ARM: handle user space mapped pages in flush_kernel_dcache_page
PATCH v5 1/1 ARM: handle user space mapped pages in flush_kernel_dcache_page
Commit f8b63c1 made flush_kernel_dcache_page a no-op assuming that the pages it needs to handle are kernel mapped only. However, for example when doing direct I/O, pages with user space mappings may occur.
Thus, continue to do lazy flushing if there are no user space mappings. Otherwise, flush the kernel cache lines directly.
---
Changes:
in V5:
- simplified highmem case; we can assume kmapped pages
in V4:
- get back to simpler version of flush_kernel_dcache_page() and use the logic from __flush_dcache_page() to flush the kernel mapping (which also takes care of highmem pages)
in V3:
- Followed Catalin's suggestion to reverse the order of the patches
in V2:
- flush_kernel_dcache_page() follows flush_dcache_page() now, except that it does not flush the user mappings
arch/arm/include/asm/cacheflush.h | 4 +--- arch/arm/mm/flush.c | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+), 3 deletions(-)
arch/arm/include/asm/cacheflush.h +1 -3
@@ -320,9 +320,7 @@ static inline void flush_anon_page(struct vm_area_struct *vma, }#define ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE -static inline void flush_kernel_dcache_page (struct page *page) -{ -} +extern void flush_kernel_dcache_page (struct page *);#define flush_dcache_mmap_lock (mapping) \ spin_lock_irq(&(mapping)->tree_lock)
arch/arm/mm/flush.c +33 -0
@@ -301,6 +301,39 @@ void flush_dcache_page(struct page *page)EXPORT_SYMBOL (flush_dcache_page);/* +* Ensure cache coherency for the kernel mapping of this page. We can +* assume that the page is pinned via kmap. +* +* If the page only exists in the page cache and there are no user +* space mappings, this is a no-op since the page was already marked +* dirty at creation. Otherwise, we need to flush the dirty kernel +* cache lines directly. +*/ +void flush_kernel_dcache_page (struct page *page) +{ +if (cache_is_vivt () ||cache_is_vipt_aliasing ()) { +struct address_space *mapping; + + mapping =page_mapping (page); + +if (!mapping ||mapping_mapped (mapping)) { +void *addr; + + addr =page_address (page); +/* +* kmap_atomic() doesn't set the page virtual +* address for highmem pages, and +* kunmap_atomic() takes care of cache +* flushing already. +*/ +if (!IS_ENABLED (CONFIG_HIGHMEM ) || addr) +__cpuc_flush_dcache_area (addr,PAGE_SIZE ); + } + } +} +EXPORT_SYMBOL (flush_kernel_dcache_page); + +/* * Flush an anonymous page so that users of get_user_pages() * can safely access the data. The expected sequence is: *
Signature · 1 line
1.7.9.5
PATCH v5 1/1 ARM: handle user space mapped pages in flush_kernel_dcache_page
Quoted 11 lines · Simon Baatz
Commit f8b63c1 made
flush_kernel_dcache_pagea no-op assuming that the pages it needs to handle are kernel mapped only. However, for example when doing direct I/O, pages with user space mappings may occur.Thus, continue to do lazy flushing if there are no user space mappings. Otherwise, flush the kernel cache lines directly.
Signed-off-by Simon Baatz <[email protected]>Cc <[email protected]> # 3.2+CC Catalin Marinas <[email protected]>Cc Russell King <[email protected]>
PATCH v5 1/1 ARM: handle user space mapped pages in flush_kernel_dcache_page
Hi Catalin,
Quoted 8 lines · Catalin Marinas
Quoted 7 lines · Simon Baatz
Commit f8b63c1 made
flush_kernel_dcache_pagea no-op assuming that the pages it needs to handle are kernel mapped only. However, for example when doing direct I/O, pages with user space mappings may occur.Thus, continue to do lazy flushing if there are no user space mappings. Otherwise, flush the kernel cache lines directly.
Quoted 6 lines
Quoted 4 lines
Signed-off-by Simon Baatz <[email protected]>Cc <[email protected]> # 3.2+CC Catalin Marinas <[email protected]>Cc Russell King <[email protected]>Reviewed-by Catalin Marinas <[email protected]>
Thanks for the review. This is submitted now as patch #7755/1 in Russell's patch system.
- Simon