From: "Matthew Wilcox (Oracle)" <willy@infradead.org> To: Russell King <linux@armlinux.org.uk>, Andrew Morton <akpm@linux-foundation.org> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>, Marek Szyprowski <m.szyprowski@samsung.com>, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org Subject: [PATCH] Fix folio conversion in __dma_page_dev_to_cpu() Date: Wed, 23 Aug 2023 20:18:52 +0100 [thread overview] Message-ID: <20230823191852.1556561-1-willy@infradead.org> (raw) Russell and Marek pointed out some assumptions I was making about how sg lists work; eg that they are limited to 2GB and that the initial offset lies within the first page (or at least within the first folio that a page belongs to). While I think those assumptions are true, it's not too hard to write a version which does not have those assumptions and also calculates folio_size() only once per loop iteration. --- arch/arm/mm/dma-mapping.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 0474840224d9..5409225b4abc 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -695,7 +695,6 @@ static void __dma_page_cpu_to_dev(struct page *page, unsigned long off, static void __dma_page_dev_to_cpu(struct page *page, unsigned long off, size_t size, enum dma_data_direction dir) { - struct folio *folio = page_folio(page); phys_addr_t paddr = page_to_phys(page) + off; /* FIXME: non-speculating: not required */ @@ -710,18 +709,19 @@ static void __dma_page_dev_to_cpu(struct page *page, unsigned long off, * Mark the D-cache clean for these pages to avoid extra flushing. */ if (dir != DMA_TO_DEVICE && size >= PAGE_SIZE) { - ssize_t left = size; + struct folio *folio = pfn_folio(paddr / PAGE_SIZE); size_t offset = offset_in_folio(folio, paddr); - if (offset) { - left -= folio_size(folio) - offset; - folio = folio_next(folio); - } + for (;;) { + size_t sz = folio_size(folio) - offset; - while (left >= (ssize_t)folio_size(folio)) { - left -= folio_size(folio); - set_bit(PG_dcache_clean, &folio->flags); - if (!left) + if (size < sz) + break; + if (!offset) + set_bit(PG_dcache_clean, &folio->flags); + offset = 0; + size -= sz; + if (!size) break; folio = folio_next(folio); } -- 2.40.1
WARNING: multiple messages have this Message-ID (diff)
From: "Matthew Wilcox (Oracle)" <willy@infradead.org> To: Russell King <linux@armlinux.org.uk>, Andrew Morton <akpm@linux-foundation.org> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>, Marek Szyprowski <m.szyprowski@samsung.com>, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org Subject: [PATCH] Fix folio conversion in __dma_page_dev_to_cpu() Date: Wed, 23 Aug 2023 20:18:52 +0100 [thread overview] Message-ID: <20230823191852.1556561-1-willy@infradead.org> (raw) Russell and Marek pointed out some assumptions I was making about how sg lists work; eg that they are limited to 2GB and that the initial offset lies within the first page (or at least within the first folio that a page belongs to). While I think those assumptions are true, it's not too hard to write a version which does not have those assumptions and also calculates folio_size() only once per loop iteration. --- arch/arm/mm/dma-mapping.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 0474840224d9..5409225b4abc 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -695,7 +695,6 @@ static void __dma_page_cpu_to_dev(struct page *page, unsigned long off, static void __dma_page_dev_to_cpu(struct page *page, unsigned long off, size_t size, enum dma_data_direction dir) { - struct folio *folio = page_folio(page); phys_addr_t paddr = page_to_phys(page) + off; /* FIXME: non-speculating: not required */ @@ -710,18 +709,19 @@ static void __dma_page_dev_to_cpu(struct page *page, unsigned long off, * Mark the D-cache clean for these pages to avoid extra flushing. */ if (dir != DMA_TO_DEVICE && size >= PAGE_SIZE) { - ssize_t left = size; + struct folio *folio = pfn_folio(paddr / PAGE_SIZE); size_t offset = offset_in_folio(folio, paddr); - if (offset) { - left -= folio_size(folio) - offset; - folio = folio_next(folio); - } + for (;;) { + size_t sz = folio_size(folio) - offset; - while (left >= (ssize_t)folio_size(folio)) { - left -= folio_size(folio); - set_bit(PG_dcache_clean, &folio->flags); - if (!left) + if (size < sz) + break; + if (!offset) + set_bit(PG_dcache_clean, &folio->flags); + offset = 0; + size -= sz; + if (!size) break; folio = folio_next(folio); } -- 2.40.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2023-08-23 19:19 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-08-23 19:18 Matthew Wilcox (Oracle) [this message] 2023-08-23 19:18 ` [PATCH] Fix folio conversion in __dma_page_dev_to_cpu() Matthew Wilcox (Oracle) 2023-08-24 16:39 ` Robin Murphy 2023-08-24 16:39 ` Robin Murphy 2023-08-24 16:49 ` Matthew Wilcox 2023-08-24 16:49 ` Matthew Wilcox 2023-08-24 17:14 ` Robin Murphy 2023-08-24 17:14 ` Robin Murphy
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