[PATCH AUTOSEL 5.4 129/130] cdrom: Reset sector_size back it is not 2048.

[Sasha Levin]

From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

[ Upstream commit b5f32555567cfe0a5d5dbe7c1e85ebe37b3f545a ]

In v2.4.0-test2pre2 mmc_ioctl_cdrom_read_data() was extended by issuing
a MODE_SELECT opcode to change the sector size and READ_10 to perform
the actual read if the READ_CD opcode is not support.
The sector size is never changed back to the previous value of 2048
bytes which is however denoted by the comment for version 3.09 of the
cdrom.c file.

Use cdrom_switch_blocksize() to change the sector size only if the
requested size deviates from 2048. Change it back to 2048 after the read
operation if a change was mode.

Link: https://lkml.kernel.org/r/20201204164803.ovwurzs3257em2rp@xxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/cdrom/cdrom.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index eebdcbef0578f..f2e82390ef70c 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -2996,13 +2996,15 @@ static noinline int mmc_ioctl_cdrom_read_data(struct cdrom_device_info *cdi,
 		 * SCSI-II devices are not required to support
 		 * READ_CD, so let's try switching block size
 		 */
-		/* FIXME: switch back again... */
-		ret = cdrom_switch_blocksize(cdi, blocksize);
-		if (ret)
-			goto out;
+		if (blocksize != CD_FRAMESIZE) {
+			ret = cdrom_switch_blocksize(cdi, blocksize);
+			if (ret)
+				goto out;
+		}
 		cgc->sshdr = NULL;
 		ret = cdrom_read_cd(cdi, cgc, lba, blocksize, 1);
-		ret |= cdrom_switch_blocksize(cdi, blocksize);
+		if (blocksize != CD_FRAMESIZE)
+			ret |= cdrom_switch_blocksize(cdi, CD_FRAMESIZE);
 	}
 	if (!ret && copy_to_user(arg, cgc->buffer, blocksize))
 		ret = -EFAULT;
-- 
2.27.0