linux-kernel - [PATCH v2] nios2: Fix flush_dcache_page() for usage from irq context

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Date:   Tue, 22 Aug 2023 16:27:49 +0200
From:   Helge Deller <deller@....de>
To:     Dinh Nguyen <dinguyen@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] nios2: Fix flush_dcache_page() for usage from irq context

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 NIOS2
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: Dinh Nguyen <dinguyen@...nel.org>
Signed-off-by: Helge Deller <deller@....de>

---
v2:
- rebased patch on top of for-next series, to be applied
  after the folio patches

---

diff --git a/arch/nios2/include/asm/cacheflush.h b/arch/nios2/include/asm/cacheflush.h
index 7c48c5213fb7..348cea097792 100644
--- a/arch/nios2/include/asm/cacheflush.h
+++ b/arch/nios2/include/asm/cacheflush.h
@@ -52,5 +52,9 @@ extern void invalidate_dcache_range(unsigned long start, unsigned long end);
 
 #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)
 
 #endif /* _ASM_NIOS2_CACHEFLUSH_H */
diff --git a/arch/nios2/mm/cacheflush.c b/arch/nios2/mm/cacheflush.c
index 28b805f465a8..0ee9c5f02e08 100644
--- a/arch/nios2/mm/cacheflush.c
+++ b/arch/nios2/mm/cacheflush.c
@@ -75,12 +75,13 @@ static void flush_aliases(struct address_space *mapping, struct folio *folio)
 {
 	struct mm_struct *mm = current->active_mm;
 	struct vm_area_struct *vma;
+	unsigned long flags;
 	pgoff_t pgoff;
 	unsigned long nr = folio_nr_pages(folio);
 
 	pgoff = folio->index;
 
-	flush_dcache_mmap_lock(mapping);
+	flush_dcache_mmap_lock_irqsave(mapping, flags);
 	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff + nr - 1) {
 		unsigned long start;
 
@@ -92,7 +93,7 @@ static void flush_aliases(struct address_space *mapping, struct folio *folio)
 		start = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
 		flush_cache_range(vma, start, start + nr * PAGE_SIZE);
 	}
-	flush_dcache_mmap_unlock(mapping);
+	flush_dcache_mmap_unlock_irqrestore(mapping, flags);
 }
 
 void flush_cache_all(void)