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Message-ID: <20140312145611.GD14688@cmpxchg.org>
Date: Wed, 12 Mar 2014 10:56:11 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Michal Hocko <mhocko@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 4/8] mm: memcg: push !mm handling out to page cache
charge function
On Wed, Mar 12, 2014 at 02:11:52PM +0100, Michal Hocko wrote:
> On Tue 11-03-14 21:28:30, Johannes Weiner wrote:
> [...]
> > @@ -4070,6 +4061,12 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
> > return 0;
> >
> > if (!PageSwapCache(page)) {
> > + /*
> > + * Page cache insertions can happen without an actual
> > + * task context, e.g. during disk probing on boot.
>
> We read a page cache during disk probing? I have tried to find such a
> code path but failed. Could you point me to such a path, please?
> I thought that such probing is done from udev context but I am not
> familiar with this area TBH.
Yes, I tried to remove the !mm case entirely and hit the following
during boot:
[ 1.869561] BUG: unable to handle kernel NULL pointer dereference at 0000000000000320
[ 1.869565] IP: [<ffffffff811369a2>] get_mem_cgroup_from_mm+0x32/0x80
[ 1.869566] PGD 0
[ 1.869567] Oops: 0000 [#1] SMP
[ 1.869569] CPU: 3 PID: 65 Comm: kworker/u8:6 Not tainted 3.14.0-rc6-00007-g3856318f53a0-dirty #133
[ 1.869569] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./H61M-DGS, BIOS P1.30 05/10/2012
[ 1.869573] Workqueue: events_unbound async_run_entry_fn
[ 1.869573] task: ffff8800ce82d3c0 ti: ffff8800ce8c6000 task.ti: ffff8800ce8c6000
[ 1.869575] RIP: 0010:[<ffffffff811369a2>] [<ffffffff811369a2>] get_mem_cgroup_from_mm+0x32/0x80
[ 1.869576] RSP: 0000:ffff8800ce8c78f8 EFLAGS: 00010246
[ 1.869576] RAX: 003fffc000000001 RBX: 0000000000000000 RCX: 0000000000000001
[ 1.869577] RDX: 00000000000000d0 RSI: 0000000000000000 RDI: 0000000000000000
[ 1.869577] RBP: ffff8800ce8c7908 R08: ffffffff81713232 R09: ffffea00033a1680
[ 1.869578] R10: 0000000000001723 R11: ffffc90004e4dfff R12: 0000000000000000
[ 1.869578] R13: 0000000000000001 R14: 0000000000000000 R15: 00000000000000d0
[ 1.869579] FS: 0000000000000000(0000) GS:ffff88021f380000(0000) knlGS:0000000000000000
[ 1.869579] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1.869580] CR2: 0000000000000320 CR3: 00000000017a5000 CR4: 00000000000407e0
[ 1.869580] Stack:
[ 1.869581] 0000000000000000 ffffea00033a1640 ffff8800ce8c7948 ffffffff8113a112
[ 1.869582] 00000001ce8c7978 0000000000000000 ffffea00033a1640 00000000000200d0
[ 1.869583] 0000000000000000 ffffffff81174520 ffff8800ce8c7970 ffffffff8113be0a
[ 1.869583] Call Trace:
[ 1.869586] [<ffffffff8113a112>] mem_cgroup_charge_common+0x42/0xf0
[ 1.869589] [<ffffffff81174520>] ? blkdev_write_begin+0x30/0x30
[ 1.869590] [<ffffffff8113be0a>] mem_cgroup_cache_charge+0x7a/0xb0
[ 1.869592] sd 1:0:0:0: [sdb] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB)
[ 1.869594] [<ffffffff810db06d>] add_to_page_cache_locked+0x3d/0x150
[ 1.869595] [<ffffffff810db19a>] add_to_page_cache_lru+0x1a/0x40
[ 1.869597] [<ffffffff810dbdef>] do_read_cache_page+0x6f/0x1a0
[ 1.869598] [<ffffffff810dce79>] read_cache_page+0x19/0x30
[ 1.869601] [<ffffffff8123952d>] read_dev_sector+0x2d/0x90
[ 1.869603] [<ffffffff8123a21f>] read_lba+0xef/0x1a0
[ 1.869604] [<ffffffff8123a663>] ? find_valid_gpt+0xc3/0x640
[ 1.869605] [<ffffffff8123a681>] find_valid_gpt+0xe1/0x640
[ 1.869607] [<ffffffff81249e6b>] ? string.isra.4+0x3b/0xf0
[ 1.869609] [<ffffffff8123abe0>] ? find_valid_gpt+0x640/0x640
[ 1.869610] [<ffffffff8123ac56>] efi_partition+0x76/0x3f0
[ 1.869611] [<ffffffff8124aec4>] ? vsnprintf+0x1f4/0x610
[ 1.869612] [<ffffffff8124b799>] ? snprintf+0x39/0x40
[ 1.869613] [<ffffffff8123abe0>] ? find_valid_gpt+0x640/0x640
[ 1.869615] [<ffffffff812396c8>] check_partition+0x108/0x240
[ 1.869616] [<ffffffff81239264>] rescan_partitions+0xb4/0x2c0
[ 1.869617] [<ffffffff8117584c>] __blkdev_get+0x2dc/0x400
[ 1.869618] [<ffffffff81175b1d>] blkdev_get+0x1ad/0x320
[ 1.869619] sd 1:0:0:0: [sdb] Write Protect is off
[ 1.869621] [<ffffffff81157603>] ? unlock_new_inode+0x43/0x70
[ 1.869622] sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
[ 1.869622] [<ffffffff81174f66>] ? bdget+0x136/0x150
[ 1.869624] [<ffffffff81236b34>] add_disk+0x394/0x4a0
[ 1.869627] [<ffffffff8135b327>] sd_probe_async+0x127/0x1d0
[ 1.869628] [<ffffffff81065c87>] async_run_entry_fn+0x37/0x130
[ 1.869629] [<ffffffff810595fe>] process_one_work+0x16e/0x3e0
[ 1.869630] [<ffffffff81059991>] worker_thread+0x121/0x3a0
[ 1.869631] [<ffffffff81059870>] ? process_one_work+0x3e0/0x3e0
[ 1.869633] [<ffffffff810602c2>] kthread+0xd2/0xf0
[ 1.869634] sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 1.869636] [<ffffffff810601f0>] ? __kthread_parkme+0x70/0x70
[ 1.869638] [<ffffffff815dbaac>] ret_from_fork+0x7c/0xb0
[ 1.869639] [<ffffffff810601f0>] ? __kthread_parkme+0x70/0x70
[ 1.869648] Code: 89 e5 41 54 49 89 fc 53 eb 21 0f 1f 80 00 00 00 00 f6 43 48 01 75 52 48 8b 43 18 a8 03 75 52 65 ff 00 b8 01 00 00 00 84 c0 75 3e <49> 8b 84 24 20 03 00 00 48 85 c0 74 10 48 8b 80 98 06 00 00 48
[ 1.869650] RIP [<ffffffff811369a2>] get_mem_cgroup_from_mm+0x32/0x80
[ 1.869650] RSP <ffff8800ce8c78f8>
[ 1.869650] CR2: 0000000000000320
[ 1.869653] ---[ end trace 4cda1f5484a90d6d ]---
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