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Re: [xfs-masters] [RESEND][PATCH 6/7] xfs: Remove code handling bio_allo

To: Nikanth Karthikesan <knikanth@xxxxxxx>
Subject: Re: [xfs-masters] [RESEND][PATCH 6/7] xfs: Remove code handling bio_alloc failure with __GFP_WAIT
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 20 Apr 2009 11:02:37 +1000
Cc: xfs-masters@xxxxxxxxxxx, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Jens Axboe <jens.axboe@xxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <200904151609.30677.knikanth@xxxxxxx>
References: <200904151609.30677.knikanth@xxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Wed, Apr 15, 2009 at 04:09:30PM +0530, Nikanth Karthikesan wrote:
> Resending as I accidentally missed Jens earlier.
> Jens, can you merge this as well.
> Thanks
> Nikanth
> Remove code handling bio_alloc failure with __GFP_WAIT.
> GFP_NOIO implies __GFP_WAIT.

Not sure that is right. The intent of the code is that if we can't
get a large bio immediately, try a smaller one which is more likely
to succeed when we are under memory pressure. i.e. we will get IO
moving faster than if we waited for a maximally sized biovec to be

IOWs, I don't think __GFP_WAIT is implied by this code, regardless
of what GFP_NOIO actually means now. The same code fragment can be
found in NILFS, and it uses GFP_NOWAIT, not GFP_NOIO. I suspect that
this is what this XFS code should be changed to use to retain the
original intent of the code....


Dave Chinner

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