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    SubjectRe: inode_unused list corruption in 2.4.26 - spin_lock problem?
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    On Sat, 19 Jun 2004, Marcelo Tosatti wrote:
    > On Fri, Jun 18, 2004 at 05:47:05PM -0700, Chris Caputo wrote:
    > > In 2.4.26 on two different dual-proc x86 machines (one dual-P4 Xeon based,
    > > the other dual-PIII) I am seeing crashes which are the result of the
    > > inode_unused doubly linked list in fs/inode.c becoming corrupted.
    >
    > What steps are required to reproduce the problem?

    Unfortunately I don't yet know how to (or if I can) repro this with a
    stock kernel. I am using 2.4.26 + Ingo's tux3-2.4.23-A3 patch in
    conjunction with a filesystem I wrote. (the tux module itself is not
    being used, just the patches to the existing kernel)

    > > A particular instance of the corruption I have isolated is in a call from
    > > iput() to __refile_inode(). To try to diagnose this further I placed list
    > > verification code before and after the list_del() and list_add() calls in
    > > __refile_inode() and observed a healthy list become corrupted after the
    > > del/add was completed.
    >
    > Can you show us this data in more detail?

    In __refile_inode() before and after the list_add()/del() calls I call a
    function which checks up to the first 10 items on the inode_unused list to
    see if next and prev pointers are valid.
    (inode->next->prev == inode && inode->prev->next == inode)

    So what I observed was a case here where iput() inline __refile_inode():

    1) checked inode_unused and saw that it was good
    2) put an item on the inode_unused list
    3) checked inode_unused and saw that it was now bad and that the item
    added was the culprit.

    This all happened within __refile_inode() with the inode_lock spinlock
    grabbed by iput() and so I tend to think some other code is accessing the
    inode_unused list _without_ grabbing the spinlock. I've checked the
    inode.c code over and over, plus my filesystem code, and haven't yet found
    a culprit. I also checked the tux diffs to see if it was messing with
    inode objects in an inappropriate way.

    Is it safe to assume that the x86 version of atomic_dec_and_lock(), which
    iput() uses, is well trusted? I figure it's got to be, but doesn't hurt
    to ask.

    > > It would seem to me that list corruption on otherwise healthy machines
    > > would only be the result of the inode_lock spinlock not being properly
    > > locked prior to the call to __refile_inode(), but as far as I can tell,
    > > the call to atomic_dec_and_lock() in iput() is doing that properly.
    > >
    > > So I am at a loss. Has anyone else seen this or does anyone have any idea
    > > what routes I should be exploring to fix this problem?
    >
    > The changes between 2.4.25->2.4.26 (which introduce __refile_inode() and
    > the unused_pagecache list) must have something to do with this.

    __refile_inode() was introduced in 2.4.25. I'll try 2.4.24 to see if I
    can reproduce there.

    Marcelo, you asked for some oops' relating to the problem. Here are some.

    Thanks,
    Chris

    ---

    Oops: 0000
    CPU: 0
    EIP: 0010:[<c015b465>] Not tainted
    Using defaults from ksymoops -t elf32-i386 -a i386
    EFLAGS: 00010a93
    eax: 8d12e0e2 ebx: 7b402366 ecx: c40fdf18 edx: d9c92888
    esi: 7b40235e edi: 7b402366 ebp: 000007cf esp: c40fdf10
    ds: 0018 es: 0018 ss: 0018
    Process kswapd (pid: 7, stackpage=c40fd000)
    Stack: e3b85380 000004e5 e3b85388 c9812688 00000002 c25caf40 c0317fd8 00023dd2
    c015b664 00000cb4 c0138f35 00000006 000001d0 ffffffff 000001d0 00000002
    00000006 000001d0 c0317fd8 c0317fd8 c013936a c40fdf84 000001d0 0000003c
    Call Trace: [<c015b664>] [<c0138f35>] [<c013936a>] [<c01393e2>] [<c0139596>]
    [<c0139608>] [<c0139748>] [<c01396b0>] [<c0105000>] [<c010587e>]
    [<c01396b0>]
    Code: 8b 5b 04 8b 86 1c 01 00 00 a8 38 0f 84 5d 01 00 00 81 fb 08


    >>EIP; c015b465 <prune_icache+45/220> <=====

    >>ecx; c40fdf18 <_end+3d3ffec/38676134>
    >>edx; d9c92888 <_end+198d495c/38676134>
    >>esp; c40fdf10 <_end+3d3ffe4/38676134>

    Trace; c015b664 <shrink_icache_memory+24/40>
    Trace; c0138f35 <shrink_cache+185/410>
    Trace; c013936a <shrink_caches+4a/60>
    Trace; c01393e2 <try_to_free_pages_zone+62/f0>
    Trace; c0139596 <kswapd_balance_pgdat+66/b0>
    Trace; c0139608 <kswapd_balance+28/40>
    Trace; c0139748 <kswapd+98/c0>
    Trace; c01396b0 <kswapd+0/c0>
    Trace; c0105000 <_stext+0/0>
    Trace; c010587e <arch_kernel_thread+2e/40>
    Trace; c01396b0 <kswapd+0/c0>

    Code; c015b465 <prune_icache+45/220>
    00000000 <_EIP>:
    Code; c015b465 <prune_icache+45/220> <=====
    0: 8b 5b 04 mov 0x4(%ebx),%ebx <=====
    Code; c015b468 <prune_icache+48/220>
    3: 8b 86 1c 01 00 00 mov 0x11c(%esi),%eax
    Code; c015b46e <prune_icache+4e/220>
    9: a8 38 test $0x38,%al
    Code; c015b470 <prune_icache+50/220>
    b: 0f 84 5d 01 00 00 je 16e <_EIP+0x16e>
    Code; c015b476 <prune_icache+56/220>
    11: 81 fb 08 00 00 00 cmp $0x8,%ebx

    ---

    Oops: 0000
    CPU: 0
    EIP: 0010:[<c015b465>] Not tainted
    Using defaults from ksymoops -t elf32-i386 -a i386
    EFLAGS: 00010a97
    eax: 830418da ebx: 5954e741 ecx: c40fdf18 edx: c0318f08
    esi: 5954e739 edi: 5954e741 ebp: 000001b4 esp: c40fdf10
    ds: 0018 es: 0018 ss: 0018
    Process kswapd (pid: 7, stackpage=c40fd000)
    Stack: f718b780 000013a1 f718b788 d04d3988 00000001 c3cfe850 c0317fd8 00023d9e
    c015b664 00001555 c0138f35 00000006 000001d0 ffffffff 000001d0 00000001
    00000004 000001d0 c0317fd8 c0317fd8 c013936a c40fdf84 000001d0 0000003c
    Call Trace: [<c015b664>] [<c0138f35>] [<c013936a>] [<c01393e2>] [<c0139596>]
    [<c0139608>] [<c0139748>] [<c01396b0>] [<c0105000>] [<c010587e>]
    [<c01396b0>]
    Code: 8b 5b 04 8b 86 1c 01 00 00 a8 38 0f 84 5d 01 00 00 81 fb 08


    >>EIP; c015b465 <prune_icache+45/220> <=====

    >>edx; c0318f08 <inode_unused+0/8>

    Trace; c015b664 <shrink_icache_memory+24/40>
    Trace; c0138f35 <shrink_cache+185/410>
    Trace; c013936a <shrink_caches+4a/60>
    Trace; c01393e2 <try_to_free_pages_zone+62/f0>
    Trace; c0139596 <kswapd_balance_pgdat+66/b0>
    Trace; c0139608 <kswapd_balance+28/40>
    Trace; c0139748 <kswapd+98/c0>
    Trace; c01396b0 <kswapd+0/c0>
    Trace; c0105000 <_stext+0/0>
    Trace; c010587e <arch_kernel_thread+2e/40>
    Trace; c01396b0 <kswapd+0/c0>

    Code; c015b465 <prune_icache+45/220>
    00000000 <_EIP>:
    Code; c015b465 <prune_icache+45/220> <=====
    0: 8b 5b 04 mov 0x4(%ebx),%ebx <=====
    Code; c015b468 <prune_icache+48/220>
    3: 8b 86 1c 01 00 00 mov 0x11c(%esi),%eax
    Code; c015b46e <prune_icache+4e/220>
    9: a8 38 test $0x38,%al
    Code; c015b470 <prune_icache+50/220>
    b: 0f 84 5d 01 00 00 je 16e <_EIP+0x16e>
    Code; c015b476 <prune_icache+56/220>
    11: 81 fb 08 00 00 00 cmp $0x8,%ebx

    ---

    I think this one was an infinite loop which I used alt-sysrq-p to get
    deduce:

    Pid: 7, comm: kswapd
    EIP: 0010:[<c014dd1c>] CPU: 2 EFLAGS: 00000246 Not tainted
    Using defaults from ksymoops -t elf32-i386 -a i386
    EAX: c4e4f824 EBX: c4e4f804 ECX: 00000006 EDX: 00000000
    ESI: c4e4f80c EDI: c4e4f804 EBP: 000009ee DS: 0018 ES: 0018
    Warning (Oops_set_regs): garbage 'DS: 0018 ES: 0018' at end of register
    line ignored
    CR0: 8005003b CR2: bfffdfb4 CR3: 00101000 CR4: 000006d0
    Call Trace: [<c0167f8e>] [<c01681d4>] [<c013d9d0>] [<c0168254>] [<c013fe69>]
    [<c01404ae>] [<c0140533>] [<c01405b2>] [<c011a6cb>] [<c0140766>] [<c01407d8>]
    [<c0140918>] [<c0140880>] [<c010595e>] [<c0140880>]
    Warning (Oops_read): Code line not seen, dumping what data is available


    >>EIP; c014dd1c <inode_has_buffers+6c/90> <=====

    >>EAX; c4e4f824 <_end+4a6b2f8/3864fb34>
    >>EBX; c4e4f804 <_end+4a6b2d8/3864fb34>
    >>ESI; c4e4f80c <_end+4a6b2e0/3864fb34>
    >>EDI; c4e4f804 <_end+4a6b2d8/3864fb34>

    Trace; c0167f8e <prune_icache+7e/320>
    Trace; c01681d4 <prune_icache+2c4/320>
    Trace; c013d9d0 <kmem_cache_shrink+70/c0>
    Trace; c0168254 <shrink_icache_memory+24/40>
    Trace; c013fe69 <shrink_cache+1d9/6d0>
    Trace; c01404ae <refill_inactive+14e/160>
    Trace; c0140533 <shrink_caches+73/90>
    Trace; c01405b2 <try_to_free_pages_zone+62/f0>
    Trace; c011a6cb <schedule+34b/5f0>
    Trace; c0140766 <kswapd_balance_pgdat+66/b0>
    Trace; c01407d8 <kswapd_balance+28/40>
    Trace; c0140918 <kswapd+98/c0>
    Trace; c0140880 <kswapd+0/c0>
    Trace; c010595e <arch_kernel_thread+2e/40>
    Trace; c0140880 <kswapd+0/c0>

    ---

    Another infinite loop (alt-sysrq-p):

    Pid: 7, comm: kswapd
    EIP: 0010:[<c0167bc8>] CPU: 3 EFLAGS: 00000206 Not tainted
    Using defaults from ksymoops -t elf32-i386 -a i386
    EAX: 00000001 EBX: ebe7f40c ECX: 00000002 EDX: 00000000
    ESI: ebe7f60c EDI: ebe7f604 EBP: c2851ee4 DS: 0018 ES: 0018
    Warning (Oops_set_regs): garbage 'DS: 0018 ES: 0018' at end of register
    line ignored
    CR0: 8005003b CR2: 40014000 CR3: 00101000 CR4: 000006d0
    Call Trace: [<c013d7e2>] [<c0167eb7>] [<c013fd05>] [<c0140360>] [<c01403e2>]
    [<c0140462>] [<c0140638>] [<c01406a8>] [<c01407fa>] [<c0140760>] [<c010596e>]
    [<c0140760>]

    >>EIP; c0167bc8 <prune_icache+78/340> <=====

    Trace; c013d7e2 <kmem_cache_shrink+72/c0>
    Trace; c0167eb7 <shrink_icache_memory+27/40>
    Trace; c013fd05 <shrink_cache+1d5/6d0>
    Trace; c0140360 <refill_inactive+160/170>
    Trace; c01403e2 <shrink_caches+72/90>
    Trace; c0140462 <try_to_free_pages_zone+62/f0>
    Trace; c0140638 <kswapd_balance_pgdat+78/c0>
    Trace; c01406a8 <kswapd_balance+28/40>
    Trace; c01407fa <kswapd+9a/c0>
    Trace; c0140760 <kswapd+0/c0>
    Trace; c010596e <arch_kernel_thread+2e/40>
    Trace; c0140760 <kswapd+0/c0>

    ---

    Infinite loop (alt-sysrq-p):

    Pid: 9, comm: kupdated
    EIP: 0010:[<c0168df3>] CPU: 2 EFLAGS: 00000282 Not tainted
    Using defaults from ksymoops -t elf32-i386 -a i386
    EAX: f7bea000 EBX: f7bea000 ECX: f7bebfd0 EDX: 00000000
    ESI: f7bebfc8 EDI: f7bebfd8 EBP: f7bebf10 DS: 0018 ES: 0018
    Warning (Oops_set_regs): garbage 'DS: 0018 ES: 0018' at end of register
    line ignored
    CR0: 8005003b CR2: 40013090 CR3: 00101000 CR4: 000006d0
    Call Trace: [<c011a1b2>] [<c0151333>] [<c015185e>] [<c0107a42>]
    [<c010596e>] [<c0151690>]

    >>EIP; c0168df3 <.text.lock.inode+69/256> <=====

    >>EAX; f7bea000 <_end+377ffb74/38649bd4>
    >>EBX; f7bea000 <_end+377ffb74/38649bd4>
    >>ECX; f7bebfd0 <_end+37801b44/38649bd4>
    >>ESI; f7bebfc8 <_end+37801b3c/38649bd4>
    >>EDI; f7bebfd8 <_end+37801b4c/38649bd4>
    >>EBP; f7bebf10 <_end+37801a84/38649bd4>

    Trace; c011a1b2 <schedule_timeout+62/b0>
    Trace; c0151333 <sync_old_buffers+53/160>
    Trace; c015185e <kupdate+1ce/230>
    Trace; c0107a42 <ret_from_fork+6/20>
    Trace; c010596e <arch_kernel_thread+2e/40>
    Trace; c0151690 <kupdate+0/230>

    ---

    Infinite loop (alt-sysrq-p):

    Pid: 7, comm: kswapd
    EIP: 0010:[<c0167be0>] CPU: 3 EFLAGS: 00000202 Not tainted
    Using defaults from ksymoops -t elf32-i386 -a i386
    EAX: 00000020 EBX: dcbc120c ECX: 00000086 EDX: daae3044
    ESI: dcbc120c EDI: dcbc1204 EBP: c2851ee4 DS: 0018 ES: 0018
    Warning (Oops_set_regs): garbage 'DS: 0018 ES: 0018' at end of register
    line ign
    ored
    CR0: 8005003b CR2: 0807f260 CR3: 00101000 CR4: 000006d0
    Call Trace: [<c013d7e2>] [<c0167ed7>] [<c013fd05>] [<c0140360>] [<c01403e2>]
    [<c011a55b>] [<c0140462>] [<c0140638>] [<c01406a8>] [<c01407fa>] [<c0140760>]
    [<c010596e>] [<c0140760>]

    >>EIP; c0167be0 <prune_icache+90/360> <=====

    >>EBX; dcbc120c <_end+1c7d6d80/38649bd4>
    >>EDX; daae3044 <_end+1a6f8bb8/38649bd4>
    >>ESI; dcbc120c <_end+1c7d6d80/38649bd4>
    >>EDI; dcbc1204 <_end+1c7d6d78/38649bd4>
    >>EBP; c2851ee4 <_end+2467a58/38649bd4>

    Trace; c013d7e2 <kmem_cache_shrink+72/c0>
    Trace; c0167ed7 <shrink_icache_memory+27/40>
    Trace; c013fd05 <shrink_cache+1d5/6d0>
    Trace; c0140360 <refill_inactive+160/170>
    Trace; c01403e2 <shrink_caches+72/90>
    Trace; c011a55b <schedule+34b/5f0>
    Trace; c0140462 <try_to_free_pages_zone+62/f0>
    Trace; c0140638 <kswapd_balance_pgdat+78/c0>
    Trace; c01406a8 <kswapd_balance+28/40>
    Trace; c01407fa <kswapd+9a/c0>
    Trace; c0140760 <kswapd+0/c0>
    Trace; c010596e <arch_kernel_thread+2e/40>
    Trace; c0140760 <kswapd+0/c0>

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