On Mon, 24 Jul 2023 at 16:04, Muhammad Usama Anjum usama.anjum@collabora.com wrote:
Fixed found bugs. Testing it further.
- Split and backoff in case buffer full case as well
- Fix the wrong breaking of loop if page isn't interesting, skip intead
- Untag the address and save them into struct
- Round off the end address to next page
Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com
fs/proc/task_mmu.c | 54 ++++++++++++++++++++++++++-------------------- 1 file changed, 31 insertions(+), 23 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index add21fdf3c9a..64b326d0ec6d 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1985,18 +1989,19 @@ static int pagemap_scan_output(unsigned long categories, unsigned long n_pages, total_pages; int ret = 0;
if (!p->vec_buf)return 0;if (!pagemap_scan_is_interesting_page(categories, p)) { *end = addr; return 0; }
if (!p->vec_buf)return 0;categories &= p->arg.return_mask;
This is wrong - is_interesting() check must happen before output as the `*end = addr` means the range should be skipped, but return 0 requests continuing of the walk.
@@ -2044,7 +2050,7 @@ static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start, * Break huge page into small pages if the WP operation * need to be performed is on a portion of the huge page. */
if (end != start + HPAGE_SIZE) {
if (end != start + HPAGE_SIZE || ret == -ENOSPC) {
Why is it needed? If `end == start + HPAGE_SIZE` then we're handling a full hugepage anyway.
@@ -2066,8 +2072,8 @@ static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, { struct pagemap_scan_private *p = walk->private; struct vm_area_struct *vma = walk->vma;
unsigned long addr, categories, next; pte_t *pte, *start_pte;
unsigned long addr; bool flush = false; spinlock_t *ptl; int ret;@@ -2088,12 +2094,14 @@ static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, }
for (addr = start; addr != end; pte++, addr += PAGE_SIZE) {
unsigned long categories = p->cur_vma_category |pagemap_page_category(vma, addr, ptep_get(pte));unsigned long next = addr + PAGE_SIZE;
categories = p->cur_vma_category |pagemap_page_category(vma, addr, ptep_get(pte));next = addr + PAGE_SIZE;
Why moving the variable declarations out of the loop?
ret = pagemap_scan_output(categories, p, addr, &next);
if (next == addr)
if (ret == 0 && next == addr)continue;else if (next == addr) break;
Ah, this indeed was a bug. Nit:
if (next == addr) { if (!ret) continue; break; }
@@ -2204,8 +2212,6 @@ static const struct mm_walk_ops pagemap_scan_ops = { static int pagemap_scan_get_args(struct pm_scan_arg *arg, unsigned long uarg) {
unsigned long start, end, vec;if (copy_from_user(arg, (void __user *)uarg, sizeof(*arg))) return -EFAULT;@@ -2219,22 +2225,24 @@ static int pagemap_scan_get_args(struct pm_scan_arg *arg, arg->category_anyof_mask | arg->return_mask) & ~PM_SCAN_CATEGORIES) return -EINVAL;
start = untagged_addr((unsigned long)arg->start);end = untagged_addr((unsigned long)arg->end);vec = untagged_addr((unsigned long)arg->vec);
arg->start = untagged_addr((unsigned long)arg->start);arg->end = untagged_addr((unsigned long)arg->end);arg->vec = untagged_addr((unsigned long)arg->vec);
BTW, We should we keep the tag in args writeback().
/* Validate memory pointers */
if (!IS_ALIGNED(start, PAGE_SIZE))
if (!IS_ALIGNED(arg->start, PAGE_SIZE)) return -EINVAL;
if (!access_ok((void __user *)start, end - start))
if (!access_ok((void __user *)arg->start, arg->end - arg->start)) return -EFAULT;
if (!vec && arg->vec_len)
if (!arg->vec && arg->vec_len) return -EFAULT;
if (vec && !access_ok((void __user *)vec,
if (arg->vec && !access_ok((void __user *)arg->vec, arg->vec_len * sizeof(struct page_region))) return -EFAULT; /* Fixup default values */arg->end = (arg->end & ~PAGE_MASK) ?((arg->end & PAGE_MASK) + PAGE_SIZE) : (arg->end);
arg->end = ALIGN(arg->end, PAGE_SIZE);
if (!arg->max_pages) arg->max_pages = ULONG_MAX;
Best Regards Michał Mirosław