Booting under 3.15.1 I can see and do the following:
# free -m 
             total       used       free     shared    buffers     cached
Mem:          2011        380       1631         10         22        253
-/+ buffers/cache:        104       1907
Swap:         8191          0       8191
# blkid
/dev/mmcblk0p1: LABEL="_/boot" UUID="8b227b31-d2a9-4364-9b92-6ccd926c7441" TYPE="ext4" PARTUUID="0008d0a9-01" 
/dev/mmcblk0p2: LABEL="swap" UUID="11beef80-bf9c-4f4e-b78f-ec8c860cf300" TYPE="swap" PARTUUID="0008d0a9-02" 
/dev/mmcblk0p3: LABEL="_/" UUID="7ee85ed8-de4a-4779-8658-2daed0d35e97" TYPE="ext4" PARTUUID="0008d0a9-03" 
/dev/mmcblk0: PTUUID="0008d0a9" PTTYPE="dos" 
# swapoff -a
# swapon -a

But under 3.16-rc2 I end up with:
# free -m
             total       used       free     shared    buffers     cached
Mem:          2011        374       1636         10         22        253
-/+ buffers/cache:         98       1912
Swap:            0          0          0
# blkid
/dev/mmcblk0p1: LABEL="_/boot" UUID="8b227b31-d2a9-4364-9b92-6ccd926c7441" TYPE="ext4" PARTUUID="0008d0a9-01" 
/dev/mmcblk0p3: LABEL="_/" UUID="7ee85ed8-de4a-4779-8658-2daed0d35e97" TYPE="ext4" PARTUUID="0008d0a9-03" 
/dev/mmcblk0: PTUUID="0008d0a9" PTTYPE="dos" 
/dev/mmcblk0p2: PARTUUID="0008d0a9-02" 
# swapon -a
swapon: /dev/mmcblk0p2: read swap header failed: Success
# mkswap -L swap /dev/mmcblk0p2
Setting up swapspace version 1, size = 8388604 KiB
LABEL=swap, UUID=6bc4c1a0-cf67-4064-a99b-a2d7635a3bf8
# swapon -a
swapon: /dev/mmcblk0p2: read swap header failed: Success

I can plug a thumb drive into USB and create and mount a swap partition at /dev/sda1 or even using a swapfile, but not for mmcblk0p2.

I've seen some annecdotal evidence[1][2] of others having problems with mounting swap partitions as well, but I've yet to see another BZ or anything more concete.

[1] First comment on https://plus.google.com/u/0/104877287288155269055/posts/JTNvi2VH9qq
[2] http://forums.fedoraforum.org/showthread.php?t=299520