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Shutemov" , Yang Shi , David Hildenbrand , Jiaqi Yan , linux-kernel@vger.kernel.org, David Stevens Subject: [PATCH v6 2/4] mm/khugepaged: refactor collapse_file control flow Date: Tue, 4 Apr 2023 21:01:15 +0900 Message-Id: <20230404120117.2562166-3-stevensd@google.com> X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog In-Reply-To: <20230404120117.2562166-1-stevensd@google.com> References: <20230404120117.2562166-1-stevensd@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: David Stevens 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 Acked-by: Peter Xu Reviewed-by: Yang Shi Acked-by: Hugh Dickins --- mm/khugepaged.c | 230 ++++++++++++++++++++++++------------------------ 1 file changed, 113 insertions(+), 117 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 90577247cfaf..90828272a065 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1890,6 +1890,12 @@ static int collapse_file(struct mm_struct *mm, unsig= ned long addr, if (result !=3D SCAN_SUCCEED) goto out; =20 + __SetPageLocked(hpage); + if (is_shmem) + __SetPageSwapBacked(hpage); + hpage->index =3D start; + hpage->mapping =3D 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 @@ -1902,16 +1908,10 @@ static int collapse_file(struct mm_struct *mm, unsi= gned long addr, xas_unlock_irq(&xas); if (!xas_nomem(&xas, GFP_KERNEL)) { result =3D SCAN_FAIL; - goto out; + goto rollback; } } while (1); =20 - __SetPageLocked(hpage); - if (is_shmem) - __SetPageSwapBacked(hpage); - hpage->index =3D start; - hpage->mapping =3D 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 @@ -2137,137 +2137,133 @@ static int collapse_file(struct mm_struct *mm, un= signed long addr, */ try_to_unmap_flush(); =20 - if (result =3D=3D SCAN_SUCCEED) { - /* - * Replacing old pages with new one has succeeded, now we - * attempt to copy the contents. - */ - index =3D start; - list_for_each_entry(page, &pagelist, lru) { - while (index < page->index) { - clear_highpage(hpage + (index % HPAGE_PMD_NR)); - index++; - } - if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR), - page) > 0) { - result =3D SCAN_COPY_MC; - break; - } - index++; - } - while (result =3D=3D SCAN_SUCCEED && index < end) { + if (result !=3D SCAN_SUCCEED) + goto rollback; + + /* + * Replacing old pages with new one has succeeded, now we + * attempt to copy the contents. + */ + index =3D start; + list_for_each_entry(page, &pagelist, lru) { + while (index < page->index) { clear_highpage(hpage + (index % HPAGE_PMD_NR)); index++; } + if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR), page) > 0) { + result =3D SCAN_COPY_MC; + goto rollback; + } + index++; + } + while (index < end) { + clear_highpage(hpage + (index % HPAGE_PMD_NR)); + index++; + } + + /* + * 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 =3D NULL; + page_ref_unfreeze(page, 1); + ClearPageActive(page); + ClearPageUnevictable(page); + unlock_page(page); + put_page(page); } =20 nr =3D thp_nr_pages(hpage); - if (result =3D=3D 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 =3D 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); =20 - 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); =20 - 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 =3D page_folio(hpage); + folio_mark_uptodate(folio); + folio_ref_add(folio, HPAGE_PMD_NR - 1); =20 - folio =3D 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); =20 - 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 =3D 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 -=3D nr_none; + shmem_uncharge(mapping->host, nr_none); + } =20 - /* - * Remove pte page tables, so we can re-fault the page as huge. - */ - result =3D retract_page_tables(mapping, start, mm, addr, hpage, - cc); - unlock_page(hpage); - hpage =3D NULL; - } else { - /* Something went wrong: roll back page cache changes */ - xas_lock_irq(&xas); - if (nr_none) { - mapping->nrpages -=3D nr_none; - shmem_uncharge(mapping->host, nr_none); + xas_set(&xas, start); + xas_for_each(&xas, page, end - 1) { + page =3D 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; } =20 - xas_set(&xas, start); - xas_for_each(&xas, page, end - 1) { - page =3D 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 !=3D xas.xa_index, page); =20 - VM_BUG_ON_PAGE(page->index !=3D 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); + /* 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 =3D=3D SCAN_COPY_MC) { + filemap_nr_thps_dec(mapping); /* - * 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. + * Paired with smp_mb() in do_dentry_open() to + * ensure the update to nr_thps is visible. */ - if (!is_shmem && result =3D=3D 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(); - } + smp_mb(); + } =20 - xas_unlock_irq(&xas); + xas_unlock_irq(&xas); =20 - hpage->mapping =3D NULL; - } + hpage->mapping =3D NULL; =20 - if (hpage) - unlock_page(hpage); + unlock_page(hpage); + put_page(hpage); out: VM_BUG_ON(!list_empty(&pagelist)); - if (hpage) - put_page(hpage); - trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file,= nr, result); return result; } --=20 2.40.0.348.gf938b09366-goog