[PATCH 4.19 19/37] xen-blkfront: allow discard-* nodes to be optional

Greg Kroah-Hartman
2021-02-02T14:53:09Z

From: Roger Pau Monne <roger.pau@citrix.com>

commit 0549cd67b01016b579047bce045b386202a8bcfc upstream.

This is inline with the specification described in blkif.h:

* discard-granularity: should be set to the physical block size if
node is not present.
* discard-alignment, discard-secure: should be set to 0 if node not
present.

This was detected as QEMU would only create the discard-granularity
node but not discard-alignment, and thus the setup done in
blkfront_setup_discard would fail.

Fix blkfront_setup_discard to not fail on missing nodes, and also fix
blkif_set_queue_limits to set the discard granularity to the physical
block size if none is specified in xenbus.

Fixes: ed30bf317c5ce ('xen-blkfront: Handle discard requests.')
Reported-by: Arthur Borsboom <arthurborsboom@gmail.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Tested-By: Arthur Borsboom <arthurborsboom@gmail.com>
Link: https://lore.kernel.org/r/20210119105727.95173-1-roger.pau@citrix.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/block/xen-blkfront.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)

--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -936,7 +936,8 @@ static void blkif_set_queue_limits(struc
if (info->feature_discard) {
blk_queue_flag_set(QUEUE_FLAG_DISCARD, rq);
blk_queue_max_discard_sectors(rq, get_capacity(gd));
- rq->limits.discard_granularity = info->discard_granularity;
+ rq->limits.discard_granularity = info->discard_granularity ?:
+ info->physical_sector_size;
rq->limits.discard_alignment = info->discard_alignment;
if (info->feature_secdiscard)
blk_queue_flag_set(QUEUE_FLAG_SECERASE, rq);
@@ -2169,19 +2170,12 @@ static void blkfront_closing(struct blkf

static void blkfront_setup_discard(struct blkfront_info *info)
{
- int err;
- unsigned int discard_granularity;
- unsigned int discard_alignment;
-
info->feature_discard = 1;
- err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
- "discard-granularity", "%u", &discard_granularity,
- "discard-alignment", "%u", &discard_alignment,
- NULL);
- if (!err) {
- info->discard_granularity = discard_granularity;
- info->discard_alignment = discard_alignment;
- }
+ info->discard_granularity = xenbus_read_unsigned(info->xbdev->otherend,
+ "discard-granularity",
+ 0);
+ info->discard_alignment = xenbus_read_unsigned(info->xbdev->otherend,
+ "discard-alignment", 0);
info->feature_secdiscard =
!!xenbus_read_unsigned(info->xbdev->otherend, "discard-secure",
0);