linux-kernel - Re: [PATCH v2 00/28] Convert GUP to folios

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Date:   Mon, 10 Jan 2022 17:26:37 +0000
From:   William Kucharski <william.kucharski@...cle.com>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        John Hubbard <jhubbard@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH v2 00/28] Convert GUP to folios

Series still looks good.

Reviewed-by: William Kucharski <william.kucharski@...cle.com>

> On Jan 9, 2022, at 9:23 PM, Matthew Wilcox (Oracle) <willy@...radead.org> wrote:
> 
> This patch series is against my current folio for-next branch.  I know
> it won't apply to sfr's next tree, and it's not for-next material yet.
> I intend to submit it for 5.18 after I've rebased it to one of the
> 5.17-rc releases.
> 
> The overall effect of this (ignoring the primary "preparing for folios
> that are not PAGE or PMD sized" purpose) is to reduce the size of gup.o
> by ~700 bytes in the config I normally test with.
> 
> This patchset just converts existing implementations to use folios.
> There's no new API for consumers here to provide information in a more
> efficient (address, length) format.  That will be a separate patchset.
> 
> In v2, I've tried to address all the comments from the reviews I got
> on v1.  Apologies if I missed anything; I got a lot of good feedback.
> Primarily I separated out the folio changes (later) from the "While
> I'm looking at this ..." changes (earlier).  I'm not sure the story
> of the patchset is necessarily coherent this way, but it should be
> easier to review.
> 
> Another big change is that compound_pincount is now available to all
> compound pages, not just those that are order-2-or-higher.  Patch 11.
> 
> I did notice one bug in my original patchset which I'm disappointed GCC
> didn't diagnose:
> 
> 		pages[nr++] = nth_page(page, nr);
> 
> Given the massive reorg of the patchset, I didn't feel right using
> anyone's SoB from v1 on any of the patches.  But, despite the increased
> number of patches, I hope it's easier to review than v1.
> 
> And I'd dearly love a better name than 'folio_nth'.  page_nth() is
> a temporary construct, so doesn't need a better name.  If you need
> context, it's in the gup_folio_range_next() patch and its job
> is to tell you, given a page and a folio, what # page it is within
> a folio (so a number between [0 and folio_nr_pages())).
> 
> Matthew Wilcox (Oracle) (28):
>  gup: Remove for_each_compound_range()
>  gup: Remove for_each_compound_head()
>  gup: Change the calling convention for compound_range_next()
>  gup: Optimise compound_range_next()
>  gup: Change the calling convention for compound_next()
>  gup: Fix some contiguous memmap assumptions
>  gup: Remove an assumption of a contiguous memmap
>  gup: Handle page split race more efficiently
>  gup: Turn hpage_pincount_add() into page_pincount_add()
>  gup: Turn hpage_pincount_sub() into page_pincount_sub()
>  mm: Make compound_pincount always available
>  mm: Add folio_put_refs()
>  mm: Add folio_pincount_ptr()
>  mm: Convert page_maybe_dma_pinned() to use a folio
>  gup: Add try_get_folio() and try_grab_folio()
>  mm: Remove page_cache_add_speculative() and
>    page_cache_get_speculative()
>  gup: Add gup_put_folio()
>  hugetlb: Use try_grab_folio() instead of try_grab_compound_head()
>  gup: Convert try_grab_page() to call try_grab_folio()
>  gup: Convert gup_pte_range() to use a folio
>  gup: Convert gup_hugepte() to use a folio
>  gup: Convert gup_huge_pmd() to use a folio
>  gup: Convert gup_huge_pud() to use a folio
>  gup: Convert gup_huge_pgd() to use a folio
>  gup: Convert compound_next() to gup_folio_next()
>  gup: Convert compound_range_next() to gup_folio_range_next()
>  mm: Add isolate_lru_folio()
>  gup: Convert check_and_migrate_movable_pages() to use a folio
> 
> Documentation/core-api/pin_user_pages.rst |  18 +-
> arch/powerpc/include/asm/mmu_context.h    |   1 -
> include/linux/mm.h                        |  70 +++--
> include/linux/mm_types.h                  |  13 +-
> include/linux/pagemap.h                   |  11 -
> mm/debug.c                                |  14 +-
> mm/folio-compat.c                         |   8 +
> mm/gup.c                                  | 359 ++++++++++------------
> mm/hugetlb.c                              |   7 +-
> mm/internal.h                             |   8 +-
> mm/page_alloc.c                           |   3 +-
> mm/rmap.c                                 |   6 +-
> mm/vmscan.c                               |  43 ++-
> 13 files changed, 263 insertions(+), 298 deletions(-)
> 
> -- 
> 2.33.0
>