Re: direct-IO writes strange behavior

[Alberto Nava <beto@xxxxxxxxxxx>]

Nathan Scott wrote:

> Hi Alberto,
>
> I spent some time this morning looking into this.  Firstly, the
> fs/direct-io.c code has moved on from what you were looking at
> in test9 -- I've been testing using test11 this morning and the
> code snippet you've pasted above is no longer the same (Andrews
> comment above has modified - ENOTBLK is never returned now).
>
> Secondly, I cannot reproduce the behaviour you've described --
> direct IO into both unwritten and newly allocated extents works
> correctly, and using your test case I got nice big 512k chunks
> every time.  There have been no changes in XFS in this area that
> could have affected this, so I wonder what led you to suspect
> the buffer was unmapped (your first "XXXXXX" above) originally?
>
> Did you put a printk in there that was being triggered?  (I did,
> and it didn't, using -test11).  I also put the printks into XFS
> as I described in my previous mail, and we are definately giving
> large IOs back to the generic direct IO code, for both cases -
> pre-allocated and and not-pre-allocated cases.

thanks for looking into this. Yes I had some printk on the "XXXXX" 
lines, plus I've added some traces to test9 that allow you to get
information about BIO that are submitted to the scheduler. This showed
a 4k vs 512k requests.

I'll try to reproduce it with test11. It might take me some
time as I need to merge my trace gathering code.

Thanks
beto

> Any chance you could retry your tests on the current kernel just
> to verify that there is no problem here for me?
>
> thanks!