On 01/04/2020 05.31, Huang, Ying wrote:
Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> writes:
On 31/03/2020 11.56, Huang, Ying wrote:
From: Huang Ying <ying.huang@xxxxxxxxx>
Now, when read /proc/PID/smaps, the PMD migration entry in page table is simply
ignored. To improve the accuracy of /proc/PID/smaps, its parsing and processing
is added.
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx>
Cc: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8d382d4ec067..b5b3aef8cb3b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -548,8 +548,17 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
bool locked = !!(vma->vm_flags & VM_LOCKED);
struct page *page;
struct page *page = NULL;
Looks good. Will do this in the next version.
- /* FOLL_DUMP will return -EFAULT on huge zero page */
- page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
+ if (pmd_present(*pmd)) {
+ /* FOLL_DUMP will return -EFAULT on huge zero page */
+ page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
+ } else if (unlikely(is_swap_pmd(*pmd))) {
+ swp_entry_t entry = pmd_to_swp_entry(*pmd);
+
+ VM_BUG_ON(!is_migration_entry(entry));
+ page = migration_entry_to_page(entry);
if (is_migration_entry(entry))
page = migration_entry_to_page(entry);
Seems safer and doesn't add much code.
With this, we lose an opportunity to capture some bugs during debugging.
Right?
You can keep VM_BUG_ON or VM_WARN_ON_ONCE
Off-by-page in statistics isn't a big deal and not a good reason to crash (even debug) kernel.
But for normal build should use safe behaviour if this isn't hard.
Best Regards,
Huang, Ying
+ } else {
+ return;
+ }
if (IS_ERR_OR_NULL(page))
return;
if (PageAnon(page))
@@ -578,8 +587,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
- if (pmd_present(*pmd))
- smaps_pmd_entry(pmd, addr, walk);
+ smaps_pmd_entry(pmd, addr, walk);
spin_unlock(ptl);
goto out;
}
