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Subject[PATCH 1/3] arm: Fix flush_dcache_page() for usage from irq context
Date
Since at least kernel 6.1, flush_dcache_page() is called with IRQs
disabled, e.g. from aio_complete().

But the current implementation for flush_dcache_page() on ARM
unintentionally re-enables IRQs, which may lead to deadlocks.

Fix it by using xa_lock_irqsave() and xa_unlock_irqrestore()
for the flush_dcache_mmap_*lock() macros instead.

Cc: Russell King (Oracle) <linux@armlinux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Helge Deller <deller@gmx.de>
---
arch/arm/include/asm/cacheflush.h | 4 ++++
arch/arm/mm/flush.c | 5 +++--
2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index a094f964c869..5b8a1ef0dc50 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -315,6 +315,10 @@ static inline void flush_anon_page(struct vm_area_struct *vma,

#define flush_dcache_mmap_lock(mapping) xa_lock_irq(&mapping->i_pages)
#define flush_dcache_mmap_unlock(mapping) xa_unlock_irq(&mapping->i_pages)
+#define flush_dcache_mmap_lock_irqsave(mapping, flags) \
+ xa_lock_irqsave(&mapping->i_pages, flags)
+#define flush_dcache_mmap_unlock_irqrestore(mapping, flags) \
+ xa_unlock_irqrestore(&mapping->i_pages, flags)

/*
* We don't appear to need to do anything here. In fact, if we did, we'd
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 7ff9feea13a6..d57ec9165520 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -238,6 +238,7 @@ static void __flush_dcache_aliases(struct address_space *mapping, struct page *p
{
struct mm_struct *mm = current->active_mm;
struct vm_area_struct *mpnt;
+ unsigned long flags;
pgoff_t pgoff;

/*
@@ -248,7 +249,7 @@ static void __flush_dcache_aliases(struct address_space *mapping, struct page *p
*/
pgoff = page->index;

- flush_dcache_mmap_lock(mapping);
+ flush_dcache_mmap_lock_irqsave(mapping, flags);
vma_interval_tree_foreach(mpnt, &mapping->i_mmap, pgoff, pgoff) {
unsigned long offset;

@@ -262,7 +263,7 @@ static void __flush_dcache_aliases(struct address_space *mapping, struct page *p
offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
flush_cache_page(mpnt, mpnt->vm_start + offset, page_to_pfn(page));
}
- flush_dcache_mmap_unlock(mapping);
+ flush_dcache_mmap_unlock_irqrestore(mapping, flags);
}

#if __LINUX_ARM_ARCH__ >= 6
--
2.38.1
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