Subject: [PATCH][RESEND] arm: Fix flush_dcache_page() for usage from irq context

From: Helge Deller <[email-masked]>
Date: Fri, 18 Aug 2023 22:58:09 +0200

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 (32-bit)
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)" <[email-masked]>
Cc: Arnd Bergmann <[email-masked]>
Cc: [email-masked]
Reviewed-by: Arnd Bergmann <[email-masked]>
Signed-off-by: Helge Deller <[email-masked]>

---

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 2508be91b7a0..e70dd5e354ae 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

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