[gnome-multi-writer] Check some return codes when talking to the device

[Richard Hughes <rhughes src gnome org>]

commit 3a9919bf121d236ad786890cd0b4dd1ab33ac3f9
Author: Richard Hughes <richard hughsie com>
Date:   Wed Nov 9 20:38:32 2016 +0000

    Check some return codes when talking to the device
    
    Found using Coverity.

 src/gmw-probe.c |   15 ++++++++++-----
 1 files changed, 10 insertions(+), 5 deletions(-)
---
diff --git a/src/gmw-probe.c b/src/gmw-probe.c
index aec89ab..c6ff7d2 100644
--- a/src/gmw-probe.c
+++ b/src/gmw-probe.c
@@ -138,9 +138,12 @@ gmw_probe_device_open (GmwProbeDevice *dev, GError **error)
        }
 
        /* do not use the OS cache */
-       posix_fadvise (dev->fd, 0, 0, POSIX_FADV_DONTNEED |
-                                     POSIX_FADV_RANDOM |
-                                     POSIX_FADV_NOREUSE);
+       if (posix_fadvise (dev->fd, 0, 0,
+                          POSIX_FADV_DONTNEED |
+                          POSIX_FADV_RANDOM |
+                          POSIX_FADV_NOREUSE) != 0) {
+               g_warning ("Unable to call fadvise on %s", dev->block_dev);
+       }
        return TRUE;
 }
 
@@ -166,7 +169,8 @@ static gsize
 gmw_probe_device_read (GmwProbeDevice *dev, guint64 addr, guint8 *buf, gssize len)
 {
        gsize bytes_read;
-       lseek (dev->fd, addr, SEEK_SET);
+       if (lseek (dev->fd, addr, SEEK_SET) < 0)
+               return 0;
        bytes_read = read (dev->fd, buf, len);
        g_debug ("read %" G_GSIZE_FORMAT " @ %" G_GUINT64_FORMAT "MB",
                 bytes_read, addr / ONE_MB);
@@ -180,7 +184,8 @@ static gsize
 gmw_probe_device_write (GmwProbeDevice *dev, guint64 addr, const guint8 *buf, gssize len)
 {
        gsize bytes_written;
-       lseek (dev->fd, addr, SEEK_SET);
+       if (lseek (dev->fd, addr, SEEK_SET) < 0)
+               return 0;
        bytes_written = write (dev->fd, buf, len);
        g_debug ("wrote %" G_GSIZE_FORMAT " @ %" G_GUINT64_FORMAT "MB",
                 bytes_written, addr / ONE_MB);