[PATCH] uml: better error reporting for read_output

Do precise error handling: print precise error messages, distinguishing short
reads and read errors.  This functions fails frequently enough for me so I
bothered doing this fix.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 22 insertions, 12 deletions

diff --git a/arch/um/drivers/net_user.c b/arch/um/drivers/net_user.c
index 098fa65981ab..0e2f06187ea7 100644
--- a/arch/um/drivers/net_user.c
+++ b/arch/um/drivers/net_user.c
@@ -47,10 +47,12 @@ void tap_check_ips(char *gate_addr, unsigned char *eth_addr)
         }
 }
 
+/* Do reliable error handling as this fails frequently enough. */
 void read_output(int fd, char *output, int len)
 {
-        int remain, n, actual;
+        int remain, ret, expected;
         char c;
+        char *str;
 
         if(output == NULL){
                 output = &c;
@@ -58,23 +60,31 @@ void read_output(int fd, char *output, int len)
         }
                 
         *output = '\0';
-        n = os_read_file(fd, &remain, sizeof(remain));
-        if(n != sizeof(remain)){
-                printk("read_output - read of length failed, err = %d\n", -n);
-                return;
+        ret = os_read_file(fd, &remain, sizeof(remain));
+
+        if (ret != sizeof(remain)) {
+                expected = sizeof(remain);
+                str = "length";
+                goto err;
         }
 
         while(remain != 0){
-                n = (remain < len) ? remain : len;
-                actual = os_read_file(fd, output, n);
-                if(actual != n){
-                        printk("read_output - read of data failed, "
-                               "err = %d\n", -actual);
-                        return;
+                expected = (remain < len) ? remain : len;
+                ret = os_read_file(fd, output, expected);
+                if (ret != expected) {
+                        str = "data";
+                        goto err;
                 }
-                remain -= actual;
+                remain -= ret;
         }
+
         return;
+
+err:
+        if (ret < 0)
+                printk("read_output - read of %s failed, errno = %d\n", str, -ret);
+        else
+                printk("read_output - read of %s failed, read only %d of %d bytes\n", str, ret, expected);
 }
 
 int net_read(int fd, void *buf, int len)