On 02.04.24 14:55, 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()
The weird hugepd stuff:
* gup_huge_pd() -> gup_fast_hugepd()
* gup_hugepte() -> gup_fast_hugepte()
I just realized that we end up calling these from follow_hugepd() as
well. And something seems to be off, because gup_fast_hugepd() won't
have the VMA even in the slow-GUP case to pass it to gup_must_unshare().
So these are GUP-fast functions and the terminology seem correct. But
the usage from follow_hugepd() is questionable,
commit a12083d721d703f985f4403d6b333cc449f838f6
Author: Peter Xu <peterx@xxxxxxxxxx>
Date: Wed Mar 27 11:23:31 2024 -0400
mm/gup: handle hugepd for follow_page()
states "With previous refactors on fast-gup gup_huge_pd(), most of the
code can be leveraged", which doesn't look quite true just staring the
the gup_must_unshare() call where we don't pass the VMA. Also,
"unlikely(pte_val(pte) != pte_val(ptep_get(ptep)" doesn't make any sense
for slow GUP ...
@Peter, any insights?
--
Cheers,
David / dhildenb
