Ceph » Linux kernel client

3.8 kernel module, mount params (read ahead = 0):

x.x.x.x:/ on /srv/videos type ceph (name=test,rsize=0,rasize=0,key=client.test)

there is a little test program to read 4 bytes from the begining of a file (source code)

Here is the strace log, so the app really reads 4 bytes:

open("/srv/videos/x.mp4", O_RDONLY) = 3
read(3, "\0\0\0 ", 4)                   = 4
close(3)                                = 0

But the ceph kernel debug say:

[370581.014576] ceph:  aio_read ffff8803e19d3738 10000011749.fffffffffffffffe 0~4 got cap refs on Fcr
[370581.014581] ceph:  readpages ffff8803e19d3738 file ffff880425d49800 nr_pages 4 max 0
[370581.014583] ceph:  start_read ffff8803e19d3738 nr_pages 4 is 0~16384

And i see ~16k bytes data transfer from osd.