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Date: Mon, 15 Nov 2021 22:33:01 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Matthew Wilcox <willy@...radead.org>
Cc: Christoph Hellwig <hch@...radead.org>,
"Darrick J . Wong " <djwong@...nel.org>, linux-xfs@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-block@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH v2 01/28] csky,sparc: Declare flush_dcache_folio()
On Mon, Nov 15, 2021 at 03:54:47PM +0000, Matthew Wilcox wrote:
> There are three ways to implement flush_dcache_folio(). The first is
> as a noop (this is what xtensa does, which is the only architecture
> to define ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO; it's also done
> automatically by asm-generic if the architecture doesn't define
> ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE). The second is as a loop which calls
> flush_dcache_page() for each page in the folio. That's the default
> implementation which you found in mm/util.c. The third way, which I
> hope architecture maintainers actually implement, is to just set the
> needs-flush bit on the head page. But that requires knowledge of each
> architecture; they need to check the needs-flush bit on the head page
> instead of the precise page. So I've done the safe, slow thing for
> all architectures. The only reason that csky and sparc are "special"
> is that they don't include asm-generic/cacheflush.h and the buildbots
> didn't catch that before the merge window.
>
> I'm doing the exact same thing for csky and sparc that I did for
> arc/arm/m68k/mips/nds32/nios2/parisc/sh. Nothing more, nothing less.
I see how this works no, but it is pretty horrible. Why not something
simple like the patch below? If/when an architecture actually
wants to override flush_dcache_folio we can find out how to best do
it:
diff --git a/arch/arc/include/asm/cacheflush.h b/arch/arc/include/asm/cacheflush.h
index e8c2c7469e107..e201b4b1655af 100644
--- a/arch/arc/include/asm/cacheflush.h
+++ b/arch/arc/include/asm/cacheflush.h
@@ -36,7 +36,6 @@ void __flush_dcache_page(phys_addr_t paddr, unsigned long vaddr);
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
void flush_dcache_page(struct page *page);
-void flush_dcache_folio(struct folio *folio);
void dma_cache_wback_inv(phys_addr_t start, unsigned long sz);
void dma_cache_inv(phys_addr_t start, unsigned long sz);
diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index e68fb879e4f9d..5e56288e343bb 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -290,7 +290,6 @@ extern void flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr
*/
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
extern void flush_dcache_page(struct page *);
-void flush_dcache_folio(struct folio *folio);
#define ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE 1
static inline void flush_kernel_vmap_range(void *addr, int size)
diff --git a/arch/csky/abiv1/inc/abi/cacheflush.h b/arch/csky/abiv1/inc/abi/cacheflush.h
index 432aef1f1dc23..ed62e2066ba76 100644
--- a/arch/csky/abiv1/inc/abi/cacheflush.h
+++ b/arch/csky/abiv1/inc/abi/cacheflush.h
@@ -9,7 +9,6 @@
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
extern void flush_dcache_page(struct page *);
-void flush_dcache_folio(struct folio *folio);
#define flush_cache_mm(mm) dcache_wbinv_all()
#define flush_cache_page(vma, page, pfn) cache_wbinv_all()
diff --git a/arch/csky/abiv2/inc/abi/cacheflush.h b/arch/csky/abiv2/inc/abi/cacheflush.h
index 7e8bef60958c6..a565e00c3f70b 100644
--- a/arch/csky/abiv2/inc/abi/cacheflush.h
+++ b/arch/csky/abiv2/inc/abi/cacheflush.h
@@ -25,8 +25,6 @@ static inline void flush_dcache_page(struct page *page)
clear_bit(PG_dcache_clean, &page->flags);
}
-void flush_dcache_folio(struct folio *folio);
-
#define flush_dcache_mmap_lock(mapping) do { } while (0)
#define flush_dcache_mmap_unlock(mapping) do { } while (0)
#define flush_icache_page(vma, page) do { } while (0)
diff --git a/arch/m68k/include/asm/cacheflush_mm.h b/arch/m68k/include/asm/cacheflush_mm.h
index 8ab46625ddd32..1ac55e7b47f01 100644
--- a/arch/m68k/include/asm/cacheflush_mm.h
+++ b/arch/m68k/include/asm/cacheflush_mm.h
@@ -250,7 +250,6 @@ static inline void __flush_page_to_ram(void *vaddr)
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
#define flush_dcache_page(page) __flush_page_to_ram(page_address(page))
-void flush_dcache_folio(struct folio *folio);
#define flush_dcache_mmap_lock(mapping) do { } while (0)
#define flush_dcache_mmap_unlock(mapping) do { } while (0)
#define flush_icache_page(vma, page) __flush_page_to_ram(page_address(page))
diff --git a/arch/mips/include/asm/cacheflush.h b/arch/mips/include/asm/cacheflush.h
index f207388541d50..b3dc9c589442a 100644
--- a/arch/mips/include/asm/cacheflush.h
+++ b/arch/mips/include/asm/cacheflush.h
@@ -61,8 +61,6 @@ static inline void flush_dcache_page(struct page *page)
SetPageDcacheDirty(page);
}
-void flush_dcache_folio(struct folio *folio);
-
#define flush_dcache_mmap_lock(mapping) do { } while (0)
#define flush_dcache_mmap_unlock(mapping) do { } while (0)
diff --git a/arch/nds32/include/asm/cacheflush.h b/arch/nds32/include/asm/cacheflush.h
index 3fc0bb7d6487c..c2a222ebfa2af 100644
--- a/arch/nds32/include/asm/cacheflush.h
+++ b/arch/nds32/include/asm/cacheflush.h
@@ -27,7 +27,6 @@ void flush_cache_vunmap(unsigned long start, unsigned long end);
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
void flush_dcache_page(struct page *page);
-void flush_dcache_folio(struct folio *folio);
void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
unsigned long vaddr, void *dst, void *src, int len);
void copy_from_user_page(struct vm_area_struct *vma, struct page *page,
diff --git a/arch/nios2/include/asm/cacheflush.h b/arch/nios2/include/asm/cacheflush.h
index 1999561b22aa5..d0b71dd712872 100644
--- a/arch/nios2/include/asm/cacheflush.h
+++ b/arch/nios2/include/asm/cacheflush.h
@@ -29,7 +29,6 @@ extern void flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr,
unsigned long pfn);
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
void flush_dcache_page(struct page *page);
-void flush_dcache_folio(struct folio *folio);
extern void flush_icache_range(unsigned long start, unsigned long end);
extern void flush_icache_page(struct vm_area_struct *vma, struct page *page);
diff --git a/arch/parisc/include/asm/cacheflush.h b/arch/parisc/include/asm/cacheflush.h
index da0cd4b3a28f2..859b8a34adcfb 100644
--- a/arch/parisc/include/asm/cacheflush.h
+++ b/arch/parisc/include/asm/cacheflush.h
@@ -50,7 +50,6 @@ void invalidate_kernel_vmap_range(void *vaddr, int size);
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
void flush_dcache_page(struct page *page);
-void flush_dcache_folio(struct folio *folio);
#define flush_dcache_mmap_lock(mapping) xa_lock_irq(&mapping->i_pages)
#define flush_dcache_mmap_unlock(mapping) xa_unlock_irq(&mapping->i_pages)
diff --git a/arch/sh/include/asm/cacheflush.h b/arch/sh/include/asm/cacheflush.h
index c7a97f32432fb..481a664287e2e 100644
--- a/arch/sh/include/asm/cacheflush.h
+++ b/arch/sh/include/asm/cacheflush.h
@@ -43,7 +43,6 @@ extern void flush_cache_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end);
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
void flush_dcache_page(struct page *page);
-void flush_dcache_folio(struct folio *folio);
extern void flush_icache_range(unsigned long start, unsigned long end);
#define flush_icache_user_range flush_icache_range
extern void flush_icache_page(struct vm_area_struct *vma,
diff --git a/arch/sparc/include/asm/cacheflush_32.h b/arch/sparc/include/asm/cacheflush_32.h
index 9991c18f4980c..41c6d734a4741 100644
--- a/arch/sparc/include/asm/cacheflush_32.h
+++ b/arch/sparc/include/asm/cacheflush_32.h
@@ -37,7 +37,6 @@
void sparc_flush_page_to_ram(struct page *page);
-void flush_dcache_folio(struct folio *folio);
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
#define flush_dcache_page(page) sparc_flush_page_to_ram(page)
#define flush_dcache_mmap_lock(mapping) do { } while (0)
diff --git a/arch/sparc/include/asm/cacheflush_64.h b/arch/sparc/include/asm/cacheflush_64.h
index 9ab59a73c28b1..b9341836597ec 100644
--- a/arch/sparc/include/asm/cacheflush_64.h
+++ b/arch/sparc/include/asm/cacheflush_64.h
@@ -47,7 +47,6 @@ void flush_dcache_page_all(struct mm_struct *mm, struct page *page);
void __flush_dcache_range(unsigned long start, unsigned long end);
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
void flush_dcache_page(struct page *page);
-void flush_dcache_folio(struct folio *folio);
#define flush_icache_page(vma, pg) do { } while(0)
diff --git a/arch/xtensa/include/asm/cacheflush.h b/arch/xtensa/include/asm/cacheflush.h
index a8a041609c5d0..7b4359312c257 100644
--- a/arch/xtensa/include/asm/cacheflush.h
+++ b/arch/xtensa/include/asm/cacheflush.h
@@ -121,7 +121,6 @@ void flush_cache_page(struct vm_area_struct*,
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
void flush_dcache_page(struct page *);
-void flush_dcache_folio(struct folio *);
void local_flush_cache_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end);
@@ -138,9 +137,7 @@ void local_flush_cache_page(struct vm_area_struct *vma,
#define flush_cache_vunmap(start,end) do { } while (0)
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
-#define ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
#define flush_dcache_page(page) do { } while (0)
-static inline void flush_dcache_folio(struct folio *folio) { }
#define flush_icache_range local_flush_icache_range
#define flush_cache_page(vma, addr, pfn) do { } while (0)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 265c7f8e71342..218df77641802 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -4,6 +4,7 @@
* Copyright (C) 2016-2019 Christoph Hellwig.
*/
#include <linux/module.h>
+#include <linux/cacheflush.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/iomap.h>
@@ -658,6 +659,7 @@ static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
size_t copied, struct folio *folio)
{
struct iomap_page *iop = to_iomap_page(folio);
+
flush_dcache_folio(folio);
/*
diff --git a/include/asm-generic/cacheflush.h b/include/asm-generic/cacheflush.h
index fedc0dfa4877c..eeaea7bd97bbf 100644
--- a/include/asm-generic/cacheflush.h
+++ b/include/asm-generic/cacheflush.h
@@ -49,14 +49,7 @@ static inline void flush_cache_page(struct vm_area_struct *vma,
static inline void flush_dcache_page(struct page *page)
{
}
-
-static inline void flush_dcache_folio(struct folio *folio) { }
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
-#define ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
-#endif
-
-#ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
-void flush_dcache_folio(struct folio *folio);
#endif
#ifndef flush_dcache_mmap_lock
diff --git a/include/linux/cacheflush.h b/include/linux/cacheflush.h
new file mode 100644
index 0000000000000..c28359bac8aa5
--- /dev/null
+++ b/include/linux/cacheflush.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CACHEFLUSH_H
+#define _LINUX_CACHEFLUSH_H
+
+#include <asm/cacheflush.h>
+
+#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
+void flush_dcache_folio(struct folio *folio);
+#else
+static inline void flush_dcache_folio(struct folio *folio)
+{
+}
+#endif /* ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE */
+
+#endif /* _LINUX_CACHEFLUSH_H */
diff --git a/mm/util.c b/mm/util.c
index e58151a612555..61ffa71adb644 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -1090,7 +1090,7 @@ void page_offline_end(void)
}
EXPORT_SYMBOL(page_offline_end);
-#ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
+#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
void flush_dcache_folio(struct folio *folio)
{
long i, nr = folio_nr_pages(folio);
@@ -1098,5 +1098,4 @@ void flush_dcache_folio(struct folio *folio)
for (i = 0; i < nr; i++)
flush_dcache_page(folio_page(folio, i));
}
-EXPORT_SYMBOL(flush_dcache_folio);
#endif
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