it? This may become more complex in the future if we start dealing * with IO-aperture pages in kiobufs. */ static inline struct page * get_page_map(struct page *page) { if (!VALID_PAGE(page)) return 0; return page; } /* * Force in an entire range of pages from the current process's user VA, * and pin them in physical memory. */ #define dprintk(x...) int map_user_kiobuf(int rw, struct kiobuf *iobuf, unsigned long va, size_t len) { unsigned long ptr, end; int err; struct mm_struct * mm; struct vm_area_struct * vma = 0; struct page * map; int i; int datain = (rw == READ); /* Make sure the iobuf is not already mapped somewhere. */ if (iobuf->nr_pages) return -EINVAL; mm = current->mm; dprintk ("map_user_kiobuf: begin\n"); ptr = va & PAGE_MASK; end = (va + len + PAGE_SIZE - 1) & PAGE_MASK; err = expand_kiobuf(iobuf, (end - ptr) >> PAGE_SHIFT); if (err) return err; down(&mm->mmap_sem); err = -EFAULT; iobuf->locked = 0; iobuf->offset = va & ~PAGE_MASK; iobuf->length = len; i = 0; /* * First of all, try to fault in all of the necessary pages */ while (ptr < end) { if (!vma || ptr >= vma->vm_end) { vma = find_vma(current->mm, ptr); if (!vma) goto out_unlock; if (vma->vm_start > ptr) { if (!(vma->vm_flags & VM_GROWSDOWN)) goto out_unlock; if (expand_stack(vma, ptr)) goto out_unlock; } if (((datain) && (!(vma->vm_flags & VM_WRITE))) || (!(vma->vm_flags & VM_READ))) { err = -EACCES; goto out_unlock; } } if (handle_mm_fault(current->mm, vma, ptr, datain) <= 0) goto out_unlock; spin_lock(&mm->page_table_lock); map = follow_page(ptr); if (!map) { spin_unlock(&mm->page_table_lock); dprintk (KERN_ERR "Missing page in map_user_kiobuf\n"); goto out_unlock; } map = get_page_map(map); if (map) atomic_inc(&map->count); else printk (KERN_INFO "Mapped page missing [%d]\n", i); spin_unlock(&mm->page_table_lock); iobuf->maplist[i] = map; iobuf->nr_pages = ++i; ptr += PAGE_SIZE; } up(&mm->mmap_sem); dprintk ("map_user_kiobuf: end OK\n"); return 0; out_unlock: up(&mm->mmap_sem); unmap_kiobuf(iobuf); dprintk ("map_user_kiobuf: end %d\n", err); return err; } /* * Unmap all of the pages referenced by a kiobuf. We release the pages, * and unlock them if they were locked. */ void unmap_kiobuf (struct kiobuf *iobuf) { int i; struct page *map; for (i = 0; i < iobuf->nr_pages; i++) { map = iobuf->maplist[i]; if (map) { if (iobuf->locked) UnlockPage(map); __free_page(map); } } iobuf->nr_pages = 0; iobuf->locked = 0; } /* * Lock down all of the pages of a kiovec for IO. * * If any page is mapped twice in the kiovec, we return the error -EINVAL. * * The optional wait parameter causes the lock call to block until all * pages can be locked if set. If wait==0, the lock operation is * aborted if any locked pages are found and -EAGAIN is returned. */ int lock_kiovec(int nr, struct kiobuf *iovec[], int wait) { struct kiobuf *iobuf; int i, j; struct page *page, **ppage; int doublepage = 0; int repeat = 0; repeat: for (i = 0; i < nr; i++) { iobuf = iovec[i]; if (iobuf->locked) continue; iobuf->locked = 1; ppage = iobuf->maplist; for (j = 0; j < iobuf->nr_pages; ppage++, j++) { page = *ppage; if (!page) continue; if (TryLockPage(page)) goto retry; } } return 0; retry: /* * We couldn't lock one of the pages. Undo the locking so far, * wait on the page we got to, and try again. */ unlock_kiovec(nr, iovec); if (!wait) return -EAGAIN; /* * Did the release also unlock the page we got stuck on? */ if (!PageLocked(page)) { /* * If so, we may well have the page mapped twice * in the IO address range. Bad news. Of * course, it _might_ just be a coincidence, * but if it happens more than once, chances * are we have a double-mapped page. */ if (++doublepage >= 3) return -EINVAL; /* Try again... */ wait_on_page(page); } if (++repeat < 16) goto repeat; return -EAGAIN; } /* * Unlock all of the pages of a kiovec after IO. */ int unlock_kiovec(int nr, struct kiobuf *iovec[]) { struct kiobuf *iobuf; int i, j; struct page *page, **ppage; for (i = 0; i < nr; i++) { iobuf = iovec[i]; if (!iobuf->locked) continue; iobuf->locked = 0; ppage = iobuf->maplist; for (j = 0; j < iobuf->nr_pages; ppage++, j++) { page = *ppage; if (!page) continue; UnlockPage(page); } } return 0; } static inline void zeromap_pte_range(pte_t * pte, unsigned long address, unsigned long size, pgprot_t prot) { unsigned long end; address &= ~PMD_MASK; end = address + size; if (end > PMD_SIZE) end = PMD_SIZE; do { pte_t zero_pte = pte_wrprotect(mk_pte(ZERO_PAGE(address), prot)); pte_t oldpage = *pte; set_pte(pte, zero_pte); forget_pte(oldpage); address += PAGE_SIZE; pte++; } while (address && (address < end)); } static inline int zeromap_pmd_range(pmd_t * pmd, unsigned long address, unsigned long size, pgprot_t prot) { unsigned long end; address &= ~PGDIR_MASK; end = address + size; if (end > PGDIR_SIZE) end = PGDIR_SIZE; do { pte_t * pte = pte_alloc(pmd, address); if (!pte) return -ENOMEM; zeromap_pte_range(pte, address, end - address, prot); address = (address + PMD_SIZE) & PMD_MASK; pmd++; } while (address && (address < end)); return 0; } int zeromap_page_range(unsigned long address, unsigned long size, pgprot_t prot) { int error = 0; pgd_t * dir; unsigned long beg = address; unsigned long end = address + size; dir = pgd_offset(current->mm, address); flush_cache_range(current->mm, beg, end); if (address >= end) BUG(); do { pmd_t *pmd = pmd_alloc(dir, address); error = -ENOMEM; if (!pmd) break; error = zeromap_pmd_range(pmd, address, end - address, prot); if (error) break; address = (address + PGDIR_SIZE) & PGDIR_MASK; dir++; } while (address && (address < end)); flush_tlb_range(current->mm, beg, end); return error; } /* * maps a range of physical memory into the requested pages. the old * mappings are removed. any references to nonexistent pages results * in null mappings (currently treated as "copy-on-access") */ static inline void remap_pte_range(pte_t * pte, unsigned long address, unsigned long size, unsigned long phys_addr, pgprot_t prot) { unsigned long end; address &= ~PMD_MASK; end = address + size; if (end > PMD_SIZE) end = PMD_SIZE; do { struct page *page; pte_t oldpage = *pte; pte_clear(pte); page = virt_to_page(__va(phys_addr)); if ((!VALID_PAGE(page)) || PageReserved(page)) set_pte(pte, mk_pte_phys(phys_addr, prot)); forget_pte(oldpage); address += PAGE_SIZE; phys_addr += PAGE_SIZE; pte++; } while (address && (address < end)); } static inline int remap_pmd_range(pmd_t * pmd, unsigned long address, unsigned long size, unsigned long phys_addr, pgprot_t prot) { unsigned long end; address &= ~PGDIR_MASK; end = address + size; if (end > PGDIR_SIZE) end = PGDIR_SIZE; phys_addr -= address; do { pte_t * pte = pte_alloc(pmd, address); if (!pte) return -ENOMEM; remap_pte_range(pte, address, end - address, address + phys_addr, prot); address = (address + PMD_SIZE) & PMD_MASK; pmd++; } while (address && (address < end)); return 0; } int remap_page_range(unsigned long from, unsigned long phys_addr, unsigned long size, pgprot_t prot) { int error = 0; pgd_t * dir; unsigned long beg = from; unsigned long end = from + size; phys_addr -= from; dir = pgd_offset(current->mm, from); flush_cache_range(current->mm, beg, end); if (from >= end) BUG(); do { pmd_t *pmd = pmd_alloc(dir, from); error = -ENOMEM; if (!pmd) break; error = remap_pmd_range(pmd, from, end - from, phys_addr + from, prot); if (error) break; from = (from + PGDIR_SIZE) & PGDIR_MASK; dir++; } while (from && (from < end)); flush_tlb_range(current->mm, beg, end); return error; } /* * Establish a new mapping: * - flush the old one * - update the page tables * - inform the TLB about the new one */ static inline void establish_pte(struct vm_area_struct * vma, unsigned long address, pte_t *page_table, pte_t entry) { flush_tlb_page(vma, address); set_pte(page_table, entry); update_mmu_cache(vma, address, entry); } static inline void break_cow(struct vm_area_struct * vma, struct page * old_page, struct page * new_page, unsigned long address, pte_t *page_table) { copy_cow_page(old_page,new_page,address); flush_page_to_ram(new_page); flush_cache_page(vma, address); establish_pte(vma, address, page_table, pte_mkwrite(pte_mkdirty(mk_pte(new_page, vma->vm_page_prot)))); } /* * This routine handles present pages, when users try to write * to a shared page. It is done by copying the page to a new address * and decrementing the shared-page counter for the old page. * * Goto-purists beware: the only reason for goto's here is that it results * in better assembly code.. The "default" path will see no jumps at all. * * Note that this routine assumes that the protection checks have been * done by the caller (the low-level page fault routine in most cases). * Thus we can safely just mark it writable once we've done any necessary * COW. * * We also mark the page dirty at this point even though the page will * change only once the write actually happens. This avoids a few races, * and potentially makes it more efficient. * * We enter with the page table read-lock held, and need to exit without * it. */ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma, unsigned long address, pte_t *page_table, pte_t pte) { struct page *old_page, *new_page; old_page = pte_page(pte); if (!VALID_PAGE(old_page)) goto bad_wp_page; /* * We can avoid the copy if: * - we're the only user (count == 1) * - the only other user is the swap cache, * and the only swap cache user is itself, * in which case we can remove the page * from the swap cache. */ switch (page_count(old_page)) { case 2: /* * Lock the page so that no one can look it up from * the swap cache, grab a reference and start using it. * Can not do lock_page, holding page_table_lock. */ if (!PageSwapCache(old_page) || TryLockPage(old_page)) break; if (is_page_shared(old_page)) { UnlockPage(old_page); break; } delete_from_swap_cache_nolock(old_page); UnlockPage(old_page); /* FallThrough */ case 1: flush_cache_page(vma, address); establish_pte(vma, address, page_table, pte_mkyoung(pte_mkdirty(pte_mkwrite(pte)))); spin_unlock(&mm->page_table_lock); return 1; /* Minor fault */ } /* * Ok, we need to copy. Oh, well.. */ spin_unlock(&mm->page_table_lock); new_page = page_cache_alloc(); if (!new_page) return -1; spin_lock(&mm->page_table_lock); /* * Re-check the pte - we dropped the lock */ if (pte_val(*page_table) == pte_val(pte)) { if (PageReserved(old_page)) ++mm->rss; break_cow(vma, old_page, new_page, address, page_table); /* Free the old page.. */ new_page = old_page; } spin_unlock(&mm->page_table_lock); page_cache_release(new_page); return 1; /* Minor fault */ bad_wp_page: spin_unlock(&mm->page_table_lock); printk("do_wp_page: bogus page at address %08lx (page 0x%lx)\n",address,(unsigned long)old_page); return -1; } /* * This function zeroes out partial mmap'ed pages at truncation time.. */ static void partial_clear(struct vm_area_struct *vma, unsigned long address) { unsigned int offset; struct page *page; pgd_t *page_dir; pmd_t *page_middle; pte_t *page_table, pte; page_dir = pgd_offset(vma->vm_mm, address); if (pgd_none(*page_dir)) return; if (pgd_bad(*page_dir)) { pgd_ERROR(*page_dir); pgd_clear(page_dir); return; } page_middle = pmd_offset(page_dir, address); if (pmd_none(*page_middle)) return; if (pmd_bad(*page_middle)) { pmd_ERROR(*page_middle); pmd_clear(page_middle); return; } page_table = pte_offset(page_middle, address); pte = *page_table; if (!pte_present(pte)) return; flush_cache_page(vma, address); page = pte_page(pte); if ((!VALID_PAGE(page)) || PageReserved(page)) return; offset = address & ~PAGE_MASK; memclear_highpage_flush(page, offset, PAGE_SIZE - offset); } /* * Handle all mappings that got truncated by a "truncate()" * system call. * * NOTE! We have to be ready to update the memory sharing * between the file and the memory map for a potential last * incomplete page. Ugly, but necessary. */ void vmtruncate(struct inode * inode, loff_t offset) { unsigned long partial, pgoff; struct vm_area_struct * mpnt; struct address_space *mapping = inode->i_mapping; unsigned long limit; if (inode->i_size < offset) goto do_expand; inode->i_size = offset; truncate_inode_pages(mapping, offset); spin_lock(&mapping->i_shared_lock); if (!mapping->i_mmap) goto out_unlock; pgoff = (offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; partial = (unsigned long)offset & (PAGE_CACHE_SIZE - 1); mpnt = mapping->i_mmap; do { struct mm_struct *mm = mpnt->vm_mm; unsigned long start = mpnt->vm_start; unsigned long end = mpnt->vm_end; unsigned long len = end - start; unsigned long diff; /* mapping wholly truncated? */ if (mpnt->vm_pgoff >= pgoff) { flush_cache_range(mm, start, end); zap_page_range(mm, start, len); flush_tlb_range(mm, start, end); continue; } /* mapping wholly unaffected? */ len = len >> PAGE_SHIFT; diff = pgoff - mpnt->vm_pgoff; if (diff >= len) continue; /* Ok, partially affected.. */ start += diff << PAGE_SHIFT; len = (len - diff) << PAGE_SHIFT; if (start & ~PAGE_MASK) { partial_clear(mpnt, start); start = (start + ~PAGE_MASK) & PAGE_MASK; } flush_cache_range(mm, start, end); zap_page_range(mm, start, len); flush_tlb_range(mm, start, end); } while ((mpnt = mpnt->vm_next_share) != NULL); out_unlock: spin_unlock(&mapping->i_shared_lock); /* this should go into ->truncate */ inode->i_size = offset; if (inode->i_op && inode->i_op->truncate) inode->i_op->truncate(inode); return; do_expand: limit = current->rlim[RLIMIT_FSIZE].rlim_cur; if (limit != RLIM_INFINITY) { if (inode->i_size >= limit) { send_sig(SIGXFSZ, current, 0); goto out; } if (offset > limit) { send_sig(SIGXFSZ, current, 0); offset = limit; } } inode->i_size = offset; if (inode->i_op && inode->i_op->truncate) inode->i_op->truncate(inode); out: return; } /* * Primitive swap readahead code. We simply read an aligned block of * (1 << page_cluster) entries in the swap area. This method is chosen * because it doesn't cost us any seek time. We also make sure to queue * the 'original' request together with the readahead ones... */ void swapin_readahead(swp_entry_t entry) { int i, num; struct page *new_page; unsigned long offset; /* * Get the number of handles we should do readahead io to. Also, * grab temporary references on them, releasing them as io completes. */ num = valid_swaphandles(entry, &offset); for (i = 0; i < num; offset++, i++) { /* Don't block on I/O for read-ahead */ if (atomic_read(&nr_async_pages) >= pager_daemon.swap_cluster) { while (i++ < num) swap_free(SWP_ENTRY(SWP_TYPE(entry), offset++)); break; } /* Ok, do the async read-ahead now */ new_page = read_swap_cache_async(SWP_ENTRY(SWP_TYPE(entry), offset), 0); if (new_page != NULL) page_cache_release(new_page); swap_free(SWP_ENTRY(SWP_TYPE(entry), offset)); } return; } static int do_swap_page(struct mm_struct * mm, struct vm_area_struct * vma, unsigned long address, pte_t * page_table, swp_entry_t entry, int write_access) { struct page *page = lookup_swap_cache(entry); pte_t pte; if (!page) { lock_kernel(); swapin_readahead(entry); page = read_swap_cache(entry); unlock_kernel(); if (!page) return -1; flush_page_to_ram(page); flush_icache_page(vma, page, address); } mm->rss++; pte = mk_pte(page, vma->vm_page_prot); /* * Freeze the "shared"ness of the page, ie page_count + swap_count. * Must lock page before transferring our swap count to already * obtained page count. */ lock_page(page); swap_free(entry); if (write_access && !is_page_shared(page)) { delete_from_swap_cache_nolock(page); UnlockPage(page); page = replace_with_highmem(page); pte = mk_pte(page, vma->vm_page_prot); pte = pte_mkwrite(pte_mkdirty(pte)); } else UnlockPage(page); set_pte(page_table, pte); /* No need to invalidate - it was non-present before */ update_mmu_cache(vma, address, pte); return 1; /* Minor fault */ } /* * This only needs the MM semaphore */ static int do_anonymous_page(struct mm_struct * mm, struct vm_area_struct * vma, pte_t *page_table, int write_access, unsigned long addr) { int high = 0; struct page *page = NULL; pte_t entry = pte_wrprotect(mk_pte(ZERO_PAGE(addr), vma->vm_page_prot)); if (write_access) { page = alloc_page(GFP_HIGHUSER); if (!page) return -1; if (PageHighMem(page)) high = 1; clear_user_highpage(page, addr); entry = pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot))); mm->rss++; flush_page_to_ram(page); } set_pte(page_table, entry); /* No need to invalidate - it was non-present before */ update_mmu_cache(vma, addr, entry); return 1; /* Minor fault */ } /* * do_no_page() tries to create a new page mapping. It aggressively * tries to share with existing pages, but makes a separate copy if * the "write_access" parameter is true in order to avoid the next * page fault. * * As this is called only for pages that do not currently exist, we * do not need to flush old virtual caches or the TLB. * * This is called with the MM semaphore held. */ static int do_no_page(struct mm_struct * mm, struct vm_area_struct * vma, unsigned long address, int write_access, pte_t *page_table) { struct page * new_page; pte_t entry; if (!vma->vm_ops || !vma->vm_ops->nopage) return do_anonymous_page(mm, vma, page_table, write_access, address); /* * The third argument is "no_share", which tells the low-level code * to copy, not share the page even if sharing is possible. It's * essentially an early COW detection. */ new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, (vma->vm_flags & VM_SHARED)?0:write_access); if (new_page == NULL) /* no page was available -- SIGBUS */ return 0; if (new_page == NOPAGE_OOM) return -1; ++mm->rss; /* * This silly early PAGE_DIRTY setting removes a race * due to the bad i386 page protection. But it's valid * for other architectures too. * * Note that if write_access is true, we either now have * an exclusive copy of the page, or this is a shared mapping, * so we can make it writable and dirty to avoid having to * handle that later. */ flush_page_to_ram(new_page); flush_icache_page(vma, new_page, address); entry = mk_pte(new_page, vma->vm_page_prot); if (write_access) { entry = pte_mkwrite(pte_mkdirty(entry)); } else if (page_count(new_page) > 1 && !(vma->vm_flags & VM_SHARED)) entry = pte_wrprotect(entry); set_pte(page_table, entry); /* no need to invalidate: a not-present page shouldn't be cached */ update_mmu_cache(vma, address, entry); return 2; /* Major fault */ } /* * These routines also need to handle stuff like marking pages dirty * and/or accessed for architectures that don't do it in hardware (most * RISC architectures). The early dirtying is also good on the i386. * * There is also a hook called "update_mmu_cache()" that architectures * with external mmu caches can use to update those (ie the Sparc or * PowerPC hashed page tables that act as extended TLBs). * * Note the "page_table_lock". It is to protect against kswapd removing * pages from under us. Note that kswapd only ever _removes_ pages, never * adds them. As such, once we have noticed that the page is not present, * we can drop the lock early. * * The adding of pages is protected by the MM semaphore (which we hold), * so we don't need to worry about a page being suddenly been added into * our VM. */ static inline int handle_pte_fault(struct mm_struct *mm, struct vm_area_struct * vma, unsigned long address, int write_access, pte_t * pte) { pte_t entry; entry = *pte; if (!pte_present(entry)) { if (pte_none(entry)) return do_no_page(mm, vma, address, write_access, pte); return do_swap_page(mm, vma, address, pte, pte_to_swp_entry(entry), write_access); } /* * Ok, the entry was present, we need to get the page table * lock to synchronize with kswapd, and verify that the entry * didn't change from under us.. */ spin_lock(&mm->page_table_lock); if (pte_val(entry) == pte_val(*pte)) { if (write_access) { if (!pte_write(entry)) return do_wp_page(mm, vma, address, pte, entry); entry = pte_mkdirty(entry); } entry = pte_mkyoung(entry); establish_pte(vma, address, pte, entry); } spin_unlock(&mm->page_table_lock); return 1; } /* * By the time we get here, we already hold the mm semaphore */ int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma, unsigned long address, int write_access) { int ret = -1; pgd_t *pgd; pmd_t *pmd; pgd = pgd_offset(mm, address); pmd = pmd_alloc(pgd, address); if (pmd) { pte_t * pte = pte_alloc(pmd, address); if (pte) ret = handle_pte_fault(mm, vma, address, write_access, pte); } return ret; } /* * Simplistic page force-in.. */ int make_pages_present(unsigned long addr, unsigned long end) { int write; struct mm_struct *mm = current->mm; struct vm_area_struct * vma; vma = find_vma(mm, addr); write = (vma->vm_flags & VM_WRITE) != 0; if (addr >= end) BUG(); do { if (handle_mm_fault(mm, vma, addr, write) < 0) return -1; addr += PAGE_SIZE; } while (addr < end); return 0; }