[PATCH 5.4 35/54] mm/swapfile: do not sleep with a spin lock held

Greg Kroah-Hartman
2020-12-10T15:33:40Z

From: Qian Cai <qcai@redhat.com>

commit b11a76b37a5aa7b07c3e3eeeaae20b25475bddd3 upstream.

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

Fixes: 873d7bcfd066 ("mm/swapfile.c: use kvzalloc for swap_info_struct allocation")
Signed-off-by: Qian Cai <qcai@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201202151549.10350-1-qcai@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/swapfile.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2824,6 +2824,7 @@ 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;

@@ -2852,7 +2853,7 @@ static struct swap_info_struct *alloc_sw
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()
@@ -2865,6 +2866,7 @@ static struct swap_info_struct *alloc_sw
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);