Marks FUSE filesystem as with not persistent inodes,

disabling inode use in such case.

TODO

@@ -3,6 +3,8 @@ SnapRAID TODO
 
 This is the list of TODO items for SnapRAID.
 
++test with restore disk cp -a before and after rm
+
 - v4.x
 
 * Enable storing of creation time NTFS, crtime/birth time EXT4.

elem.c

@@ -523,6 +523,7 @@ struct snapraid_disk* disk_alloc(const char* name, const char* dir, uint64_t dev
 
 	disk->device = dev;
 	disk->first_free_block = 0;
+	disk->has_not_persistent_inodes = 0;
 	disk->mapping = -1;
 	tommy_list_init(&disk->filelist);
 	tommy_list_init(&disk->deletedlist);

elem.h

@@ -273,6 +273,7 @@ struct snapraid_disk {
 	char dir[PATH_MAX]; /**< Mount point of the disk. It always terminates with /. */
 	uint64_t device; /**< Device identifier. */
 	block_off_t first_free_block; /**< First free searching block. */
+	int has_not_persistent_inodes; /**< If the underline filesystem has dynamic inodes. */
 	int mapping; /**< Index in the mapping vector. Used only as buffer when writing the content file. */
 
 	/**<

mingw.c

@@ -1148,11 +1148,14 @@ int filephy(const char* file, struct stat* st, uint64_t* physical)
 	return 0;
 }
 
-int fstype(const char* path)
+int fsinfo(const char* path, int* has_persistent_inode)
 {
 	(void)path;
 
-	return FSTYPE_UNKNOWN;
+	/* all FAT/exFAT/NTFS when managed from Windows have persistent inodes */
+	*has_persistent_inode = 1;
+
+	return 0;
 }
 
 #undef strerror

portable.h

@@ -181,15 +181,11 @@ int devuuid(uint64_t device, char* uuid, size_t size);
  */
 int filephy(const char* path, struct stat* st, uint64_t* physical);
 
-/* Types of filesystem */
-#define FSTYPE_UNKNOWN 0
-#define FSTYPE_FUSE 1
-
 /**
- * Get the filesystem type.
- * Returns -1 on error or one of the FSTYPE define.
+ * Checks if the underline filesystem support persistent inodes.
+ * Returns -1 on error, 0 on success.
  */
-int fstype(const char* path);
+int fsinfo(const char* path, int* has_persistent_inode);
 
 /**
  * Initializes the system.

scan.c

@@ -277,10 +277,31 @@ static void scan_file_insert(struct snapraid_state* state, struct snapraid_disk*
 static void scan_file(struct snapraid_scan* scan, struct snapraid_state* state, int output, struct snapraid_disk* disk, const char* sub, const struct stat* st, uint64_t physical)
 {
 	struct snapraid_file* file;
-	uint64_t inode = st->st_ino;
 
-	/* first try finding by inode */
-	file = tommy_hashdyn_search(&disk->inodeset, file_inode_compare_to_arg, &inode, file_inode_hash(inode));
+	file = 0;
+
+	/*
+	 * If the disk has persistent inodes, try a search by inode.
+	 *
+	 * For persistent inodes we mean inodes that keep their values when the filesystem
+	 * is unmounted and remounted. This don't always happen. 
+	 *
+	 * Cases found are:
+	 * - Linux FUSE with exFAT driver from https://code.google.com/p/exfat/.
+	 *   Inodes are reassigned at every mount restarting from 1 and incrementing.
+	 *   As worse, the exFAT support in FUSE doesn't use subsecond precision in timestamps
+	 *   making inode collision more easy (exFAT by design supports 10ms precision).
+	 * - Linux VFAT kernel (3.2) driver. Inodes are fully reassigned at every mount.
+	 *
+	 * In such cases, to avoid possible random collisions, it's better to just avoid
+	 * to use inodes at all.
+	 */
+	if (!disk->has_not_persistent_inodes) {
+		/* first try finding by inode */
+		uint64_t inode = st->st_ino;
+		file = tommy_hashdyn_search(&disk->inodeset, file_inode_compare_to_arg, &inode, file_inode_hash(inode));
+	}
+
 	if (file) {
 		/* check if the file is not changed */
 		if (file->size == st->st_size
@@ -793,6 +814,8 @@ void state_scan(struct snapraid_state* state, int output)
 		struct snapraid_disk* disk = i->data;
 		struct snapraid_scan* scan;
 		tommy_node* node;
+		int ret;
+		int has_persistent_inode;
 
 		scan = malloc_nofail(sizeof(struct snapraid_scan));
 		scan->count_equal = 0;
@@ -809,6 +832,18 @@ void state_scan(struct snapraid_state* state, int output)
 
 		printf("Scanning disk %s...\n", disk->name);
 
+		/* check if the disk supports persistent inodes */
+		ret = fsinfo(disk->dir, &has_persistent_inode);
+		if (ret < 0) {
+			fprintf(stderr, "Error accessing disk '%s' to get filesystem info. %s.\n", disk->dir, strerror(errno));
+			exit(EXIT_FAILURE);
+		}
+		/* mark the disk if required */
+		if (!has_persistent_inode) {
+			fprintf(stderr, "WARNING! Inodes use disabled for disk '%s' because they are not persistent.\n", disk->dir);
+			disk->has_not_persistent_inodes = 1;
+		}
+
 		scan_dir(scan, state, output, disk, disk->dir, "");
 
 		/* check for removed files */

state.c

@@ -113,26 +113,6 @@ static void state_config_check(struct snapraid_state* state, const char* path)
 #endif
 
 			if (!state->opt.force_device) {
-				int ret;
-
-				ret = fstype(disk->dir);
-				if (ret < 0) {
-					fprintf(stderr, "Error accessing disk '%s' to get the filesystem type. %s.\n", disk->dir, strerror(errno));
-					exit(EXIT_FAILURE);
-				}
-				if (ret == FSTYPE_FUSE) {
-					fprintf(stderr, "Disk '%s' has a filesystem managed by FUSE.\n", disk->dir);
-					fprintf(stderr, "FUSE doesn't support persistent inodes, and it cannot be\n");
-					fprintf(stderr, "used safely with SnapRAID.\n");
-
-					/* in "fix" we allow to continue anyway */
-					if (strcmp(state->command, "fix") == 0) {
-						fprintf(stderr, "You can '%s' anyway, using 'snapraid --force-device %s'.\n", state->command, state->command);
-					}
-
-					exit(EXIT_FAILURE);
-				}
-
 				for(j=i->next;j!=0;j=j->next) {
 					struct snapraid_disk* other = j->data;
 					if (disk->device == other->device) {

unix.c

@@ -168,7 +168,7 @@ int filephy(const char* path, struct stat* st, uint64_t* physical)
 	return 0;
 }
 
-int fstype(const char* path)
+int fsinfo(const char* path, int* has_persistent_inode)
 {
 /* statfs() is really not portable, and to limit possible incompatibility we limit it to Linux */
 /* for example, Solaris doesn't have the f_type field, BSD has it as "short" */
@@ -178,14 +178,26 @@ int fstype(const char* path)
 	if (statfs(path, &st) != 0)
 		return -1;
 
+	/* to get the fs type check "man stat" or "stat -f -t FILE" */
+
 	switch (st.f_type) {
-	case 0x65735546 : return FSTYPE_FUSE;
+	case 0x65735546 : /* FUSE, "fuseblk" in the stat command */
+	case 0x4d44 : /* VFAT, "msdos" in the stat command */
+		*has_persistent_inode = 0;
+		break;
+	default:
+		/* by default assume yes */
+		*has_persistent_inode = 1;
+		break;
 	}
 #else
 	(void)path;
+
+	/* by default assume yes */
+	*has_persistent_inode = 1;
 #endif
 
-	return FSTYPE_UNKNOWN;
+	return 0;
 }
 
 void os_init(void)