From: Kent Overstreet <kent.overstreet@linux.dev>
To: "Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, david@fromorbit.com,
chandan.babu@oracle.com, akpm@linux-foundation.org,
mcgrof@kernel.org, ziy@nvidia.com, hare@suse.de,
djwong@kernel.org, gost.dev@samsung.com, linux-mm@kvack.org,
Pankaj Raghav <p.raghav@samsung.com>
Subject: Re: [PATCH 03/13] filemap: align the index to mapping_min_order in the page cache
Date: Tue, 27 Feb 2024 11:40:34 -0500 [thread overview]
Message-ID: <vsy43j4pwgh4thcqbhmotap7rgzg5dnet42gd5z6x4yt3zwnu4@5w4ousyue36m> (raw)
In-Reply-To: <aajarho6xwi4sphqirwvukofvqy3cl6llpe5fetomj5sz7rgzp@xo2iqdwingtf>
On Tue, Feb 27, 2024 at 05:36:09PM +0100, Pankaj Raghav (Samsung) wrote:
> On Tue, Feb 27, 2024 at 11:22:24AM -0500, Kent Overstreet wrote:
> > On Tue, Feb 27, 2024 at 11:06:37AM +0100, Pankaj Raghav (Samsung) wrote:
> > > On Mon, Feb 26, 2024 at 02:40:42PM +0000, Matthew Wilcox wrote:
> > > > On Mon, Feb 26, 2024 at 10:49:26AM +0100, Pankaj Raghav (Samsung) wrote:
> > > > > From: Luis Chamberlain <mcgrof@kernel.org>
> > > > >
> > > > > Supporting mapping_min_order implies that we guarantee each folio in the
> > > > > page cache has at least an order of mapping_min_order. So when adding new
> > > > > folios to the page cache we must ensure the index used is aligned to the
> > > > > mapping_min_order as the page cache requires the index to be aligned to
> > > > > the order of the folio.
> > > >
> > > > This seems like a remarkably complicated way of achieving:
> > > >
> > > > diff --git a/mm/filemap.c b/mm/filemap.c
> > > > index 5603ced05fb7..36105dad4440 100644
> > > > --- a/mm/filemap.c
> > > > +++ b/mm/filemap.c
> > > > @@ -2427,9 +2427,11 @@ static int filemap_update_page(struct kiocb *iocb,
> > > > }
> > > >
> > > > static int filemap_create_folio(struct file *file,
> > > > - struct address_space *mapping, pgoff_t index,
> > > > + struct address_space *mapping, loff_t pos,
> > > > struct folio_batch *fbatch)
> > > > {
> > > > + pgoff_t index;
> > > > + unsigned int min_order;
> > > > struct folio *folio;
> > > > int error;
> > > >
> > > > @@ -2451,6 +2453,8 @@ static int filemap_create_folio(struct file *file,
> > > > * well to keep locking rules simple.
> > > > */
> > > > filemap_invalidate_lock_shared(mapping);
> > > > + min_order = mapping_min_folio_order(mapping);
> > > > + index = (pos >> (min_order + PAGE_SHIFT)) << min_order;
> > >
> > > That is some cool mathfu. I will add a comment here as it might not be
> > > that obvious to some people (i.e me).
> >
> > you guys are both wrong, just use rounddown()
>
> Umm, what do you mean just use rounddown? rounddown to ...?
>
> We need to get index that are in PAGE units but aligned to min_order
> pages.
>
> The original patch did this:
>
> index = mapping_align_start_index(mapping, iocb->ki_pos >> PAGE_SHIFT);
>
> Which is essentially a rounddown operation (probably this is what you
> are suggesting?).
>
> So what willy is proposing will do the same. To me, what I proposed is
> less complicated but to willy it is the other way around.
Ok, I just found the code for mapping_align_start_index() - it is just a
round_down().
Never mind; patch looks fine (aside from perhaps some quibbling over
whether the round_down()) should be done before calling readahead or
within readahead; I think that might have been more what willy was
keying in on)
next prev parent reply other threads:[~2024-02-27 16:40 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 9:49 [PATCH 00/13] enable bs > ps in XFS Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 01/13] mm: Support order-1 folios in the page cache Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 02/13] fs: Allow fine-grained control of folio sizes Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 03/13] filemap: align the index to mapping_min_order in the page cache Pankaj Raghav (Samsung)
2024-02-26 14:40 ` Matthew Wilcox
2024-02-27 10:06 ` Pankaj Raghav (Samsung)
2024-02-27 16:22 ` Kent Overstreet
2024-02-27 16:36 ` Pankaj Raghav (Samsung)
2024-02-27 16:40 ` Kent Overstreet [this message]
2024-02-27 16:55 ` Pankaj Raghav (Samsung)
2024-02-27 17:02 ` Kent Overstreet
2024-02-27 17:09 ` Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 04/13] filemap: use mapping_min_order while allocating folios Pankaj Raghav (Samsung)
2024-02-26 14:47 ` Matthew Wilcox
2024-02-27 12:09 ` Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 05/13] readahead: set file_ra_state->ra_pages to be at least mapping_min_order Pankaj Raghav (Samsung)
2024-02-26 14:49 ` Matthew Wilcox
2024-02-27 12:42 ` Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 06/13] readahead: align index to mapping_min_order in ondemand_ra and force_ra Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 07/13] readahead: rework loop in page_cache_ra_unbounded() Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 08/13] readahead: allocate folios with mapping_min_order in ra_(unbounded|order) Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 09/13] mm: do not split a folio if it has minimum folio order requirement Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 10/13] iomap: fix iomap_dio_zero() for fs bs > system page size Pankaj Raghav (Samsung)
2024-02-26 17:58 ` Matthew Wilcox
2024-02-27 9:33 ` Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 11/13] xfs: expose block size in stat Pankaj Raghav (Samsung)
2024-02-26 12:44 ` Dave Chinner
2024-02-27 8:53 ` Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 12/13] xfs: make the calculation generic in xfs_sb_validate_fsb_count() Pankaj Raghav (Samsung)
2024-02-26 12:47 ` Dave Chinner
2024-02-26 13:21 ` Matthew Wilcox
2024-02-27 8:44 ` Pankaj Raghav (Samsung)
2024-02-26 9:49 ` [PATCH 13/13] xfs: enable block size larger than page size support Pankaj Raghav (Samsung)
2024-02-26 13:26 ` Matthew Wilcox
2024-02-26 21:18 ` Dave Chinner
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