[PATCH] zram: do not forget to endio for partial discard requests

[Sergey Senozhatsky <senozhatsky@chromium.org>]

As reported by Qu Wenruo, the following

 getconf PAGESIZE
 65536
 blkdiscard -p 4k /dev/zram0

takes literally forever to complete.  zram doesn't support
partial discards and just returns immediately w/o doing any
discard work in such cases.  The problem is that we forget
to endio on our way out, so blkdiscard sleeps forever in
submit_bio_wait().  Fix this by adding a missing bio_endio()
call.

Fixes: 0120dd6e4e202 ("zram: make zram_bio_discard more self-contained")
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reported-by: Qu Wenruo <wqu@suse.com>
Closes: https://lore.kernel.org/linux-block/92361cd3-fb8b-482e-bc89-15ff1acb9a59@suse.com
Cc: Christoph Hellwig <hch@lst.de>
---
 drivers/block/zram/zram_drv.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index dcea703a6766..b0637423953b 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2683,8 +2683,10 @@ static void zram_bio_discard(struct zram *zram, struct bio *bio)
 	 * skipping this logical block is appropriate here.
 	 */
 	if (offset) {
-		if (n <= (PAGE_SIZE - offset))
+		if (n <= (PAGE_SIZE - offset)) {
+			bio_endio(bio);
 			return;
+		}
 
 		n -= (PAGE_SIZE - offset);
 		index++;
-- 
2.53.0.1018.g2bb0e51243-goog