linux-kernel - [PATCH] LoongArch: Remove shm_align

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Message-Id: <20230828152540.1194317-1-chenhuacai@loongson.cn>
Date:   Mon, 28 Aug 2023 23:25:40 +0800
From:   Huacai Chen <chenhuacai@...ngson.cn>
To:     Arnd Bergmann <arnd@...db.de>, Huacai Chen <chenhuacai@...nel.org>
Cc:     loongarch@...ts.linux.dev, linux-arch@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Guo Ren <guoren@...nel.org>, Xuerui Wang <kernel@...0n.name>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-kernel@...r.kernel.org, loongson-kernel@...ts.loongnix.cn,
        Huacai Chen <chenhuacai@...ngson.cn>,
        Jiantao Shan <shanjiantao@...ngson.cn>
Subject: [PATCH] LoongArch: Remove shm_align_mask and use SHMLBA instead

Both shm_align_mask and SHMLBA want to avoid cache alias. But they are
inconsistent: shm_align_mask is (PAGE_SIZE - 1) while SHMLBA is SZ_64K,
but PAGE_SIZE is not always equal to SZ_64K.

This may cause problems when shmat() twice. Fix this problem by removing
shm_align_mask and using SHMLBA (SHMLBA - 1, strctly) instead.

Reported-by: Jiantao Shan <shanjiantao@...ngson.cn>
Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
---
 arch/loongarch/mm/cache.c      |  1 -
 arch/loongarch/mm/mmap.c       | 12 ++++--------
 3 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/arch/loongarch/mm/cache.c b/arch/loongarch/mm/cache.c
index 72685a48eaf0..6be04d36ca07 100644
--- a/arch/loongarch/mm/cache.c
+++ b/arch/loongarch/mm/cache.c
@@ -156,7 +156,6 @@ void cpu_cache_init(void)
 
 	current_cpu_data.cache_leaves_present = leaf;
 	current_cpu_data.options |= LOONGARCH_CPU_PREFETCH;
-	shm_align_mask = PAGE_SIZE - 1;
 }
 
 static const pgprot_t protection_map[16] = {
diff --git a/arch/loongarch/mm/mmap.c b/arch/loongarch/mm/mmap.c
index fbe1a4856fc4..c99c8015651a 100644
--- a/arch/loongarch/mm/mmap.c
+++ b/arch/loongarch/mm/mmap.c
@@ -8,12 +8,8 @@
 #include <linux/mm.h>
 #include <linux/mman.h>
 
-unsigned long shm_align_mask = PAGE_SIZE - 1;	/* Sane caches */
-EXPORT_SYMBOL(shm_align_mask);
-
-#define COLOUR_ALIGN(addr, pgoff)				\
-	((((addr) + shm_align_mask) & ~shm_align_mask) +	\
-	 (((pgoff) << PAGE_SHIFT) & shm_align_mask))
+#define COLOUR_ALIGN(addr, pgoff)			\
+	((((addr) + (SHMLBA - 1)) & ~(SHMLBA - 1)) + (((pgoff) << PAGE_SHIFT) & (SHMLBA - 1)))
 
 enum mmap_allocation_direction {UP, DOWN};
 
@@ -40,7 +36,7 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
 		 * cache aliasing constraints.
 		 */
 		if ((flags & MAP_SHARED) &&
-		    ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
+		    ((addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1)))
 			return -EINVAL;
 		return addr;
 	}
@@ -63,7 +59,7 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
 	}
 
 	info.length = len;
-	info.align_mask = do_color_align ? (PAGE_MASK & shm_align_mask) : 0;
+	info.align_mask = do_color_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
 	info.align_offset = pgoff << PAGE_SHIFT;
 
 	if (dir == DOWN) {
-- 
2.39.3