[PATCH] mm: msync() cleanup
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> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Peter Zijlstra
Linus Torvalds
parent
ee6a645788
commit
204ec841fb
198
mm/msync.c
198
mm/msync.c
@ -7,149 +7,33 @@
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/*
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* The msync() system call.
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*/
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#include <linux/slab.h>
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#include <linux/pagemap.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/mman.h>
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#include <linux/hugetlb.h>
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#include <linux/writeback.h>
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#include <linux/file.h>
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#include <linux/syscalls.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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static unsigned long msync_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
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unsigned long addr, unsigned long end)
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{
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pte_t *pte;
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spinlock_t *ptl;
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int progress = 0;
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unsigned long ret = 0;
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again:
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pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
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do {
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struct page *page;
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if (progress >= 64) {
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progress = 0;
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if (need_resched() || need_lockbreak(ptl))
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break;
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}
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progress++;
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if (!pte_present(*pte))
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continue;
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if (!pte_maybe_dirty(*pte))
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continue;
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page = vm_normal_page(vma, addr, *pte);
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if (!page)
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continue;
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if (ptep_clear_flush_dirty(vma, addr, pte) ||
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page_test_and_clear_dirty(page))
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ret += set_page_dirty(page);
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progress += 3;
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} while (pte++, addr += PAGE_SIZE, addr != end);
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pte_unmap_unlock(pte - 1, ptl);
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cond_resched();
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if (addr != end)
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goto again;
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return ret;
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}
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static inline unsigned long msync_pmd_range(struct vm_area_struct *vma,
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pud_t *pud, unsigned long addr, unsigned long end)
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{
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pmd_t *pmd;
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unsigned long next;
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unsigned long ret = 0;
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pmd = pmd_offset(pud, addr);
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do {
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next = pmd_addr_end(addr, end);
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if (pmd_none_or_clear_bad(pmd))
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continue;
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ret += msync_pte_range(vma, pmd, addr, next);
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} while (pmd++, addr = next, addr != end);
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return ret;
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}
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static inline unsigned long msync_pud_range(struct vm_area_struct *vma,
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pgd_t *pgd, unsigned long addr, unsigned long end)
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{
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pud_t *pud;
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unsigned long next;
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unsigned long ret = 0;
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pud = pud_offset(pgd, addr);
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do {
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next = pud_addr_end(addr, end);
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if (pud_none_or_clear_bad(pud))
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continue;
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ret += msync_pmd_range(vma, pud, addr, next);
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} while (pud++, addr = next, addr != end);
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return ret;
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}
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static unsigned long msync_page_range(struct vm_area_struct *vma,
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unsigned long addr, unsigned long end)
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{
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pgd_t *pgd;
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unsigned long next;
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unsigned long ret = 0;
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/* For hugepages we can't go walking the page table normally,
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* but that's ok, hugetlbfs is memory based, so we don't need
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* to do anything more on an msync().
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*/
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if (vma->vm_flags & VM_HUGETLB)
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return 0;
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BUG_ON(addr >= end);
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pgd = pgd_offset(vma->vm_mm, addr);
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flush_cache_range(vma, addr, end);
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do {
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next = pgd_addr_end(addr, end);
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if (pgd_none_or_clear_bad(pgd))
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continue;
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ret += msync_pud_range(vma, pgd, addr, next);
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} while (pgd++, addr = next, addr != end);
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return ret;
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}
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/*
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* MS_SYNC syncs the entire file - including mappings.
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*
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* MS_ASYNC does not start I/O (it used to, up to 2.5.67). Instead, it just
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* marks the relevant pages dirty. The application may now run fsync() to
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* MS_ASYNC does not start I/O (it used to, up to 2.5.67).
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* Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
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* Now it doesn't do anything, since dirty pages are properly tracked.
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*
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* The application may now run fsync() to
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* write out the dirty pages and wait on the writeout and check the result.
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* Or the application may run fadvise(FADV_DONTNEED) against the fd to start
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* async writeout immediately.
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* So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
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* applications.
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*/
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static int msync_interval(struct vm_area_struct *vma, unsigned long addr,
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unsigned long end, int flags,
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unsigned long *nr_pages_dirtied)
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{
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struct file *file = vma->vm_file;
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if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED))
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return -EBUSY;
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if (file && (vma->vm_flags & VM_SHARED))
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*nr_pages_dirtied = msync_page_range(vma, addr, end);
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return 0;
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}
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asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
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{
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unsigned long end;
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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int unmapped_error = 0;
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int error = -EINVAL;
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int done = 0;
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if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
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goto out;
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@ -169,64 +53,50 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
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* If the interval [start,end) covers some unmapped address ranges,
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* just ignore them, but return -ENOMEM at the end.
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*/
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down_read(¤t->mm->mmap_sem);
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vma = find_vma(current->mm, start);
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if (!vma) {
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error = -ENOMEM;
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goto out_unlock;
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}
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do {
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unsigned long nr_pages_dirtied = 0;
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down_read(&mm->mmap_sem);
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vma = find_vma(mm, start);
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for (;;) {
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struct file *file;
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/* Still start < end. */
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error = -ENOMEM;
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if (!vma)
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goto out_unlock;
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/* Here start < vma->vm_end. */
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if (start < vma->vm_start) {
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unmapped_error = -ENOMEM;
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start = vma->vm_start;
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if (start >= end)
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goto out_unlock;
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unmapped_error = -ENOMEM;
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}
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/* Here vma->vm_start <= start < vma->vm_end. */
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if (end <= vma->vm_end) {
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if (start < end) {
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error = msync_interval(vma, start, end, flags,
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&nr_pages_dirtied);
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if (error)
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goto out_unlock;
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}
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error = unmapped_error;
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done = 1;
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} else {
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/* Here vma->vm_start <= start < vma->vm_end < end. */
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error = msync_interval(vma, start, vma->vm_end, flags,
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&nr_pages_dirtied);
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if (error)
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if ((flags & MS_INVALIDATE) &&
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(vma->vm_flags & VM_LOCKED)) {
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error = -EBUSY;
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goto out_unlock;
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}
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file = vma->vm_file;
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start = vma->vm_end;
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if ((flags & MS_ASYNC) && file && nr_pages_dirtied) {
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get_file(file);
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up_read(¤t->mm->mmap_sem);
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balance_dirty_pages_ratelimited_nr(file->f_mapping,
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nr_pages_dirtied);
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fput(file);
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down_read(¤t->mm->mmap_sem);
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vma = find_vma(current->mm, start);
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} else if ((flags & MS_SYNC) && file &&
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if ((flags & MS_SYNC) && file &&
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(vma->vm_flags & VM_SHARED)) {
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get_file(file);
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up_read(¤t->mm->mmap_sem);
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up_read(&mm->mmap_sem);
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error = do_fsync(file, 0);
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fput(file);
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down_read(¤t->mm->mmap_sem);
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if (error)
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goto out_unlock;
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vma = find_vma(current->mm, start);
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if (error || start >= end)
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goto out;
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down_read(&mm->mmap_sem);
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vma = find_vma(mm, start);
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} else {
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if (start >= end) {
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error = 0;
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goto out_unlock;
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}
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vma = vma->vm_next;
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}
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} while (vma && !done);
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out_unlock:
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up_read(¤t->mm->mmap_sem);
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out:
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return error;
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}
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out_unlock:
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up_read(&mm->mmap_sem);
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out:
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return error ? : unmapped_error;
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}
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