On Thu, Oct 22, 2020 at 10:22:25PM +0100, Matthew Wilcox (Oracle) wrote:

quoted

+static int readpage_submit_bhs(struct page *page, struct blk_completion *cmpl,
+		unsigned int nr, struct buffer_head **bhs)
+{
+	struct bio *bio = NULL;
+	unsigned int i;
+	int err;
+
+	blk_completion_init(cmpl, nr);
+
+	for (i = 0; i < nr; i++) {
+		struct buffer_head *bh = bhs[i];
+		sector_t sector = bh->b_blocknr * (bh->b_size >> 9);
+		bool same_page;
+
+		if (buffer_uptodate(bh)) {
+			end_buffer_async_read(bh, 1);
+			blk_completion_sub(cmpl, BLK_STS_OK, 1);
+			continue;
+		}
+		if (bio) {
+			if (bio_end_sector(bio) == sector &&
+			    __bio_try_merge_page(bio, bh->b_page, bh->b_size,
+					bh_offset(bh), &same_page))
+				continue;
+			submit_bio(bio);
+		}
+		bio = bio_alloc(GFP_NOIO, 1);
+		bio_set_dev(bio, bh->b_bdev);
+		bio->bi_iter.bi_sector = sector;
+		bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
+		bio->bi_end_io = readpage_end_bio;
+		bio->bi_private = cmpl;
+		/* Take care of bh's that straddle the end of the device */
+		guard_bio_eod(bio);
+	}

The following is needed to set the bio encryption context for the
'-o inlinecrypt' case on ext4:

diff --git a/fs/buffer.c b/fs/buffer.c
index 95c338e2b99c..546a08c5003b 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c

@@ -2237,6 +2237,7 @@ static int readpage_submit_bhs(struct page *page, struct blk_completion *cmpl,
 			submit_bio(bio);
 		}
 		bio = bio_alloc(GFP_NOIO, 1);
+		fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
 		bio_set_dev(bio, bh->b_bdev);
 		bio->bi_iter.bi_sector = sector;
 		bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));