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Date: Sat, 13 Apr 2024 13:07:52 -0700
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Subject: Re: [PATCH v1 1/3] mm/gup: consistently name GUP-fast functions
To: David Hildenbrand <david@redhat.com>, <linux-kernel@vger.kernel.org>
CC: <linux-mm@kvack.org>, Andrew Morton <akpm@linux-foundation.org>, "Mike
 Rapoport" <rppt@kernel.org>, Jason Gunthorpe <jgg@nvidia.com>, Peter Xu
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References: <20240402125516.223131-1-david@redhat.com>
 <20240402125516.223131-2-david@redhat.com>
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From: John Hubbard <jhubbard@nvidia.com>
In-Reply-To: <20240402125516.223131-2-david@redhat.com>
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On 4/2/24 5:55 AM, David Hildenbrand wrote:
> Let's consistently call the "fast-only" part of GUP "GUP-fast" and rename
> all relevant internal functions to start with "gup_fast", to make it
> clearer that this is not ordinary GUP. The current mixture of
> "lockless", "gup" and "gup_fast" is confusing.
> 
> Further, avoid the term "huge" when talking about a "leaf" -- for
> example, we nowadays check pmd_leaf() because pmd_huge() is gone. For the
> "hugepd"/"hugepte" stuff, it's part of the name ("is_hugepd"), so that
> stays.
> 
> What remains is the "external" interface:
> * get_user_pages_fast_only()
> * get_user_pages_fast()
> * pin_user_pages_fast()
> 
> The high-level internal functions for GUP-fast (+slow fallback) are now:
> * internal_get_user_pages_fast() -> gup_fast_fallback()
> * lockless_pages_from_mm() -> gup_fast()
> 
> The basic GUP-fast walker functions:
> * gup_pgd_range() -> gup_fast_pgd_range()
> * gup_p4d_range() -> gup_fast_p4d_range()
> * gup_pud_range() -> gup_fast_pud_range()
> * gup_pmd_range() -> gup_fast_pmd_range()
> * gup_pte_range() -> gup_fast_pte_range()
> * gup_huge_pgd()  -> gup_fast_pgd_leaf()
> * gup_huge_pud()  -> gup_fast_pud_leaf()
> * gup_huge_pmd()  -> gup_fast_pmd_leaf()

This is my favorite cleanup of 2024 so far. The above mix was confusing
even if one worked on this file all day long--you constantly have to
translate from function name, to "is this fast or slow?". whew.


> 
> The weird hugepd stuff:
> * gup_huge_pd() -> gup_fast_hugepd()
> * gup_hugepte() -> gup_fast_hugepte()
> 
> The weird devmap stuff:
> * __gup_device_huge_pud() -> gup_fast_devmap_pud_leaf()
> * __gup_device_huge_pmd   -> gup_fast_devmap_pmd_leaf()
> * __gup_device_huge()     -> gup_fast_devmap_leaf()
> * undo_dev_pagemap()      -> gup_fast_undo_dev_pagemap()
> 
> Helper functions:
> * unpin_user_pages_lockless() -> gup_fast_unpin_user_pages()
> * gup_fast_folio_allowed() is already properly named
> * gup_fast_permitted() is already properly named
> 
> With "gup_fast()", we now even have a function that is referred to in
> comment in mm/mmu_gather.c.
> 
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>   mm/gup.c | 205 ++++++++++++++++++++++++++++---------------------------
>   1 file changed, 103 insertions(+), 102 deletions(-)
> 

Reviewed-by: John Hubbard <jhubbard@nvidia.com>


thanks,
-- 
John Hubbard
NVIDIA