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Message-Id: <20230217085439.2826375-2-stevensd@google.com>
Date: Fri, 17 Feb 2023 17:54:37 +0900
From: David Stevens <stevensd@...omium.org>
To: linux-mm@...ck.org, Peter Xu <peterx@...hat.com>,
Matthew Wilcox <willy@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
"Kirill A . Shutemov" <kirill@...temov.name>,
Yang Shi <shy828301@...il.com>,
David Hildenbrand <david@...hat.com>,
Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
David Stevens <stevensd@...omium.org>
Subject: [PATCH v4 1/3] mm/khugepaged: refactor collapse_file control flow
From: David Stevens <stevensd@...omium.org>
Add a rollback label to deal with failure, instead of continuously
checking for RESULT_SUCCESS, to make it easier to add more failure
cases. The refactoring also allows the collapse_file tracepoint to
include hpage on success (instead of NULL).
Signed-off-by: David Stevens <stevensd@...omium.org>
---
mm/khugepaged.c | 223 ++++++++++++++++++++++++------------------------
1 file changed, 110 insertions(+), 113 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 8dbc39896811..6a3d6d2e25e0 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1885,6 +1885,12 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
if (result != SCAN_SUCCEED)
goto out;
+ __SetPageLocked(hpage);
+ if (is_shmem)
+ __SetPageSwapBacked(hpage);
+ hpage->index = start;
+ hpage->mapping = mapping;
+
/*
* Ensure we have slots for all the pages in the range. This is
* almost certainly a no-op because most of the pages must be present
@@ -1897,16 +1903,10 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
xas_unlock_irq(&xas);
if (!xas_nomem(&xas, GFP_KERNEL)) {
result = SCAN_FAIL;
- goto out;
+ goto rollback;
}
} while (1);
- __SetPageLocked(hpage);
- if (is_shmem)
- __SetPageSwapBacked(hpage);
- hpage->index = start;
- hpage->mapping = mapping;
-
/*
* At this point the hpage is locked and not up-to-date.
* It's safe to insert it into the page cache, because nobody would
@@ -2123,131 +2123,128 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
*/
try_to_unmap_flush();
- if (result == SCAN_SUCCEED) {
- /*
- * Replacing old pages with new one has succeeded, now we
- * attempt to copy the contents.
- */
- index = start;
- list_for_each_entry(page, &pagelist, lru) {
- while (index < page->index) {
- clear_highpage(hpage + (index % HPAGE_PMD_NR));
- index++;
- }
- if (copy_mc_page(hpage + (page->index % HPAGE_PMD_NR),
- page) > 0) {
- result = SCAN_COPY_MC;
- break;
- }
- index++;
- }
- while (result == SCAN_SUCCEED && index < end) {
+ if (result != SCAN_SUCCEED)
+ goto rollback;
+
+ /*
+ * Replacing old pages with new one has succeeded, now we
+ * attempt to copy the contents.
+ */
+ index = start;
+ list_for_each_entry(page, &pagelist, lru) {
+ while (index < page->index) {
clear_highpage(hpage + (index % HPAGE_PMD_NR));
index++;
}
+ if (copy_mc_page(hpage + (page->index % HPAGE_PMD_NR),
+ page) > 0) {
+ result = SCAN_COPY_MC;
+ goto rollback;
+ }
+ index++;
+ }
+ while (index < end) {
+ clear_highpage(hpage + (index % HPAGE_PMD_NR));
+ index++;
}
- 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);
- ClearPageActive(page);
- ClearPageUnevictable(page);
- unlock_page(page);
- put_page(page);
- }
+ /*
+ * 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);
+ ClearPageActive(page);
+ ClearPageUnevictable(page);
+ unlock_page(page);
+ put_page(page);
+ }
- 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);
+ 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);
- 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);
+ folio_ref_add(folio, HPAGE_PMD_NR - 1);
- folio = page_folio(hpage);
- folio_mark_uptodate(folio);
- folio_ref_add(folio, HPAGE_PMD_NR - 1);
+ if (is_shmem)
+ folio_mark_dirty(folio);
+ folio_add_lru(folio);
- if (is_shmem)
- folio_mark_dirty(folio);
- folio_add_lru(folio);
+ /*
+ * Remove pte page tables, so we can re-fault the page as huge.
+ */
+ result = retract_page_tables(mapping, start, mm, addr, hpage,
+ cc);
+ unlock_page(hpage);
+ goto out;
+
+rollback:
+ /* Something went wrong: roll back page cache changes */
+ xas_lock_irq(&xas);
+ if (nr_none) {
+ mapping->nrpages -= nr_none;
+ shmem_uncharge(mapping->host, nr_none);
+ }
- /*
- * Remove pte page tables, so we can re-fault the page as huge.
- */
- result = retract_page_tables(mapping, start, mm, addr, hpage,
- cc);
- unlock_page(hpage);
- hpage = NULL;
- } else {
- /* Something went wrong: roll back page cache changes */
- xas_lock_irq(&xas);
- if (nr_none) {
- mapping->nrpages -= nr_none;
- shmem_uncharge(mapping->host, nr_none);
+ xas_set(&xas, start);
+ xas_for_each(&xas, page, end - 1) {
+ page = list_first_entry_or_null(&pagelist,
+ struct page, lru);
+ if (!page || xas.xa_index < page->index) {
+ if (!nr_none)
+ break;
+ nr_none--;
+ /* Put holes back where they were */
+ xas_store(&xas, NULL);
+ continue;
}
- xas_set(&xas, start);
- xas_for_each(&xas, page, end - 1) {
- page = list_first_entry_or_null(&pagelist,
- struct page, lru);
- if (!page || xas.xa_index < page->index) {
- if (!nr_none)
- break;
- nr_none--;
- /* Put holes back where they were */
- xas_store(&xas, NULL);
- continue;
- }
+ VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
- VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
+ /* Unfreeze the page. */
+ list_del(&page->lru);
+ page_ref_unfreeze(page, 2);
+ xas_store(&xas, page);
+ xas_pause(&xas);
+ xas_unlock_irq(&xas);
+ unlock_page(page);
+ putback_lru_page(page);
+ 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);
- /* Unfreeze the page. */
- list_del(&page->lru);
- page_ref_unfreeze(page, 2);
- xas_store(&xas, page);
- xas_pause(&xas);
- xas_unlock_irq(&xas);
- unlock_page(page);
- putback_lru_page(page);
- 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);
+ xas_unlock_irq(&xas);
- xas_unlock_irq(&xas);
+ hpage->mapping = NULL;
- hpage->mapping = NULL;
- }
+ unlock_page(hpage);
+ mem_cgroup_uncharge(page_folio(hpage));
+ put_page(hpage);
- if (hpage)
- unlock_page(hpage);
out:
VM_BUG_ON(!list_empty(&pagelist));
- if (hpage) {
- mem_cgroup_uncharge(page_folio(hpage));
- put_page(hpage);
- }
-
trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file, nr, result);
return result;
}
--
2.39.2.637.g21b0678d19-goog
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