Commit fe27d189 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'folio-5.18f' of git://git.infradead.org/users/willy/pagecache 

Pull folio fixes from Matthew Wilcox:
 "Two folio fixes for 5.18.

  Darrick and Brian have done amazing work debugging the race I created
  in the folio BIO iterator. The readahead problem was deterministic, so
  easy to fix.

   - Fix a race when we were calling folio_next() in the BIO folio iter
     without holding a reference, meaning the folio could be split or
     freed, and we'd jump to the next page instead of the intended next
     folio.

   - Fix readahead creating single-page folios instead of the intended
     large folios when doing reads that are not a power of two in size"

* tag 'folio-5.18f' of git://git.infradead.org/users/willy/pagecache:
  mm/readahead: Fix readahead with large folios
  block: Do not call folio_next() on an unreferenced folio
parents f47c960e b9ff43dd

include/linux/bio.h

+4 −1
Original line number Diff line number Diff line
@@ -269,6 +269,7 @@ struct folio_iter { 
	size_t offset;

	size_t length;

	/* private: for use by the iterator */

	struct folio *_next;

	size_t _seg_count;

	int _i;

};
@@ -283,6 +284,7 @@ static inline void bio_first_folio(struct folio_iter *fi, struct bio *bio, 
			PAGE_SIZE * (bvec->bv_page - &fi->folio->page);

	fi->_seg_count = bvec->bv_len;

	fi->length = min(folio_size(fi->folio) - fi->offset, fi->_seg_count);

	fi->_next = folio_next(fi->folio);

	fi->_i = i;

}
@@ -290,9 +292,10 @@ static inline void bio_next_folio(struct folio_iter *fi, struct bio *bio) 
{

	fi->_seg_count -= fi->length;

	if (fi->_seg_count) {

		fi->folio = folio_next(fi->folio);

		fi->folio = fi->_next;

		fi->offset = 0;

		fi->length = min(folio_size(fi->folio), fi->_seg_count);

		fi->_next = folio_next(fi->folio);

	} else if (fi->_i + 1 < bio->bi_vcnt) {

		bio_first_folio(fi, bio, fi->_i + 1);

	} else {

mm/readahead.c

+9 −6
Original line number Diff line number Diff line
@@ -474,7 +474,8 @@ static inline int ra_alloc_folio(struct readahead_control *ractl, pgoff_t index, 


	if (!folio)

		return -ENOMEM;

	if (mark - index < (1UL << order))

	mark = round_up(mark, 1UL << order);

	if (index == mark)

		folio_set_readahead(folio);

	err = filemap_add_folio(ractl->mapping, folio, index, gfp);

	if (err)
@@ -555,8 +556,9 @@ static void ondemand_readahead(struct readahead_control *ractl, 
	struct file_ra_state *ra = ractl->ra;

	unsigned long max_pages = ra->ra_pages;

	unsigned long add_pages;

	unsigned long index = readahead_index(ractl);

	pgoff_t prev_index;

	pgoff_t index = readahead_index(ractl);

	pgoff_t expected, prev_index;

	unsigned int order = folio ? folio_order(folio) : 0;



	/*

	 * If the request exceeds the readahead window, allow the read to
@@ -575,8 +577,9 @@ static void ondemand_readahead(struct readahead_control *ractl, 
	 * It's the expected callback index, assume sequential access.

	 * Ramp up sizes, and push forward the readahead window.

	 */

	if ((index == (ra->start + ra->size - ra->async_size) ||

	     index == (ra->start + ra->size))) {

	expected = round_up(ra->start + ra->size - ra->async_size,

			1UL << order);

	if (index == expected || index == (ra->start + ra->size)) {

		ra->start += ra->size;

		ra->size = get_next_ra_size(ra, max_pages);

		ra->async_size = ra->size;
@@ -662,7 +665,7 @@ static void ondemand_readahead(struct readahead_control *ractl, 
	}



	ractl->_index = ra->start;

	page_cache_ra_order(ractl, ra, folio ? folio_order(folio) : 0);

	page_cache_ra_order(ractl, ra, order);

}



void page_cache_sync_ra(struct readahead_control *ractl,