On mar., 2013-04-02 at 16:28 +0200, Sebastian Riemer wrote:
> The libudev function udev_device_get_sysattr_value() reads sysfs
> attributes cached. This is useless for checking a device state.
> There we want to see if it changes.
>
> Unfortunately, libudev doesn't provide an uncached variant. This
> is why we have to reimplement the functionality and some libudev
> internal functions here.
>
Hannes,
as the commit 058a0044cb2ab7cac6f7c3e2e17b16e00b5e57fa author, would you
sign-off this patch ? Or do you prefer the issue addressed on the udev
side ...
Best regards,
Christophe Varoqui
www.opensvc.com
> Cc: Christophe Varoqui <christophe.varoqui@xxxxxxxxxxx>
> Cc: Bart Van Assche <bvanassche@xxxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxx>
> Signed-off-by: Sebastian Riemer <sebastian.riemer@xxxxxxxxxxxxxxxx>
> ---
> libmultipath/discovery.c | 78 +++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
> index 0b5fd1d..1cb1f15 100644
> --- a/libmultipath/discovery.c
> +++ b/libmultipath/discovery.c
> @@ -132,6 +132,82 @@ path_discovery (vector pathvec, struct config * conf, int flag)
> return r;
> }
>
> +/* helpers for get_udev_device_sysattr_value() */
> +static size_t
> +strpcpy(char **dest, size_t size, const char *src)
> +{
> + size_t len;
> +
> + len = strlen(src);
> + if (len >= size) {
> + if (size > 1)
> + *dest = mempcpy(*dest, src, size-1);
> + size = 0;
> + } else {
> + if (len > 0) {
> + *dest = mempcpy(*dest, src, len);
> + size -= len;
> + }
> + }
> + *dest[0] = '\0';
> + return size;
> +}
> +
> +static size_t
> +strscpyl(char *dest, size_t size, const char *src, ...)
> +{
> + va_list va;
> + char *s;
> +
> + va_start(va, src);
> + s = dest;
> + do {
> + size = strpcpy(&s, size, src);
> + src = va_arg(va, char *);
> + } while (src != NULL);
> + va_end(va);
> +
> + return size;
> +}
> +
> +static void
> +util_remove_trailing_chars(char *path, char c)
> +{
> + size_t len;
> +
> + if (path == NULL)
> + return;
> + len = strlen(path);
> + while (len > 0 && path[len-1] == c)
> + path[--len] = '\0';
> +}
> +
> +/* like udev_device_get_sysattr_value() but uncached */
> +static const char *
> +get_udev_device_sysattr_value(struct udev_device *udev,
> + const char *sysattr)
> +{
> + const char *val = NULL;
> + char path[1024];
> + char value[4096];
> + int fd;
> + ssize_t size;
> +
> + strscpyl(path, sizeof(path), udev_device_get_syspath(udev),
> + "/", sysattr, NULL);
> + fd = open(path, O_RDONLY|O_CLOEXEC);
> + if (fd >= 0) {
> + size = read(fd, value, sizeof(value));
> + close(fd);
> + if (size >= 0 && size < sizeof(value)) {
> + value[size] = '\0';
> + util_remove_trailing_chars(value, '\n');
> + val = value;
> + }
> + }
> + return val;
> +}
> +
> #define declare_sysfs_get_str(fname) \
> extern int \
> sysfs_get_##fname (struct udev_device * udev, char * buff, size_t len) \
> @@ -141,7 +217,7 @@ sysfs_get_##fname (struct udev_device * udev, char * buff, size_t len) \
> \
> devname = udev_device_get_sysname(udev); \
> \
> - attr = udev_device_get_sysattr_value(udev, #fname); \
> + attr = get_udev_device_sysattr_value(udev, #fname); \
> if (!attr) { \
> condlog(3, "%s: attribute %s not found in sysfs", \
> devname, #fname); \
--
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