X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=mm%2Freadahead.c;h=fe1a069fb59571488af927b54abce0e9f56fd88e;hb=3332f84e0b969bd699d783e00e72a9110929eeed;hp=aa1aa23452355067af9d62179cd41d62c64e68fc;hpb=5e75c5f5d723074b1ceefe916c3005888e431d12;p=firefly-linux-kernel-4.4.55.git

diff --git a/mm/readahead.c b/mm/readahead.c
index aa1aa2345235..fe1a069fb595 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -501,6 +501,12 @@ void page_cache_sync_readahead(struct address_space *mapping,
 	if (!ra->ra_pages)
 		return;
 
+	/* be dumb */
+	if (filp && (filp->f_mode & FMODE_RANDOM)) {
+		force_page_cache_readahead(mapping, filp, offset, req_size);
+		return;
+	}
+
 	/* do read-ahead */
 	ondemand_readahead(mapping, ra, filp, false, offset, req_size);
 }
@@ -547,5 +553,17 @@ page_cache_async_readahead(struct address_space *mapping,
 
 	/* do read-ahead */
 	ondemand_readahead(mapping, ra, filp, true, offset, req_size);
+
+#ifdef CONFIG_BLOCK
+	/*
+	 * Normally the current page is !uptodate and lock_page() will be
+	 * immediately called to implicitly unplug the device. However this
+	 * is not always true for RAID conifgurations, where data arrives
+	 * not strictly in their submission order. In this case we need to
+	 * explicitly kick off the IO.
+	 */
+	if (PageUptodate(page))
+		blk_run_backing_dev(mapping->backing_dev_info, NULL);
+#endif
 }
 EXPORT_SYMBOL_GPL(page_cache_async_readahead);