From patchwork Thu Feb 10 07:28:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 12741465 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B8DAA2F4C for ; Thu, 10 Feb 2022 07:29:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=gx9MP1RQD53lcijUjor73mzwgUferDdREkTfjXIzaF0=; b=ty9KqbcrZiSE8bBiX6wRS7OYJ6 kSaQWTs/izN6Iiw+SrghKnLd4UUFKvl1sYmbRvpiq253QYdGbFjALN1NmbEo7EqY7ZG6AmVpgEFO6 qfD7OjDiioMPTftkaDtqLZbfI4IvUmES6QPyZtdZdKaS6/uTPsiHGQOUjQ/p2khYVx6FWkW89LsN+ gkCpIco3/L9lxlh++8O2L69WHvtYxhjtjuF60ToUOPgCG0BfWE4yGfKybnzkn1a0mBmlM/ZTTT7kt 0fuvpbeUt1cAvhd//WtNUQt+hPGK345vIiaeD9JDrPMkVNAug/NUks9+0bOcUBvbCm3x1UochQGvI 3RkI+coQ==; Received: from [2001:4bb8:188:3efc:8014:b2f2:fdfd:57ea] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nI3so-002rpJ-V3; Thu, 10 Feb 2022 07:28:51 +0000 From: Christoph Hellwig To: Andrew Morton , Dan Williams Cc: Felix Kuehling , Alex Deucher , =?utf-8?q?Christian_K=C3=B6nig?= , "Pan, Xinhui" , Ben Skeggs , Karol Herbst , Lyude Paul , Jason Gunthorpe , Alistair Popple , Logan Gunthorpe , Ralph Campbell , linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, nvdimm@lists.linux.dev, linux-mm@kvack.org, Jason Gunthorpe Subject: [PATCH 07/27] mm: remove the extra ZONE_DEVICE struct page refcount Date: Thu, 10 Feb 2022 08:28:08 +0100 Message-Id: <20220210072828.2930359-8-hch@lst.de> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220210072828.2930359-1-hch@lst.de> References: <20220210072828.2930359-1-hch@lst.de> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treated specially for ZONE_DEVICE pages. Note that this excludes the special idle page wakeup for fsdax pages, which still happens at refcount 1. This is a separate issue and will be sorted out later. Given that only fsdax pages require the notifiacation when the refcount hits 1 now, the PAGEMAP_OPS Kconfig symbol can go away and be replaced with a FS_DAX check for this hook in the put_page fastpath. Based on an earlier patch from Ralph Campbell . Signed-off-by: Christoph Hellwig Reviewed-by: Logan Gunthorpe Reviewed-by: Ralph Campbell Reviewed-by: Jason Gunthorpe Reviewed-by: Dan Williams Acked-by: Felix Kuehling --- arch/powerpc/kvm/book3s_hv_uvmem.c | 1 - drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 1 - drivers/gpu/drm/nouveau/nouveau_dmem.c | 1 - fs/Kconfig | 1 - include/linux/memremap.h | 12 +++-- include/linux/mm.h | 6 +-- lib/test_hmm.c | 1 - mm/Kconfig | 4 -- mm/internal.h | 2 + mm/memcontrol.c | 11 ++--- mm/memremap.c | 57 ++++++++---------------- mm/migrate.c | 6 --- mm/swap.c | 16 ++----- 13 files changed, 36 insertions(+), 83 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c index e414ca44839fd1..8b6438fa18fc2b 100644 --- a/arch/powerpc/kvm/book3s_hv_uvmem.c +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c @@ -712,7 +712,6 @@ static struct page *kvmppc_uvmem_get_page(unsigned long gpa, struct kvm *kvm) dpage = pfn_to_page(uvmem_pfn); dpage->zone_device_data = pvt; - get_page(dpage); lock_page(dpage); return dpage; out_clear: diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c index cb835f95a76e66..e27ca375876230 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c @@ -225,7 +225,6 @@ svm_migrate_get_vram_page(struct svm_range *prange, unsigned long pfn) page = pfn_to_page(pfn); svm_range_bo_ref(prange->svm_bo); page->zone_device_data = prange->svm_bo; - get_page(page); lock_page(page); } diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c index a5cdfbe32b5e54..7ba66ad68a8a1e 100644 --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c @@ -326,7 +326,6 @@ nouveau_dmem_page_alloc_locked(struct nouveau_drm *drm) return NULL; } - get_page(page); lock_page(page); return page; } diff --git a/fs/Kconfig b/fs/Kconfig index 6c7dc1387beb0f..e9433bbc48010a 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -48,7 +48,6 @@ config FS_DAX bool "File system based Direct Access (DAX) support" depends on MMU depends on !(ARM || MIPS || SPARC) - select DEV_PAGEMAP_OPS if (ZONE_DEVICE && !FS_DAX_LIMITED) select FS_IOMAP select DAX help diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 514ab46f597e5c..d6a114dd5ea8b7 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -68,9 +68,9 @@ enum memory_type { struct dev_pagemap_ops { /* - * Called once the page refcount reaches 1. (ZONE_DEVICE pages never - * reach 0 refcount unless there is a refcount bug. This allows the - * device driver to implement its own memory management.) + * Called once the page refcount reaches 0. The reference count will be + * reset to one by the core code after the method is called to prepare + * for handing out the page again. */ void (*page_free)(struct page *page); @@ -133,16 +133,14 @@ static inline unsigned long pgmap_vmemmap_nr(struct dev_pagemap *pgmap) static inline bool is_device_private_page(const struct page *page) { - return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) && - IS_ENABLED(CONFIG_DEVICE_PRIVATE) && + return IS_ENABLED(CONFIG_DEVICE_PRIVATE) && is_zone_device_page(page) && page->pgmap->type == MEMORY_DEVICE_PRIVATE; } static inline bool is_pci_p2pdma_page(const struct page *page) { - return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) && - IS_ENABLED(CONFIG_PCI_P2PDMA) && + return IS_ENABLED(CONFIG_PCI_P2PDMA) && is_zone_device_page(page) && page->pgmap->type == MEMORY_DEVICE_PCI_P2PDMA; } diff --git a/include/linux/mm.h b/include/linux/mm.h index 80fccfe31c3444..ff9f149ca2017e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1090,7 +1090,7 @@ static inline bool is_zone_movable_page(const struct page *page) return page_zonenum(page) == ZONE_MOVABLE; } -#ifdef CONFIG_DEV_PAGEMAP_OPS +#if defined(CONFIG_ZONE_DEVICE) && defined(CONFIG_FS_DAX) DECLARE_STATIC_KEY_FALSE(devmap_managed_key); bool __put_devmap_managed_page(struct page *page); @@ -1103,12 +1103,12 @@ static inline bool put_devmap_managed_page(struct page *page) return __put_devmap_managed_page(page); } -#else /* CONFIG_DEV_PAGEMAP_OPS */ +#else /* CONFIG_ZONE_DEVICE && CONFIG_FS_DAX */ static inline bool put_devmap_managed_page(struct page *page) { return false; } -#endif /* CONFIG_DEV_PAGEMAP_OPS */ +#endif /* CONFIG_ZONE_DEVICE && CONFIG_FS_DAX */ /* 127: arbitrary random number, small enough to assemble well */ #define folio_ref_zero_or_close_to_overflow(folio) \ diff --git a/lib/test_hmm.c b/lib/test_hmm.c index e5fc14ba71f33e..cfe63204783918 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -566,7 +566,6 @@ static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice) } dpage->zone_device_data = rpage; - get_page(dpage); lock_page(dpage); return dpage; diff --git a/mm/Kconfig b/mm/Kconfig index 3326ee3903f330..a1901ae6d06293 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -776,9 +776,6 @@ config ZONE_DEVICE If FS_DAX is enabled, then say Y. -config DEV_PAGEMAP_OPS - bool - # # Helpers to mirror range of the CPU page tables of a process into device page # tables. @@ -790,7 +787,6 @@ config HMM_MIRROR config DEVICE_PRIVATE bool "Unaddressable device memory (GPU memory, ...)" depends on ZONE_DEVICE - select DEV_PAGEMAP_OPS help Allows creation of struct pages to represent unaddressable device diff --git a/mm/internal.h b/mm/internal.h index d80300392a194f..a67222d17e5987 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -718,4 +718,6 @@ void vunmap_range_noflush(unsigned long start, unsigned long end); int numa_migrate_prep(struct page *page, struct vm_area_struct *vma, unsigned long addr, int page_nid, int *flags); +void free_zone_device_page(struct page *page); + #endif /* __MM_INTERNAL_H */ diff --git a/mm/memcontrol.c b/mm/memcontrol.c index fcdd96aa4380e2..510cbfb82bb62a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5504,17 +5504,12 @@ static struct page *mc_handle_swap_pte(struct vm_area_struct *vma, return NULL; /* - * Handle MEMORY_DEVICE_PRIVATE which are ZONE_DEVICE page belonging to - * a device and because they are not accessible by CPU they are store - * as special swap entry in the CPU page table. + * Handle device private pages that are not accessible by the CPU, but + * stored as special swap entries in the page table. */ if (is_device_private_entry(ent)) { page = pfn_swap_entry_to_page(ent); - /* - * MEMORY_DEVICE_PRIVATE means ZONE_DEVICE page and which have - * a refcount of 1 when free (unlike normal page) - */ - if (!page_ref_add_unless(page, 1, 1)) + if (!get_page_unless_zero(page)) return NULL; return page; } diff --git a/mm/memremap.c b/mm/memremap.c index a0ece2344c2cab..fef5734d5e4933 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -12,6 +12,7 @@ #include #include #include +#include "internal.h" static DEFINE_XARRAY(pgmap_array); @@ -37,21 +38,19 @@ unsigned long memremap_compat_align(void) EXPORT_SYMBOL_GPL(memremap_compat_align); #endif -#ifdef CONFIG_DEV_PAGEMAP_OPS +#ifdef CONFIG_FS_DAX DEFINE_STATIC_KEY_FALSE(devmap_managed_key); EXPORT_SYMBOL(devmap_managed_key); static void devmap_managed_enable_put(struct dev_pagemap *pgmap) { - if (pgmap->type == MEMORY_DEVICE_PRIVATE || - pgmap->type == MEMORY_DEVICE_FS_DAX) + if (pgmap->type == MEMORY_DEVICE_FS_DAX) static_branch_dec(&devmap_managed_key); } static void devmap_managed_enable_get(struct dev_pagemap *pgmap) { - if (pgmap->type == MEMORY_DEVICE_PRIVATE || - pgmap->type == MEMORY_DEVICE_FS_DAX) + if (pgmap->type == MEMORY_DEVICE_FS_DAX) static_branch_inc(&devmap_managed_key); } #else @@ -61,7 +60,7 @@ static void devmap_managed_enable_get(struct dev_pagemap *pgmap) static void devmap_managed_enable_put(struct dev_pagemap *pgmap) { } -#endif /* CONFIG_DEV_PAGEMAP_OPS */ +#endif /* CONFIG_FS_DAX */ static void pgmap_array_delete(struct range *range) { @@ -102,23 +101,12 @@ static unsigned long pfn_end(struct dev_pagemap *pgmap, int range_id) return (range->start + range_len(range)) >> PAGE_SHIFT; } -static unsigned long pfn_next(struct dev_pagemap *pgmap, unsigned long pfn) -{ - if (pfn % (1024 << pgmap->vmemmap_shift)) - cond_resched(); - return pfn + pgmap_vmemmap_nr(pgmap); -} - static unsigned long pfn_len(struct dev_pagemap *pgmap, unsigned long range_id) { return (pfn_end(pgmap, range_id) - pfn_first(pgmap, range_id)) >> pgmap->vmemmap_shift; } -#define for_each_device_pfn(pfn, map, i) \ - for (pfn = pfn_first(map, i); pfn < pfn_end(map, i); \ - pfn = pfn_next(map, pfn)) - static void pageunmap_range(struct dev_pagemap *pgmap, int range_id) { struct range *range = &pgmap->ranges[range_id]; @@ -147,13 +135,11 @@ static void pageunmap_range(struct dev_pagemap *pgmap, int range_id) void memunmap_pages(struct dev_pagemap *pgmap) { - unsigned long pfn; int i; percpu_ref_kill(&pgmap->ref); for (i = 0; i < pgmap->nr_range; i++) - for_each_device_pfn(pfn, pgmap, i) - put_page(pfn_to_page(pfn)); + percpu_ref_put_many(&pgmap->ref, pfn_len(pgmap, i)); wait_for_completion(&pgmap->done); percpu_ref_exit(&pgmap->ref); @@ -464,14 +450,10 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, } EXPORT_SYMBOL_GPL(get_dev_pagemap); -#ifdef CONFIG_DEV_PAGEMAP_OPS -void free_devmap_managed_page(struct page *page) +void free_zone_device_page(struct page *page) { - /* notify page idle for dax */ - if (!is_device_private_page(page)) { - wake_up_var(&page->_refcount); + if (WARN_ON_ONCE(!is_device_private_page(page))) return; - } __ClearPageWaiters(page); @@ -500,28 +482,27 @@ void free_devmap_managed_page(struct page *page) */ page->mapping = NULL; page->pgmap->ops->page_free(page); + + /* + * Reset the page count to 1 to prepare for handing out the page again. + */ + set_page_count(page, 1); } +#ifdef CONFIG_FS_DAX bool __put_devmap_managed_page(struct page *page) { - if (page->pgmap->type != MEMORY_DEVICE_PRIVATE && - page->pgmap->type != MEMORY_DEVICE_FS_DAX) + if (page->pgmap->type != MEMORY_DEVICE_FS_DAX) return false; /* - * devmap page refcounts are 1-based, rather than 0-based: if + * fsdax page refcounts are 1-based, rather than 0-based: if * refcount is 1, then the page is free and the refcount is * stable because nobody holds a reference on the page. */ - switch (page_ref_dec_return(page)) { - case 1: - free_devmap_managed_page(page); - break; - case 0: - __put_page(page); - break; - } + if (page_ref_dec_return(page) == 1) + wake_up_var(&page->_refcount); return true; } EXPORT_SYMBOL(__put_devmap_managed_page); -#endif /* CONFIG_DEV_PAGEMAP_OPS */ +#endif /* CONFIG_FS_DAX */ diff --git a/mm/migrate.c b/mm/migrate.c index c7da064b4781b8..8e0370a73f8a43 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -341,14 +341,8 @@ static int expected_page_refs(struct address_space *mapping, struct page *page) { int expected_count = 1; - /* - * Device private pages have an extra refcount as they are - * ZONE_DEVICE pages. - */ - expected_count += is_device_private_page(page); if (mapping) expected_count += compound_nr(page) + page_has_private(page); - return expected_count; } diff --git a/mm/swap.c b/mm/swap.c index 25b55c56614311..c84d6817043257 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -114,17 +114,9 @@ static void __put_compound_page(struct page *page) void __put_page(struct page *page) { - if (is_zone_device_page(page)) { - put_dev_pagemap(page->pgmap); - - /* - * The page belongs to the device that created pgmap. Do - * not return it to page allocator. - */ - return; - } - - if (unlikely(PageCompound(page))) + if (unlikely(is_zone_device_page(page))) + free_zone_device_page(page); + else if (unlikely(PageCompound(page))) __put_compound_page(page); else __put_single_page(page); @@ -933,7 +925,7 @@ void release_pages(struct page **pages, int nr) if (put_devmap_managed_page(page)) continue; if (put_page_testzero(page)) - put_dev_pagemap(page->pgmap); + free_zone_device_page(page); continue; }