vmap allocation for size 1048576 failed

[Michael Weissenbacher]

> You should describe the loop setup and all devices down to the disk. 
> Might be easier for the devs to help then.

-rw-r--r--   1 root root 2.0G Nov  9 13:01 portage-loopback

/dev/loop0 /mnt/portage xfs rw,noatime,attr2,delaylog,logbsize=256k,noquota
meta-data=/dev/loop0             isize=256    agcount=4, agsize=1048576 blks
         =                       sectsz=512   attr=2
data     =                       bsize=512    blocks=4194304, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0
log      =internal               bsize=512    blocks=65536, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

/dev/sda3 / xfs
rw,swalloc,attr2,delaylog,logbsize=256k,sunit=128,swidth=384,usrquota,grpquota
meta-data=/dev/sda3              isize=256    agcount=4, agsize=90929920
blks
         =                       sectsz=512   attr=2
data     =                       bsize=4096   blocks=363719632, imaxpct=10
         =                       sunit=16     swidth=48 blks
naming   =version 2              bsize=4096   ascii-ci=0
log      =internal               bsize=4096   blocks=32768, version=2
         =                       sectsz=512   sunit=16 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

/dev/sda is a 4-disk RAID-5 on a 3ware 8506-4LP Controller.