linux-kernel - [PATCH v2] sched_ext: Use kvzalloc for large exit

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Message-Id: <20250408-scx-v2-1-1979fc040903@debian.org>
Date: Tue, 08 Apr 2025 04:09:02 -0700
From: Breno Leitao <leitao@...ian.org>
To: Tejun Heo <tj@...nel.org>, David Vernet <void@...ifault.com>, 
 Andrea Righi <arighi@...dia.com>, Changwoo Min <changwoo@...lia.com>, 
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
 Juri Lelli <juri.lelli@...hat.com>, 
 Vincent Guittot <vincent.guittot@...aro.org>, 
 Dietmar Eggemann <dietmar.eggemann@....com>, 
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, 
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>
Cc: linux-kernel@...r.kernel.org, christophe.jaillet@...adoo.fr, 
 changwoo@...lia.com, kernel-team@...a.com, stable@...r.kernel.org, 
 Rik van Riel <riel@...riel.com>, Breno Leitao <leitao@...ian.org>
Subject: [PATCH v2] sched_ext: Use kvzalloc for large exit_dump allocation

Replace kzalloc with kvzalloc for the exit_dump buffer allocation, which
can require large contiguous memory (up to order=9) depending on the
implementation. This change prevents allocation failures by allowing the
system to fall back to vmalloc when contiguous memory allocation fails.

Since this buffer is only used for debugging purposes, physical memory
contiguity is not required, making vmalloc a suitable alternative.

Cc: stable@...r.kernel.org
Fixes: 07814a9439a3b0 ("sched_ext: Print debug dump after an error exit")
Suggested-by: Rik van Riel <riel@...riel.com>
Signed-off-by: Breno Leitao <leitao@...ian.org>
Acked-by: Andrea Righi <arighi@...dia.com>
---
Changes in v2:
- Use kvfree() on the free path as well.
- Link to v1: https://lore.kernel.org/r/20250407-scx-v1-1-774ba74a2c17@debian.org
---
 kernel/sched/ext.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 66bcd40a28ca1..db9af6a3c04fd 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4623,7 +4623,7 @@ static void scx_ops_bypass(bool bypass)
 
 static void free_exit_info(struct scx_exit_info *ei)
 {
-	kfree(ei->dump);
+	kvfree(ei->dump);
 	kfree(ei->msg);
 	kfree(ei->bt);
 	kfree(ei);
@@ -4639,7 +4639,7 @@ static struct scx_exit_info *alloc_exit_info(size_t exit_dump_len)
 
 	ei->bt = kcalloc(SCX_EXIT_BT_LEN, sizeof(ei->bt[0]), GFP_KERNEL);
 	ei->msg = kzalloc(SCX_EXIT_MSG_LEN, GFP_KERNEL);
-	ei->dump = kzalloc(exit_dump_len, GFP_KERNEL);
+	ei->dump = kvzalloc(exit_dump_len, GFP_KERNEL);
 
 	if (!ei->bt || !ei->msg || !ei->dump) {
 		free_exit_info(ei);

---
base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
change-id: 20250407-scx-11dbf94803c3

Best regards,
-- 
Breno Leitao <leitao@...ian.org>