From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f71.google.com (mail-lf0-f71.google.com [209.85.215.71]) by kanga.kvack.org (Postfix) with ESMTP id D93186B0253 for ; Sun, 7 Aug 2016 18:40:41 -0400 (EDT) Received: by mail-lf0-f71.google.com with SMTP id p85so182704395lfg.3 for ; Sun, 07 Aug 2016 15:40:41 -0700 (PDT) Received: from mail-wm0-x230.google.com (mail-wm0-x230.google.com. [2a00:1450:400c:c09::230]) by mx.google.com with ESMTPS id ag8si20674920wjc.126.2016.08.07.15.40.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 07 Aug 2016 15:40:40 -0700 (PDT) Received: by mail-wm0-x230.google.com with SMTP id f65so91205664wmi.0 for ; Sun, 07 Aug 2016 15:40:40 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20160804115809.GA447@swordfish> References: <2f8a65db-e5a8-75f0-8c08-daa41e1cd3ba@mejor.pl> <20160804115809.GA447@swordfish> From: Vitaly Wool Date: Mon, 8 Aug 2016 00:40:39 +0200 Message-ID: Subject: Re: Choosing z3fold allocator in zswap gives WARNING: CPU: 0 PID: 5140 at mm/zswap.c:503 __zswap_pool_current+0x56/0x60 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Sergey Senozhatsky Cc: Seth Jennings , Dan Streetman , Linux-MM , =?UTF-8?Q?Marcin_Miros=C5=82aw?= , Andrew Morton Hi Sergey, On Thu, Aug 4, 2016 at 1:58 PM, Sergey Senozhatsky wrote: > Hello, > > Cc Seth, Dan > > On (08/01/16 11:03), Marcin Miros=C5=82aw wrote: >> [ 429.722411] ------------[ cut here ]------------ >> [ 429.723476] WARNING: CPU: 0 PID: 5140 at mm/zswap.c:503 __zswap_pool_= current+0x56/0x60 >> [ 429.740048] Call Trace: >> [ 429.740048] [] dump_stack+0x63/0x90 >> [ 429.740048] [] __warn+0xc7/0xf0 >> [ 429.740048] [] warn_slowpath_null+0x18/0x20 >> [ 429.740048] [] __zswap_pool_current+0x56/0x60 >> [ 429.740048] [] zswap_pool_current+0x13/0x20 >> [ 429.740048] [] __zswap_param_set+0x1db/0x2f0 >> [ 429.740048] [] zswap_zpool_param_set+0x12/0x20 >> [ 429.740048] [] param_attr_store+0x5f/0xc0 >> [ 429.740048] [] module_attr_store+0x19/0x30 >> [ 429.740048] [] sysfs_kf_write+0x32/0x40 >> [ 429.740048] [] kernfs_fop_write+0x113/0x190 >> [ 429.740048] [] __vfs_write+0x32/0x150 >> [ 429.740048] [] ? __fd_install+0x2e/0xe0 >> [ 429.740048] [] ? __alloc_fd+0x41/0x180 >> [ 429.740048] [] ? percpu_down_read+0xd/0x50 >> [ 429.740048] [] vfs_write+0xb3/0x1a0 >> [ 429.740048] [] ? filp_close+0x51/0x70 >> [ 429.740048] [] SyS_write+0x50/0xc0 >> [ 429.740048] [] entry_SYSCALL_64_fastpath+0x1e/0xa8 >> [ 429.764069] ---[ end trace ff7835fbf4d983b9 ]--- > > I think it's something like this. > > suppose there are no pools available - the list is empty (see later). > __zswap_param_set(): > > pool =3D zswap_pool_find_get(type, compressor); > > gives NULL. so it creates a new one > > pool =3D zswap_pool_create(type, compressor); > > then it does > > ret =3D param_set_charp(s, kp); > > which gives 0 -- all ok. so it goes to > > if (!ret) { > put_pool =3D zswap_pool_current(); > } > > which gives WARN_ON(), as the list is still empty. > > > > now, how is this possible. for example, we init a zswap with the default > configuration; but zbud is not available (can it be?). so the pool creati= on > fails, but init_zswap() does not set zswap_init_started back to false. it > either must clear it at the error path, or set it to true right before > 'return 0'. > > one more problem here is that param_set_charp() does GFP_KERNEL > under zswap_pools_lock. > Thanks a lot for looking into this, I have very limited ability to debug stuff while on vacation :) ~vitaly -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org