Re: XFS and O_STREAMING

["Buzbee, James" <James.Buzbee@echostar.com>]

Steve Lord wrote:
> On Mon, 2002-12-09 at 12:01, Buzbee, James wrote:
> 
>>I've been looking at Robert Love's O_STREAMING patch for the kernel :
>>
>>http://www.kernel.org/pub/linux/kernel/people/rml/O_STREAMING/v2.4/O_STREAMING-rml-2.4.20-pre9-1.patch
>>
>>I find that it doesn't quite work as expected with XFS.  It patches the 
>>generic_file_read/write routines to drop pages from cache list when a 
>>file is marked as O_STREAMING, but it appears to me as if XFS doesn't 
>>use the generic_file_write routine, but has its own version.
>>
>>I have a few questions. First, does this patch make sense for XFS? 
>>Could XFS's version of the generic_file_write routine be patched the 
>>same way?  Or perhaps there is an equivalent way to accomplish the same 
>>thing using standard XFS.
> 
> 
> We do use generic_file_write, it is just buried underneath our own
> layer. O_STREAMING sounds like the old dropbehind stuff and should
> work just fine.


Hmmm... I'm trying it with 2.4.18 and xfs 1.1  For debugging, I put 
"printk's" at the top of generic_file_read and generic_file_write in 
linux/mm/filemap.c (the patched file) and I never see any output from 
the generic_file_write, just from the generic_file_read.


> 
> One issue is that we do allocation of the actual blocks at flush time,
> we end up in writepage rather than in submit_bh. 

I afraid I don't understand the ramifications of this with respect to 
the patch :-(


Jim


> 
> Steve
>