From 8a2f175cbbd9850922fb5bbb96c5a58a4a2d73c0 Mon Sep 17 00:00:00 2001
From: Karel Zak
Date: Wed, 17 Oct 2018 14:10:27 +0200
Subject: lsblk: read queue/discard_granularity only when necessary

Signed-off-by: Karel Zak <kzak@redhat.com>
---
 misc-utils/lsblk-devtree.c |  1 +
 misc-utils/lsblk.c         | 29 +++++++++++++++++------------
 misc-utils/lsblk.h         |  3 ++-
 3 files changed, 20 insertions(+), 13 deletions(-)

(limited to 'misc-utils')

diff --git a/misc-utils/lsblk-devtree.c b/misc-utils/lsblk-devtree.c
index efc165f54..9a6dba0e1 100644
--- a/misc-utils/lsblk-devtree.c
+++ b/misc-utils/lsblk-devtree.c
@@ -22,6 +22,7 @@ struct lsblk_device *lsblk_new_device(struct lsblk_devtree *tree)
 
 	dev->refcount = 1;
 	dev->removable = -1;
+	dev->discard_granularity = (uint64_t) -1;
 	dev->tree = tree;
 
         INIT_LIST_HEAD(&dev->deps);
diff --git a/misc-utils/lsblk.c b/misc-utils/lsblk.c
index aacc0e560..46f8f3260 100644
--- a/misc-utils/lsblk.c
+++ b/misc-utils/lsblk.c
@@ -702,6 +702,17 @@ done:
 	return dev->removable;
 }
 
+static uint64_t device_get_discard_granularity(struct lsblk_device *dev)
+{
+	if (dev->discard_granularity == (uint64_t) -1
+	    && ul_path_read_u64(dev->sysfs, &dev->discard_granularity,
+			        "queue/discard_granularity") != 0)
+		dev->discard_granularity = 0;
+
+	return dev->discard_granularity;
+}
+
+
 /*
  * Generates data (string) for column specified by column ID for specified device
  */
@@ -941,7 +952,7 @@ static void set_scols_data(
 		str = get_subsystems(dev);
 		break;
 	case COL_DALIGN:
-		if (dev->discard)
+		if (device_get_discard_granularity(dev) > 0)
 			ul_path_read_string(dev->sysfs, &str, "discard_alignment");
 		if (!str)
 			str = xstrdup("0");
@@ -954,12 +965,10 @@ static void set_scols_data(
 			if (sort)
 				set_sortdata_u64_from_string(ln, col, str);
 		} else {
-			uint64_t x;
-			if (ul_path_read_u64(dev->sysfs, &x, "queue/discard_granularity") == 0) {
-				str = size_to_human_string(SIZE_SUFFIX_1LETTER, x);
-				if (sort)
-					set_sortdata_u64(ln, col, x);
-			}
+			uint64_t x = device_get_discard_granularity(dev);
+			str = size_to_human_string(SIZE_SUFFIX_1LETTER, x);
+			if (sort)
+				set_sortdata_u64(ln, col, x);
 		}
 		break;
 	case COL_DMAX:
@@ -977,7 +986,7 @@ static void set_scols_data(
 		}
 		break;
 	case COL_DZERO:
-		if (dev->discard)
+		if (device_get_discard_granularity(dev) > 0)
 			ul_path_read_string(dev->sysfs, &str, "queue/discard_zeroes_data");
 		if (!str)
 			str = xstrdup("0");
@@ -1095,10 +1104,6 @@ static int initialize_device(struct lsblk_device *dev,
 	if (ul_path_read_u64(dev->sysfs, &dev->size, "size") == 0)	/* in sectors */
 		dev->size <<= 9;					/* in bytes */
 
-	if (ul_path_read_s32(dev->sysfs, &dev->discard,
-			   "queue/discard_granularity") != 0)
-		dev->discard = 0;
-
 	/* Ignore devices of zero size */
 	if (!lsblk->all_devices && dev->size == 0) {
 		DBG(DEV, ul_debugobj(dev, "zero size device -- ignore"));
diff --git a/misc-utils/lsblk.h b/misc-utils/lsblk.h
index 7cb4e3eee..6cba502cf 100644
--- a/misc-utils/lsblk.h
+++ b/misc-utils/lsblk.h
@@ -106,7 +106,8 @@ struct lsblk_device {
 				 * /sys/block/.../holders */
 	int nslaves;		/* # of devices this device maps to */
 	int maj, min;		/* devno */
-	int discard;		/* supports discard */
+
+	uint64_t discard_granularity;	/* sunknown:-1, yes:1, not:0 */
 
 	uint64_t size;		/* device size */
 	int removable;		/* unknown:-1, yes:1, not:0 */
-- 
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