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From:   Zhaoyang Huang <huangzhaoyang@gmail.com>
To:     Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>, chunyan.zhang@unisoc.com,
        Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
        linux-kernel@vger.kernel.org
Subject: [PATCH] trace : use kvmalloc instead of kmalloc
Date:   Thu, 30 Jul 2020 19:04:12 +0800
Message-Id: <1596107052-25682-1-git-send-email-zhaoyang.huang@unisoc.com>
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High order memory stuff within trace could introduce OOM, use kvmalloc instead.

Please find the bellowing for the call stack we run across in an android system. The scenario happens when traced_probes is woken up to get a large quantity of trace even if free memory is even higher than watermark_low. 

traced_probes invoked oom-killer: gfp_mask=0x140c0c0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null),  order=2, oom_score_adj=-1

traced_probes cpuset=system-background mems_allowed=0
CPU: 3 PID: 588 Comm: traced_probes Tainted: G        W  O    4.14.181 #1
Hardware name: Generic DT based system
(unwind_backtrace) from [<c010d824>] (show_stack+0x20/0x24)
(show_stack) from [<c0b2e174>] (dump_stack+0xa8/0xec)
(dump_stack) from [<c027d584>] (dump_header+0x9c/0x220)
(dump_header) from [<c027cfe4>] (oom_kill_process+0xc0/0x5c4)
(oom_kill_process) from [<c027cb94>] (out_of_memory+0x220/0x310)
(out_of_memory) from [<c02816bc>] (__alloc_pages_nodemask+0xff8/0x13a4)
(__alloc_pages_nodemask) from [<c02a6a1c>] (kmalloc_order+0x30/0x48)
(kmalloc_order) from [<c02a6a64>] (kmalloc_order_trace+0x30/0x118)
(kmalloc_order_trace) from [<c0223d7c>] (tracing_buffers_open+0x50/0xfc)
(tracing_buffers_open) from [<c02e6f58>] (do_dentry_open+0x278/0x34c)
(do_dentry_open) from [<c02e70d0>] (vfs_open+0x50/0x70)
(vfs_open) from [<c02f7c24>] (path_openat+0x5fc/0x169c)
(path_openat) from [<c02f75c4>] (do_filp_open+0x94/0xf8)
(do_filp_open) from [<c02e7650>] (do_sys_open+0x168/0x26c)
(do_sys_open) from [<c02e77bc>] (SyS_openat+0x34/0x38)
(SyS_openat) from [<c0108bc0>] (ret_fast_syscall+0x0/0x28)

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
changes since v1: change kfree to kvfree
---
 kernel/trace/trace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ca1ee65..8d70c79 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6891,7 +6891,7 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
 	if (trace_array_get(tr) < 0)
 		return -ENODEV;
 
-	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	info = kvmalloc(sizeof(*info), GFP_KERNEL);
 	if (!info) {
 		trace_array_put(tr);
 		return -ENOMEM;
@@ -7017,7 +7017,7 @@ static int tracing_buffers_release(struct inode *inode, struct file *file)
 	if (info->spare)
 		ring_buffer_free_read_page(iter->trace_buffer->buffer,
 					   info->spare_cpu, info->spare);
-	kfree(info);
+	kvfree(info);
 
 	mutex_unlock(&trace_types_lock);
 
-- 
1.9.1