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linux-2.6-mm-tracking-dirty-pages.patch
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File linux-2.6-mm-tracking-dirty-pages.patch of Package kernel
Date: Wed, 19 Jul 2006 00:03:33 +0200 From: Peter Zijlstra <pzijlstr@redhat.com> Subject: Re: [RHEL5][PATCH 1/8] mm: tracking shared dirty pages Respin against current Rawhide kernel. The other patches apply with a little offset/fuzz but end up rightly. It even compiles :-) Don, is this enough, or would you like me to repost the whole series (minus 8/8) fuzzless? --- From: Peter Zijlstra <a.p.zijlstra@chello.nl> Tracking of dirty pages in shared writeable mmap()s. The idea is simple: write protect clean shared writeable pages, catch the write-fault, make writeable and set dirty. On page write-back clean all the PTE dirty bits and write protect them once again. The implementation is a tad harder, mainly because the default backing_dev_info capabilities were too loosely maintained. Hence it is not enough to test the backing_dev_info for cap_account_dirty. The current heuristic is as follows, a VMA is eligible when: - its shared writeable (vm_flags & (VM_WRITE|VM_SHARED)) == (VM_WRITE|VM_SHARED) - it is not a 'special' mapping (vm_flags & (VM_PFNMAP|VM_INSERTPAGE)) == 0 - the backing_dev_info is cap_account_dirty mapping_cap_account_dirty(vma->vm_file->f_mapping) - f_op->mmap() didn't change the default page protection Page from remap_pfn_range() are explicitly excluded because their COW semantics are already horrid enough (see vm_normal_page() in do_wp_page()) and because they don't have a backing store anyway. mprotect() is taught about the new behaviour as well. However it fudges the last condition. Cleaning the pages on write-back is done with page_mkclean() a new rmap call. It cleans and wrprotects all PTEs of dirty accountable pages. Finally, in fs/buffers.c:try_to_free_buffers(); remove clear_page_dirty() from under ->private_lock. This seems to be safe, since ->private_lock is used to serialize access to the buffers, not the page itself. This is needed because clear_page_dirty() will call into page_mkclean() and would thereby violate locking order. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hugh Dickins <hugh@veritas Signed-off-by: Andrew Morton <akpm@osdl.org> --- fs/buffer.c | 2 - include/linux/mm.h | 34 ++++++++++++++++++++++++++ include/linux/rmap.h | 8 ++++++ mm/memory.c | 29 ++++++++++++++++++---- mm/mmap.c | 10 +++---- mm/mprotect.c | 21 ++++++---------- mm/page-writeback.c | 17 ++++++++++--- mm/rmap.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++ 8 files changed, 156 insertions(+), 30 deletions(-) Index: latest/fs/buffer.c =================================================================== --- latest.orig/fs/buffer.c +++ latest/fs/buffer.c @@ -2984,6 +2984,7 @@ int try_to_free_buffers(struct page *pag spin_lock(&mapping->private_lock); ret = drop_buffers(page, &buffers_to_free); + spin_unlock(&mapping->private_lock); if (ret) { /* * If the filesystem writes its buffers by hand (eg ext3) @@ -2995,7 +2996,6 @@ int try_to_free_buffers(struct page *pag */ clear_page_dirty(page); } - spin_unlock(&mapping->private_lock); out: if (buffers_to_free) { struct buffer_head *bh = buffers_to_free; Index: latest/include/linux/mm.h =================================================================== --- latest.orig/include/linux/mm.h +++ latest/include/linux/mm.h @@ -15,6 +15,7 @@ #include <linux/fs.h> #include <linux/mutex.h> #include <linux/debug_locks.h> +#include <linux/backing-dev.h> struct mempolicy; struct anon_vma; @@ -801,6 +802,39 @@ struct shrinker; extern struct shrinker *set_shrinker(int, shrinker_t); extern void remove_shrinker(struct shrinker *shrinker); +/* + * Some shared mappigns will want the pages marked read-only + * to track write events. If so, we'll downgrade vm_page_prot + * to the private version (using protection_map[] without the + * VM_SHARED bit). + */ +static inline int vma_wants_writenotify(struct vm_area_struct *vma) +{ + unsigned int vm_flags = vma->vm_flags; + + /* If it was private or non-writable, the write bit is already clear */ + if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED))) + return 0; + + /* The backer wishes to know when pages are first written to? */ + if (vma->vm_ops && vma->vm_ops->page_mkwrite) + return 1; + + /* The open routine did something to the protections already? */ + if (pgprot_val(vma->vm_page_prot) != + pgprot_val(protection_map[vm_flags & + (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)])) + return 0; + + /* Specialty mapping? */ + if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE)) + return 0; + + /* Can the mapping track the dirty pages? */ + return vma->vm_file && vma->vm_file->f_mapping && + mapping_cap_account_dirty(vma->vm_file->f_mapping); +} + extern pte_t *FASTCALL(get_locked_pte(struct mm_struct *mm, unsigned long addr, spinlock_t **ptl)); int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address); Index: latest/include/linux/rmap.h =================================================================== --- latest.orig/include/linux/rmap.h +++ latest/include/linux/rmap.h @@ -103,6 +103,14 @@ pte_t *page_check_address(struct page *, */ unsigned long page_address_in_vma(struct page *, struct vm_area_struct *); +/* + * Cleans the PTEs of shared mappings. + * (and since clean PTEs should also be readonly, write protects them too) + * + * returns the number of cleaned PTEs. + */ +int page_mkclean(struct page *); + #else /* !CONFIG_MMU */ #define anon_vma_init() do {} while (0) Index: latest/mm/memory.c =================================================================== --- latest.orig/mm/memory.c +++ latest/mm/memory.c @@ -1458,14 +1458,19 @@ static int do_wp_page(struct mm_struct * { struct page *old_page, *new_page; pte_t entry; - int reuse, ret = VM_FAULT_MINOR; + int reuse = 0, ret = VM_FAULT_MINOR; + struct page *dirty_page = NULL; old_page = vm_normal_page(vma, address, orig_pte); if (!old_page) goto gotten; - if (unlikely((vma->vm_flags & (VM_SHARED|VM_WRITE)) == - (VM_SHARED|VM_WRITE))) { + /* + * Only catch write-faults on shared writable pages, read-only + * shared pages can get COWed by get_user_pages(.write=1, .force=1). + */ + if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) == + (VM_WRITE|VM_SHARED))) { if (vma->vm_ops && vma->vm_ops->page_mkwrite) { /* * Notify the address space that the page is about to @@ -1494,13 +1499,12 @@ static int do_wp_page(struct mm_struct * if (!pte_same(*page_table, orig_pte)) goto unlock; } - + dirty_page = old_page; + get_page(dirty_page); reuse = 1; } else if (PageAnon(old_page) && !TestSetPageLocked(old_page)) { reuse = can_share_swap_page(old_page); unlock_page(old_page); - } else { - reuse = 0; } if (reuse) { @@ -1566,6 +1570,10 @@ gotten: page_cache_release(old_page); unlock: pte_unmap_unlock(page_table, ptl); + if (dirty_page) { + set_page_dirty(dirty_page); + put_page(dirty_page); + } return ret; oom: if (old_page) @@ -2098,6 +2106,7 @@ static int do_no_page(struct mm_struct * unsigned int sequence = 0; int ret = VM_FAULT_MINOR; int anon = 0; + struct page *dirty_page = NULL; pte_unmap(page_table); BUG_ON(vma->vm_flags & VM_PFNMAP); @@ -2192,6 +2201,10 @@ retry: } else { inc_mm_counter(mm, file_rss); page_add_file_rmap(new_page); + if (write_access) { + dirty_page = new_page; + get_page(dirty_page); + } } } else { /* One of our sibling threads was faster, back out. */ @@ -2204,6 +2217,10 @@ retry: lazy_mmu_prot_update(entry); unlock: pte_unmap_unlock(page_table, ptl); + if (dirty_page) { + set_page_dirty(dirty_page); + put_page(dirty_page); + } return ret; oom: page_cache_release(new_page); Index: latest/mm/mmap.c =================================================================== --- latest.orig/mm/mmap.c +++ latest/mm/mmap.c @@ -1097,12 +1097,6 @@ munmap_back: goto free_vma; } - /* Don't make the VMA automatically writable if it's shared, but the - * backer wishes to know when pages are first written to */ - if (vma->vm_ops && vma->vm_ops->page_mkwrite) - vma->vm_page_prot = - protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC)]; - /* We set VM_ACCOUNT in a shared mapping's vm_flags, to inform * shmem_zero_setup (perhaps called through /dev/zero's ->mmap) * that memory reservation must be checked; but that reservation @@ -1120,6 +1114,10 @@ munmap_back: pgoff = vma->vm_pgoff; vm_flags = vma->vm_flags; + if (vma_wants_writenotify(vma)) + vma->vm_page_prot = + protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC)]; + if (!file || !vma_merge(mm, prev, addr, vma->vm_end, vma->vm_flags, NULL, file, pgoff, vma_policy(vma))) { file = vma->vm_file; Index: latest/mm/mprotect.c =================================================================== --- latest.orig/mm/mprotect.c +++ latest/mm/mprotect.c @@ -124,8 +124,6 @@ mprotect_fixup(struct vm_area_struct *vm unsigned long oldflags = vma->vm_flags; long nrpages = (end - start) >> PAGE_SHIFT; unsigned long charged = 0, old_end = vma->vm_end; - unsigned int mask; - pgprot_t newprot; pgoff_t pgoff; int error; @@ -177,26 +175,23 @@ mprotect_fixup(struct vm_area_struct *vm } success: - /* Don't make the VMA automatically writable if it's shared, but the - * backer wishes to know when pages are first written to */ - mask = VM_READ|VM_WRITE|VM_EXEC|VM_SHARED; - if (vma->vm_ops && vma->vm_ops->page_mkwrite) - mask &= ~VM_SHARED; - - newprot = protection_map[newflags & mask]; - /* * vm_flags and vm_page_prot are protected by the mmap_sem * held in write mode. */ vma->vm_flags = newflags; - vma->vm_page_prot = newprot; if (oldflags & VM_EXEC) arch_remove_exec_range(current->mm, old_end); + vma->vm_page_prot = protection_map[newflags & + (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]; + if (vma_wants_writenotify(vma)) + vma->vm_page_prot = protection_map[newflags & + (VM_READ|VM_WRITE|VM_EXEC)]; + if (is_vm_hugetlb_page(vma)) - hugetlb_change_protection(vma, start, end, newprot); + hugetlb_change_protection(vma, start, end, vma->vm_page_prot); else - change_protection(vma, start, end, newprot); + change_protection(vma, start, end, vma->vm_page_prot); vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); vm_stat_account(mm, newflags, vma->vm_file, nrpages); return 0; Index: latest/mm/page-writeback.c =================================================================== --- latest.orig/mm/page-writeback.c +++ latest/mm/page-writeback.c @@ -29,6 +29,7 @@ #include <linux/sysctl.h> #include <linux/cpu.h> #include <linux/syscalls.h> +#include <linux/rmap.h> /* * The maximum number of pages to writeout in a single bdflush/kupdate @@ -550,7 +551,7 @@ int do_writepages(struct address_space * return 0; wbc->for_writepages = 1; if (mapping->a_ops->writepages) - ret = mapping->a_ops->writepages(mapping, wbc); + ret = mapping->a_ops->writepages(mapping, wbc); else ret = generic_writepages(mapping, wbc); wbc->for_writepages = 0; @@ -712,9 +713,15 @@ int test_clear_page_dirty(struct page *p radix_tree_tag_clear(&mapping->page_tree, page_index(page), PAGECACHE_TAG_DIRTY); - if (mapping_cap_account_dirty(mapping)) - __dec_zone_page_state(page, NR_FILE_DIRTY); write_unlock_irqrestore(&mapping->tree_lock, flags); + /* + * We can continue to use `mapping' here because the + * page is locked, which pins the address_space + */ + if (mapping_cap_account_dirty(mapping)) { + page_mkclean(page); + dec_zone_page_state(page, NR_FILE_DIRTY); + } return 1; } write_unlock_irqrestore(&mapping->tree_lock, flags); @@ -744,8 +751,10 @@ int clear_page_dirty_for_io(struct page if (mapping) { if (TestClearPageDirty(page)) { - if (mapping_cap_account_dirty(mapping)) + if (mapping_cap_account_dirty(mapping)) { + page_mkclean(page); dec_zone_page_state(page, NR_FILE_DIRTY); + } return 1; } return 0; Index: latest/mm/rmap.c =================================================================== --- latest.orig/mm/rmap.c +++ latest/mm/rmap.c @@ -434,6 +434,71 @@ int page_referenced(struct page *page, i return referenced; } +static int page_mkclean_one(struct page *page, struct vm_area_struct *vma) +{ + struct mm_struct *mm = vma->vm_mm; + unsigned long address; + pte_t *pte, entry; + spinlock_t *ptl; + int ret = 0; + + address = vma_address(page, vma); + if (address == -EFAULT) + goto out; + + pte = page_check_address(page, mm, address, &ptl); + if (!pte) + goto out; + + if (!pte_dirty(*pte) && !pte_write(*pte)) + goto unlock; + + entry = ptep_get_and_clear(mm, address, pte); + entry = pte_mkclean(entry); + entry = pte_wrprotect(entry); + ptep_establish(vma, address, pte, entry); + lazy_mmu_prot_update(entry); + ret = 1; + +unlock: + pte_unmap_unlock(pte, ptl); +out: + return ret; +} + +static int page_mkclean_file(struct address_space *mapping, struct page *page) +{ + pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); + struct vm_area_struct *vma; + struct prio_tree_iter iter; + int ret = 0; + + BUG_ON(PageAnon(page)); + + spin_lock(&mapping->i_mmap_lock); + vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { + if (vma->vm_flags & VM_SHARED) + ret += page_mkclean_one(page, vma); + } + spin_unlock(&mapping->i_mmap_lock); + return ret; +} + +int page_mkclean(struct page *page) +{ + int ret = 0; + + BUG_ON(!PageLocked(page)); + + if (page_mapped(page)) { + struct address_space *mapping = page_mapping(page); + if (mapping) + ret = page_mkclean_file(mapping, page); + } + + return ret; +} + /** * page_set_anon_rmap - setup new anonymous rmap * @page: the page to add the mapping to Date: Mon, 17 Jul 2006 20:32:34 +0200 From: pzijlstr@redhat.com Subject: [RHEL5][PATCH 2/8] mm: balance dirty pages From: Peter Zijlstra <a.p.zijlstra@chello.nl> Now that we can detect writers of shared mappings, throttle them. Avoids OOM by surprise. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> --- include/linux/writeback.h | 1 + mm/memory.c | 5 +++-- mm/page-writeback.c | 10 ++++++++++ 3 files changed, 14 insertions(+), 2 deletions(-) Index: latest/include/linux/writeback.h =================================================================== --- latest.orig/include/linux/writeback.h +++ latest/include/linux/writeback.h @@ -115,6 +115,7 @@ int sync_page_range(struct inode *inode, loff_t pos, loff_t count); int sync_page_range_nolock(struct inode *inode, struct address_space *mapping, loff_t pos, loff_t count); +void set_page_dirty_balance(struct page *page); /* pdflush.c */ extern int nr_pdflush_threads; /* Global so it can be exported to sysctl Index: latest/mm/memory.c =================================================================== --- latest.orig/mm/memory.c +++ latest/mm/memory.c @@ -49,6 +49,7 @@ #include <linux/module.h> #include <linux/delayacct.h> #include <linux/init.h> +#include <linux/writeback.h> #include <asm/pgalloc.h> #include <asm/uaccess.h> @@ -1571,7 +1572,7 @@ gotten: unlock: pte_unmap_unlock(page_table, ptl); if (dirty_page) { - set_page_dirty(dirty_page); + set_page_dirty_balance(dirty_page); put_page(dirty_page); } return ret; @@ -2218,7 +2219,7 @@ retry: unlock: pte_unmap_unlock(page_table, ptl); if (dirty_page) { - set_page_dirty(dirty_page); + set_page_dirty_balance(dirty_page); put_page(dirty_page); } return ret; Index: latest/mm/page-writeback.c =================================================================== --- latest.orig/mm/page-writeback.c +++ latest/mm/page-writeback.c @@ -244,6 +244,16 @@ static void balance_dirty_pages(struct a pdflush_operation(background_writeout, 0); } +void set_page_dirty_balance(struct page *page) +{ + if (set_page_dirty(page)) { + struct address_space *mapping = page_mapping(page); + + if (mapping) + balance_dirty_pages_ratelimited(mapping); + } +} + /** * balance_dirty_pages_ratelimited_nr - balance dirty memory state * @mapping: address_space which was dirtied Date: Mon, 17 Jul 2006 20:32:41 +0200 From: pzijlstr@redhat.com Subject: [RHEL5][PATCH 3/8] mm: optimize the new mprotect code a bit From: Peter Zijlstra <a.p.zijlstra@chello.nl> mprotect() resets the page protections, which could result in extra write faults for those pages whose dirty state we track using write faults and are dirty already. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- mm/mprotect.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) Index: latest/mm/mprotect.c =================================================================== --- latest.orig/mm/mprotect.c +++ latest/mm/mprotect.c @@ -28,7 +28,8 @@ #include <asm/tlbflush.h> static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, - unsigned long addr, unsigned long end, pgprot_t newprot) + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable) { pte_t *pte, oldpte; spinlock_t *ptl; @@ -43,7 +44,14 @@ static void change_pte_range(struct mm_s * bits by wiping the pte and then setting the new pte * into place. */ - ptent = pte_modify(ptep_get_and_clear(mm, addr, pte), newprot); + ptent = ptep_get_and_clear(mm, addr, pte); + ptent = pte_modify(ptent, newprot); + /* + * Avoid taking write faults for pages we know to be + * dirty. + */ + if (dirty_accountable && pte_dirty(ptent)) + ptent = pte_mkwrite(ptent); set_pte_at(mm, addr, pte, ptent); lazy_mmu_prot_update(ptent); #ifdef CONFIG_MIGRATION @@ -67,7 +75,8 @@ static void change_pte_range(struct mm_s } static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, - unsigned long addr, unsigned long end, pgprot_t newprot) + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable) { pmd_t *pmd; unsigned long next; @@ -77,12 +86,13 @@ static inline void change_pmd_range(stru next = pmd_addr_end(addr, end); if (pmd_none_or_clear_bad(pmd)) continue; - change_pte_range(mm, pmd, addr, next, newprot); + change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); } while (pmd++, addr = next, addr != end); } static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, - unsigned long addr, unsigned long end, pgprot_t newprot) + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable) { pud_t *pud; unsigned long next; @@ -92,12 +102,13 @@ static inline void change_pud_range(stru next = pud_addr_end(addr, end); if (pud_none_or_clear_bad(pud)) continue; - change_pmd_range(mm, pud, addr, next, newprot); + change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); } while (pud++, addr = next, addr != end); } static void change_protection(struct vm_area_struct *vma, - unsigned long addr, unsigned long end, pgprot_t newprot) + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable) { struct mm_struct *mm = vma->vm_mm; pgd_t *pgd; @@ -111,7 +122,7 @@ static void change_protection(struct vm_ next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) continue; - change_pud_range(mm, pgd, addr, next, newprot); + change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); } while (pgd++, addr = next, addr != end); flush_tlb_range(vma, start, end); } @@ -126,6 +137,7 @@ mprotect_fixup(struct vm_area_struct *vm unsigned long charged = 0, old_end = vma->vm_end; pgoff_t pgoff; int error; + int dirty_accountable = 0; if (newflags == oldflags) { *pprev = vma; @@ -184,14 +196,16 @@ success: arch_remove_exec_range(current->mm, old_end); vma->vm_page_prot = protection_map[newflags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]; - if (vma_wants_writenotify(vma)) + if (vma_wants_writenotify(vma)) { vma->vm_page_prot = protection_map[newflags & (VM_READ|VM_WRITE|VM_EXEC)]; + dirty_accountable = 1; + } if (is_vm_hugetlb_page(vma)) hugetlb_change_protection(vma, start, end, vma->vm_page_prot); else - change_protection(vma, start, end, vma->vm_page_prot); + change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); vm_stat_account(mm, newflags, vma->vm_file, nrpages); return 0; Date: Mon, 17 Jul 2006 20:32:49 +0200 From: pzijlstr@redhat.com Subject: [RHEL5][PATCH 4/8] mm: small cleanup of install_page() From: Peter Zijlstra <a.p.zijlstra@chello.nl> Smallish cleanup to install_page(), could save a memory read (haven't checked the asm output) and sure looks nicer. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> --- mm/fremap.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) Index: latest/mm/fremap.c =================================================================== --- latest.orig/mm/fremap.c +++ latest/mm/fremap.c @@ -81,9 +81,9 @@ int install_page(struct mm_struct *mm, s inc_mm_counter(mm, file_rss); flush_icache_page(vma, page); - set_pte_at(mm, addr, pte, mk_pte(page, prot)); + pte_val = mk_pte(page, prot); + set_pte_at(mm, addr, pte, pte_val); page_add_file_rmap(page); - pte_val = *pte; update_mmu_cache(vma, addr, pte_val); lazy_mmu_prot_update(pte_val); err = 0; Date: Mon, 17 Jul 2006 20:32:56 +0200 From: pzijlstr@redhat.com Subject: [RHEL5][PATCH 5/8] mm: fixup do_wp_page() From: Peter Zijlstra <a.p.zijlstra@chello.nl> Wrt. the recent modifications in do_wp_page() Hugh Dickins pointed out: "I now realize it's right to the first order (normal case) and to the second order (ptrace poke), but not to the third order (ptrace poke anon page here to be COWed - perhaps can't occur without intervening mprotects)." This patch restores the old COW behaviour for anonymous pages. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> --- mm/memory.c | 19 +++++++++++++------ 1 files changed, 13 insertions(+), 6 deletions(-) Index: latest/mm/memory.c =================================================================== --- latest.orig/mm/memory.c +++ latest/mm/memory.c @@ -1467,11 +1467,21 @@ static int do_wp_page(struct mm_struct * goto gotten; /* - * Only catch write-faults on shared writable pages, read-only - * shared pages can get COWed by get_user_pages(.write=1, .force=1). + * Take out anonymous pages first, anonymous shared vmas are + * not dirty accountable. */ - if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) == + if (PageAnon(old_page)) { + if (!TestSetPageLocked(old_page)) { + reuse = can_share_swap_page(old_page); + unlock_page(old_page); + } + } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) == (VM_WRITE|VM_SHARED))) { + /* + * Only catch write-faults on shared writable pages, + * read-only shared pages can get COWed by + * get_user_pages(.write=1, .force=1). + */ if (vma->vm_ops && vma->vm_ops->page_mkwrite) { /* * Notify the address space that the page is about to @@ -1503,9 +1513,6 @@ static int do_wp_page(struct mm_struct * dirty_page = old_page; get_page(dirty_page); reuse = 1; - } else if (PageAnon(old_page) && !TestSetPageLocked(old_page)) { - reuse = can_share_swap_page(old_page); - unlock_page(old_page); } if (reuse) { Date: Mon, 17 Jul 2006 20:33:03 +0200 From: pzijlstr@redhat.com Subject: [RHEL5][PATCH 6/8] mm: msync cleanup From: Peter Zijlstra <a.p.zijlstra@chello.nl> With the tracking of dirty pages properly done now, msync doesn't need to scan the PTEs anymore to determine the dirty status. From: Hugh Dickins <hugh@veritas.com> In looking to do that, I made some other tidyups: can remove several #includes, and sys_msync loop termination not quite right. Most of those points are criticisms of the existing sys_msync, not of your patch. In particular, the loop termination errors were introduced in 2.6.17: I did notice this shortly before it came out, but decided I was more likely to get it wrong myself, and make matters worse if I tried to rush a last-minute fix in. And it's not terribly likely to go wrong, nor disastrous if it does go wrong (may miss reporting an unmapped area; may also fsync file of a following vma). Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> --- mm/msync.c | 196 ++++++++------------------------------------------- 1 file changed, 33 insertions(+), 163 deletions(-) Index: latest/mm/msync.c =================================================================== --- latest.orig/mm/msync.c +++ latest/mm/msync.c @@ -7,149 +7,33 @@ /* * The msync() system call. */ -#include <linux/slab.h> -#include <linux/pagemap.h> #include <linux/fs.h> #include <linux/mm.h> #include <linux/mman.h> -#include <linux/hugetlb.h> -#include <linux/writeback.h> #include <linux/file.h> #include <linux/syscalls.h> -#include <asm/pgtable.h> -#include <asm/tlbflush.h> - -static unsigned long msync_pte_range(struct vm_area_struct *vma, pmd_t *pmd, - unsigned long addr, unsigned long end) -{ - pte_t *pte; - spinlock_t *ptl; - int progress = 0; - unsigned long ret = 0; - -again: - pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); - do { - struct page *page; - - if (progress >= 64) { - progress = 0; - if (need_resched() || need_lockbreak(ptl)) - break; - } - progress++; - if (!pte_present(*pte)) - continue; - if (!pte_maybe_dirty(*pte)) - continue; - page = vm_normal_page(vma, addr, *pte); - if (!page) - continue; - if (ptep_clear_flush_dirty(vma, addr, pte) || - page_test_and_clear_dirty(page)) - ret += set_page_dirty(page); - progress += 3; - } while (pte++, addr += PAGE_SIZE, addr != end); - pte_unmap_unlock(pte - 1, ptl); - cond_resched(); - if (addr != end) - goto again; - return ret; -} - -static inline unsigned long msync_pmd_range(struct vm_area_struct *vma, - pud_t *pud, unsigned long addr, unsigned long end) -{ - pmd_t *pmd; - unsigned long next; - unsigned long ret = 0; - - pmd = pmd_offset(pud, addr); - do { - next = pmd_addr_end(addr, end); - if (pmd_none_or_clear_bad(pmd)) - continue; - ret += msync_pte_range(vma, pmd, addr, next); - } while (pmd++, addr = next, addr != end); - return ret; -} - -static inline unsigned long msync_pud_range(struct vm_area_struct *vma, - pgd_t *pgd, unsigned long addr, unsigned long end) -{ - pud_t *pud; - unsigned long next; - unsigned long ret = 0; - - pud = pud_offset(pgd, addr); - do { - next = pud_addr_end(addr, end); - if (pud_none_or_clear_bad(pud)) - continue; - ret += msync_pmd_range(vma, pud, addr, next); - } while (pud++, addr = next, addr != end); - return ret; -} - -static unsigned long msync_page_range(struct vm_area_struct *vma, - unsigned long addr, unsigned long end) -{ - pgd_t *pgd; - unsigned long next; - unsigned long ret = 0; - - /* For hugepages we can't go walking the page table normally, - * but that's ok, hugetlbfs is memory based, so we don't need - * to do anything more on an msync(). - */ - if (vma->vm_flags & VM_HUGETLB) - return 0; - - BUG_ON(addr >= end); - pgd = pgd_offset(vma->vm_mm, addr); - flush_cache_range(vma, addr, end); - do { - next = pgd_addr_end(addr, end); - if (pgd_none_or_clear_bad(pgd)) - continue; - ret += msync_pud_range(vma, pgd, addr, next); - } while (pgd++, addr = next, addr != end); - return ret; -} - /* * MS_SYNC syncs the entire file - including mappings. * - * MS_ASYNC does not start I/O (it used to, up to 2.5.67). Instead, it just - * marks the relevant pages dirty. The application may now run fsync() to + * MS_ASYNC does not start I/O (it used to, up to 2.5.67). + * Nor does it marks the relevant pages dirty (it used to up to 2.6.17). + * Now it doesn't do anything, since dirty pages are properly tracked. + * + * The application may now run fsync() to * write out the dirty pages and wait on the writeout and check the result. * Or the application may run fadvise(FADV_DONTNEED) against the fd to start * async writeout immediately. * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to * applications. */ -static int msync_interval(struct vm_area_struct *vma, unsigned long addr, - unsigned long end, int flags, - unsigned long *nr_pages_dirtied) -{ - struct file *file = vma->vm_file; - - if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED)) - return -EBUSY; - - if (file && (vma->vm_flags & VM_SHARED)) - *nr_pages_dirtied = msync_page_range(vma, addr, end); - return 0; -} - asmlinkage long sys_msync(unsigned long start, size_t len, int flags) { unsigned long end; + struct mm_struct *mm = current->mm; struct vm_area_struct *vma; int unmapped_error = 0; int error = -EINVAL; - int done = 0; if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC)) goto out; @@ -169,64 +53,50 @@ asmlinkage long sys_msync(unsigned long * If the interval [start,end) covers some unmapped address ranges, * just ignore them, but return -ENOMEM at the end. */ - down_read(¤t->mm->mmap_sem); - vma = find_vma(current->mm, start); - if (!vma) { - error = -ENOMEM; - goto out_unlock; - } - do { - unsigned long nr_pages_dirtied = 0; + down_read(&mm->mmap_sem); + vma = find_vma(mm, start); + for (;;) { struct file *file; + /* Still start < end. */ + error = -ENOMEM; + if (!vma) + goto out_unlock; /* Here start < vma->vm_end. */ if (start < vma->vm_start) { - unmapped_error = -ENOMEM; start = vma->vm_start; + if (start >= end) + goto out_unlock; + unmapped_error = -ENOMEM; } /* Here vma->vm_start <= start < vma->vm_end. */ - if (end <= vma->vm_end) { - if (start < end) { - error = msync_interval(vma, start, end, flags, - &nr_pages_dirtied); - if (error) - goto out_unlock; - } - error = unmapped_error; - done = 1; - } else { - /* Here vma->vm_start <= start < vma->vm_end < end. */ - error = msync_interval(vma, start, vma->vm_end, flags, - &nr_pages_dirtied); - if (error) - goto out_unlock; + if ((flags & MS_INVALIDATE) && + (vma->vm_flags & VM_LOCKED)) { + error = -EBUSY; + goto out_unlock; } file = vma->vm_file; start = vma->vm_end; - if ((flags & MS_ASYNC) && file && nr_pages_dirtied) { - get_file(file); - up_read(¤t->mm->mmap_sem); - balance_dirty_pages_ratelimited_nr(file->f_mapping, - nr_pages_dirtied); - fput(file); - down_read(¤t->mm->mmap_sem); - vma = find_vma(current->mm, start); - } else if ((flags & MS_SYNC) && file && + if ((flags & MS_SYNC) && file && (vma->vm_flags & VM_SHARED)) { get_file(file); - up_read(¤t->mm->mmap_sem); + up_read(&mm->mmap_sem); error = do_fsync(file, 0); fput(file); - down_read(¤t->mm->mmap_sem); - if (error) - goto out_unlock; - vma = find_vma(current->mm, start); + if (error || start >= end) + goto out; + down_read(&mm->mmap_sem); + vma = find_vma(mm, start); } else { + if (start >= end) { + error = 0; + goto out_unlock; + } vma = vma->vm_next; } - } while (vma && !done); + } out_unlock: - up_read(¤t->mm->mmap_sem); + up_read(&mm->mmap_sem); out: - return error; + return error ? : unmapped_error; } Date: Mon, 17 Jul 2006 20:33:11 +0200 From: pzijlstr@redhat.com Subject: [RHEL5][PATCH 7/8] mm: tracking shared dirty pages checks From: Andrew Morton <akpm@osdl.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@osdl.org> --- mm/page-writeback.c | 2 ++ 1 files changed, 2 insertions(+) Index: latest/mm/page-writeback.c =================================================================== --- latest.orig/mm/page-writeback.c +++ latest/mm/page-writeback.c @@ -717,6 +717,7 @@ int test_clear_page_dirty(struct page *p struct address_space *mapping = page_mapping(page); unsigned long flags; + WARN_ON_ONCE(!PageLocked(page)); if (mapping) { write_lock_irqsave(&mapping->tree_lock, flags); if (TestClearPageDirty(page)) { @@ -759,6 +760,7 @@ int clear_page_dirty_for_io(struct page { struct address_space *mapping = page_mapping(page); + WARN_ON_ONCE(!PageLocked(page)); if (mapping) { if (TestClearPageDirty(page)) { if (mapping_cap_account_dirty(mapping)) { Date: Mon, 17 Jul 2006 20:33:18 +0200 From: pzijlstr@redhat.com Subject: [RHEL5][PATCH 8/8] mm: tracking shared dirty pages wimp.patch From: Andrew Morton <akpm@osdl.org> I'm not so sure, and if this is wrong, we wreck an -mm release. Please don't wreck -mm releases. Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> --- mm/rmap.c | 2 +- 1 files changed, 1 insertion(+), 1 deletion(-) Index: latest/mm/rmap.c =================================================================== --- latest.orig/mm/rmap.c +++ latest/mm/rmap.c @@ -488,7 +488,7 @@ int page_mkclean(struct page *page) { int ret = 0; - BUG_ON(!PageLocked(page)); + WARN_ON_ONCE(!PageLocked(page)); if (page_mapped(page)) { struct address_space *mapping = page_mapping(page);
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