Libguestfs - Apr 2010 - [PATCH] Check error returns from posix_fallocate (RHBZ#579664).

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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>From 557f413e0bd1ad7bd0180ca28a5bfec854f23790 Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones at redhat.com>
Date: Tue, 6 Apr 2010 11:03:03 +0100
Subject: [PATCH] Check error returns from posix_fallocate (RHBZ#579664).

posix_fallocate has a non-standard way to return error indications.
Thus all our calls to posix_fallocate were effectively unchecked.  For
example:

  $ guestfish alloc test.img 1P
  $ echo $?
  0
  $ ll test.img
  -rw-rw-r--. 1 rjones rjones 0 2010-04-06 11:02 test.img
  $ rm test.img

With this change, errors are detected and reported properly:

  $ ./fish/guestfish alloc test.img 1P
  fallocate: File too large

This is a fix for:
https://bugzilla.redhat.com/show_bug.cgi?id=579664
---
 daemon/fallocate.c |    8 ++++----
 fish/alloc.c       |    5 ++++-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/daemon/fallocate.c b/daemon/fallocate.c
index 7f17f8b..4947430 100644
--- a/daemon/fallocate.c
+++ b/daemon/fallocate.c
@@ -23,6 +23,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <errno.h>
 
 #include "daemon.h"
 #include "actions.h"
@@ -41,10 +42,9 @@ do_fallocate (const char *path, int len)
   }
 
 #ifdef HAVE_POSIX_FALLOCATE
-  int r;
-
-  r = posix_fallocate (fd, 0, len);
-  if (r == -1) {
+  int err = posix_fallocate (fd, 0, len);
+  if (err != 0) {
+    errno = err;
     reply_with_perror ("%s", path);
     close (fd);
     return -1;
diff --git a/fish/alloc.c b/fish/alloc.c
index 28c990f..93cd8af 100644
--- a/fish/alloc.c
+++ b/fish/alloc.c
@@ -24,6 +24,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <inttypes.h>
+#include <errno.h>
 
 #include "fish.h"
 
@@ -55,7 +56,9 @@ do_alloc (const char *cmd, int argc, char *argv[])
   }
 
 #ifdef HAVE_POSIX_FALLOCATE
-  if (posix_fallocate (fd, 0, size) == -1) {
+  int err = posix_fallocate (fd, 0, size);
+  if (err != 0) {
+    errno = err;
     perror ("fallocate");
     close (fd);
     unlink (argv[0]);
-- 
1.6.6.1

Richard W.M. Jones wrote:
> Subject: [PATCH] Check error returns from posix_fallocate (RHBZ#579664).
>
> posix_fallocate has a non-standard way to return error indications.
> Thus all our calls to posix_fallocate were effectively unchecked.  For
> example:
>
>   $ guestfish alloc test.img 1P
>   $ echo $?
>   0
>   $ ll test.img
>   -rw-rw-r--. 1 rjones rjones 0 2010-04-06 11:02 test.img
>   $ rm test.img
>
> With this change, errors are detected and reported properly:
>
>   $ ./fish/guestfish alloc test.img 1P
>   fallocate: File too large
>
> This is a fix for:
> https://bugzilla.redhat.com/show_bug.cgi?id=579664
> ---
>  daemon/fallocate.c |    8 ++++----
>  fish/alloc.c       |    5 ++++-
>  2 files changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/daemon/fallocate.c b/daemon/fallocate.c
...
> +  int err = posix_fallocate (fd, 0, len);
> +  if (err != 0) {
> +    errno = err;
Confirmed that those are the two sole uses (at least in my
out-of-date repo -- git pull fails, today), and that the fix
makes the usage agree with what POSIX and the posix_fallocate man
page say the function does.

What a shame to have *standardized* such a surprising interface.

ACK.