Date:   Mon, 26 Aug 2019 16:12:51 +0800
From:   Shaokun Zhang <zhangshaokun@...ilicon.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>, <linux-ext4@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Yang Guo <guoyang2@...wei.com>,
        "Andreas Dilger" <adilger.kernel@...ger.ca>
Subject: Re: [PATCH] ext4: change the type of ext4 cache stats to
 percpu_counter to improve performance

Hi Eric,

On 2019/8/26 1:28, Eric Biggers wrote:
> On Sat, Aug 24, 2019 at 11:25:24PM -0400, Theodore Y. Ts'o wrote:
>> On Fri, Aug 23, 2019 at 10:47:34AM +0800, Shaokun Zhang wrote:
>>> From: Yang Guo <guoyang2@...wei.com>
>>>
>>> @es_stats_cache_hits and @es_stats_cache_misses are accessed frequently in
>>> ext4_es_lookup_extent function, it would influence the ext4 read/write
>>> performance in NUMA system.
>>> Let's optimize it using percpu_counter, it is profitable for the
>>> performance.
>>>
>>> The test command is as below:
>>> fio -name=randwrite -numjobs=8 -filename=/mnt/test1 -rw=randwrite
>>> -ioengine=libaio -direct=1 -iodepth=64 -sync=0 -norandommap -group_reporting
>>> -runtime=120 -time_based -bs=4k -size=5G
>>>
>>> And the result is better 10% than the initial implement:
>>> without the patch，IOPS=197k, BW=770MiB/s (808MB/s)(90.3GiB/120002msec)
>>> with the patch,  IOPS=218k, BW=852MiB/s (894MB/s)(99.9GiB/120002msec)
>>>
>>> Cc: "Theodore Ts'o" <tytso@....edu>
>>> Cc: Andreas Dilger <adilger.kernel@...ger.ca>
>>> Signed-off-by: Yang Guo <guoyang2@...wei.com>
>>> Signed-off-by: Shaokun Zhang <zhangshaokun@...ilicon.com>
>>
>> Applied with some adjustments so it would apply.  I also changed the patch summary to:
>>
>>     ext4: use percpu_counters for extent_status cache hits/misses
>>
>>     	      		      	  		- Ted
> 
> This patch is causing the following.  Probably because there's no calls to
> percpu_counter_destroy() for the new counters?
> 

Apologies, We missed it and let's fix it soon.

Thanks,
Shaokun

> ==================================================================
> BUG: KASAN: use-after-free in __list_del_entry_valid+0x168/0x180 lib/list_debug.c:51
> Read of size 8 at addr ffff888063168fa8 by task umount/611
> 
> CPU: 1 PID: 611 Comm: umount Not tainted 5.3.0-rc4-00015-gcc08b68e62ec #6
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x86/0xca lib/dump_stack.c:113
>  print_address_description+0x6e/0x2e7 mm/kasan/report.c:351
>  __kasan_report.cold+0x1b/0x35 mm/kasan/report.c:482
>  kasan_report+0x12/0x17 mm/kasan/common.c:612
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
>  __list_del_entry_valid+0x168/0x180 lib/list_debug.c:51
>  __list_del_entry include/linux/list.h:131 [inline]
>  list_del include/linux/list.h:139 [inline]
>  percpu_counter_destroy+0x5d/0x230 lib/percpu_counter.c:157
>  ext4_put_super+0x319/0xbb0 fs/ext4/super.c:1010
>  generic_shutdown_super+0x128/0x320 fs/super.c:458
>  kill_block_super+0x97/0xe0 fs/super.c:1310
>  deactivate_locked_super+0x7b/0xd0 fs/super.c:331
>  deactivate_super+0x138/0x150 fs/super.c:362
>  cleanup_mnt+0x298/0x3f0 fs/namespace.c:1102
>  __cleanup_mnt+0xd/0x10 fs/namespace.c:1109
>  task_work_run+0x103/0x180 kernel/task_work.c:113
>  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>  exit_to_usermode_loop+0x10b/0x130 arch/x86/entry/common.c:163
>  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
>  do_syscall_64+0x343/0x450 arch/x86/entry/common.c:299
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x7f7caed23d77
> Code: 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 8
> RSP: 002b:00007ffe960e7c98 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
> RAX: 0000000000000000 RBX: 0000560c039e1060 RCX: 00007f7caed23d77
> RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000560c039e3c90
> RBP: 0000560c039e3c90 R08: 0000560c039e2ec0 R09: 0000000000000014
> R10: 00000000000006b4 R11: 0000000000000246 R12: 00007f7caf225e64
> R13: 0000000000000000 R14: 0000560c039e1240 R15: 00007ffe960e7f20
> 
> Allocated by task 596:
>  save_stack mm/kasan/common.c:69 [inline]
>  set_track mm/kasan/common.c:77 [inline]
>  __kasan_kmalloc.part.0+0x41/0xb0 mm/kasan/common.c:487
>  __kasan_kmalloc.constprop.0+0xba/0xc0 mm/kasan/common.c:468
>  kasan_kmalloc+0x9/0x10 mm/kasan/common.c:501
>  kmem_cache_alloc_trace+0x11e/0x2e0 mm/slab.c:3550
>  kmalloc include/linux/slab.h:552 [inline]
>  kzalloc include/linux/slab.h:748 [inline]
>  ext4_fill_super+0x111/0x80a0 fs/ext4/super.c:3610
>  mount_bdev+0x286/0x350 fs/super.c:1283
>  ext4_mount+0x10/0x20 fs/ext4/super.c:6007
>  legacy_get_tree+0x101/0x1f0 fs/fs_context.c:661
>  vfs_get_tree+0x86/0x2e0 fs/super.c:1413
>  do_new_mount fs/namespace.c:2791 [inline]
>  do_mount+0x1093/0x1b30 fs/namespace.c:3111
>  ksys_mount+0x7d/0xd0 fs/namespace.c:3320
>  __do_sys_mount fs/namespace.c:3334 [inline]
>  __se_sys_mount fs/namespace.c:3331 [inline]
>  __x64_sys_mount+0xb9/0x150 fs/namespace.c:3331
>  do_syscall_64+0x8f/0x450 arch/x86/entry/common.c:296
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 600:
>  save_stack mm/kasan/common.c:69 [inline]
>  set_track mm/kasan/common.c:77 [inline]
>  __kasan_slab_free+0x127/0x1f0 mm/kasan/common.c:449
>  kasan_slab_free+0xe/0x10 mm/kasan/common.c:457
>  __cache_free mm/slab.c:3425 [inline]
>  kfree+0xc1/0x1e0 mm/slab.c:3756
>  ext4_put_super+0x78c/0xbb0 fs/ext4/super.c:1061
>  generic_shutdown_super+0x128/0x320 fs/super.c:458
>  kill_block_super+0x97/0xe0 fs/super.c:1310
>  deactivate_locked_super+0x7b/0xd0 fs/super.c:331
>  deactivate_super+0x138/0x150 fs/super.c:362
>  cleanup_mnt+0x298/0x3f0 fs/namespace.c:1102
>  __cleanup_mnt+0xd/0x10 fs/namespace.c:1109
>  task_work_run+0x103/0x180 kernel/task_work.c:113
>  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>  exit_to_usermode_loop+0x10b/0x130 arch/x86/entry/common.c:163
>  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
>  do_syscall_64+0x343/0x450 arch/x86/entry/common.c:299
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> The buggy address belongs to the object at ffff888063168980
>  which belongs to the cache kmalloc-4k of size 4096
> The buggy address is located 1576 bytes inside of
>  4096-byte region [ffff888063168980, ffff888063169980)
> The buggy address belongs to the page:
> page:ffffea00015acec0 refcount:1 mapcount:0 mapping:ffff88806d000900 index:0x0 compound_mapcount: 0
> flags: 0x100000000010200(slab|head)
> raw: 0100000000010200 ffffea00015b9f08 ffffea0001749e58 ffff88806d000900
> raw: 0000000000000000 ffff888063168980 0000000100000001
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff888063168e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff888063168f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ffff888063168f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                   ^
>  ffff888063169000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff888063169080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> .
> 

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