[PATCH 2/2] Revert "s390/dasd: Add discard support for ESE volumes"

[Stefan Haberland <sth@linux.ibm.com>]

This reverts commit 7e64db1597fe114b83fe17d0ba96c6aa5fca419a.

The thin provisioning feature introduces an IOCTL and the discard support
to allow userspace tools and filesystems to release unused and previously
allocated space respectively.

During some internal performance improvements and further tests, the
release of allocated space revealed some issues that may lead to data
corruption in some configurations when filesystems are mounted with
discard support enabled.

While we're working on a fix and trying to clarify the situation,
this commit reverts the discard support for ESE volumes to prevent
potential data corruption.

Cc: <stable@vger.kernel.org> # 5.3
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 drivers/s390/block/dasd_eckd.c | 57 ++--------------------------------
 1 file changed, 3 insertions(+), 54 deletions(-)

diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index b213c40d1a51..c94184d080f8 100644
--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -2055,9 +2055,6 @@ dasd_eckd_check_characteristics(struct dasd_device *device)
 	if (readonly)
 		set_bit(DASD_FLAG_DEVICE_RO, &device->flags);
 
-	if (dasd_eckd_is_ese(device))
-		dasd_set_feature(device->cdev, DASD_FEATURE_DISCARD, 1);
-
 	dev_info(&device->cdev->dev, "New DASD %04X/%02X (CU %04X/%02X) "
 		 "with %d cylinders, %d heads, %d sectors%s\n",
 		 private->rdc_data.dev_type,
@@ -3691,14 +3688,6 @@ static int dasd_eckd_release_space(struct dasd_device *device,
 		return -EINVAL;
 }
 
-static struct dasd_ccw_req *
-dasd_eckd_build_cp_discard(struct dasd_device *device, struct dasd_block *block,
-			   struct request *req, sector_t first_trk,
-			   sector_t last_trk)
-{
-	return dasd_eckd_dso_ras(device, block, req, first_trk, last_trk, 1);
-}
-
 static struct dasd_ccw_req *dasd_eckd_build_cp_cmd_single(
 					       struct dasd_device *startdev,
 					       struct dasd_block *block,
@@ -4443,10 +4432,6 @@ static struct dasd_ccw_req *dasd_eckd_build_cp(struct dasd_device *startdev,
 	cmdwtd = private->features.feature[12] & 0x40;
 	use_prefix = private->features.feature[8] & 0x01;
 
-	if (req_op(req) == REQ_OP_DISCARD)
-		return dasd_eckd_build_cp_discard(startdev, block, req,
-						  first_trk, last_trk);
-
 	cqr = NULL;
 	if (cdlspecial || dasd_page_cache) {
 		/* do nothing, just fall through to the cmd mode single case */
@@ -4725,14 +4710,12 @@ static struct dasd_ccw_req *dasd_eckd_build_alias_cp(struct dasd_device *base,
 						     struct dasd_block *block,
 						     struct request *req)
 {
-	struct dasd_device *startdev = NULL;
 	struct dasd_eckd_private *private;
-	struct dasd_ccw_req *cqr;
+	struct dasd_device *startdev;
 	unsigned long flags;
+	struct dasd_ccw_req *cqr;
 
-	/* Discard requests can only be processed on base devices */
-	if (req_op(req) != REQ_OP_DISCARD)
-		startdev = dasd_alias_get_start_dev(base);
+	startdev = dasd_alias_get_start_dev(base);
 	if (!startdev)
 		startdev = base;
 	private = startdev->private;
@@ -6513,20 +6496,8 @@ static void dasd_eckd_setup_blk_queue(struct dasd_block *block)
 	unsigned int logical_block_size = block->bp_block;
 	struct request_queue *q = block->request_queue;
 	struct dasd_device *device = block->base;
-	struct dasd_eckd_private *private;
-	unsigned int max_discard_sectors;
-	unsigned int max_bytes;
-	unsigned int ext_bytes; /* Extent Size in Bytes */
-	int recs_per_trk;
-	int trks_per_cyl;
-	int ext_limit;
-	int ext_size; /* Extent Size in Cylinders */
 	int max;
 
-	private = device->private;
-	trks_per_cyl = private->rdc_data.trk_per_cyl;
-	recs_per_trk = recs_per_track(&private->rdc_data, 0, logical_block_size);
-
 	if (device->features & DASD_FEATURE_USERAW) {
 		/*
 		 * the max_blocks value for raw_track access is 256
@@ -6547,28 +6518,6 @@ static void dasd_eckd_setup_blk_queue(struct dasd_block *block)
 	/* With page sized segments each segment can be translated into one idaw/tidaw */
 	blk_queue_max_segment_size(q, PAGE_SIZE);
 	blk_queue_segment_boundary(q, PAGE_SIZE - 1);
-
-	if (dasd_eckd_is_ese(device)) {
-		/*
-		 * Depending on the extent size, up to UINT_MAX bytes can be
-		 * accepted. However, neither DASD_ECKD_RAS_EXTS_MAX nor the
-		 * device limits should be exceeded.
-		 */
-		ext_size = dasd_eckd_ext_size(device);
-		ext_limit = min(private->real_cyl / ext_size, DASD_ECKD_RAS_EXTS_MAX);
-		ext_bytes = ext_size * trks_per_cyl * recs_per_trk *
-			logical_block_size;
-		max_bytes = UINT_MAX - (UINT_MAX % ext_bytes);
-		if (max_bytes / ext_bytes > ext_limit)
-			max_bytes = ext_bytes * ext_limit;
-
-		max_discard_sectors = max_bytes / 512;
-
-		blk_queue_max_discard_sectors(q, max_discard_sectors);
-		blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
-		q->limits.discard_granularity = ext_bytes;
-		q->limits.discard_alignment = ext_bytes;
-	}
 }
 
 static struct ccw_driver dasd_eckd_driver = {
-- 
2.17.1