logsave: Fix warn_unused_result warnings from gcc

Fixed a potential bug where by partial returns from the write(2)
system call could some bytes to be lost when writing to the log file.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/misc/logsave.c b/misc/logsave.c
index f0011f8..81ac9f6 100644 (file)
--- a/misc/logsave.c
+++ b/misc/logsave.c
@@ -49,6 +49,29 @@ static void usage(char *progname)
 #define SEND_CONSOLE   0x02
 #define SEND_BOTH      0x03
 
+/*
+ * Helper function that does the right thing if write returns a
+ * partial write, or an EGAIN/EINTR error.
+ */
+static int write_all(int fd, const char *buf, size_t count)
+{
+       ssize_t ret;
+       int c = 0;
+
+       while (count > 0) {
+               ret = write(fd, buf, count);
+               if (ret < 0) {
+                       if ((errno == EAGAIN) || (errno == EINTR))
+                               continue;
+                       return -1;
+               }
+               count -= ret;
+               buf += ret;
+               c += ret;
+       }
+       return c;
+}
+
 static void send_output(const char *buffer, int c, int flag)
 {
        char    *n;
@@ -57,11 +80,11 @@ static void send_output(const char *buffer, int c, int flag)
                c = strlen(buffer);
 
        if (flag & SEND_CONSOLE)
-               write(1, buffer, c);
+               write_all(1, buffer, c);
        if (!(flag & SEND_LOG))
                return;
        if (outfd > 0)
-               write(outfd, buffer, c);
+               write_all(outfd, buffer, c);
        else {
                n = realloc(outbuf, outbufsize + c);
                if (n) {
@@ -280,7 +303,7 @@ int main(int argc, char **argv)
                        outfd = open(outfn, openflags, 0644);
                        sleep(1);
                }
-               write(outfd, outbuf, outbufsize);
+               write_all(outfd, outbuf, outbufsize);
                free(outbuf);
        }
        close(outfd);