Re: delalloc and reservation.

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Alex Tomas wrote:
> Hi,
> 
> could you try the patch attached. it should fix the issue. the idea
> was to align requests in order to help raid5-like setups. but somewhere
> I lost one bit in mballoc: it should pre-allocate all crossed stripes,
> but it didn't.
> 
> as for discard, lustre doesn't use open/close for data, so discard-on-close
> makes zero sense in our case. I'm not very positive whether we need to
> drop preallocation on file close in case of delayed allocation as writeback
> can be started while file is open and finish after close(2).
> 
> 

mballoc by default doesn't give the particular layout only if i force small
size to use inode preallocation i am hitting the problem. ie to change the
below line in ext4_mb_group_or_file

 if (ac->ac_o_ex.fe_len >= sbi->s_mb_small_req)

to 

if (ac->ac_o_ex.fe_len <= sbi->s_mb_small_req)

Do you want to test the patch with this change ?

We are observing the problem with delalloc and nomballoc.


-aneesh