shred: avoid a data pass on empty files

* src/shred.c (do_wipefd): Don't increase the size written
for an empty file up to a full block.  Also increase the size
to OFF_T_MAX in the edge case where we do overflow.
* NEWS: Mention the shred improvements from recent changes.
* tests/misc/shred-passes.sh: Adjust as we no longer
write a BLKSIZE of data for empty files.

1 files changed, 5 insertions, 5 deletions

diff --git a/src/shred.c b/src/shred.c
index 732d3afb1..ed370513d 100644
--- a/src/shred.c
+++ b/src/shred.c
@@ -428,7 +428,7 @@ dopass (int fd, struct stat const *st, char const *qname, off_t *sizep,
   size_t soff;			/* Offset into buffer for next write */
   ssize_t ssize;		/* Return value from write */
 
-  /* Do nothing for --size=0 or regular empty files with --exact.  */
+  /* Do nothing for --size=0 or regular empty files.  */
   if (size == 0)
     return 0;
 
@@ -887,15 +887,15 @@ do_wipefd (int fd, char const *qname, struct randint_source *s,
 
           if (! flags->exact)
             {
-              /* Round up to the nearest blocksize.  If the file is
-                 empty output a block anyway, in case the file system
-                 stores small files in the inode.  */
+              /* Round up to the nearest blocksize to clear slack space.  */
               off_t remainder = size % ST_BLKSIZE (st);
-              if (remainder != 0 || size == 0)
+              if (remainder != 0)
                 {
                   off_t size_incr = ST_BLKSIZE (st) - remainder;
                   if (! INT_ADD_OVERFLOW (size, size_incr))
                     size += size_incr;
+                  else
+                    size = OFF_T_MAX;
                 }
             }
         }