device-mapper-multipath/0016-libmultipath-sysfs_attr_set_value-don-t-return-0-on-.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Martin Wilck <mwilck@suse.com>
Date: Tue, 5 Jul 2022 17:51:41 +0200
Subject: [PATCH] libmultipath: sysfs_attr_set_value(): don't return 0 on
 partial write

sysfs_attr_set_value() returned 0 if not all requested bytes were written.
Change this to return the number of bytes written. Error checking is now
somewhat more involved; provide a helper macro for it.

Signed-off-by: Martin Wilck <mwilck@suse.com>
Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
---
 libmultipath/configure.c | 10 ++++--
 libmultipath/discovery.c | 74 +++++++++++++++++++++++++---------------
 libmultipath/sysfs.c     |  6 ++--
 libmultipath/sysfs.h     | 10 ++++++
 4 files changed, 66 insertions(+), 34 deletions(-)

diff --git a/libmultipath/configure.c b/libmultipath/configure.c
index 467bbaa6..0607dbac 100644
--- a/libmultipath/configure.c
+++ b/libmultipath/configure.c
@@ -568,6 +568,7 @@ sysfs_set_max_sectors_kb(struct multipath *mpp, int is_reload)
 	struct pathgroup * pgp;
 	struct path *pp;
 	char buff[11];
+	ssize_t len;
 	int i, j, ret, err = 0;
 	struct udev_device *udd;
 	int max_sectors_kb;
@@ -600,14 +601,17 @@ sysfs_set_max_sectors_kb(struct multipath *mpp, int is_reload)
 		}
 	}
 	snprintf(buff, 11, "%d", max_sectors_kb);
+	len = strlen(buff);
 
 	vector_foreach_slot (mpp->pg, pgp, i) {
 		vector_foreach_slot(pgp->paths, pp, j) {
 			ret = sysfs_attr_set_value(pp->udev,
 						   "queue/max_sectors_kb",
-						   buff, strlen(buff));
-			if (ret < 0) {
-				condlog(1, "failed setting max_sectors_kb on %s : %s", pp->dev, strerror(-ret));
+						   buff, len);
+			if (ret != len) {
+				log_sysfs_attr_set_value(1, ret,
+					"failed setting max_sectors_kb on %s",
+					pp->dev);
 				err = 1;
 			}
 		}
diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
index 54b1caf0..ee290093 100644
--- a/libmultipath/discovery.c
+++ b/libmultipath/discovery.c
@@ -598,13 +598,15 @@ sysfs_set_eh_deadline(struct path *pp)
 		len = sprintf(value, "%d", pp->eh_deadline);
 
 	ret = sysfs_attr_set_value(hostdev, "eh_deadline",
-				   value, len + 1);
+				   value, len);
 	/*
 	 * not all scsi drivers support setting eh_deadline, so failing
 	 * is totally reasonable
 	 */
-	if (ret <= 0)
-		condlog(3, "%s: failed to set eh_deadline to %s, error %d", udev_device_get_sysname(hostdev), value, -ret);
+	if (ret != len)
+		log_sysfs_attr_set_value(3, ret,
+			"%s: failed to set eh_deadline to %s",
+			udev_device_get_sysname(hostdev), value);
 
 	udev_device_unref(hostdev);
 	return (ret <= 0);
@@ -667,19 +669,22 @@ sysfs_set_rport_tmo(struct multipath *mpp, struct path *pp)
 	    pp->fast_io_fail != MP_FAST_IO_FAIL_OFF) {
 		/* Check if we need to temporarily increase dev_loss_tmo */
 		if ((unsigned int)pp->fast_io_fail >= tmo) {
+			ssize_t len;
+
 			/* Increase dev_loss_tmo temporarily */
 			snprintf(value, sizeof(value), "%u",
 				 (unsigned int)pp->fast_io_fail + 1);
+			len = strlen(value);
 			ret = sysfs_attr_set_value(rport_dev, "dev_loss_tmo",
-						   value, strlen(value));
-			if (ret <= 0) {
+						   value, len);
+			if (ret != len) {
 				if (ret == -EBUSY)
 					condlog(3, "%s: rport blocked",
 						rport_id);
 				else
-					condlog(0, "%s: failed to set "
-						"dev_loss_tmo to %s, error %d",
-						rport_id, value, -ret);
+					log_sysfs_attr_set_value(0, ret,
+						"%s: failed to set dev_loss_tmo to %s",
+						rport_id, value);
 				goto out;
 			}
 		}
@@ -691,32 +696,39 @@ sysfs_set_rport_tmo(struct multipath *mpp, struct path *pp)
 		pp->dev_loss = DEFAULT_DEV_LOSS_TMO;
 	}
 	if (pp->fast_io_fail != MP_FAST_IO_FAIL_UNSET) {
+		ssize_t len;
+
 		if (pp->fast_io_fail == MP_FAST_IO_FAIL_OFF)
 			sprintf(value, "off");
 		else if (pp->fast_io_fail == MP_FAST_IO_FAIL_ZERO)
 			sprintf(value, "0");
 		else
 			snprintf(value, 16, "%u", pp->fast_io_fail);
+		len = strlen(value);
 		ret = sysfs_attr_set_value(rport_dev, "fast_io_fail_tmo",
-					   value, strlen(value));
-		if (ret <= 0) {
+					   value, len);
+		if (ret != len) {
 			if (ret == -EBUSY)
 				condlog(3, "%s: rport blocked", rport_id);
 			else
-				condlog(0, "%s: failed to set fast_io_fail_tmo to %s, error %d",
-					rport_id, value, -ret);
+				log_sysfs_attr_set_value(0, ret,
+					"%s: failed to set fast_io_fail_tmo to %s",
+					rport_id, value);
 		}
 	}
 	if (pp->dev_loss != DEV_LOSS_TMO_UNSET) {
+		ssize_t len;
+
 		snprintf(value, 16, "%u", pp->dev_loss);
-		ret = sysfs_attr_set_value(rport_dev, "dev_loss_tmo",
-					   value, strlen(value));
-		if (ret <= 0) {
+		len = strlen(value);
+		ret = sysfs_attr_set_value(rport_dev, "dev_loss_tmo", value, len);
+		if (ret != len) {
 			if (ret == -EBUSY)
 				condlog(3, "%s: rport blocked", rport_id);
 			else
-				condlog(0, "%s: failed to set dev_loss_tmo to %s, error %d",
-					rport_id, value, -ret);
+				log_sysfs_attr_set_value(0, ret,
+					"%s: failed to set dev_loss_tmo to %s",
+					rport_id, value);
 		}
 	}
 out:
@@ -754,12 +766,16 @@ sysfs_set_session_tmo(struct path *pp)
 			condlog(3, "%s: can't set fast_io_fail_tmo to '0'"
 				"on iSCSI", pp->dev);
 		} else {
+			ssize_t len, ret;
+
 			snprintf(value, 11, "%u", pp->fast_io_fail);
-			if (sysfs_attr_set_value(session_dev, "recovery_tmo",
-						 value, strlen(value)) <= 0) {
-				condlog(3, "%s: Failed to set recovery_tmo, "
-					" error %d", pp->dev, errno);
-			}
+			len = strlen(value);
+			ret = sysfs_attr_set_value(session_dev, "recovery_tmo",
+						   value, len);
+			if (ret != len)
+				log_sysfs_attr_set_value(3, ret,
+					"%s: Failed to set recovery_tmo to %s",
+							 pp->dev, value);
 		}
 	}
 	udev_device_unref(session_dev);
@@ -802,12 +818,16 @@ sysfs_set_nexus_loss_tmo(struct path *pp)
 		pp->sg_id.channel, pp->sg_id.scsi_id, end_dev_id);
 
 	if (pp->dev_loss != DEV_LOSS_TMO_UNSET) {
+		ssize_t len, ret;
+
 		snprintf(value, 11, "%u", pp->dev_loss);
-		if (sysfs_attr_set_value(sas_dev, "I_T_nexus_loss_timeout",
-					 value, strlen(value)) <= 0)
-			condlog(3, "%s: failed to update "
-				"I_T Nexus loss timeout, error %d",
-				pp->dev, errno);
+		len = strlen(value);
+		ret = sysfs_attr_set_value(sas_dev, "I_T_nexus_loss_timeout",
+					   value, len);
+		if (ret != len)
+			log_sysfs_attr_set_value(3, ret,
+				"%s: failed to update I_T Nexus loss timeout",
+				pp->dev);
 	}
 	udev_device_unref(sas_dev);
 	return;
diff --git a/libmultipath/sysfs.c b/libmultipath/sysfs.c
index 125f1c2b..9c84af70 100644
--- a/libmultipath/sysfs.c
+++ b/libmultipath/sysfs.c
@@ -134,7 +134,7 @@ ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
 	/* write attribute value */
 	fd = open(devpath, O_WRONLY);
 	if (fd < 0) {
-		condlog(2, "%s: attribute '%s' can not be opened: %s",
+		condlog(3, "%s: attribute '%s' can not be opened: %s",
 			__func__, devpath, strerror(errno));
 		return -errno;
 	}
@@ -144,11 +144,9 @@ ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
 		size = -errno;
 		condlog(3, "%s: write to %s failed: %s", __func__, 
 			devpath, strerror(errno));
-	} else if (size < (ssize_t)value_len) {
+	} else if (size < (ssize_t)value_len)
 		condlog(3, "%s: underflow writing %zu bytes to %s. Wrote %zd bytes",
 			__func__, value_len, devpath, size);
-		size = 0;
-	}
 
 	close(fd);
 	return size;
diff --git a/libmultipath/sysfs.h b/libmultipath/sysfs.h
index cdc84e40..799f68e9 100644
--- a/libmultipath/sysfs.h
+++ b/libmultipath/sysfs.h
@@ -5,6 +5,7 @@
 #ifndef _LIBMULTIPATH_SYSFS_H
 #define _LIBMULTIPATH_SYSFS_H
 #include <stdbool.h>
+#include "strbuf.h"
 
 ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
 			     const char * value, size_t value_len);
@@ -25,6 +26,15 @@ ssize_t sysfs_bin_attr_get_value(struct udev_device *dev, const char *attr_name,
 		sysfs_attr_value_ok(__rc, __l); \
 	})
 
+#define log_sysfs_attr_set_value(prio, rc, fmt, __args...)		\
+do {									\
+	STRBUF_ON_STACK(__buf);						\
+	if (print_strbuf(&__buf, fmt, ##__args) >= 0 &&			\
+	    print_strbuf(&__buf, ": %s", rc < 0 ? strerror(-rc) :	\
+					"write underflow") >= 0)	\
+		condlog(prio, "%s", get_strbuf_str(&__buf));		\
+} while(0)
+
 int sysfs_get_size (struct path *pp, unsigned long long * size);
 int sysfs_check_holders(char * check_devt, char * new_devt);
 bool sysfs_is_multipathed(struct path *pp, bool set_wwid);