More robust file content copy in copy_tree()

Bail out on read(2) failure, continue on EINTR, support short writes and
increase chunk size.

diff --git a/libmisc/copydir.c b/libmisc/copydir.c
index 90895cfb0e83aa84c326d7e85b02fdc661c44fcc..95042187b7cda9b66d2f203cf2fa706d190a5e95 100644 (file)
--- a/libmisc/copydir.c
+++ b/libmisc/copydir.c
@@ -691,6 +691,42 @@ static int copy_special (const char *src, const char *dst,
        return err;
 }
 
+/*
+ * full_write - write entire buffer
+ *
+ * Write up to count bytes from the buffer starting at buf to the
+ * file referred to by the file descriptor fd.
+ * Retry in case of a short write.
+ *
+ * Returns the number of bytes written on success, -1 on error.
+ */
+static ssize_t full_write(int fd, const void *buf, size_t count) {
+       ssize_t written = 0;
+
+       while (count > 0) {
+               ssize_t res;
+
+               res = write(fd, buf, count);
+               if (res < 0) {
+                       if (errno == EINTR) {
+                               continue;
+                       }
+
+                       return res;
+               }
+
+               if (res == 0) {
+                       break;
+               }
+
+               written += res;
+               buf = (const unsigned char*)buf + res;
+               count -= (size_t)res;
+       }
+
+       return written;
+}
+
 /*
  * copy_file - copy a file
  *
@@ -710,8 +746,6 @@ static int copy_file (const char *src, const char *dst,
        int err = 0;
        int ifd;
        int ofd;
-       char buf[1024];
-       ssize_t cnt;
 
        ifd = open (src, O_RDONLY|O_NOFOLLOW);
        if (ifd < 0) {
@@ -753,8 +787,24 @@ static int copy_file (const char *src, const char *dst,
                return -1;
        }
 
-       while ((cnt = read (ifd, buf, sizeof buf)) > 0) {
-               if (write (ofd, buf, (size_t)cnt) != cnt) {
+       while (true) {
+               char buf[8192];
+               ssize_t cnt;
+
+               cnt = read (ifd, buf, sizeof buf);
+               if (cnt < 0) {
+                       if (errno == EINTR) {
+                               continue;
+                       }
+                       (void) close (ofd);
+                       (void) close (ifd);
+                       return -1;
+               }
+               if (cnt == 0) {
+                       break;
+               }
+
+               if (full_write (ofd, buf, (size_t)cnt) < 0) {
                        (void) close (ofd);
                        (void) close (ifd);
                        return -1;