Re: [PATCH net-next -v5 3/4] mm: introduce __get_page() and __put_page()
From: John Hubbard <jhubbard@nvidia.com>
Date: 2021-10-09 19:49:38
Also in:
linux-mm, lkml
On 10/9/21 02:37, Yunsheng Lin wrote:
Introduce __get_page() and __put_page() to operate on the base page or head of a compound page for the cases when a page is known to be a base page or head of a compound page.
Hi, I wonder if you are aware of a much larger, 137-patch seriesto do that: folio/pageset [1]? The naming you are proposing here does not really improve clarity. There is nothing about __get_page() that makes it clear that it's meant only for head/base pages, while get_page() tail pages as well. And the well-known and widely used get_page() and put_page() get their meaning shifted. This area is hard to get right, and that's why there have been 15 versions, and a lot of contention associated with [1]. If you have an alternate approach, I think it would be better in its own separate series, with a cover letter that, at a minimum, explains how it compares to folios/pagesets. So in case it's not clear, I'd like to request that you drop this one patch from your series. [1] https://lore.kernel.org/r/YSPwmNNuuQhXNToQ@casper.infradead.org (local) thanks, -- John Hubbard NVIDIA
quoted hunk ↗ jump to hunk
Signed-off-by: Yunsheng Lin <redacted> --- include/linux/mm.h | 21 ++++++++++++++------- mm/swap.c | 6 +++--- 2 files changed, 17 insertions(+), 10 deletions(-)diff --git a/include/linux/mm.h b/include/linux/mm.h index 73a52aba448f..5683313c3e9d 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h@@ -902,7 +902,7 @@ static inline struct page *virt_to_head_page(const void *x) return compound_head(page); } -void __put_page(struct page *page); +void __put_single_or_compound_page(struct page *page); void put_pages_list(struct list_head *pages);@@ -1203,9 +1203,8 @@ static inline bool is_pci_p2pdma_page(const struct page *page) #define page_ref_zero_or_close_to_overflow(page) \ ((unsigned int) page_ref_count(page) + 127u <= 127u) -static inline void get_page(struct page *page) +static inline void __get_page(struct page *page) { - page = compound_head(page); /* * Getting a normal page or the head of a compound page * requires to already have an elevated page->_refcount.@@ -1214,6 +1213,11 @@ static inline void get_page(struct page *page) page_ref_inc(page); } +static inline void get_page(struct page *page) +{ + __get_page(compound_head(page)); +} + bool __must_check try_grab_page(struct page *page, unsigned int flags); struct page *try_grab_compound_head(struct page *page, int refs, unsigned int flags);@@ -1228,10 +1232,8 @@ static inline __must_check bool try_get_page(struct page *page) return true; } -static inline void put_page(struct page *page) +static inline void __put_page(struct page *page) { - page = compound_head(page); - /* * For devmap managed pages we need to catch refcount transition from * 2 to 1, when refcount reach one it means the page is free and we@@ -1244,7 +1246,12 @@ static inline void put_page(struct page *page) } if (put_page_testzero(page)) - __put_page(page); + __put_single_or_compound_page(page); +} + +static inline void put_page(struct page *page) +{ + __put_page(compound_head(page)); } /*diff --git a/mm/swap.c b/mm/swap.c index af3cad4e5378..565cbde1caea 100644 --- a/mm/swap.c +++ b/mm/swap.c@@ -111,7 +111,7 @@ static void __put_compound_page(struct page *page) destroy_compound_page(page); } -void __put_page(struct page *page) +void __put_single_or_compound_page(struct page *page) { if (is_zone_device_page(page)) { put_dev_pagemap(page->pgmap);@@ -128,7 +128,7 @@ void __put_page(struct page *page) else __put_single_page(page); } -EXPORT_SYMBOL(__put_page); +EXPORT_SYMBOL(__put_single_or_compound_page); /** * put_pages_list() - release a list of pages@@ -1153,7 +1153,7 @@ void put_devmap_managed_page(struct page *page) if (count == 1) free_devmap_managed_page(page); else if (!count) - __put_page(page); + __put_single_or_compound_page(page); } EXPORT_SYMBOL(put_devmap_managed_page); #endif