It seems that I am struck by this very bug as well since several months now.

Fedora 21, kernel-3.17.7-300.fc21.x86_64 (but it started on Fedora 20, around
kernel-3.15.5-200.fc20.x86_64)

Graphics card:
01:00.0 VGA compatible controller: NVIDIA Corporation GF108 [GeForce GT 630]
(rev a1) (prog-if 00 [VGA controller])
        Subsystem: Micro-Star International Co., Ltd. [MSI] Device 8a90
        Flags: bus master, fast devsel, latency 0, IRQ 43
        Memory at f6000000 (32-bit, non-prefetchable) [size=16M]
        Memory at e8000000 (64-bit, prefetchable) [size=128M]
        Memory at f0000000 (64-bit, prefetchable) [size=32M]
        I/O ports at e000 [size=128]
        Expansion ROM at f7000000 [disabled] [size=512K]
        Capabilities: [60] Power Management version 3
        Capabilities: [68] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [78] Express Endpoint, MSI 00
        Capabilities: [b4] Vendor Specific Information: Len=14 <?>
        Capabilities: [100] Virtual Channel
        Capabilities: [128] Power Budgeting <?>
        Capabilities: [600] Vendor Specific Information: ID=0001 Rev=1 Len=024
<?>
        Kernel driver in use: nouveau
        Kernel modules: nouveau

It seems as if problems started with this commit:
http://lists.freedesktop.org/archives/nouveau/2014-March/016589.html
At least reverting this patch to the nouveau source is a workaround, see
discussion on Redhat bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=1121331

BTW, isn't bug 84721 a duplicate of this one? It is the very same NVIDIA
controller as mine that is affected.