diff --git a/mm/readahead.c b/mm/readahead.c index cf0dcf89eb69..5100eaf5b0ee 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -148,7 +148,7 @@ static void read_pages(struct readahead_control *rac, struct list_head *pages, blk_finish_plug(&plug); - BUG_ON(!list_empty(pages)); + BUG_ON(pages && !list_empty(pages)); BUG_ON(readahead_count(rac)); out: @@ -431,11 +431,103 @@ static int try_context_readahead(struct address_space *mapping, return 1; } +/* + * There are some parts of the kernel which assume that PMD entries + * are exactly HPAGE_PMD_ORDER. Those should be fixed, but until then, + * limit the maximum allocation order to PMD size. I'm not aware of any + * assumptions about maximum order if THP are disabled, but 8 seems like + * a good order (that's 1MB if you're using 4kB pages) + */ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +#define MAX_PAGECACHE_ORDER HPAGE_PMD_ORDER +#else +#define MAX_PAGECACHE_ORDER 8 +#endif + +static inline int ra_alloc_folio(struct readahead_control *ractl, pgoff_t index, + pgoff_t mark, unsigned int order, gfp_t gfp) +{ + int err; + struct folio *folio = filemap_alloc_folio(gfp, order); + + if (!folio) + return -ENOMEM; + if (mark - index < (1UL << order)) + folio_set_readahead(folio); + err = filemap_add_folio(ractl->mapping, folio, index, gfp); + if (err) + folio_put(folio); + else + ractl->_nr_pages += 1UL << order; + return err; +} + +static void page_cache_ra_order(struct readahead_control *ractl, + struct file_ra_state *ra, unsigned int new_order) +{ + struct address_space *mapping = ractl->mapping; + pgoff_t index = readahead_index(ractl); + pgoff_t limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT; + pgoff_t mark = index + ra->size - ra->async_size; + int err = 0; + gfp_t gfp = readahead_gfp_mask(mapping); + + if (!mapping_large_folio_support(mapping) || ra->size < 4) + goto fallback; + + limit = min(limit, index + ra->size - 1); + + if (new_order < MAX_PAGECACHE_ORDER) { + new_order += 2; + if (new_order > MAX_PAGECACHE_ORDER) + new_order = MAX_PAGECACHE_ORDER; + while ((1 << new_order) > ra->size) + new_order--; + } + + while (index <= limit) { + unsigned int order = new_order; + + /* Align with smaller pages if needed */ + if (index & ((1UL << order) - 1)) { + order = __ffs(index); + if (order == 1) + order = 0; + } + /* Don't allocate pages past EOF */ + while (index + (1UL << order) - 1 > limit) { + if (--order == 1) + order = 0; + } + err = ra_alloc_folio(ractl, index, mark, order, gfp); + if (err) + break; + index += 1UL << order; + } + + if (index > limit) { + ra->size += index - limit - 1; + ra->async_size += index - limit - 1; + } + + read_pages(ractl, NULL, false); + + /* + * If there were already pages in the page cache, then we may have + * left some gaps. Let the regular readahead code take care of this + * situation. + */ + if (!err) + return; +fallback: + do_page_cache_ra(ractl, ra->size, ra->async_size); +} + /* * A minimal readahead algorithm for trivial sequential/random reads. */ static void ondemand_readahead(struct readahead_control *ractl, - bool hit_readahead_marker, unsigned long req_size) + struct folio *folio, unsigned long req_size) { struct backing_dev_info *bdi = inode_to_bdi(ractl->mapping->host); struct file_ra_state *ra = ractl->ra; @@ -470,12 +562,12 @@ static void ondemand_readahead(struct readahead_control *ractl, } /* - * Hit a marked page without valid readahead state. + * Hit a marked folio without valid readahead state. * E.g. interleaved reads. * Query the pagecache for async_size, which normally equals to * readahead size. Ramp it up and use it as the new readahead size. */ - if (hit_readahead_marker) { + if (folio) { pgoff_t start; rcu_read_lock(); @@ -548,7 +640,7 @@ static void ondemand_readahead(struct readahead_control *ractl, } ractl->_index = ra->start; - do_page_cache_ra(ractl, ra->size, ra->async_size); + page_cache_ra_order(ractl, ra, folio ? folio_order(folio) : 0); } void page_cache_sync_ra(struct readahead_control *ractl, @@ -576,7 +668,7 @@ void page_cache_sync_ra(struct readahead_control *ractl, } /* do read-ahead */ - ondemand_readahead(ractl, false, req_count); + ondemand_readahead(ractl, NULL, req_count); } EXPORT_SYMBOL_GPL(page_cache_sync_ra); @@ -605,7 +697,7 @@ void page_cache_async_ra(struct readahead_control *ractl, return; /* do read-ahead */ - ondemand_readahead(ractl, true, req_count); + ondemand_readahead(ractl, folio, req_count); } EXPORT_SYMBOL_GPL(page_cache_async_ra);