linux-kernel - Re: [PATCH AUTOSEL 5.7 37/53] cifs: Fix double add page to memcg when cifs

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Date:   Thu, 2 Jul 2020 09:08:45 -0700
From:   Pavel Shilovsky <piastryyy@...il.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Stable <stable@...r.kernel.org>,
        Zhang Xiaoxu <zhangxiaoxu5@...wei.com>,
        Hulk Robot <hulkci@...wei.com>,
        Steve French <stfrench@...rosoft.com>,
        Ronnie Sahlberg <lsahlber@...hat.com>,
        linux-cifs <linux-cifs@...r.kernel.org>,
        samba-technical <samba-technical@...ts.samba.org>
Subject: Re: [PATCH AUTOSEL 5.7 37/53] cifs: Fix double add page to memcg when cifs_readpages

ср, 1 июл. 2020 г. в 18:35, Sasha Levin <sashal@...nel.org>:
>
> From: Zhang Xiaoxu <zhangxiaoxu5@...wei.com>
>
> [ Upstream commit 95a3d8f3af9b0d63b43f221b630beaab9739d13a ]
>
> When xfstests generic/451, there is an BUG at mm/memcontrol.c:
>   page:ffffea000560f2c0 refcount:2 mapcount:0 mapping:000000008544e0ea
>        index:0xf
>   mapping->aops:cifs_addr_ops dentry name:"tst-aio-dio-cycle-write.451"
>   flags: 0x2fffff80000001(locked)
>   raw: 002fffff80000001 ffffc90002023c50 ffffea0005280088 ffff88815cda0210
>   raw: 000000000000000f 0000000000000000 00000002ffffffff ffff88817287d000
>   page dumped because: VM_BUG_ON_PAGE(page->mem_cgroup)
>   page->mem_cgroup:ffff88817287d000
>   ------------[ cut here ]------------
>   kernel BUG at mm/memcontrol.c:2659!
>   invalid opcode: 0000 [#1] SMP
>   CPU: 2 PID: 2038 Comm: xfs_io Not tainted 5.8.0-rc1 #44
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_
>     073836-buildvm-ppc64le-16.ppc.4
>   RIP: 0010:commit_charge+0x35/0x50
>   Code: 0d 48 83 05 54 b2 02 05 01 48 89 77 38 c3 48 c7
>         c6 78 4a ea ba 48 83 05 38 b2 02 05 01 e8 63 0d9
>   RSP: 0018:ffffc90002023a50 EFLAGS: 00010202
>   RAX: 0000000000000000 RBX: ffff88817287d000 RCX: 0000000000000000
>   RDX: 0000000000000000 RSI: ffff88817ac97ea0 RDI: ffff88817ac97ea0
>   RBP: ffffea000560f2c0 R08: 0000000000000203 R09: 0000000000000005
>   R10: 0000000000000030 R11: ffffc900020237a8 R12: 0000000000000000
>   R13: 0000000000000001 R14: 0000000000000001 R15: ffff88815a1272c0
>   FS:  00007f5071ab0800(0000) GS:ffff88817ac80000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 000055efcd5ca000 CR3: 000000015d312000 CR4: 00000000000006e0
>   DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>   DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>   Call Trace:
>    mem_cgroup_charge+0x166/0x4f0
>    __add_to_page_cache_locked+0x4a9/0x710
>    add_to_page_cache_locked+0x15/0x20
>    cifs_readpages+0x217/0x1270
>    read_pages+0x29a/0x670
>    page_cache_readahead_unbounded+0x24f/0x390
>    __do_page_cache_readahead+0x3f/0x60
>    ondemand_readahead+0x1f1/0x470
>    page_cache_async_readahead+0x14c/0x170
>    generic_file_buffered_read+0x5df/0x1100
>    generic_file_read_iter+0x10c/0x1d0
>    cifs_strict_readv+0x139/0x170
>    new_sync_read+0x164/0x250
>    __vfs_read+0x39/0x60
>    vfs_read+0xb5/0x1e0
>    ksys_pread64+0x85/0xf0
>    __x64_sys_pread64+0x22/0x30
>    do_syscall_64+0x69/0x150
>    entry_SYSCALL_64_after_hwframe+0x44/0xa9
>   RIP: 0033:0x7f5071fcb1af
>   Code: Bad RIP value.
>   RSP: 002b:00007ffde2cdb8e0 EFLAGS: 00000293 ORIG_RAX: 0000000000000011
>   RAX: ffffffffffffffda RBX: 00007ffde2cdb990 RCX: 00007f5071fcb1af
>   RDX: 0000000000001000 RSI: 000055efcd5ca000 RDI: 0000000000000003
>   RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
>   R10: 0000000000001000 R11: 0000000000000293 R12: 0000000000000001
>   R13: 000000000009f000 R14: 0000000000000000 R15: 0000000000001000
>   Modules linked in:
>   ---[ end trace 725fa14a3e1af65c ]---
>
> Since commit 3fea5a499d57 ("mm: memcontrol: convert page cache to a new
> mem_cgroup_charge() API") not cancel the page charge, the pages maybe
> double add to pagecache:
> thread1                       | thread2
> cifs_readpages
> readpages_get_pages
>  add_to_page_cache_locked(head,index=n)=0
>                               | readpages_get_pages
>                               | add_to_page_cache_locked(head,index=n+1)=0
>  add_to_page_cache_locked(head, index=n+1)=-EEXIST
>  then, will next loop with list head page's
>  index=n+1 and the page->mapping not NULL
> readpages_get_pages
> add_to_page_cache_locked(head, index=n+1)
>  commit_charge
>   VM_BUG_ON_PAGE
>
> So, we should not do the next loop when any page add to page cache
> failed.
>
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@...wei.com>
> Signed-off-by: Steve French <stfrench@...rosoft.com>
> Acked-by: Ronnie Sahlberg <lsahlber@...hat.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

Hi Sasha,

The patch description mentions the commit 3fea5a499d57 that changed
the behavior and was introduced in v5.8-rc1. I noticed that you are
targeting this patch for 4.9, 4.14, 4.19, 5.4 and 5.7 stable branches.
Are you going to backport the commit 3fea5a499d57 as well?

--
Best regards,
Pavel Shilovsky