moby: Concurrent pulls fail

This issue seems to be triggered while pulling multiple images which map up to an identical base image. A reproducible example is below. This has been reproduced on Ubuntu 14.04 with DeviceMapper and the Amazon ECS-Optimized Amazon Linux AMI. This has also been reproduced on Docker 1.3.3 and Docker 1.4.1.

    [ec2-user@ip-172-31-35-232 ~]$ docker version
    Client version: 1.4.1
    Client API version: 1.16
    Go version (client): go1.3.3
    Git commit (client): 5bc2ff8
    OS/Arch (client): linux/amd64
    Server version: 1.4.1
    Server API version: 1.16
    Go version (server): go1.3.3
    Git commit (server): 5bc2ff8
    [ec2-user@ip-172-31-35-232 ~]$ 
    [ec2-user@ip-172-31-35-232 ~]$ docker -D info
    Containers: 0
    Images: 0
    Storage Driver: devicemapper
    Pool Name: docker-202:1-1835239-pool
    Pool Blocksize: 65.54 kB
    Data file: /var/lib/docker/devicemapper/devicemapper/data
    Metadata file: /var/lib/docker/devicemapper/devicemapper/metadata
    Data Space Used: 307.2 MB
    Data Space Total: 107.4 GB
    Metadata Space Used: 725 kB
    Metadata Space Total: 2.147 GB
    Library Version: 1.02.82-git (2013-10-04)
    Execution Driver: native-0.2
    Kernel Version: 3.14.26-24.46.amzn1.x86_64
    Operating System: Amazon Linux AMI 2014.09
    CPUs: 1
    Total Memory: 1.957 GiB
    Name: ip-172-31-35-232
    ID: 2RCA:OSRS:4M6S:XHJG:MAUC:IYAA:KIGE:K2HM:VBRF:SCXN:LTRD:T3WP
    Debug mode (server): false
    Debug mode (client): true
    Fds: 57
    Goroutines: 58
    EventsListeners: 0
    Init Path: /usr/bin/docker
    Docker Root Dir: /var/lib/docker
    [ec2-user@ip-172-31-35-232 ~]$ uname -a
    Linux ip-172-31-35-232 3.14.26-24.46.amzn1.x86_64 #1 SMP Wed Dec 10 10:02:43 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
    [ec2-user@ip-172-31-35-232 ~]$ docker images
    REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
    [ec2-user@ip-172-31-35-232 ~]$ cat repro
    docker run nginx &
    docker run mysql &
    [ec2-user@ip-172-31-35-232 ~]$ sh repro
    [ec2-user@ip-172-31-35-232 ~]$ Unable to find image 'mysql:latest' locally
    Unable to find image 'nginx:latest' locally
    mysql:latest: The image you are pulling has been verified

    f10807909bc5: Pulling fs layer
    f6fab3b798be: Pulling fs layer
    d832c6f40cc3: Pulling fs layer
    cfab4f0d8972: Pulling fs layer
    cf8221608a63: Pulling fs layer
    4755e012c4cf: Pulling fs layer
    e012a865bac8: Pulling fs layer
    e2778dfe9ae9: Pulling fs layer
    b15206a696ec: Pulling fs layer
    9280b0f1af9a: Pulling fs layer
    9f1c487e78cd: Pulling fs layer
    10491040baf9: Pulling fs layer
    d8978d323757: Pulling fs layer
    f10807909bc5: Download complete
    f10807909bc5: Extracting [=================================================> ] 89.69 MB/90.17 MB 0
    d832c6f40cc3: Download complete
    f10807909bc5: Pull complete
    f10807909bc5: Download complete
    f6fab3b798be: Error downloading dependent layers
    d21beea329f5: Download complete
    04499cf33a0e: Download complete
    b15206a696ec: Downloading [====> ] 10.8 MB/118.7 MB 19s
    b15206a696ec: Download complete
    92360dceda1a: Download complete
    9495a555677d: Download complete
    911e2df03930: Download complete
    88daddf047c6: Download complete
    db8a64f62509: Download complete
    e46b3488b010: Download complete
    e46b3488b010: Error pulling image (latest) from nginx, Driver devicemapper failed to create image rootfs f10807909bc552de261ca7463effc467600c3dca68d8e7704425283a6911d2ca: device f10807909bc552de261ca7463effc467600c3dca68d8e7704425283a6911d2ca already exists 3dca68d8e7704425283a6911d2ca already exists
    FATA[0032] Error pulling image (latest) from nginx, Driver devicemapper failed to create image rootfs f10807909bc552de261ca7463effc467600c3dca68d8e7704425283a6911d2ca: device f10807909bc552dea385835786ac: Error pulling image (latest) from mysql, Error mounting '/dev/mapper/docker-202:1-1835239-f6fab3b798be3174f45aa1eb731f8182705555f89c9026d8c1ef230cbf8301dd' on '/var/lib/docker/devicemapper/mnt/f6fab3b798be3174f45aa1eb731f8182705555f89c9026d8c1ef230cbf8301dd': invalid argument 9c9026d8c1ef230cbf8301dd': invalid argument
    FATA[0034] Error pulling image (latest) from mysql, Error mounting '/dev/mapper/docker-202:1-1835239-f6fab3b798be3174f45aa1eb731f8182705555f89c9026d8c1ef230cbf8301dd' on '/var/lib/docker/devicemapper/mnt/f6fab3b798be3174f45aa1eb731f8182705555f89c9026d8c1ef230cbf8301dd': invalid argument
    ^C
    [ec2-user@ip-172-31-35-232 ~]$ docker ps -a
    CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
    [ec2-user@ip-172-31-35-232 ~]$ docker images
    REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
    <none> <none> f10807909bc5 5 weeks ago 85.1 MB