Support moving between two different filesystems

crew-mvdir.c

@@ -32,20 +32,52 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdbool.h>
+#include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
 #include <limits.h>
 #include <string.h>
 #include <ftw.h>
+#include <sys/sendfile.h>
 #include <sys/stat.h>
 
-bool verbose = false, no_clobber = false;
+bool same_fs = true, verbose = false, no_clobber = false;
 char src[PATH_MAX], dst[PATH_MAX];
 
-int move_file(const char *src_path, const struct stat *sb, int flag, struct FTW *ftwbuf) {
-  char dst_path[PATH_MAX] = {0};
+void copy_and_delete_file(const struct stat *src_info, const char *src_path, const char *dst_path) {
+  // copy_and_delete_file(): copy a file and delete it after copying, used as a fallback when rename() does not work
+  //                         (i.e source and destination are not in the same filesystem)
+  int src_fd = open(src_path, O_RDONLY),
+      dst_fd = open(dst_path, O_CREAT | O_WRONLY, src_info->st_mode);
+
+  if (src_fd == -1) {
+    fprintf(stderr, "%s: open() failed: %s\n", src_path, strerror(errno));
+    exit(errno);
+  } else if (dst_fd == -1) {
+    fprintf(stderr, "%s: open() failed: %s\n", dst_path, strerror(errno));
+    exit(errno);
+  }
+
+  // copy contents
+  if (sendfile(dst_fd, src_fd, (off_t*) 0, src_info->st_size) == -1) {
+    fprintf(stderr, "%s: sendfile() failed: %s\n", dst_path, strerror(errno));
+    exit(errno);
+  }
+
+  close(src_fd);
+  close(dst_fd);
+
+  // remove source file after copying
+  if (remove(src_path) == -1) {
+    fprintf(stderr, "%s: failed to remove file: %s\n", src_path, strerror(errno));
+    exit(errno);
+  }
+}
+
+int move_file(const char *src_path, const struct stat *src_info, int flag, struct FTW *ftwbuf) {
+  char dst_path[PATH_MAX];
+
   strcpy(dst_path, dst);
-  strcat(dst_path, "/");
   strcat(dst_path, src_path + strlen(src));
 
   if (strcmp(src_path, ".") == 0) return 0;
@@ -54,33 +86,64 @@ int move_file(const char *src_path, const struct stat *sb, int flag, struct FTW
   switch (flag) {
     case FTW_F:
     case FTW_SL:
-      // file/symlink: Move file to dest, override files with same filename in dest (mode/owner remain unchanged)
+    case FTW_SLN:
       if (access(dst_path, F_OK) == 0) {
         // do not touch existing files if -n specified
-        if ( !(no_clobber || remove(dst_path) == 0) ) {
+        if (!(no_clobber || remove(dst_path) == 0)) {
           // remove file with same name in dest (if exist)
           fprintf(stderr, "%s: failed to remove file: %s\n", dst_path, strerror(errno));
           exit(errno);
         }
       }
 
       // move (rename) file to dest
-      if ( !(access(dst_path, F_OK) == 0 || rename(src_path, dst_path) == 0) ) {
-        fprintf(stderr, "%s: rename() failed: %s\n", src_path, strerror(errno));
-        exit(errno);
+      if (same_fs) {
+        // (when source and destination are in the same filesystem)
+        // file/symlink: move file to dest, override files with same filename in dest (mode/owner remain unchanged)
+        if (rename(src_path, dst_path) == -1) {
+          if (errno == EXDEV) {
+            // fallback to copying-deleting if source and destination are not in the same filesystem
+            same_fs = false;
+            if (verbose) fprintf(stderr, "Warning: destination is not in the same filesystem, will fallback to sendfile() instead.\n");
+            return move_file(src_path, src_info, flag, ftwbuf);
+          }
+
+          fprintf(stderr, "%s: rename() failed: %s\n", src_path, strerror(errno));
+          exit(errno);
+        }
+      } else {
+        // (when source and destination are not in the same filesystem)
+        if (flag == FTW_F) {
+          // file: copy source file to destination and delete it (mode will be transferred)
+          copy_and_delete_file(src_info, src_path, dst_path);
+        } else {
+          // symlink: create an identical symlink and delete the source (mode will be transferred)
+          char target[PATH_MAX];
+
+          ssize_t target_len = readlink(src_path, target, PATH_MAX - 1);
+          target[target_len] = 0;
+
+          if (symlink(target, dst_path) == -1) {
+            fprintf(stderr, "%s: symlink() failed: %s\n", dst_path, strerror(errno));
+            exit(errno);
+          }
+
+          // remove source after copying
+          if (remove(src_path) == -1) {
+            fprintf(stderr, "%s: failed to remove symlink: %s\n", src_path, strerror(errno));
+            exit(errno);
+          }
+        }
       }
 
       break;
     case FTW_D:
-      // directory
-      // create an identical directory in dest (with same permission) if the directory does not exist in dest
-      if (access(dst_path, F_OK) != 0) {
-        struct stat path_stat;
-        stat(src_path, &path_stat);
-        mode_t dir_mode = path_stat.st_mode;
+      // directory: create an identical directory in destination if not exist (mode will be transferred)
+      if (access(dst_path, F_OK) == -1) {
+        mode_t dir_mode = src_info->st_mode;
 
         if (verbose) fprintf(stderr, "Creating directory %s\n", dst_path);
-        if (mkdir(dst_path, dir_mode) != 0) {
+        if (mkdir(dst_path, dir_mode) == -1) {
           fprintf(stderr, "%s: mkdir() failed: %s\n", src_path, strerror(errno));
           exit(errno);
         }
@@ -123,9 +186,20 @@ int main(int argc, char** argv) {
   strcpy(src, argv[optind]);
   strcpy(dst, argv[optind + 1]);
 
+  struct stat src_info, dst_info;
+  stat(src, &src_info);
+  stat(dst, &dst_info);
+
+  // trailing slashes in path are required in order to make move_file() works
+  int src_len = strlen(src),
+      dst_len = strlen(dst);
+
+  if (src[src_len - 1] != '/') src[src_len] = '/';
+  if (dst[dst_len - 1] != '/') dst[dst_len] = '/';
+
   // call move_file() with files in src recursively
-  if (nftw(src, move_file, 100, FTW_PHYS) != 0) {
-    fprintf(stderr, "%s: %s\n", src, strerror(errno));
+  if (nftw(src, move_file, 100, FTW_PHYS | FTW_MOUNT) == -1) {
+    fprintf(stderr, "%s: nftw() failed: %s\n", src, strerror(errno));
     exit(errno);
   }