| Message ID | 20230307052036.1520708-2-stevensd@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/khugepaged: fix khugepaged+shmem races | expand |
On Tue, 7 Mar 2023, David Stevens wrote: > From: David Stevens <stevensd@chromium.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@chromium.org> > Acked-by: Peter Xu <peterx@redhat.com> > Reviewed-by: Yang Shi <shy828301@gmail.com> This one looks like a nice de-indentation to me, even if it's not followed by 2/3 and 3/3. Acked-by: Hugh Dickins <hughd@google.com> > --- > mm/khugepaged.c | 219 ++++++++++++++++++++++++------------------------ > 1 file changed, 108 insertions(+), 111 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 3ea2aa55c2c5..b954e3c685e7 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1907,6 +1907,12 @@ 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 > @@ -1919,16 +1925,10 @@ 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 > @@ -2145,129 +2145,126 @@ 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_highpage(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_highpage(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); > - 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); > + /* > + * 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); > + } > + > + 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); > + put_page(hpage); > > - if (hpage) > - unlock_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; > } > -- > 2.40.0.rc0.216.gc4246ad0f0-goog > >
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 3ea2aa55c2c5..b954e3c685e7 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1907,6 +1907,12 @@ 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 @@ -1919,16 +1925,10 @@ 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 @@ -2145,129 +2145,126 @@ 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_highpage(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_highpage(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); - 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); + /* + * 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); + } + + 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); + put_page(hpage); - if (hpage) - unlock_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; }