[PATCH] mm/swapfile: Do not sleep with a spin lock held

* [PATCH] mm/swapfile: Do not sleep with a spin lock held
@ 2020-12-02 15:15 Qian Cai
  2020-12-02 23:15 ` Andrew Morton
  0 siblings, 1 reply; 3+ messages in thread
From: Qian Cai @ 2020-12-02 15:15 UTC (permalink / raw)
  To: Andrew Morton; +Cc: linux-mm, linux-kernel, Qian Cai

We can't call kvfree() with a spin lock held, so defer it.

Signed-off-by: Qian Cai <qcai@redhat.com>
---
 mm/swapfile.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index c4a613688a17..d58361109066 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2867,6 +2867,7 @@ late_initcall(max_swapfiles_check);
 static struct swap_info_struct *alloc_swap_info(void)
 {
 	struct swap_info_struct *p;
+	struct swap_info_struct *defer = NULL;
 	unsigned int type;
 	int i;
 
@@ -2895,7 +2896,7 @@ static struct swap_info_struct *alloc_swap_info(void)
 		smp_wmb();
 		WRITE_ONCE(nr_swapfiles, nr_swapfiles + 1);
 	} else {
-		kvfree(p);
+		defer = p;
 		p = swap_info[type];
 		/*
 		 * Do not memset this entry: a racing procfs swap_next()
@@ -2908,6 +2909,7 @@ static struct swap_info_struct *alloc_swap_info(void)
 		plist_node_init(&p->avail_lists[i], 0);
 	p->flags = SWP_USED;
 	spin_unlock(&swap_lock);
+	kvfree(defer);
 	spin_lock_init(&p->lock);
 	spin_lock_init(&p->cont_lock);
 
-- 
2.28.0


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