Direct IO on CephFS for blocks larger than 8MB

["Huang, Xiwei" <xiwei.huang@xxxxxxxxx>]

Hi, all, 
    I noticed that CephFS fails to support Direct IO for blocks larger than 8MB, say:
			sudo dd if=/dev/zero of=mnt/cephfs/foo bs=16M count=1 oflag=direct
			dd: writing `mnt/cephfs/foo: Bad address
			1+0 records in
			0+0 records out
			0 bytes (0 B) copied, 0.213948 s, 0.0 kB/s
   My version Ceph is 0.56.1. 
　　I also found the bug has been already reported as Bug #2657.
   Is this fixed in the new 0.58 version? 
   Thanks!
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Huang Xiwei
DRD/SSG/Intel

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