linux-kernel - Re: [PATCH] mm/filemap: allocate folios according to the blocksize

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Message-ID: <20230420150355.GG360881@frogsfrogsfrogs>
Date:   Thu, 20 Apr 2023 08:03:55 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Pankaj Raghav <p.raghav@...sung.com>
Cc:     Hannes Reinecke <hare@...e.de>,
        Matthew Wilcox <willy@...radead.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        mcgrof@...nel.org, SSDR Gost Dev <gost.dev@...sung.com>
Subject: Re: [PATCH] mm/filemap: allocate folios according to the blocksize

On Thu, Apr 20, 2023 at 02:28:36PM +0200, Pankaj Raghav wrote:
> On 2023-04-20 14:19, Hannes Reinecke wrote:
> >>
> >> **Questions on the future work**:
> >>
> >> As willy pointed out, we have to do this `order = mapping->host->i_blkbits - PAGE_SHIFT` in
> >> many places. Should we pursue something that willy suggested: encapsulating order in the
> >> mapping->flags as a next step?[1]
> >>
> >>
> >> [1] https://lore.kernel.org/lkml/ZDty+PQfHkrGBojn@casper.infradead.org/

I wouldn't mind XFS gaining a means to control folio sizes, personally.
At least that would make it easier to explore things like copy on write
with large weird file allocation unit sizes (2MB, 28k, etc).

> > 
> > Well ... really, not sure.
> > Yes, continue updating buffer_heads would be a logical thing as it could be done incrementally.
> >
> > But really, the end-goal should be to move away from buffer_heads for fs and mm usage. So I wonder
> > if we shouldn't rather look in that direction..
> >
> Yeah, I understand that part. Hopefully, this will be discussed as a part of LSFMM.

Agree.

--D

> 
> But the changes that are done in filemap and readahead needs to be done anyway irrespective of the
> underlying aops right? Or Am I missing something.
> 
> > Cheers,
> > 
> > Hannes
> >