mkswap, readahead: stop using fdlength, it is reported to be unreliable

3 files changed, 15 insertions, 4 deletions

diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index 25c36bd07..445e07717 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -475,6 +475,7 @@ void xsetuid(uid_t uid)
 }
 
 // Return how long the file at fd is, if there's any way to determine it.
+#ifdef UNUSED
 off_t fdlength(int fd)
 {
         off_t bottom = 0, top = 0, pos;
@@ -513,6 +514,7 @@ off_t fdlength(int fd)
 
         return pos + 1;
 }
+#endif
 
 int bb_putchar(int ch)
 {
diff --git a/miscutils/readahead.c b/miscutils/readahead.c
index 7b375cfff..fb71ce85f 100644
--- a/miscutils/readahead.c
+++ b/miscutils/readahead.c
@@ -22,9 +22,16 @@ int readahead_main(int argc, char **argv)
         while (*++argv) {
                 int fd = open_or_warn(*argv, O_RDONLY);
                 if (fd >= 0) {
-                        int r = readahead(fd, 0, fdlength(fd));
+                        off_t len;
+                        int r;
+
+                        /* fdlength was reported to be unreliable - use seek */
+                        len = xlseek(fd, 0, SEEK_END);
+                        xlseek(fd, 0, SEEK_SET);
+                        r = readahead(fd, 0, len);
                         close(fd);
-                        if (r >= 0) continue;
+                        if (r >= 0)
+                                continue;
                 }
                 retval = EXIT_FAILURE;
         }
diff --git a/util-linux/mkswap.c b/util-linux/mkswap.c
index 8e1fbc384..f047cce26 100644
--- a/util-linux/mkswap.c
+++ b/util-linux/mkswap.c
@@ -64,9 +64,11 @@ int mkswap_main(int argc, char **argv)
         // Figure out how big the device is and announce our intentions.
 
         fd = xopen(argv[1], O_RDWR);
-        len = fdlength(fd);
+        /* fdlength was reported to be unreliable - use seek */
+        len = xlseek(fd, 0, SEEK_END);
+        xlseek(fd, 0, SEEK_SET);
         pagesize = getpagesize();
-        printf("Setting up swapspace version 1, size = %"OFF_FMT"d bytes\n",
+        printf("Setting up swapspace version 1, size = %"OFF_FMT"u bytes\n",
                         len - pagesize);
         mkswap_selinux_setcontext(fd, argv[1]);