From: Christoph Hellwig Date: Fri, 1 Jun 2018 16:03:06 +0000 (-0700) Subject: mm: split ->readpages calls to avoid non-contiguous pages lists X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b3751e6ab45a3b92da1e4acd42ada7b6a4122f2b;p=linux.git mm: split ->readpages calls to avoid non-contiguous pages lists That way file systems don't have to go spotting for non-contiguous pages and work around them. It also kicks off I/O earlier, allowing it to finish earlier and reduce latency. Signed-off-by: Christoph Hellwig Reviewed-by: Dave Chinner Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- diff --git a/mm/readahead.c b/mm/readahead.c index fa4d4b767130f..e273f0de33769 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -140,8 +140,8 @@ out: } /* - * __do_page_cache_readahead() actually reads a chunk of disk. It allocates all - * the pages first, then submits them all for I/O. This avoids the very bad + * __do_page_cache_readahead() actually reads a chunk of disk. It allocates + * the pages first, then submits them for I/O. This avoids the very bad * behaviour which would occur if page allocations are causing VM writeback. * We really don't want to intermingle reads and writes like that. * @@ -177,8 +177,18 @@ unsigned int __do_page_cache_readahead(struct address_space *mapping, rcu_read_lock(); page = radix_tree_lookup(&mapping->i_pages, page_offset); rcu_read_unlock(); - if (page && !radix_tree_exceptional_entry(page)) + if (page && !radix_tree_exceptional_entry(page)) { + /* + * Page already present? Kick off the current batch of + * contiguous pages before continuing with the next + * batch. + */ + if (nr_pages) + read_pages(mapping, filp, &page_pool, nr_pages, + gfp_mask); + nr_pages = 0; continue; + } page = __page_cache_alloc(gfp_mask); if (!page)