configure.ac: add pwritev check

Signed-off-by: Haomai Wang <[email protected]>
bitfehler · Jan 30, 2016 · b1e27a5 · b1e27a5
1 parent aa7b505
commit b1e27a5
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Showing 2 changed files with 12 additions and 1 deletion.
diff --git a/configure.ac b/configure.ac
@@ -1065,6 +1065,7 @@ AC_CHECK_HEADERS([sys/prctl.h])
 AC_CHECK_FUNCS([prctl])
 AC_CHECK_FUNCS([pipe2])
 AC_CHECK_FUNCS([posix_fadvise])
+AC_CHECK_FUNCS([pwritev], AC_DEFINE([HAVE_PWRITEV], [1], [we have pwritev]))
 
 AC_MSG_CHECKING([for fdatasync])
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[

diff --git a/src/common/buffer.cc b/src/common/buffer.cc
@@ -1954,8 +1954,18 @@ int buffer::list::write_file(const char *fn, int mode)
 
 static int do_writev(int fd, struct iovec *vec, uint64_t offset, unsigned veclen, unsigned bytes)
 {
+  ssize_t r = 0;
   while (bytes > 0) {
-    ssize_t r = ::pwritev(fd, vec, veclen, offset);
+#ifdef HAVE_PWRITEV
+    r = ::pwritev(fd, vec, veclen, offset);
+#else
+    r = ::lseek64(fd, offset, SEEK_SET);
+    if (r != offset) {
+      r = -errno;
+      return r;
+    }
+    r = ::writev(fd, vec, veclen);
+#endif
     if (r < 0) {
       if (errno == EINTR)
         continue;