Use fancy and more efficient syscalls to copy (sparse) files on Linux

The FICLONE ioctl() is the most efficient way to copy a file
inside one file system if available and supported.
copy_file_range() is an alternative that can provide similar
efficiency, but also only works inside one file system and
requires us to take care of holes in files. sendfile() is very
similar, but unline copy_file_range() it doesn't support
reflinks.

Ticket: CFE-4380
Changelog: FileSparseCopy() now uses FICLONE ioctl(),
           copy_file_range() or sendfile() on Linux
           platforms (if available)

configure.ac

@@ -885,6 +885,14 @@ dnl Fancy new Linux syscalls for file/data copying
 dnl ######################################################################
 AC_CHECK_HEADERS([linux/fs.h])
 AC_CHECK_DECLS([FICLONE], [], [], [#include <linux/fs.h>])
+AC_CHECK_DECLS([SEEK_DATA], [], [], [
+#define _GNU_SOURCE
+#include <unistd.h>
+])
+AC_CHECK_DECLS([FALLOC_FL_PUNCH_HOLE], [], [], [
+#define _GNU_SOURCE
+#include <fcntl.h>
+])
 AC_CHECK_HEADERS([sys/sendfile.h])
 AC_CHECK_FUNCS([sendfile])
 AC_CHECK_FUNCS([copy_file_range])

libutils/file_lib.c

@@ -1529,9 +1529,11 @@ bool FileSparseWrite(int fd, const void *buf, size_t count,
  */
 #ifdef __linux__
 #if HAVE_SENDFILE || HAVE_COPY_FILE_RANGE
+#if HAVE_DECL_SEEK_DATA && HAVE_DECL_FALLOC_FL_PUNCH_HOLE
 #define SMART_FILE_COPY_SYSCALLS_AVAILABLE 1
 #define SMART_SYSCALLS_UNUSED ARG_UNUSED
-#endif
+#endif  /* HAVE_DECL_SEEK_DATA && HAVE_DECL_FALLOC_FL_PUNCH_HOLE */
+#endif  /* HAVE_SENDFILE || HAVE_COPY_FILE_RANGE */
 #endif  /* __linux__ */
 #ifndef SMART_FILE_COPY_SYSCALLS_AVAILABLE
 #define SMART_FILE_COPY_SYSCALLS_AVAILABLE 0
@@ -1782,9 +1784,20 @@ bool FileSparseCopy(int sd, const char *src_name,
 bool FileSparseClose(int fd, const
                      char *filename,
                      bool do_sync,
-                     size_t total_bytes_written,
-                     bool last_write_was_hole)
+                     SMART_SYSCALLS_UNUSED size_t total_bytes_written,
+                     SMART_SYSCALLS_UNUSED bool last_write_was_hole)
 {
+#if SMART_FILE_COPY_SYSCALLS_AVAILABLE
+    /* Not much to do here with smart syscalls (see above). */
+    bool success = true;
+    if (do_sync && (fsync(fd) != 0))
+    {
+        Log(LOG_LEVEL_WARNING, "Could not sync to disk file '%s': %m)", filename);
+        success = false;
+    }
+    close(fd);
+    return success;
+#else
     if (last_write_was_hole)
     {
         ssize_t ret1 = FullWrite(fd, "", 1);
@@ -1828,7 +1841,9 @@ bool FileSparseClose(int fd, const
     }
 
     return true;
+#endif /* SMART_FILE_COPY_SYSCALLS_AVAILABLE */
 }
+#undef SMART_FILE_COPY_SYSCALLS_AVAILABLE
 
 ssize_t CfReadLine(char **buff, size_t *size, FILE *fp)
 {