[PATCH AUTOSEL 6.1 04/42] s390/mm: Add cond_resched() to cmm_alloc/free_pages()

Sasha Levin
2024-10-04T18:27:27Z

From: Gerald Schaefer <gerald.schaefer@linux.ibm.com>

[ Upstream commit 131b8db78558120f58c5dc745ea9655f6b854162 ]

Adding/removing large amount of pages at once to/from the CMM balloon
can result in rcu_sched stalls or workqueue lockups, because of busy
looping w/o cond_resched().

Prevent this by adding a cond_resched(). cmm_free_pages() holds a
spin_lock while looping, so it cannot be added directly to the existing
loop. Instead, introduce a wrapper function that operates on maximum 256
pages at once, and add it there.

Signed-off-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/mm/cmm.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/s390/mm/cmm.c b/arch/s390/mm/cmm.c
index 9141ed4c52e90..02e030ad38c5f 100644
--- a/arch/s390/mm/cmm.c
+++ b/arch/s390/mm/cmm.c
@@ -95,11 +95,12 @@ static long cmm_alloc_pages(long nr, long *counter,
(*counter)++;
spin_unlock(&cmm_lock);
nr--;
+ cond_resched();
}
return nr;
}

-static long cmm_free_pages(long nr, long *counter, struct cmm_page_array **list)
+static long __cmm_free_pages(long nr, long *counter, struct cmm_page_array **list)
{
struct cmm_page_array *pa;
unsigned long addr;
@@ -123,6 +124,21 @@ static long cmm_free_pages(long nr, long *counter, struct cmm_page_array **list)
return nr;
}

+static long cmm_free_pages(long nr, long *counter, struct cmm_page_array **list)
+{
+ long inc = 0;
+
+ while (nr) {
+ inc = min(256L, nr);
+ nr -= inc;
+ inc = __cmm_free_pages(inc, counter, list);
+ if (inc)
+ break;
+ cond_resched();
+ }
+ return nr + inc;
+}
+
static int cmm_oom_notify(struct notifier_block *self,
unsigned long dummy, void *parm)
{
--
2.43.0