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Re: [PATCH] xfs: pull up stack_switch check into xfs_bmapi_write

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: [PATCH] xfs: pull up stack_switch check into xfs_bmapi_write
From: Ben Myers <bpm@xxxxxxx>
Date: Thu, 17 Jan 2013 15:41:08 -0600
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1358446289-871-1-git-send-email-bfoster@xxxxxxxxxx>
References: <1358446289-871-1-git-send-email-bfoster@xxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
Hey Brian,

On Thu, Jan 17, 2013 at 01:11:29PM -0500, Brian Foster wrote:
> The stack_switch check currently occurs in __xfs_bmapi_allocate,
> which means the stack switch only occurs when xfs_bmapi_allocate()
> is called in a loop. Pull the check up before the loop in
> xfs_bmapi_write() such that the first iteration of the loop has
> consistent behavior.
> 
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> ---
> 
> I was reading through this code and confused myself over whether the stack
> switch ever actually occurs. Eric and Ben pointed out on irc (simultaneously,
> I might add) the surrounding loop that I had missed, but it wasn't clear 
> whether
> the behavior to enable the stack switch after the first iteration was
> intentional or not. I'm throwing this out there to either fix the issue or 
> seek
> out an explanation for the existing behavior. Thanks!

To me this looks to be the correct behavior.  It might be better to
just get rid of the XFS_BMAPI_STACK_SWITCH flag entirely.  Nice find.

-Ben

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