+/*
+ * Given a filesystem name, or a pathname of a file on a lustre filesystem,
+ * tries to determine the path to the filesystem's clilov directory under /proc
+ *
+ * fsname is limited to MTI_NAME_MAXLEN in lustre_idl.h
+ * The NUL terminator is compensated by the additional "%s" bytes. */
+#define LOV_LEN (sizeof("/proc/fs/lustre/lov/%s-clilov-*") + MTI_NAME_MAXLEN)
+static int clilovpath(const char *fsname, const char *const pathname,
+ char *clilovpath)
+{
+ int rc;
+ char pattern[LOV_LEN];
+ char buffer[PATH_MAX + 1];
+
+ if (fsname == NULL) {
+ if ((rc = llapi_search_fsname(pathname, buffer)) != 0)
+ return rc;
+ fsname = buffer;
+ }
+
+ snprintf(pattern, sizeof(pattern), "/proc/fs/lustre/lov/%s-clilov-*",
+ fsname);
+
+ if ((rc = first_match(pattern, buffer)) != 0)
+ return rc;
+
+ strncpy(clilovpath, buffer, sizeof(buffer));
+
+ return 0;
+}
+
+/*
+ * Given the path to a stripe attribute proc file, tries to open and
+ * read the attribute and return the value using the attr parameter
+ */
+static int sattr_read_attr(const char *const fpath,
+ unsigned int *attr)
+{
+
+ FILE *f;
+ char line[PATH_MAX + 1];
+ int rc = 0;
+
+ if ((f = fopen(fpath, "r")) == NULL) {
+ llapi_err(LLAPI_MSG_ERROR, "Cannot open '%s'", fpath);
+ return errno;
+ }
+
+ if (fgets(line, sizeof(line), f) != NULL) {
+ *attr = atoi(line);
+ } else {
+ llapi_err(LLAPI_MSG_ERROR, "Cannot read from '%s'", fpath);
+ rc = 1;
+ }
+
+ fclose(f);
+ return rc;
+}
+
+/*
+ * Tries to determine the default stripe attributes for a given filesystem. The
+ * filesystem to check should be specified by fsname, or will be determined
+ * using pathname.
+ */
+static int sattr_get_defaults(const char *const fsname,
+ const char *const pathname,
+ unsigned int *scount,
+ unsigned int *ssize,
+ unsigned int *soffset)
+{
+ int rc;
+ char dpath[PATH_MAX + 1];
+ char fpath[PATH_MAX + 1];
+
+ if ((rc = clilovpath(fsname, pathname, dpath)) != 0)
+ return rc;
+
+ if (scount) {
+ snprintf(fpath, PATH_MAX, "%s/stripecount", dpath);
+ if ((rc = sattr_read_attr(fpath, scount)) != 0)
+ return rc;
+ }
+
+ if (ssize) {
+ snprintf(fpath, PATH_MAX, "%s/stripesize", dpath);
+ if ((rc = sattr_read_attr(fpath, ssize)) != 0)
+ return rc;
+ }
+
+ if (soffset) {
+ snprintf(fpath, PATH_MAX, "%s/stripeoffset", dpath);
+ if ((rc = sattr_read_attr(fpath, soffset)) != 0)
+ return rc;
+ }
+
+ return 0;
+}
+
+/*
+ * Tries to gather the default stripe attributes for a given filesystem. If
+ * the attributes can be determined, they are cached for easy retreival the
+ * next time they are needed. Only a single filesystem's attributes are
+ * cached at a time.
+ */
+static int sattr_cache_get_defaults(const char *const fsname,
+ const char *const pathname,
+ unsigned int *scount,
+ unsigned int *ssize,
+ unsigned int *soffset)
+{
+ static struct {
+ char fsname[PATH_MAX + 1];
+ unsigned int stripecount;
+ unsigned int stripesize;
+ unsigned int stripeoffset;
+ } cache = {
+ .fsname = {'\0'}
+ };
+
+ int rc;
+ char fsname_buf[PATH_MAX + 1];
+ unsigned int tmp[3];
+
+ if (fsname == NULL)
+ llapi_search_fsname(pathname, fsname_buf);
+ else
+ strncpy(fsname_buf, fsname, PATH_MAX);
+
+ if (strncmp(fsname_buf, cache.fsname, PATH_MAX) != 0) {
+ /*
+ * Ensure all 3 sattrs (count, size, and offset) are
+ * successfully retrieved and stored in tmp before writing to
+ * cache.
+ */
+ if ((rc = sattr_get_defaults(fsname_buf, NULL, &tmp[0],
+ &tmp[1], &tmp[2])) != 0)
+ return rc;
+
+ cache.stripecount = tmp[0];
+ cache.stripesize = tmp[1];
+ cache.stripeoffset = tmp[2];
+ strncpy(cache.fsname, fsname_buf, PATH_MAX);
+ }
+
+ if (scount)
+ *scount = cache.stripecount;
+ if (ssize)
+ *ssize = cache.stripesize;
+ if (soffset)
+ *soffset = cache.stripeoffset;
+
+ return 0;
+}
+