From 65500d234e74fc4e8f18e1a429bc24e51e75de4a Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Sat, 29 Oct 2005 18:15:59 -0700 Subject: [PATCH] [PATCH] mm: page fault handlers tidyup Impose a little more consistency on the page fault handlers do_wp_page, do_swap_page, do_anonymous_page, do_no_page, do_file_page: why not pass their arguments in the same order, called the same names? break_cow is all very well, but what it did was inlined elsewhere: easier to compare if it's brought back into do_wp_page. do_file_page's fallback to do_no_page dates from a time when we were testing pte_file by using it wherever possible: currently it's peculiar to nonlinear vmas, so just check that. BUG_ON if not? Better not, it's probably page table corruption, so just show the pte: hmm, there's a pte_ERROR macro, let's use that for do_wp_page's invalid pfn too. Hah! Someone in the ppc64 world noticed pte_ERROR was unused so removed it: restored (and say "pud" not "pmd" in its pud_ERROR). Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-ppc64/pgtable.h | 4 +- mm/filemap.c | 2 +- mm/memory.c | 220 +++++++++++++++++++------------------------- mm/shmem.c | 2 +- 4 files changed, 102 insertions(+), 126 deletions(-) diff --git a/include/asm-ppc64/pgtable.h b/include/asm-ppc64/pgtable.h index c83679c..2eb1778 100644 --- a/include/asm-ppc64/pgtable.h +++ b/include/asm-ppc64/pgtable.h @@ -478,10 +478,12 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long addr, #define __HAVE_ARCH_PTE_SAME #define pte_same(A,B) (((pte_val(A) ^ pte_val(B)) & ~_PAGE_HPTEFLAGS) == 0) +#define pte_ERROR(e) \ + printk("%s:%d: bad pte %08lx.\n", __FILE__, __LINE__, pte_val(e)) #define pmd_ERROR(e) \ printk("%s:%d: bad pmd %08lx.\n", __FILE__, __LINE__, pmd_val(e)) #define pud_ERROR(e) \ - printk("%s:%d: bad pmd %08lx.\n", __FILE__, __LINE__, pud_val(e)) + printk("%s:%d: bad pud %08lx.\n", __FILE__, __LINE__, pud_val(e)) #define pgd_ERROR(e) \ printk("%s:%d: bad pgd %08lx.\n", __FILE__, __LINE__, pgd_val(e)) diff --git a/mm/filemap.c b/mm/filemap.c index 1c31b2f..8aa344e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1520,7 +1520,7 @@ repeat: page_cache_release(page); return err; } - } else { + } else if (vma->vm_flags & VM_NONLINEAR) { /* No page was found just because we can't read it in now (being * here implies nonblock != 0), but the page may exist, so set * the PTE to fault it in later. */ diff --git a/mm/memory.c b/mm/memory.c index 1366768..eaf7903 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1213,28 +1213,10 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) } /* - * We hold the mm semaphore for reading and vma->vm_mm->page_table_lock - */ -static inline void break_cow(struct vm_area_struct * vma, struct page * new_page, unsigned long address, - pte_t *page_table) -{ - pte_t entry; - - entry = maybe_mkwrite(pte_mkdirty(mk_pte(new_page, vma->vm_page_prot)), - vma); - ptep_establish(vma, address, page_table, entry); - update_mmu_cache(vma, address, entry); - lazy_mmu_prot_update(entry); -} - -/* * 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 @@ -1247,25 +1229,22 @@ static inline void break_cow(struct vm_area_struct * vma, struct page * new_page * We hold the mm semaphore and the page_table_lock on entry and exit * with the page_table_lock released. */ -static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma, - unsigned long address, pte_t *page_table, pmd_t *pmd, pte_t pte) +static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pte_t *page_table, pmd_t *pmd, + pte_t orig_pte) { struct page *old_page, *new_page; - unsigned long pfn = pte_pfn(pte); + unsigned long pfn = pte_pfn(orig_pte); pte_t entry; - int ret; + int ret = VM_FAULT_MINOR; if (unlikely(!pfn_valid(pfn))) { /* - * This should really halt the system so it can be debugged or - * at least the kernel stops what it's doing before it corrupts - * data, but for the moment just pretend this is OOM. + * Page table corrupted: show pte and kill process. */ - pte_unmap(page_table); - printk(KERN_ERR "do_wp_page: bogus page at address %08lx\n", - address); - spin_unlock(&mm->page_table_lock); - return VM_FAULT_OOM; + pte_ERROR(orig_pte); + ret = VM_FAULT_OOM; + goto unlock; } old_page = pfn_to_page(pfn); @@ -1274,52 +1253,57 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma, unlock_page(old_page); if (reuse) { flush_cache_page(vma, address, pfn); - entry = maybe_mkwrite(pte_mkyoung(pte_mkdirty(pte)), - vma); + entry = pte_mkyoung(orig_pte); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); ptep_set_access_flags(vma, address, page_table, entry, 1); update_mmu_cache(vma, address, entry); lazy_mmu_prot_update(entry); - pte_unmap(page_table); - spin_unlock(&mm->page_table_lock); - return VM_FAULT_MINOR|VM_FAULT_WRITE; + ret |= VM_FAULT_WRITE; + goto unlock; } } - pte_unmap(page_table); /* * Ok, we need to copy. Oh, well.. */ if (!PageReserved(old_page)) page_cache_get(old_page); + pte_unmap(page_table); spin_unlock(&mm->page_table_lock); if (unlikely(anon_vma_prepare(vma))) - goto no_new_page; + goto oom; if (old_page == ZERO_PAGE(address)) { new_page = alloc_zeroed_user_highpage(vma, address); if (!new_page) - goto no_new_page; + goto oom; } else { new_page = alloc_page_vma(GFP_HIGHUSER, vma, address); if (!new_page) - goto no_new_page; + goto oom; copy_user_highpage(new_page, old_page, address); } + /* * Re-check the pte - we dropped the lock */ - ret = VM_FAULT_MINOR; spin_lock(&mm->page_table_lock); page_table = pte_offset_map(pmd, address); - if (likely(pte_same(*page_table, pte))) { + if (likely(pte_same(*page_table, orig_pte))) { if (PageAnon(old_page)) dec_mm_counter(mm, anon_rss); if (PageReserved(old_page)) inc_mm_counter(mm, rss); else page_remove_rmap(old_page); + flush_cache_page(vma, address, pfn); - break_cow(vma, new_page, address, page_table); + entry = mk_pte(new_page, vma->vm_page_prot); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + ptep_establish(vma, address, page_table, entry); + update_mmu_cache(vma, address, entry); + lazy_mmu_prot_update(entry); + lru_cache_add_active(new_page); page_add_anon_rmap(new_page, vma, address); @@ -1327,13 +1311,13 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma, new_page = old_page; ret |= VM_FAULT_WRITE; } - pte_unmap(page_table); page_cache_release(new_page); page_cache_release(old_page); +unlock: + pte_unmap(page_table); spin_unlock(&mm->page_table_lock); return ret; - -no_new_page: +oom: page_cache_release(old_page); return VM_FAULT_OOM; } @@ -1661,17 +1645,19 @@ void swapin_readahead(swp_entry_t entry, unsigned long addr,struct vm_area_struc * We hold the mm semaphore and the page_table_lock on entry and * should release the pagetable lock on exit.. */ -static int do_swap_page(struct mm_struct * mm, - struct vm_area_struct * vma, unsigned long address, - pte_t *page_table, pmd_t *pmd, pte_t orig_pte, int write_access) +static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pte_t *page_table, pmd_t *pmd, + int write_access, pte_t orig_pte) { struct page *page; - swp_entry_t entry = pte_to_swp_entry(orig_pte); + swp_entry_t entry; pte_t pte; int ret = VM_FAULT_MINOR; pte_unmap(page_table); spin_unlock(&mm->page_table_lock); + + entry = pte_to_swp_entry(orig_pte); page = lookup_swap_cache(entry); if (!page) { swapin_readahead(entry, address, vma); @@ -1685,11 +1671,7 @@ static int do_swap_page(struct mm_struct * mm, page_table = pte_offset_map(pmd, address); if (likely(pte_same(*page_table, orig_pte))) ret = VM_FAULT_OOM; - else - ret = VM_FAULT_MINOR; - pte_unmap(page_table); - spin_unlock(&mm->page_table_lock); - goto out; + goto unlock; } /* Had to read the page from swap area: Major fault */ @@ -1745,6 +1727,7 @@ static int do_swap_page(struct mm_struct * mm, /* No need to invalidate - it was non-present before */ update_mmu_cache(vma, address, pte); lazy_mmu_prot_update(pte); +unlock: pte_unmap(page_table); spin_unlock(&mm->page_table_lock); out: @@ -1754,7 +1737,7 @@ out_nomap: spin_unlock(&mm->page_table_lock); unlock_page(page); page_cache_release(page); - goto out; + return ret; } /* @@ -1762,17 +1745,15 @@ out_nomap: * spinlock held to protect against concurrent faults in * multithreaded programs. */ -static int -do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, - pte_t *page_table, pmd_t *pmd, int write_access, - unsigned long addr) +static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pte_t *page_table, pmd_t *pmd, + int write_access) { pte_t entry; /* Mapping of ZERO_PAGE - vm_page_prot is readonly */ entry = mk_pte(ZERO_PAGE(addr), vma->vm_page_prot); - /* ..except if it's a write access */ if (write_access) { struct page *page; @@ -1781,39 +1762,36 @@ do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, spin_unlock(&mm->page_table_lock); if (unlikely(anon_vma_prepare(vma))) - goto no_mem; - page = alloc_zeroed_user_highpage(vma, addr); + goto oom; + page = alloc_zeroed_user_highpage(vma, address); if (!page) - goto no_mem; + goto oom; spin_lock(&mm->page_table_lock); - page_table = pte_offset_map(pmd, addr); + page_table = pte_offset_map(pmd, address); if (!pte_none(*page_table)) { - pte_unmap(page_table); page_cache_release(page); - spin_unlock(&mm->page_table_lock); - goto out; + goto unlock; } inc_mm_counter(mm, rss); - entry = maybe_mkwrite(pte_mkdirty(mk_pte(page, - vma->vm_page_prot)), - vma); + entry = mk_pte(page, vma->vm_page_prot); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); lru_cache_add_active(page); SetPageReferenced(page); - page_add_anon_rmap(page, vma, addr); + page_add_anon_rmap(page, vma, address); } - set_pte_at(mm, addr, page_table, entry); - pte_unmap(page_table); + set_pte_at(mm, address, page_table, entry); /* No need to invalidate - it was non-present before */ - update_mmu_cache(vma, addr, entry); + update_mmu_cache(vma, address, entry); lazy_mmu_prot_update(entry); +unlock: + pte_unmap(page_table); spin_unlock(&mm->page_table_lock); -out: return VM_FAULT_MINOR; -no_mem: +oom: return VM_FAULT_OOM; } @@ -1829,20 +1807,17 @@ no_mem: * This is called with the MM semaphore held and the page table * spinlock held. Exit with the spinlock released. */ -static int -do_no_page(struct mm_struct *mm, struct vm_area_struct *vma, - unsigned long address, int write_access, pte_t *page_table, pmd_t *pmd) +static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pte_t *page_table, pmd_t *pmd, + int write_access) { - struct page * new_page; + struct page *new_page; struct address_space *mapping = NULL; pte_t entry; unsigned int sequence = 0; int ret = VM_FAULT_MINOR; int anon = 0; - if (!vma->vm_ops || !vma->vm_ops->nopage) - return do_anonymous_page(mm, vma, page_table, - pmd, write_access, address); pte_unmap(page_table); spin_unlock(&mm->page_table_lock); @@ -1852,7 +1827,6 @@ do_no_page(struct mm_struct *mm, struct vm_area_struct *vma, smp_rmb(); /* serializes i_size against truncate_count */ } retry: - cond_resched(); new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, &ret); /* * No smp_rmb is needed here as long as there's a full @@ -1892,9 +1866,11 @@ retry: * retry getting the page. */ if (mapping && unlikely(sequence != mapping->truncate_count)) { - sequence = mapping->truncate_count; spin_unlock(&mm->page_table_lock); page_cache_release(new_page); + cond_resched(); + sequence = mapping->truncate_count; + smp_rmb(); goto retry; } page_table = pte_offset_map(pmd, address); @@ -1924,25 +1900,22 @@ retry: page_add_anon_rmap(new_page, vma, address); } else page_add_file_rmap(new_page); - pte_unmap(page_table); } else { /* One of our sibling threads was faster, back out. */ - pte_unmap(page_table); page_cache_release(new_page); - spin_unlock(&mm->page_table_lock); - goto out; + goto unlock; } /* no need to invalidate: a not-present page shouldn't be cached */ update_mmu_cache(vma, address, entry); lazy_mmu_prot_update(entry); +unlock: + pte_unmap(page_table); spin_unlock(&mm->page_table_lock); -out: return ret; oom: page_cache_release(new_page); - ret = VM_FAULT_OOM; - goto out; + return VM_FAULT_OOM; } /* @@ -1950,29 +1923,28 @@ oom: * from the encoded file_pte if possible. This enables swappable * nonlinear vmas. */ -static int do_file_page(struct mm_struct * mm, struct vm_area_struct * vma, - unsigned long address, int write_access, pte_t *pte, pmd_t *pmd) +static int do_file_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pte_t *page_table, pmd_t *pmd, + int write_access, pte_t orig_pte) { - unsigned long pgoff; + pgoff_t pgoff; int err; - BUG_ON(!vma->vm_ops || !vma->vm_ops->nopage); - /* - * Fall back to the linear mapping if the fs does not support - * ->populate: - */ - if (!vma->vm_ops->populate || - (write_access && !(vma->vm_flags & VM_SHARED))) { - pte_clear(mm, address, pte); - return do_no_page(mm, vma, address, write_access, pte, pmd); - } - - pgoff = pte_to_pgoff(*pte); - - pte_unmap(pte); + pte_unmap(page_table); spin_unlock(&mm->page_table_lock); - err = vma->vm_ops->populate(vma, address & PAGE_MASK, PAGE_SIZE, vma->vm_page_prot, pgoff, 0); + if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) { + /* + * Page table corrupted: show pte and kill process. + */ + pte_ERROR(orig_pte); + return VM_FAULT_OOM; + } + /* We can then assume vm->vm_ops && vma->vm_ops->populate */ + + pgoff = pte_to_pgoff(orig_pte); + err = vma->vm_ops->populate(vma, address & PAGE_MASK, PAGE_SIZE, + vma->vm_page_prot, pgoff, 0); if (err == -ENOMEM) return VM_FAULT_OOM; if (err) @@ -2002,23 +1974,25 @@ static int do_file_page(struct mm_struct * mm, struct vm_area_struct * vma, * release it when done. */ static inline int handle_pte_fault(struct mm_struct *mm, - struct vm_area_struct * vma, unsigned long address, - int write_access, pte_t *pte, pmd_t *pmd) + struct vm_area_struct *vma, unsigned long address, + pte_t *pte, pmd_t *pmd, int write_access) { pte_t entry; entry = *pte; if (!pte_present(entry)) { - /* - * If it truly wasn't present, we know that kswapd - * and the PTE updates will not touch it later. So - * drop the lock. - */ - if (pte_none(entry)) - return do_no_page(mm, vma, address, write_access, pte, pmd); + if (pte_none(entry)) { + if (!vma->vm_ops || !vma->vm_ops->nopage) + return do_anonymous_page(mm, vma, address, + pte, pmd, write_access); + return do_no_page(mm, vma, address, + pte, pmd, write_access); + } if (pte_file(entry)) - return do_file_page(mm, vma, address, write_access, pte, pmd); - return do_swap_page(mm, vma, address, pte, pmd, entry, write_access); + return do_file_page(mm, vma, address, + pte, pmd, write_access, entry); + return do_swap_page(mm, vma, address, + pte, pmd, write_access, entry); } if (write_access) { @@ -2038,7 +2012,7 @@ static inline int handle_pte_fault(struct mm_struct *mm, /* * 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, +int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access) { pgd_t *pgd; @@ -2072,7 +2046,7 @@ int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma, if (!pte) goto oom; - return handle_pte_fault(mm, vma, address, write_access, pte, pmd); + return handle_pte_fault(mm, vma, address, pte, pmd, write_access); oom: spin_unlock(&mm->page_table_lock); diff --git a/mm/shmem.c b/mm/shmem.c index 55e04a0..6796311 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1201,7 +1201,7 @@ static int shmem_populate(struct vm_area_struct *vma, page_cache_release(page); return err; } - } else { + } else if (vma->vm_flags & VM_NONLINEAR) { /* No page was found just because we can't read it in * now (being here implies nonblock != 0), but the page * may exist, so set the PTE to fault it in later. */ -- 1.8.2.3