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Date: Mon, 10 Jan 2022 23:49:02 -0800
From: John Hubbard <jhubbard@...dia.com>
To: "Matthew Wilcox (Oracle)" <willy@...radead.org>, linux-mm@...ck.org
Cc: Christoph Hellwig <hch@...radead.org>,
William Kucharski <william.kucharski@...cle.com>,
linux-kernel@...r.kernel.org, Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH v2 27/28] mm: Add isolate_lru_folio()
On 1/9/22 20:24, Matthew Wilcox (Oracle) wrote:
> Turn isolate_lru_page() into a wrapper around isolate_lru_folio().
> TestClearPageLRU() would have always failed on a tail page, so
> returning -EBUSY is the same behaviour.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
> arch/powerpc/include/asm/mmu_context.h | 1 -
> mm/folio-compat.c | 8 +++++
> mm/internal.h | 3 +-
> mm/vmscan.c | 43 ++++++++++++--------------
> 4 files changed, 29 insertions(+), 26 deletions(-)
Reviewed-by: John Hubbard <jhubbard@...dia.com>
thanks,
--
John Hubbard
NVIDIA
>
> diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
> index 9ba6b585337f..b9cab0a11421 100644
> --- a/arch/powerpc/include/asm/mmu_context.h
> +++ b/arch/powerpc/include/asm/mmu_context.h
> @@ -21,7 +21,6 @@ extern void destroy_context(struct mm_struct *mm);
> #ifdef CONFIG_SPAPR_TCE_IOMMU
> struct mm_iommu_table_group_mem_t;
>
> -extern int isolate_lru_page(struct page *page); /* from internal.h */
> extern bool mm_iommu_preregistered(struct mm_struct *mm);
> extern long mm_iommu_new(struct mm_struct *mm,
> unsigned long ua, unsigned long entries,
> diff --git a/mm/folio-compat.c b/mm/folio-compat.c
> index 749555a232a8..782e766cd1ee 100644
> --- a/mm/folio-compat.c
> +++ b/mm/folio-compat.c
> @@ -7,6 +7,7 @@
> #include <linux/migrate.h>
> #include <linux/pagemap.h>
> #include <linux/swap.h>
> +#include "internal.h"
>
> struct address_space *page_mapping(struct page *page)
> {
> @@ -151,3 +152,10 @@ int try_to_release_page(struct page *page, gfp_t gfp)
> return filemap_release_folio(page_folio(page), gfp);
> }
> EXPORT_SYMBOL(try_to_release_page);
> +
> +int isolate_lru_page(struct page *page)
> +{
> + if (WARN_RATELIMIT(PageTail(page), "trying to isolate tail page"))
> + return -EBUSY;
> + return isolate_lru_folio((struct folio *)page);
> +}
> diff --git a/mm/internal.h b/mm/internal.h
> index 9a72d1ecdab4..8b90db90e7f2 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -157,7 +157,8 @@ extern unsigned long highest_memmap_pfn;
> /*
> * in mm/vmscan.c:
> */
> -extern int isolate_lru_page(struct page *page);
> +int isolate_lru_page(struct page *page);
> +int isolate_lru_folio(struct folio *folio);
> extern void putback_lru_page(struct page *page);
> extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason);
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index fb9584641ac7..ac2f5b76cdb2 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2168,45 +2168,40 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> }
>
> /**
> - * isolate_lru_page - tries to isolate a page from its LRU list
> - * @page: page to isolate from its LRU list
> + * isolate_lru_folio - Try to isolate a folio from its LRU list.
> + * @folio: Folio to isolate from its LRU list.
> *
> - * Isolates a @page from an LRU list, clears PageLRU and adjusts the
> - * vmstat statistic corresponding to whatever LRU list the page was on.
> + * Isolate a @folio from an LRU list and adjust the vmstat statistic
> + * corresponding to whatever LRU list the folio was on.
> *
> - * Returns 0 if the page was removed from an LRU list.
> - * Returns -EBUSY if the page was not on an LRU list.
> - *
> - * The returned page will have PageLRU() cleared. If it was found on
> - * the active list, it will have PageActive set. If it was found on
> - * the unevictable list, it will have the PageUnevictable bit set. That flag
> + * The folio will have its LRU flag cleared. If it was found on the
> + * active list, it will have the Active flag set. If it was found on the
> + * unevictable list, it will have the Unevictable flag set. These flags
> * may need to be cleared by the caller before letting the page go.
> *
> - * The vmstat statistic corresponding to the list on which the page was
> - * found will be decremented.
> - *
> - * Restrictions:
> + * Context:
> *
> * (1) Must be called with an elevated refcount on the page. This is a
> - * fundamental difference from isolate_lru_pages (which is called
> + * fundamental difference from isolate_lru_pages() (which is called
> * without a stable reference).
> - * (2) the lru_lock must not be held.
> - * (3) interrupts must be enabled.
> + * (2) The lru_lock must not be held.
> + * (3) Interrupts must be enabled.
> + *
> + * Return: 0 if the folio was removed from an LRU list.
> + * -EBUSY if the folio was not on an LRU list.
> */
> -int isolate_lru_page(struct page *page)
> +int isolate_lru_folio(struct folio *folio)
> {
> - struct folio *folio = page_folio(page);
> int ret = -EBUSY;
>
> - VM_BUG_ON_PAGE(!page_count(page), page);
> - WARN_RATELIMIT(PageTail(page), "trying to isolate tail page");
> + VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
>
> - if (TestClearPageLRU(page)) {
> + if (folio_test_clear_lru(folio)) {
> struct lruvec *lruvec;
>
> - get_page(page);
> + folio_get(folio);
> lruvec = folio_lruvec_lock_irq(folio);
> - del_page_from_lru_list(page, lruvec);
> + lruvec_del_folio(lruvec, folio);
> unlock_page_lruvec_irq(lruvec);
> ret = 0;
> }
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