storage: Try opening the slot-suffixed partition

Some devices ship 2 copies of remote partitions (see e.g. #22), which
the current code can't cope with.

Add parsing of a slot suffix (via '-S', single character) and if
passed, retry opening partition (via a partlabel) with it.

Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

rmtfs.c

@@ -27,6 +27,7 @@
 
 static struct rmtfs_mem *rmem;
 static sig_atomic_t sig_int_count;
+static char slot_suffix[SLOT_SUFFIX_LEN];
 
 static bool dbgprintf_enabled;
 static void dbgprintf(const char *fmt, ...)
@@ -69,7 +70,7 @@ static void rmtfs_open(int sock, const struct qrtr_packet *pkt)
 		goto respond;
 	}
 
-	rmtfd = storage_open(pkt->node, req.path);
+	rmtfd = storage_open(pkt->node, req.path, slot_suffix);
 	if (!rmtfd) {
 		qmi_result_error(&resp.result, QMI_RMTFS_ERR_INTERNAL);
 		goto respond;
@@ -504,7 +505,7 @@ int main(int argc, char **argv)
 	int option;
 	const char *storage_root = NULL;
 
-	while ((option = getopt(argc, argv, "o:Prsv")) != -1) {
+	while ((option = getopt(argc, argv, "oS:Prsv")) != -1) {
 		switch (option) {
 		/*
 		 * -o sets the directory where EFS images are stored,
@@ -535,6 +536,20 @@ int main(int argc, char **argv)
 
 			break;
 
+		/* Partlabel slot suffix on A/B devices */
+		case 'S':
+			if (strnlen(optarg, 1 + 1) != 1) {
+				fprintf(stderr, "Couldn't parse slot name (too long?)\n");
+				return -1;
+			}
+
+			ret = snprintf(slot_suffix, SLOT_SUFFIX_LEN, "_%s", optarg);
+			if (ret != SLOT_SUFFIX_LEN - 1)
+				return -1;
+
+			dbgprintf("Using slot %s\n", slot_suffix);
+			break;
+
 		/* -v is for verbose */
 		case 'v':
 			dbgprintf_enabled = 1;

rmtfs.h

@@ -26,7 +26,8 @@ ssize_t rmtfs_mem_write(struct rmtfs_mem *rmem, unsigned long phys_address, cons
 struct rmtfd;
 
 int storage_init(const char *storage_root, bool read_only, bool use_partitions);
-struct rmtfd *storage_open(unsigned node, const char *path);
+#define SLOT_SUFFIX_LEN	(2 + 1) /* "_a" or "_b", null-terminated */
+struct rmtfd *storage_open(unsigned node, const char *path, const char *slot_suffix);
 struct rmtfd *storage_get(unsigned node, int caller_id);
 void storage_close(struct rmtfd *rmtfd);
 int storage_get_caller_id(const struct rmtfd *rmtfd);

storage.c

@@ -74,16 +74,43 @@ int storage_init(const char *storage_root, bool read_only, bool use_partitions)
 	return 0;
 }
 
-struct rmtfd *storage_open(unsigned node, const char *path)
+static int fd_open(struct rmtfd *rmtfd, const char *fspath, const struct partition *part)
+{
+	int saved_errno;
+	int ret;
+	int fd;
+
+	if (!storage_read_only) {
+		fd = open(fspath, O_RDWR);
+		if (fd < 0) {
+			saved_errno = errno;
+			fprintf(stderr, "[storage] failed to open '%s' (requested '%s'): %s\n",
+					fspath, part->path, strerror(saved_errno));
+			return saved_errno;
+		}
+		rmtfd->fd = fd;
+		rmtfd->shadow_len = 0;
+	} else {
+		ret = storage_populate_shadow_buf(rmtfd, fspath);
+		if (ret < 0) {
+			saved_errno = errno;
+			fprintf(stderr, "[storage] failed to open '%s' (requested '%s'): %s\n",
+					fspath, part->path, strerror(saved_errno));
+			return saved_errno;
+		}
+	}
+
+	return 0;
+}
+
+struct rmtfd *storage_open(unsigned node, const char *path, const char *slot_suffix)
 {
 	char *fspath;
 	const struct partition *part;
 	struct rmtfd *rmtfd = NULL;
 	const char *file;
 	size_t pathlen;
-	int saved_errno;
 	int ret;
-	int fd;
 	int i;
 
 	for (part = partition_table; part->path; part++) {
@@ -119,29 +146,19 @@ found:
 	else
 		file = part->actual;
 
-	pathlen = strlen(storage_dir) + strlen(file) + 2;
+	pathlen = strlen(storage_dir) + strlen(file) + 2 + strnlen(slot_suffix, SLOT_SUFFIX_LEN);
 	fspath = alloca(pathlen);
 	snprintf(fspath, pathlen, "%s/%s", storage_dir, file);
-	if (!storage_read_only) {
+	ret = fd_open(rmtfd, fspath, part);
-		fd = open(fspath, O_RDWR);
+	if (ret) {
-		if (fd < 0) {
+		/* Try again with the slot suffix before giving up */
-			saved_errno = errno;
+		if (!slot_suffix)
-			fprintf(stderr, "[storage] failed to open '%s' (requested '%s'): %s\n",
-					fspath, part->path, strerror(saved_errno));
-			errno = saved_errno;
 			return NULL;
-		}
+
-		rmtfd->fd = fd;
+		snprintf(fspath, pathlen, "%s/%s%s", storage_dir, file, slot_suffix);
-		rmtfd->shadow_len = 0;
+		ret = fd_open(rmtfd, fspath, part);
-	} else {
+		if (ret)
-		ret = storage_populate_shadow_buf(rmtfd, fspath);
-		if (ret < 0) {
-			saved_errno = errno;
-			fprintf(stderr, "[storage] failed to open '%s' (requested '%s'): %s\n",
-					fspath, part->path, strerror(saved_errno));
-			errno = saved_errno;
 			return NULL;
-		}
 	}
 
 	rmtfd->node = node;