From: Joe Jin <joe.jin@oracle.com>
Date: Thu, 6 Apr 2017 23:56:57 +0000 (+0800)
Subject: I/O ERROR WHEN A FILE ON ACFS FILESYSTEM IS ATTACHED TO THE GUEST DOMU
X-Git-Tag: v4.1.12-102.0.20170529_2200~7
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=6f4f658526229c5f2476f5b66dfaef30dca5fa31;p=users%2Fjedix%2Flinux-maple.git

I/O ERROR WHEN A FILE ON ACFS FILESYSTEM IS ATTACHED TO THE GUEST DOMU

Orabug: 25831471

commit "block: loop: prepare for supporing direct IO" used old codes
from lkml, synced it with upstream codes.

Signed-off-by: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Aniket Alshi <aniket.alshi@oracle.com>
Reviewed-by: Jack Vogel <jack.vogel@oracle.com>
---

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 58696da97649e..062dfb6dded95 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -549,24 +549,35 @@ struct switch_request {
 static void __loop_update_dio(struct loop_device *lo, bool dio)
 {
 	struct file *file = lo->lo_backing_file;
-	struct inode *inode = file->f_mapping->host;
+	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = mapping->host;
+	unsigned short sb_bsize = 0;
+	unsigned dio_align = 0;
 	bool use_dio;
 
+	if (inode->i_sb->s_bdev) {
+		sb_bsize = bdev_logical_block_size(inode->i_sb->s_bdev);
+		dio_align = sb_bsize - 1;
+	}
+
 	/*
-	 * loop block's logical block size is 512, now
-	 * we support direct I/O only if the backing
-	 * block devices' minimize I/O size is 512 and
-	 * the offset is aligned with 512.
+	 * We support direct I/O only if lo_offset is aligned with the
+	 * logical I/O size of backing device, and the logical block
+	 * size of loop is bigger than the backing device's and the loop
+	 * needn't transform transfer.
+	 *
+	 * TODO: the above condition may be loosed in the future, and
+	 * direct I/O may be switched runtime at that time because most
+	 * of requests in sane applications should be PAGE_SIZE aligned
 	 */
 	if (dio) {
-		if (inode->i_sb->s_bdev) {
-			if (bdev_io_min(inode->i_sb->s_bdev) == 512 &&
-			    !(lo->lo_offset & 511))
-				use_dio = true;
-			else
-				use_dio = false;
-		} else
+		if (queue_logical_block_size(lo->lo_queue) >= sb_bsize &&
+				!(lo->lo_offset & dio_align) &&
+				mapping->a_ops->direct_IO &&
+				!lo->transfer)
 			use_dio = true;
+		else
+			use_dio = false;
 	} else {
 		use_dio = false;
 	}