linux-kernel - [PATCH 2/2] sparc: Allow nesting of lazy MMU mode

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Message-Id: <20231012195415.282357-3-willy@infradead.org>
Date:   Thu, 12 Oct 2023 20:54:15 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-sparc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Erhard Furtner <erhard_f@...lbox.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Juergen Gross <jgross@...e.com>
Subject: [PATCH 2/2] sparc: Allow nesting of lazy MMU mode

As noted in commit 49147beb0ccb ("x86/xen: allow nesting of same lazy
mode"), we can now nest calls to arch_enter_lazy_mmu_mode().  Use ->active
as a counter instead of a flag and only drain the batch when the counter
hits 0.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Fixes: bcc6cc832573 ("mm: add default definition of set_ptes()")
---
 arch/sparc/mm/tlb.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/sparc/mm/tlb.c b/arch/sparc/mm/tlb.c
index b44d79d778c7..a82c7c32e47d 100644
--- a/arch/sparc/mm/tlb.c
+++ b/arch/sparc/mm/tlb.c
@@ -54,16 +54,15 @@ void arch_enter_lazy_mmu_mode(void)
 {
 	struct tlb_batch *tb = this_cpu_ptr(&tlb_batch);
 
-	tb->active = 1;
+	tb->active++;
 }
 
 void arch_leave_lazy_mmu_mode(void)
 {
 	struct tlb_batch *tb = this_cpu_ptr(&tlb_batch);
 
-	if (tb->tlb_nr)
+	if ((--tb->active == 0) && tb->tlb_nr)
 		flush_tlb_pending();
-	tb->active = 0;
 }
 
 static void tlb_batch_add_one(struct mm_struct *mm, unsigned long vaddr,
-- 
2.40.1