Use __fpurge to ensure single-line writes to cache files

[nfs-utils.git] / support / nfs / cacheio.c

diff --git a/support/nfs/cacheio.c b/support/nfs/cacheio.c
index a76915bcf22992129efe3c1df9a25f83d44bfd70..9d271cd4733d77328a6f2b3e5ec8a80b5da8a73b 100644 (file)
--- a/support/nfs/cacheio.c
+++ b/support/nfs/cacheio.c
@@ -17,6 +17,7 @@
 
 #include <nfslib.h>
 #include <stdio.h>
+#include <stdio_ext.h>
 #include <ctype.h>
 #include <unistd.h>
 #include <sys/types.h>
@@ -111,7 +112,18 @@ void qword_printint(FILE *f, int num)
 
 int qword_eol(FILE *f)
 {
+       int err;
+
        fprintf(f,"\n");
+       err = fflush(f);
+       /*
+        * We must send one line (and one line only) in a single write
+        * call.  In case of a write error, libc may accumulate the
+        * unwritten data and try to write it again later, resulting in a
+        * multi-line write.  So we must explicitly ask it to throw away
+        * any such cached data:
+        */
+       __fpurge(f);
        return fflush(f);
 }