The patch titled
Subject: mm/khugepaged: don't check pmd value twice in collapse_pte_mapped_thp()
has been added to the -mm mm-unstable branch. Its filename is
mm-madvise-add-file-and-shmem-support-to-madv_collapse-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-madvise-add-file-and-shmem-support-to-madv_collapse-fix.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: "Zach O'Keefe" <zokeefe@xxxxxxxxxx>
Subject: mm/khugepaged: don't check pmd value twice in collapse_pte_mapped_thp()
Date: Mon, 26 Sep 2022 20:38:54 -0700
During the v3 -> v4 merge of series "mm: add file/shmem support to
MADV_COLLAPSE", a line deletion was accidentally dropped, which left
collapse_pte_mapped_thp() in state:
---8<---
<mmap_lock held exclusively>
result = find_pmd_or_thp_or_none(mm, haddr, &pmd);
<other checks that don't change "result" unless fail>
(*) if (find_pmd_or_thp_or_none(mm, haddr, &pmd) != SCAN_SUCCEED)
result = find_pmd_or_thp_or_none(mm, haddr, &pmd);
switch (result) {
case SCAN_SUCCEED:
---8<---
Where (*) is the line that should have been deleted (note that this is
still legal C). Since the selftests are still passing, this mistake
highlights the fact that the second (intended) find_pmd_or_thp_or_none()
isn't necessary: the first one is called with mmap_lock held
exclusively, we don't drop the lock in this function, and "result" isn't
changed between assignment and use in the switch-statement (except for
failure paths which either return early or skip to "drop_hpage" label).
Remove the second (intended) find_pmd_or_thp_or_none() check, and the
misplaced find_pmd_or_thp_or_none() if-statement line.
Link: https://lkml.kernel.org/r/20220927033854.477018-1-zokeefe@xxxxxxxxxx
Fixes: c27451af51cc ("mm/madvise: add file and shmem support to MADV_COLLAPSE")
Signed-off-by: Zach O'Keefe <zokeefe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/khugepaged.c~mm-madvise-add-file-and-shmem-support-to-madv_collapse-fix
+++ a/mm/khugepaged.c
@@ -1463,8 +1463,6 @@ int collapse_pte_mapped_thp(struct mm_st
goto drop_hpage;
}
- if (find_pmd_or_thp_or_none(mm, haddr, &pmd) != SCAN_SUCCEED)
- result = find_pmd_or_thp_or_none(mm, haddr, &pmd);
switch (result) {
case SCAN_SUCCEED:
break;
_
Patches currently in -mm which might be from zokeefe@xxxxxxxxxx are
mm-khugepaged-check-compound_order-in-collapse_pte_mapped_thp.patch
mm-madvise-madv_collapse-return-eagain-when-page-cannot-be-isolated.patch
selftests-vm-retry-on-eagain-for-madv_collapse-selftest.patch
mm-shmem-add-flag-to-enforce-shmem-thp-in-hugepage_vma_check.patch
mm-khugepaged-attempt-to-map-file-shmem-backed-pte-mapped-thps-by-pmds.patch
mm-madvise-add-file-and-shmem-support-to-madv_collapse.patch
mm-madvise-add-file-and-shmem-support-to-madv_collapse-fix.patch
mm-khugepaged-add-tracepoint-to-hpage_collapse_scan_file.patch
selftests-vm-dedup-thp-helpers.patch
selftests-vm-modularize-thp-collapse-memory-operations.patch
selftests-vm-add-thp-collapse-file-and-tmpfs-testing.patch
selftests-vm-add-thp-collapse-shmem-testing.patch
selftests-vm-add-file-shmem-madv_collapse-selftest-for-cleared-pmd.patch
selftests-vm-add-selftest-for-madv_collapse-of-uffd-minor-memory.patch
