lkml.org 
[lkml]   [2003]   [Oct]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [RFC] invalidate_mmap_range() misses remap_file_pages()-affected targets
William Lee Irwin III <wli@holomorphy.com> wrote:
>> It would seem that mincore() shares a similar issue on account of its
>> algorithm

On Sun, Oct 12, 2003 at 04:56:44AM -0700, Andrew Morton wrote:
> Yes, I think it makes sense to fix mincore(). I don't fully understand the
> reasoning behind the three cases though:

Probably because the second case is broken.


William Lee Irwin III <wli@holomorphy.com> wrote:
> + if (pte_file(*pte))
> + present = mincore_linear_page(vma, pte_to_pgoff(*pte));
> + else if (!(vma->vm_flags | (VM_READ|VM_WRITE|VM_MAYREAD|VM_MAYWRITE)))
> + present = pte_present(*pte);
> + else
> + present = mincore_linear_page(vma, pgoff);

On Sun, Oct 12, 2003 at 04:56:44AM -0700, Andrew Morton wrote:
> Could you explain the logic behind each of these? Perhaps with permanent
> comments?

I think the PROT_NONE handling is bogus; since we have the pte, we can
just override the pgoff-based lookup if the pte is present and ignore
vm_flags, and the behavior isn't unique to PROT_NONE anyway. The prior
post flubs the case of pte_present(*pte) with unaligned pgoff and rw
or ro vma protection.

Mike Galbraith also spotted a typical locking booboo in mincore_page(),
fixed here.


-- wli


diff -prauN rfp-2.6.0-test7-bk3-1/mm/mincore.c rfp-2.6.0-test7-bk3-2/mm/mincore.c
--- rfp-2.6.0-test7-bk3-1/mm/mincore.c 2003-10-08 12:24:51.000000000 -0700
+++ rfp-2.6.0-test7-bk3-2/mm/mincore.c 2003-10-12 12:36:52.000000000 -0700
@@ -22,7 +22,7 @@
* and is up to date; i.e. that no page-in operation would be required
* at this time if an application were to map and access this page.
*/
-static unsigned char mincore_page(struct vm_area_struct * vma,
+static unsigned char mincore_linear_page(struct vm_area_struct *vma,
unsigned long pgoff)
{
unsigned char present = 0;
@@ -38,6 +38,67 @@ static unsigned char mincore_page(struct
return present;
}

+static unsigned char mincore_nonlinear_page(struct vm_area_struct *vma,
+ unsigned long pgoff)
+{
+ unsigned char present = 0;
+ unsigned long vaddr;
+ pgd_t *pgd;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ spin_lock(&vma->vm_mm->page_table_lock);
+ vaddr = PAGE_SIZE*(pgoff - vma->vm_pgoff) + vma->vm_start;
+ pgd = pgd_offset(vma->vm_mm, vaddr);
+ if (pgd_none(*pgd))
+ goto out;
+ else if (pgd_bad(*pgd)) {
+ pgd_ERROR(*pgd);
+ pgd_clear(pgd);
+ goto out;
+ }
+ pmd = pmd_offset(pgd, vaddr);
+ if (pmd_none(*pmd))
+ goto out;
+ else if (pmd_ERROR(*pmd)) {
+ pmd_ERROR(*pmd);
+ pmd_clear(pmd);
+ goto out;
+ }
+
+ pte = pte_offset_map(pmd, vaddr);
+
+ /* PTE_FILE ptes have the same file, but pgoff can differ */
+ if (pte_file(*pte))
+ present = mincore_linear_page(vma, pte_to_pgoff(*pte));
+
+ /* pte presence overrides the calculated offset */
+ else if (pte_present(*pte))
+ present = 1;
+
+ /* matching offsets are the faulted in if the pte isn't set */
+ else
+ present = mincore_linear_page(vma, pgoff);
+ pte_unmap(pte);
+out:
+ spin_unlock(&vma->vm_mm->page_table_lock);
+ return present;
+}
+
+static inline unsigned char mincore_page(struct vm_area_struct *vma,
+ unsigned long pgoff)
+{
+ unsigned char ret;
+ struct address_space *as = vma->vm_file->f_dentry->d_inode->i_mapping;
+ down(&as->i_shared_sem);
+ if (vma->vm_flags & VM_NONLINEAR)
+ ret = mincore_nonlinear_page(vma, pgoff);
+ else
+ ret = mincore_linear_page(vma, pgoff);
+ up(&as->i_shared_sem);
+ return ret;
+}
+
static long mincore_vma(struct vm_area_struct * vma,
unsigned long start, unsigned long end, unsigned char __user * vec)
{
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2005-03-22 13:49    [W:0.043 / U:0.412 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site