[dm-devel] [PATCH v3 09/20] libmultipath: functions to indicate mapping failure in /dev/shm

[Martin Wilck]

Create a simple API that indicates failure to create a map for a
certain WWID. This will allow multipathd to indicate to other tools
(in particular, "multipath -u" during udev processing) that
an attempt to create a map for a certain wwid failed.

The indicator is simply the existence of a file under
/dev/shm/multipath/failed_wwids.

Signed-off-by: Martin Wilck <mwilck at suse.com>
---
 libmultipath/defaults.h |   1 +
 libmultipath/wwids.c    | 110 ++++++++++++++++++++++++++++++++++++++++++++++++
 libmultipath/wwids.h    |  11 +++++
 3 files changed, 122 insertions(+)

diff --git a/libmultipath/defaults.h b/libmultipath/defaults.h
index 690182c..19ad2bf 100644
--- a/libmultipath/defaults.h
+++ b/libmultipath/defaults.h
@@ -53,5 +53,6 @@
 #define DEFAULT_WWIDS_FILE	"/etc/multipath/wwids"
 #define DEFAULT_PRKEYS_FILE    "/etc/multipath/prkeys"
 #define DEFAULT_CONFIG_DIR	"/etc/multipath/conf.d"
+#define MULTIPATH_SHM_BASE	"/dev/shm/multipath/"
 
 char * set_default (char * str);
diff --git a/libmultipath/wwids.c b/libmultipath/wwids.c
index 5a2e86d..5351e3c 100644
--- a/libmultipath/wwids.c
+++ b/libmultipath/wwids.c
@@ -5,6 +5,7 @@
 #include <limits.h>
 #include <stdio.h>
 #include <sys/types.h>
+#include <sys/stat.h>
 
 #include "checkers.h"
 #include "vector.h"
@@ -331,3 +332,112 @@ remember_wwid(char *wwid)
 		condlog(4, "wwid %s already in wwids file", wwid);
 	return ret;
 }
+
+static const char shm_dir[] = MULTIPATH_SHM_BASE "failed_wwids";
+static const char shm_lock[] = ".lock";
+static const char shm_header[] = "multipath shm lock file, don't edit";
+static char _shm_lock_path[sizeof(shm_dir)+sizeof(shm_lock)];
+static const char *shm_lock_path = &_shm_lock_path[0];
+
+static void init_shm_paths(void)
+{
+	snprintf(_shm_lock_path, sizeof(_shm_lock_path),
+		 "%s/%s", shm_dir, shm_lock);
+}
+
+static pthread_once_t shm_path_once = PTHREAD_ONCE_INIT;
+
+static int multipath_shm_open(bool rw)
+{
+	int fd;
+	int can_write;
+
+	pthread_once(&shm_path_once, init_shm_paths);
+	fd = open_file(shm_lock_path, &can_write, shm_header);
+
+	if (fd >= 0 && rw && !can_write) {
+		close(fd);
+		condlog(1, "failed to open %s for writing", shm_dir);
+		return -1;
+	}
+
+	return fd;
+}
+
+static void multipath_shm_close(void *arg)
+{
+	long fd = (long)arg;
+
+	close(fd);
+	unlink(shm_lock_path);
+}
+
+static int _failed_wwid_op(const char *wwid, bool rw,
+			   int(*func)(const char*), const char *msg)
+{
+	char path[PATH_MAX];
+	long lockfd;
+	int r = -1;
+
+	if (snprintf(path, sizeof(path), "%s/%s", shm_dir, wwid)
+	    >= sizeof(path)) {
+		condlog(1, "%s: path name overflow", __func__);
+		return -1;
+	}
+
+	lockfd = multipath_shm_open(rw);
+	if (lockfd == -1)
+		return -1;
+
+	pthread_cleanup_push(multipath_shm_close, (void*)lockfd);
+	r = func(path);
+	pthread_cleanup_pop(1);
+
+	if (r == WWID_FAILED_ERROR)
+		condlog(1, "%s: %s: %s", msg, wwid, strerror(errno));
+	else if (r == WWID_FAILED_CHANGED)
+		condlog(3, "%s: %s", msg, wwid);
+	else if (!rw)
+		condlog(4, "%s: %s is %s", msg, wwid,
+			r == WWID_IS_FAILED ? "failed" : "good");
+
+	return r;
+}
+
+static int _is_failed(const char *path)
+{
+	struct stat st;
+
+	if (lstat(path, &st) == 0)
+		return WWID_IS_FAILED;
+	else if (errno == ENOENT)
+		return WWID_IS_NOT_FAILED;
+	else
+		return WWID_FAILED_ERROR;
+}
+
+static int _mark_failed(const char *path)
+{
+	/* Called from _failed_wwid_op: we know that shm_lock_path exists */
+	if (_is_failed(path) == WWID_IS_FAILED)
+		return WWID_FAILED_UNCHANGED;
+	return (link(shm_lock_path, path) == 0 ? WWID_FAILED_CHANGED :
+		WWID_FAILED_ERROR);
+}
+
+static int _unmark_failed(const char *path)
+{
+	if (_is_failed(path) == WWID_IS_NOT_FAILED)
+		return WWID_FAILED_UNCHANGED;
+	return (unlink(path) == 0 ? WWID_FAILED_CHANGED : WWID_FAILED_ERROR);
+}
+
+#define declare_failed_wwid_op(op, rw) \
+int op ## _wwid(const char *wwid) \
+{ \
+	return _failed_wwid_op(wwid, (rw), _ ## op, #op); \
+}
+
+declare_failed_wwid_op(is_failed, false)
+declare_failed_wwid_op(mark_failed, true)
+declare_failed_wwid_op(unmark_failed, true)
diff --git a/libmultipath/wwids.h b/libmultipath/wwids.h
index d9a78b3..0c6ee54 100644
--- a/libmultipath/wwids.h
+++ b/libmultipath/wwids.h
@@ -18,4 +18,15 @@ int check_wwids_file(char *wwid, int write_wwid);
 int remove_wwid(char *wwid);
 int replace_wwids(vector mp);
 
+enum {
+	WWID_IS_NOT_FAILED = 0,
+	WWID_IS_FAILED,
+	WWID_FAILED_UNCHANGED,
+	WWID_FAILED_CHANGED,
+	WWID_FAILED_ERROR = -1,
+};
+
+int is_failed_wwid(const char *wwid);
+int mark_failed_wwid(const char *wwid);
+int unmark_failed_wwid(const char *wwid);
 #endif /* _WWIDS_H */
-- 
2.16.1