When we've modified an sysfs attribute via sysfs_attr_set_value()
we cannot use libudev-provided functions to read the current
value from that attribute, as libudev will return the stale
cached value here.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
libmultipath/sysfs.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++
libmultipath/sysfs.h | 2 ++
2 files changed, 58 insertions(+)
diff --git a/libmultipath/sysfs.c b/libmultipath/sysfs.c
index da228e4..22b73b1 100644
--- a/libmultipath/sysfs.c
+++ b/libmultipath/sysfs.c
@@ -38,6 +38,62 @@
#include "debug.h"
#include "devmapper.h"
+/*
+ * When we modify an attribute value we cannot rely on libudev for now,
+ * as libudev lacks the capability to update an attribute value.
+ * So for modified attributes we need to implement our own function.
+ */
+ssize_t sysfs_attr_get_value(struct udev_device *dev, const char *attr_name,
+ char * value, size_t value_len)
+{
+ char devpath[PATH_SIZE];
+ struct stat statbuf;
+ int fd;
+ ssize_t size = -1;
+
+ if (!dev || !attr_name || !value)
+ return 0;
+
+ snprintf(devpath, PATH_SIZE, "%s/%s", udev_device_get_syspath(dev),
+ attr_name);
+ condlog(4, "open '%s'", devpath);
+ if (stat(devpath, &statbuf) != 0) {
+ condlog(4, "stat '%s' failed: %s", devpath, strerror(errno));
+ return 0;
+ }
+
+ /* skip directories */
+ if (S_ISDIR(statbuf.st_mode)) {
+ condlog(4, "%s is a directory", devpath);
+ return 0;
+ }
+
+ /* skip non-writeable files */
+ if ((statbuf.st_mode & S_IRUSR) == 0) {
+ condlog(4, "%s is not readable", devpath);
+ return 0;
+ }
+
+ /* read attribute value */
+ fd = open(devpath, O_RDONLY);
+ if (fd < 0) {
+ condlog(4, "attribute '%s' can not be opened: %s",
+ devpath, strerror(errno));
+ return 0;
+ }
+ size = read(fd, value, value_len);
+ if (size < 0) {
+ condlog(4, "read from %s failed: %s", devpath, strerror(errno));
+ size = 0;
+ } else if (size == value_len) {
+ condlog(4, "overflow while reading from %s", devpath);
+ size = 0;
+ }
+
+ close(fd);
+ return size;
+}
+
ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
char * value, size_t value_len)
{
diff --git a/libmultipath/sysfs.h b/libmultipath/sysfs.h
index 13d7545..34f3e00 100644
--- a/libmultipath/sysfs.h
+++ b/libmultipath/sysfs.h
@@ -7,6 +7,8 @@
ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
char * value, size_t value_len);
+ssize_t sysfs_attr_get_value(struct udev_device *dev, const char *attr_name,
+ char * value, size_t value_len);
int sysfs_get_size (struct path *pp, unsigned long long * size);
int sysfs_check_holders(char * check_devt, char * new_devt);
#endif
--
1.7.10.4
--
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