fadvise: new module providing a simpler interface to posix_fadvise

* bootstrap.conf: Include the new module
* gl/lib/fadvise.c: Provide a simpler interface to posix_fadvise.
(fadvise): Provide hint to the whole file associated with a stream.
(fdadvise): Provide hint to the specific portion of a file
associated with a file descriptor.
* gl/lib/fadvise.h: Redefine POSIX_FADV_* to FADVISE_* enums.
* gl/modules/fadvise: New file.
* m4/jm-macros.m4: Remove the no longer needed posix_fadvise check.
* .x-sc_program_name: Exclude test-fadvise.c from this check.
* gl/tests/test-fadvise (main): New test program.
* gl/modules/fadvise-testss: A new index to reference the tests.
* src/sort.c (stream_open): Use the new interface.
* src/dd.c (iwrite): Likewise.

1 files changed, 2 insertions, 5 deletions

diff --git a/src/dd.c b/src/dd.c
index ab8b84c22..b6643e2e1 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -27,10 +27,10 @@
 #include "system.h"
 #include "close-stream.h"
 #include "error.h"
+#include "fadvise.h"
 #include "fd-reopen.h"
 #include "gethrxtime.h"
 #include "human.h"
-#include "ignore-value.h"
 #include "long-options.h"
 #include "quote.h"
 #include "quotearg.h"
@@ -849,12 +849,9 @@ iwrite (int fd, char const *buf, size_t size)
          posix_fadvise to tell the system not to pollute the buffer
          cache with this data.  Don't bother to diagnose lseek or
          posix_fadvise failure. */
-#ifdef POSIX_FADV_DONTNEED
       off_t off = lseek (STDOUT_FILENO, 0, SEEK_CUR);
       if (0 <= off)
-        ignore_value (posix_fadvise (STDOUT_FILENO,
-                                     off, 0, POSIX_FADV_DONTNEED));
-#endif
+        fdadvise (STDOUT_FILENO, off, 0, FADVISE_DONTNEED);
 
       /* Attempt to ensure that that final block is committed
          to disk as quickly as possible.  */