James Dingwall wrote:
> --- xfs_super.c 2013-04-29 10:28:22.000000000 +0100
> +++ xfs_super.cleancache.c      2013-05-01 13:22:44.367763564 +0100
> @@ -61,6 +61,7 @@
>  #include <linux/kthread.h>
>  #include <linux/freezer.h>
>  #include <linux/parser.h>
> +#include <linux/cleancache.h>
>
>  static const struct super_operations xfs_super_operations;
>  static kmem_zone_t *xfs_ioend_zone;
> @@ -1489,6 +1490,8 @@
>                 goto out_unmount;
>         }
>
> +       cleancache_init_fs(sb);
> +
>         return 0;
>
>   out_filestream_unmount: 
I have tested this patch with xfstests 
(dd3b5268312e0518ae695e8ee2a618f13805c425) and the output is attached.  
I had four reported failures with and without, one seems due to my 
locale settings but I don't know what to make of the others.  These were 
the commands that I ran to prepare my system and execute the tests.  If 
it would be worth performing more runs or using a different group of 
tests please suggest what it would be worth doing.  I have also 
published the patch in git at:

https://github.com/JKDingwall/linux.git xfs-enable-cleancache

Thanks,
James

# mkfs -t xfs /dev/xvdc1
meta-data=/dev/xvdc1             isize=256    agcount=4, agsize=1048512 blks
          =                       sectsz=512   attr=2, projid32bit=0
data     =                       bsize=4096   blocks=4194048, imaxpct=25
          =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0
log      =internal log           bsize=4096   blocks=2560, version=2
          =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

# mkdir /tmp/test
# mkdir /tmp/scratch
# TEST_DEV="/dev/xvdc1" ; export TEST_DEV
# TEST_DIR="/tmp/test" ; export TEST_DIR
# SCRATCH_DEV="/dev/xvdd1" ; export SCRATCH_DEV
# SCRATCH_MNT="/tmp/scratch" ; export SCRATCH_MNT
# mount /dev/xvdc1 /tmp/test


# ./check -xfs -g rw # run 1 - 3.9.0 with cleancache patch
# ./check -xfs -g rw # run 3 - 3.9.1 no patch