Replace pte_offset_map_lock() usage in the pagefault path with pte_map_lock() which when called with .flags & FAULT_FLAG_SPECULATIVE can fail, in which case we should return VM_FAULT_RETRY, meaning we need to retry the fault (or do one with mmap_sem held). This patch adds both FAULT_FLAG_SPECULATIVE, VM_FAULT_RETRY and the error paths. Signed-off-by: Peter Zijlstra --- include/linux/mm.h | 2 mm/memory.c | 119 ++++++++++++++++++++++++++++++++++++++--------------- 2 files changed, 88 insertions(+), 33 deletions(-) Index: linux-2.6/include/linux/mm.h =================================================================== --- linux-2.6.orig/include/linux/mm.h +++ linux-2.6/include/linux/mm.h @@ -136,6 +136,7 @@ extern pgprot_t protection_map[16]; #define FAULT_FLAG_WRITE 0x01 /* Fault was a write access */ #define FAULT_FLAG_NONLINEAR 0x02 /* Fault was via a nonlinear mapping */ #define FAULT_FLAG_MKWRITE 0x04 /* Fault was mkwrite of existing pte */ +#define FAULT_FLAG_SPECULATIVE 0x08 /* * This interface is used by x86 PAT code to identify a pfn mapping that is @@ -711,6 +712,7 @@ static inline int page_mapped(struct pag #define VM_FAULT_NOPAGE 0x0100 /* ->fault installed the pte, not return page */ #define VM_FAULT_LOCKED 0x0200 /* ->fault locked the returned page */ +#define VM_FAULT_RETRY 0x0400 #define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_HWPOISON) Index: linux-2.6/mm/memory.c =================================================================== --- linux-2.6.orig/mm/memory.c +++ linux-2.6/mm/memory.c @@ -1957,6 +1957,14 @@ static inline void cow_user_page(struct copy_user_highpage(dst, src, va, vma); } +static int pte_map_lock(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd, unsigned int flags, + pte_t **ptep, spinlock_t **ptl) +{ + *ptep = pte_offset_map_lock(mm, pmd, address, ptl); + return 1; +} + /* * 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 @@ -1977,7 +1985,7 @@ static inline void cow_user_page(struct */ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pte_t *page_table, pmd_t *pmd, - spinlock_t *ptl, pte_t orig_pte) + spinlock_t *ptl, unsigned int flags, pte_t orig_pte) { struct page *old_page, *new_page; pte_t entry; @@ -2009,8 +2017,14 @@ static int do_wp_page(struct mm_struct * page_cache_get(old_page); pte_unmap_unlock(page_table, ptl); lock_page(old_page); - page_table = pte_offset_map_lock(mm, pmd, address, - &ptl); + + if (!pte_map_lock(mm, vma, address, pmd, flags, + &page_table, &ptl)) { + unlock_page(old_page); + ret = VM_FAULT_RETRY; + goto err; + } + if (!pte_same(*page_table, orig_pte)) { unlock_page(old_page); page_cache_release(old_page); @@ -2052,14 +2066,14 @@ static int do_wp_page(struct mm_struct * if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) { ret = tmp; - goto unwritable_page; + goto err; } if (unlikely(!(tmp & VM_FAULT_LOCKED))) { lock_page(old_page); if (!old_page->mapping) { ret = 0; /* retry the fault */ unlock_page(old_page); - goto unwritable_page; + goto err; } } else VM_BUG_ON(!PageLocked(old_page)); @@ -2070,8 +2084,13 @@ static int do_wp_page(struct mm_struct * * they did, we just return, as we can count on the * MMU to tell us if they didn't also make it writable. */ - page_table = pte_offset_map_lock(mm, pmd, address, - &ptl); + if (!pte_map_lock(mm, vma, address, pmd, flags, + &page_table, &ptl)) { + unlock_page(old_page); + ret = VM_FAULT_RETRY; + goto err; + } + if (!pte_same(*page_table, orig_pte)) { unlock_page(old_page); page_cache_release(old_page); @@ -2103,17 +2122,23 @@ reuse: gotten: pte_unmap_unlock(page_table, ptl); - if (unlikely(anon_vma_prepare(vma))) - goto oom; + if (unlikely(anon_vma_prepare(vma))) { + ret = VM_FAULT_OOM; + goto err; + } if (is_zero_pfn(pte_pfn(orig_pte))) { new_page = alloc_zeroed_user_highpage_movable(vma, address); - if (!new_page) - goto oom; + if (!new_page) { + ret = VM_FAULT_OOM; + goto err; + } } else { new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); - if (!new_page) - goto oom; + if (!new_page) { + ret = VM_FAULT_OOM; + goto err; + } cow_user_page(new_page, old_page, address, vma); } __SetPageUptodate(new_page); @@ -2128,13 +2153,20 @@ gotten: unlock_page(old_page); } - if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)) - goto oom_free_new; + if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)) { + ret = VM_FAULT_OOM; + goto err_free_new; + } /* * Re-check the pte - we dropped the lock */ - page_table = pte_offset_map_lock(mm, pmd, address, &ptl); + if (!pte_map_lock(mm, vma, address, pmd, flags, &page_table, &ptl)) { + mem_cgroup_uncharge_page(new_page); + ret = VM_FAULT_RETRY; + goto err_free_new; + } + if (likely(pte_same(*page_table, orig_pte))) { if (old_page) { if (!PageAnon(old_page)) { @@ -2233,9 +2265,9 @@ unlock: file_update_time(vma->vm_file); } return ret; -oom_free_new: +err_free_new: page_cache_release(new_page); -oom: +err: if (old_page) { if (page_mkwrite) { unlock_page(old_page); @@ -2243,10 +2275,6 @@ oom: } page_cache_release(old_page); } - return VM_FAULT_OOM; - -unwritable_page: - page_cache_release(old_page); return ret; } @@ -2496,6 +2524,10 @@ static int do_swap_page(struct mm_struct entry = pte_to_swp_entry(orig_pte); if (unlikely(non_swap_entry(entry))) { if (is_migration_entry(entry)) { + if (flags & FAULT_FLAG_SPECULATIVE) { + ret = VM_FAULT_RETRY; + goto out; + } migration_entry_wait(mm, pmd, address); } else if (is_hwpoison_entry(entry)) { ret = VM_FAULT_HWPOISON; @@ -2516,7 +2548,11 @@ static int do_swap_page(struct mm_struct * Back out if somebody else faulted in this pte * while we released the pte lock. */ - page_table = pte_offset_map_lock(mm, pmd, address, &ptl); + if (!pte_map_lock(mm, vma, address, pmd, flags, + &page_table, &ptl)) { + ret = VM_FAULT_RETRY; + goto out; + } if (likely(pte_same(*page_table, orig_pte))) ret = VM_FAULT_OOM; delayacct_clear_flag(DELAYACCT_PF_SWAPIN); @@ -2553,7 +2589,11 @@ static int do_swap_page(struct mm_struct /* * Back out if somebody else already faulted in this pte. */ - page_table = pte_offset_map_lock(mm, pmd, address, &ptl); + if (!pte_map_lock(mm, vma, address, pmd, flags, &page_table, &ptl)) { + ret = VM_FAULT_RETRY; + goto out_nolock; + } + if (unlikely(!pte_same(*page_table, orig_pte))) goto out_nomap; @@ -2594,7 +2634,7 @@ static int do_swap_page(struct mm_struct unlock_page(page); if (flags & FAULT_FLAG_WRITE) { - ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte); + ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, flags, pte); if (ret & VM_FAULT_ERROR) ret &= VM_FAULT_ERROR; goto out; @@ -2607,8 +2647,9 @@ unlock: out: return ret; out_nomap: - mem_cgroup_cancel_charge_swapin(ptr); pte_unmap_unlock(page_table, ptl); +out_nolock: + mem_cgroup_cancel_charge_swapin(ptr); out_page: unlock_page(page); out_release: @@ -2631,7 +2672,9 @@ static int do_anonymous_page(struct mm_s if (!(flags & FAULT_FLAG_WRITE)) { entry = pte_mkspecial(pfn_pte(my_zero_pfn(address), vma->vm_page_prot)); - page_table = pte_offset_map_lock(mm, pmd, address, &ptl); + if (!pte_map_lock(mm, vma, address, pmd, flags, + &page_table, &ptl)) + return VM_FAULT_RETRY; if (!pte_none(*page_table)) goto unlock; goto setpte; @@ -2654,7 +2697,12 @@ static int do_anonymous_page(struct mm_s if (vma->vm_flags & VM_WRITE) entry = pte_mkwrite(pte_mkdirty(entry)); - page_table = pte_offset_map_lock(mm, pmd, address, &ptl); + if (!pte_map_lock(mm, vma, address, pmd, flags, &page_table, &ptl)) { + mem_cgroup_uncharge_page(page); + page_cache_release(page); + return VM_FAULT_RETRY; + } + if (!pte_none(*page_table)) goto release; @@ -2793,7 +2841,10 @@ static int __do_fault(struct mm_struct * } - page_table = pte_offset_map_lock(mm, pmd, address, &ptl); + if (!pte_map_lock(mm, vma, address, pmd, flags, &page_table, &ptl)) { + ret = VM_FAULT_RETRY; + goto out_uncharge; + } /* * This silly early PAGE_DIRTY setting removes a race @@ -2826,7 +2877,10 @@ static int __do_fault(struct mm_struct * /* no need to invalidate: a not-present page won't be cached */ update_mmu_cache(vma, address, entry); + pte_unmap_unlock(page_table, ptl); } else { + pte_unmap_unlock(page_table, ptl); +out_uncharge: if (charged) mem_cgroup_uncharge_page(page); if (anon) @@ -2835,8 +2889,6 @@ static int __do_fault(struct mm_struct * anon = 1; /* no anon but release faulted_page */ } - pte_unmap_unlock(page_table, ptl); - out: if (dirty_page) { struct address_space *mapping = page->mapping; @@ -2945,13 +2997,14 @@ static inline int handle_pte_fault(struc pmd, flags, entry); } - pte = pte_offset_map_lock(mm, pmd, address, &ptl); + if (!pte_map_lock(mm, vma, address, pmd, flags, &pte, &ptl)) + return VM_FAULT_RETRY; if (unlikely(!pte_same(*pte, entry))) goto unlock; if (flags & FAULT_FLAG_WRITE) { if (!pte_write(entry)) return do_wp_page(mm, vma, address, - pte, pmd, ptl, entry); + pte, pmd, ptl, flags, entry); entry = pte_mkdirty(entry); } entry = pte_mkyoung(entry); -- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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