linux-kernel - Re: [PATCH] printk: use kvmalloc instead of kmalloc for devkmsg

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Date:   Tue, 7 Sep 2021 15:23:03 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     이용택 <ytk.lee@...sung.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "john.ogness@...utronix.de" <john.ogness@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] printk: use kvmalloc instead of kmalloc for devkmsg_user

On Wed 2021-09-01 08:02:09, Sergey Senozhatsky wrote:
> On (21/08/31 14:42), Petr Mladek wrote:
> > On Mon 2021-08-30 16:17:01, 이용택 wrote:
> > > Size of struct devkmsg_user increased to 16784 by commit 896fbe20b4e2
> > > ("printk: use the lockless ringbuffer") so order3(32kb) is needed for
> > > kmalloc. Under stress conditions the kernel may temporary fail to
> > > allocate 32k with kmalloc. Use kvmalloc instead of kmalloc to aviod
> > > this issue.
> > > 
> > > qseecomd invoked oom-killer: gfp_mask=0x40cc0(GFP_KERNEL|__GFP_COMP), order=3, oom_score_adj=-1000
> > > Call trace:
> > >  dump_backtrace+0x0/0x34c
> > >  dump_stack_lvl+0xd4/0x16c
> > >  dump_header+0x5c/0x338
> > >  out_of_memory+0x374/0x4cc
> > >  __alloc_pages_slowpath+0xbc8/0x1130
> > >  __alloc_pages_nodemask+0x170/0x1b0
> > >  kmalloc_order+0x5c/0x24c
> > >  devkmsg_open+0x1f4/0x558
> > >  memory_open+0x94/0xf0
> > >  chrdev_open+0x288/0x3dc
> > >  do_dentry_open+0x2b4/0x618
> > >  path_openat+0xce4/0xfa8
> > >  do_filp_open+0xb0/0x164
> > >  do_sys_openat2+0xa8/0x264
> > >  __arm64_sys_openat+0x70/0xa0
> > >  el0_svc_common+0xc4/0x270
> > >  el0_svc+0x34/0x9c
> > >  el0_sync_handler+0x88/0xf0
> > >  el0_sync+0x1bc/0x200
> > > 
> > >  DMA32: 4521*4kB (UMEC) 1377*8kB (UMECH) 73*16kB (UM) 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 30268kB
> > >  Normal: 2490*4kB (UMEH) 277*8kB (UMH) 27*16kB (UH) 1*32kB (H) 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 12640kB
> > > 
> > > Signed-off-by: Yong-Taek Lee <ytk.lee@...sung.com>
> > 
> > Reviewed-by: Petr Mladek <pmladek@...e.com>
> 
> Acked-by: Sergey Senozhatsky <senozhatsky@...omium.org>

The patch has been comitted into printk/linux.git, branch for-5.16.

Best Regards,
Petr