> Force file times update at the next write reference after
> calling the msync() system call with the MS_ASYNC flag.
>
> Signed-off-by: Anton Salikhmetov <[EMAIL PROTECTED]>
> ---
> mm/msync.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++------
> 1 files changed, 82 insertions(+), 10 deletions(-)
>
> diff --git a/mm/msync.c b/mm/msync.c
> index 60efa36..87f990e 100644
> --- a/mm/msync.c
> +++ b/mm/msync.c
> @@ -5,6 +5,7 @@
> * Copyright (C) 2008 Anton Salikhmetov <[EMAIL PROTECTED]>
> */
>
> +#include <asm/tlbflush.h>
> #include <linux/file.h>
> #include <linux/fs.h>
> #include <linux/mm.h>
> @@ -12,6 +13,73 @@
> #include <linux/sched.h>
> #include <linux/syscalls.h>
>
> +static void vma_wrprotect_pmd_range(struct vm_area_struct *vma, pmd_t *pmd,
> + unsigned long start, unsigned long end)
> +{
> + while (start < end) {
> + spinlock_t *ptl;
> + pte_t *pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
> +
> + if (pte_dirty(*pte) && pte_write(*pte)) {
> + pte_t entry = ptep_clear_flush(vma, start, pte);
> +
> + entry = pte_wrprotect(entry);
> + set_pte_at(vma->vm_mm, start, pte, entry);
> + }
> +
> + pte_unmap_unlock(pte, ptl);
> + start += PAGE_SIZE;
> + }
> +}
Why can't the pte_offset_map_lock/unlock be moved outside the loop, as
in Peter's example? My guess is, it could have some impact on
performance.
> +
> +static void vma_wrprotect_pud_range(struct vm_area_struct *vma, pud_t *pud,
> + unsigned long start, unsigned long end)
> +{
> + pmd_t *pmd = pmd_offset(pud, start);
> +
> + while (start < end) {
> + unsigned long next = pmd_addr_end(start, end);
> +
> + if (!pmd_none_or_clear_bad(pmd))
> + vma_wrprotect_pmd_range(vma, pmd, start, next);
> +
> + ++pmd;
> + start = next;
> + }
> +}
> +
> +static void vma_wrprotect_pgd_range(struct vm_area_struct *vma, pgd_t *pgd,
> + unsigned long start, unsigned long end)
> +{
> + pud_t *pud = pud_offset(pgd, start);
> +
> + while (start < end) {
> + unsigned long next = pud_addr_end(start, end);
> +
> + if (!pud_none_or_clear_bad(pud))
> + vma_wrprotect_pud_range(vma, pud, start, next);
> +
> + ++pud;
> + start = next;
> + }
> +}
> +
> +static void vma_wrprotect(struct vm_area_struct *vma)
> +{
> + unsigned long addr = vma->vm_start;
> + pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
> +
Need to check mapping_cap_account_dirty(). Otherwise we would be
inconsistent with write protecting ram-backed filesystems.
> + while (addr < vma->vm_end) {
> + unsigned long next = pgd_addr_end(addr, vma->vm_end);
> +
> + if (!pgd_none_or_clear_bad(pgd))
> + vma_wrprotect_pgd_range(vma, pgd, addr, next);
> +
> + ++pgd;
> + addr = next;
> + }
> +}
> +
> /*
> * MS_SYNC syncs the entire file - including mappings.
> *
> @@ -78,16 +146,20 @@ asmlinkage long sys_msync(unsigned long start, size_t
> len, int flags)
> error = 0;
> start = vma->vm_end;
> file = vma->vm_file;
> - if (file && (vma->vm_flags & VM_SHARED) && (flags & MS_SYNC)) {
> - get_file(file);
> - up_read(&mm->mmap_sem);
> - error = do_fsync(file, 0);
> - fput(file);
> - if (error || start >= end)
> - goto out;
> - down_read(&mm->mmap_sem);
> - vma = find_vma(mm, start);
> - continue;
> + if (file && (vma->vm_flags & VM_SHARED)) {
> + if ((flags & MS_ASYNC))
> + vma_wrprotect(vma);
> + if (flags & MS_SYNC) {
> + get_file(file);
> + up_read(&mm->mmap_sem);
> + error = do_fsync(file, 0);
> + fput(file);
> + if (error || start >= end)
> + goto out;
> + down_read(&mm->mmap_sem);
> + vma = find_vma(mm, start);
> + continue;
> + }
> }
>
> vma = vma->vm_next;
> --
> 1.4.4.4
>
>
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