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[Libguestfs] [PATCH 4/5] fuse: Fix read for empty files.



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Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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>From 3c5d63be17d281634f036f53aa32103ad4ab1c41 Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones redhat com>
Date: Tue, 17 Nov 2009 17:02:45 +0000
Subject: [PATCH 4/5] fuse: Fix read for empty files.

Error handling for the guestfs_pread call was incorrect, which
meant that empty files could produce spurious error messages.
---
 fuse/guestmount.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/fuse/guestmount.c b/fuse/guestmount.c
index 9d16cef..669bf80 100644
--- a/fuse/guestmount.c
+++ b/fuse/guestmount.c
@@ -621,8 +621,14 @@ fg_read (const char *path, char *buf, size_t size, off_t offset,
   if (size > limit)
     size = limit;
 
+  /* Note the correct error handling here is tricky, because in the
+   * case where the call returns a zero-length buffer, it might return
+   * NULL.  However it won't adjust rsize along the error path, so we
+   * can set rsize to something beforehand and use that as a flag.
+   */
+  rsize = 1;
   r = guestfs_pread (g, path, size, offset, &rsize);
-  if (r == NULL)
+  if (rsize == 1 && r == NULL)
     return error ();
 
   /* This should never happen, but at least it stops us overflowing
-- 
1.6.5.2


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