The quilt patch titled
Subject: mm/khugepaged: recover from poisoned file-backed memory
has been removed from the -mm tree. Its filename was
mm-khugepaged-recover-from-poisoned-file-backed-memory.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Jiaqi Yan <jiaqiyan@xxxxxxxxxx>
Subject: mm/khugepaged: recover from poisoned file-backed memory
Date: Wed, 29 Mar 2023 08:11:21 -0700
Make collapse_file roll back when copying pages failed. More concretely:
- extract copying operations into a separate loop
- postpone the updates for nr_none until both scanning and copying
succeeded
- postpone joining small xarray entries until both scanning and copying
succeeded
- postpone the update operations to NR_XXX_THPS until both scanning and
copying succeeded
- for non-SHMEM file, roll back filemap_nr_thps_inc if scan succeeded but
copying failed
Tested manually:
0. Enable khugepaged on system under test. Mount tmpfs at /mnt/ramdisk.
1. Start a two-thread application. Each thread allocates a chunk of
non-huge memory buffer from /mnt/ramdisk.
2. Pick 4 random buffer address (2 in each thread) and inject
uncorrectable memory errors at physical addresses.
3. Signal both threads to make their memory buffer collapsible, i.e.
calling madvise(MADV_HUGEPAGE).
4. Wait and then check kernel log: khugepaged is able to recover from
poisoned pages by skipping them.
5. Signal both threads to inspect their buffer contents and make sure no
data corruption.
Link: https://lkml.kernel.org/r/20230329151121.949896-4-jiaqiyan@xxxxxxxxxx
Signed-off-by: Jiaqi Yan <jiaqiyan@xxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: David Stevens <stevensd@xxxxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Tong Tiangen <tongtiangen@xxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/khugepaged.c | 87 +++++++++++++++++++++++++++++-----------------
1 file changed, 56 insertions(+), 31 deletions(-)
--- a/mm/khugepaged.c~mm-khugepaged-recover-from-poisoned-file-backed-memory
+++ a/mm/khugepaged.c
@@ -1877,6 +1877,9 @@ static int collapse_file(struct mm_struc
{
struct address_space *mapping = file->f_mapping;
struct page *hpage;
+ struct page *page;
+ struct page *tmp;
+ struct folio *folio;
pgoff_t index = 0, end = start + HPAGE_PMD_NR;
LIST_HEAD(pagelist);
XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
@@ -1921,8 +1924,7 @@ static int collapse_file(struct mm_struc
xas_set(&xas, start);
for (index = start; index < end; index++) {
- struct page *page = xas_next(&xas);
- struct folio *folio;
+ page = xas_next(&xas);
VM_BUG_ON(index != xas.xa_index);
if (is_shmem) {
@@ -2116,12 +2118,8 @@ out_unlock:
put_page(page);
goto xa_unlocked;
}
- nr = thp_nr_pages(hpage);
- if (is_shmem)
- __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
- else {
- __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
+ if (!is_shmem) {
filemap_nr_thps_inc(mapping);
/*
* Paired with smp_mb() in do_dentry_open() to ensure
@@ -2132,21 +2130,10 @@ out_unlock:
smp_mb();
if (inode_is_open_for_write(mapping->host)) {
result = SCAN_FAIL;
- __mod_lruvec_page_state(hpage, NR_FILE_THPS, -nr);
filemap_nr_thps_dec(mapping);
- goto xa_locked;
}
}
- if (nr_none) {
- __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
- /* nr_none is always 0 for non-shmem. */
- __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
- }
-
- /* Join all the small entries into a single multi-index entry */
- xas_set_order(&xas, start, HPAGE_PMD_ORDER);
- xas_store(&xas, hpage);
/* Here we can't get an ENOMEM (because entries were
* previously allocated) But let's check for errors
* (XArray implementation can be changed in the future)
@@ -2164,21 +2151,36 @@ xa_unlocked:
try_to_unmap_flush();
if (result == SCAN_SUCCEED) {
- struct page *page, *tmp;
- struct folio *folio;
-
/*
* Replacing old pages with new one has succeeded, now we
- * need to copy the content and free the old pages.
+ * attempt to copy the contents.
*/
index = start;
- list_for_each_entry_safe(page, tmp, &pagelist, lru) {
+ list_for_each_entry(page, &pagelist, lru) {
while (index < page->index) {
clear_highpage(hpage + (index % HPAGE_PMD_NR));
index++;
}
- copy_highpage(hpage + (page->index % HPAGE_PMD_NR),
- page);
+ if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR),
+ page) > 0) {
+ result = SCAN_COPY_MC;
+ break;
+ }
+ index++;
+ }
+ while (result == SCAN_SUCCEED && index < end) {
+ clear_highpage(hpage + (index % HPAGE_PMD_NR));
+ index++;
+ }
+ }
+
+ nr = thp_nr_pages(hpage);
+ if (result == SCAN_SUCCEED) {
+ /*
+ * Copying old pages to huge one has succeeded, now we
+ * need to free the old pages.
+ */
+ list_for_each_entry_safe(page, tmp, &pagelist, lru) {
list_del(&page->lru);
page->mapping = NULL;
page_ref_unfreeze(page, 1);
@@ -2186,12 +2188,23 @@ xa_unlocked:
ClearPageUnevictable(page);
unlock_page(page);
put_page(page);
- index++;
}
- while (index < end) {
- clear_highpage(hpage + (index % HPAGE_PMD_NR));
- index++;
+
+ xas_lock_irq(&xas);
+ if (is_shmem)
+ __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
+ else
+ __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
+
+ if (nr_none) {
+ __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
+ /* nr_none is always 0 for non-shmem. */
+ __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
}
+ /* Join all the small entries into a single multi-index entry. */
+ xas_set_order(&xas, start, HPAGE_PMD_ORDER);
+ xas_store(&xas, hpage);
+ xas_unlock_irq(&xas);
folio = page_folio(hpage);
folio_mark_uptodate(folio);
@@ -2209,8 +2222,6 @@ xa_unlocked:
unlock_page(hpage);
hpage = NULL;
} else {
- struct page *page;
-
/* Something went wrong: roll back page cache changes */
xas_lock_irq(&xas);
if (nr_none) {
@@ -2244,6 +2255,20 @@ xa_unlocked:
xas_lock_irq(&xas);
}
VM_BUG_ON(nr_none);
+ /*
+ * Undo the updates of filemap_nr_thps_inc for non-SHMEM
+ * file only. This undo is not needed unless failure is
+ * due to SCAN_COPY_MC.
+ */
+ if (!is_shmem && result == SCAN_COPY_MC) {
+ filemap_nr_thps_dec(mapping);
+ /*
+ * Paired with smp_mb() in do_dentry_open() to
+ * ensure the update to nr_thps is visible.
+ */
+ smp_mb();
+ }
+
xas_unlock_irq(&xas);
hpage->mapping = NULL;
_
Patches currently in -mm which might be from jiaqiyan@xxxxxxxxxx are
