On Thu, 6 Apr 2023 at 23:12, Muhammad Usama Anjum usama.anjum@collabora.com wrote:
On 4/7/23 1:12 AM, Michał Mirosław wrote:
On Thu, 6 Apr 2023 at 09:40, Muhammad Usama Anjum usama.anjum@collabora.com wrote: [...]
--- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c
[...]
+static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
unsigned long end, struct mm_walk *walk)+{
[...]
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
ptl = pmd_trans_huge_lock(pmd, vma);if (ptl) {[...]
return ret;}+process_smaller_pages:
if (pmd_trans_unstable(pmd))return 0;Why pmd_trans_unstable() is needed here and not only after split_huge_pmd()?
I'm not entirely sure. But the idea is if THP is unstable, we should return. As it doesn't seem like after splitting THP can be unstable, we should not check it. Do you agree with the following?
The description of pmd_trans_unstable() [1] seems to indicate that it is needed only after split_huge_pmd().
[1] https://elixir.bootlin.com/linux/v6.3-rc5/source/include/linux/pgtable.h#L13...
Best Regards Michał Mirosław