From b9a8a4195c7d3a51235a4fc974a46ad4e9689ffd Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Wed, 27 May 2020 17:59:22 -0400 Subject: truncate,shmem: Handle truncates that split large folios Handle folio splitting in the parts of the truncation functions which already handle partial pages. Factor all that code out into a new function called truncate_inode_partial_folio(). Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Jan Kara Reviewed-by: William Kucharski --- mm/truncate.c | 117 +++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 75 insertions(+), 42 deletions(-) (limited to 'mm/truncate.c') diff --git a/mm/truncate.c b/mm/truncate.c index 2d1dae085acb..5c87cdc70e7b 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -228,6 +228,58 @@ int truncate_inode_folio(struct address_space *mapping, struct folio *folio) return 0; } +/* + * Handle partial folios. The folio may be entirely within the + * range if a split has raced with us. If not, we zero the part of the + * folio that's within the [start, end] range, and then split the folio if + * it's large. split_page_range() will discard pages which now lie beyond + * i_size, and we rely on the caller to discard pages which lie within a + * newly created hole. + * + * Returns false if splitting failed so the caller can avoid + * discarding the entire folio which is stubbornly unsplit. + */ +bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end) +{ + loff_t pos = folio_pos(folio); + unsigned int offset, length; + + if (pos < start) + offset = start - pos; + else + offset = 0; + length = folio_size(folio); + if (pos + length <= (u64)end) + length = length - offset; + else + length = end + 1 - pos - offset; + + folio_wait_writeback(folio); + if (length == folio_size(folio)) { + truncate_inode_folio(folio->mapping, folio); + return true; + } + + /* + * We may be zeroing pages we're about to discard, but it avoids + * doing a complex calculation here, and then doing the zeroing + * anyway if the page split fails. + */ + folio_zero_range(folio, offset, length); + + cleancache_invalidate_page(folio->mapping, &folio->page); + if (folio_has_private(folio)) + do_invalidatepage(&folio->page, offset, length); + if (!folio_test_large(folio)) + return true; + if (split_huge_page(&folio->page) == 0) + return true; + if (folio_test_dirty(folio)) + return false; + truncate_inode_folio(folio->mapping, folio); + return true; +} + /* * Used to get rid of pages on hardware memory corruption. */ @@ -294,20 +346,16 @@ void truncate_inode_pages_range(struct address_space *mapping, { pgoff_t start; /* inclusive */ pgoff_t end; /* exclusive */ - unsigned int partial_start; /* inclusive */ - unsigned int partial_end; /* exclusive */ struct folio_batch fbatch; pgoff_t indices[PAGEVEC_SIZE]; pgoff_t index; int i; + struct folio *folio; + bool same_folio; if (mapping_empty(mapping)) goto out; - /* Offsets within partial pages */ - partial_start = lstart & (PAGE_SIZE - 1); - partial_end = (lend + 1) & (PAGE_SIZE - 1); - /* * 'start' and 'end' always covers the range of pages to be fully * truncated. Partial pages are covered with 'partial_start' at the @@ -340,47 +388,32 @@ void truncate_inode_pages_range(struct address_space *mapping, cond_resched(); } - if (partial_start) { - struct page *page = find_lock_page(mapping, start - 1); - if (page) { - unsigned int top = PAGE_SIZE; - if (start > end) { - /* Truncation within a single page */ - top = partial_end; - partial_end = 0; - } - wait_on_page_writeback(page); - zero_user_segment(page, partial_start, top); - cleancache_invalidate_page(mapping, page); - if (page_has_private(page)) - do_invalidatepage(page, partial_start, - top - partial_start); - unlock_page(page); - put_page(page); + same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT); + folio = __filemap_get_folio(mapping, lstart >> PAGE_SHIFT, FGP_LOCK, 0); + if (folio) { + same_folio = lend < folio_pos(folio) + folio_size(folio); + if (!truncate_inode_partial_folio(folio, lstart, lend)) { + start = folio->index + folio_nr_pages(folio); + if (same_folio) + end = folio->index; } + folio_unlock(folio); + folio_put(folio); + folio = NULL; } - if (partial_end) { - struct page *page = find_lock_page(mapping, end); - if (page) { - wait_on_page_writeback(page); - zero_user_segment(page, 0, partial_end); - cleancache_invalidate_page(mapping, page); - if (page_has_private(page)) - do_invalidatepage(page, 0, - partial_end); - unlock_page(page); - put_page(page); - } + + if (!same_folio) + folio = __filemap_get_folio(mapping, lend >> PAGE_SHIFT, + FGP_LOCK, 0); + if (folio) { + if (!truncate_inode_partial_folio(folio, lstart, lend)) + end = folio->index; + folio_unlock(folio); + folio_put(folio); } - /* - * If the truncation happened within a single page no pages - * will be released, just zeroed, so we can bail out now. - */ - if (start >= end) - goto out; index = start; - for ( ; ; ) { + while (index < end) { cond_resched(); if (!find_get_entries(mapping, index, end - 1, &fbatch, indices)) { -- cgit v1.2.3-58-ga151