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    Subject[PATCH 3.10 027/268] ocfs2: fix crash caused by stale lvb with fsdlm plugin
    Date
    From: Eric Ren <zren@suse.com>

    commit e7ee2c089e94067d68475990bdeed211c8852917 upstream.

    The crash happens rather often when we reset some cluster nodes while
    nodes contend fiercely to do truncate and append.

    The crash backtrace is below:

    dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover_grant 1 locks on 971 resources
    dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover 9 generation 5 done: 4 ms
    ocfs2: Begin replay journal (node 318952601, slot 2) on device (253,18)
    ocfs2: End replay journal (node 318952601, slot 2) on device (253,18)
    ocfs2: Beginning quota recovery on device (253,18) for slot 2
    ocfs2: Finishing quota recovery on device (253,18) for slot 2
    (truncate,30154,1):ocfs2_truncate_file:470 ERROR: bug expression: le64_to_cpu(fe->i_size) != i_size_read(inode)
    (truncate,30154,1):ocfs2_truncate_file:470 ERROR: Inode 290321, inode i_size = 732 != di i_size = 937, i_flags = 0x1
    ------------[ cut here ]------------
    kernel BUG at /usr/src/linux/fs/ocfs2/file.c:470!
    invalid opcode: 0000 [#1] SMP
    Modules linked in: ocfs2_stack_user(OEN) ocfs2(OEN) ocfs2_nodemanager ocfs2_stackglue(OEN) quota_tree dlm(OEN) configfs fuse sd_mod iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi af_packet iscsi_ibft iscsi_boot_sysfs softdog xfs libcrc32c ppdev parport_pc pcspkr parport joydev virtio_balloon virtio_net i2c_piix4 acpi_cpufreq button processor ext4 crc16 jbd2 mbcache ata_generic cirrus virtio_blk ata_piix drm_kms_helper ahci syscopyarea libahci sysfillrect sysimgblt fb_sys_fops ttm floppy libata drm virtio_pci virtio_ring uhci_hcd virtio ehci_hcd usbcore serio_raw usb_common sg dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc scsi_dh_alua scsi_mod autofs4
    Supported: No, Unsupported modules are loaded
    CPU: 1 PID: 30154 Comm: truncate Tainted: G OE N 4.4.21-69-default #1
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.1-0-g4adadbd-20151112_172657-sheep25 04/01/2014
    task: ffff88004ff6d240 ti: ffff880074e68000 task.ti: ffff880074e68000
    RIP: 0010:[<ffffffffa05c8c30>] [<ffffffffa05c8c30>] ocfs2_truncate_file+0x640/0x6c0 [ocfs2]
    RSP: 0018:ffff880074e6bd50 EFLAGS: 00010282
    RAX: 0000000000000074 RBX: 000000000000029e RCX: 0000000000000000
    RDX: 0000000000000001 RSI: 0000000000000246 RDI: 0000000000000246
    RBP: ffff880074e6bda8 R08: 000000003675dc7a R09: ffffffff82013414
    R10: 0000000000034c50 R11: 0000000000000000 R12: ffff88003aab3448
    R13: 00000000000002dc R14: 0000000000046e11 R15: 0000000000000020
    FS: 00007f839f965700(0000) GS:ffff88007fc80000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
    CR2: 00007f839f97e000 CR3: 0000000036723000 CR4: 00000000000006e0
    Call Trace:
    ocfs2_setattr+0x698/0xa90 [ocfs2]
    notify_change+0x1ae/0x380
    do_truncate+0x5e/0x90
    do_sys_ftruncate.constprop.11+0x108/0x160
    entry_SYSCALL_64_fastpath+0x12/0x6d
    Code: 24 28 ba d6 01 00 00 48 c7 c6 30 43 62 a0 8b 41 2c 89 44 24 08 48 8b 41 20 48 c7 c1 78 a3 62 a0 48 89 04 24 31 c0 e8 a0 97 f9 ff <0f> 0b 3d 00 fe ff ff 0f 84 ab fd ff ff 83 f8 fc 0f 84 a2 fd ff
    RIP [<ffffffffa05c8c30>] ocfs2_truncate_file+0x640/0x6c0 [ocfs2]

    It's because ocfs2_inode_lock() get us stale LVB in which the i_size is
    not equal to the disk i_size. We mistakenly trust the LVB because the
    underlaying fsdlm dlm_lock() doesn't set lkb_sbflags with
    DLM_SBF_VALNOTVALID properly for us. But, why?

    The current code tries to downconvert lock without DLM_LKF_VALBLK flag
    to tell o2cb don't update RSB's LVB if it's a PR->NULL conversion, even
    if the lock resource type needs LVB. This is not the right way for
    fsdlm.

    The fsdlm plugin behaves different on DLM_LKF_VALBLK, it depends on
    DLM_LKF_VALBLK to decide if we care about the LVB in the LKB. If
    DLM_LKF_VALBLK is not set, fsdlm will skip recovering RSB's LVB from
    this lkb and set the right DLM_SBF_VALNOTVALID appropriately when node
    failure happens.

    The following diagram briefly illustrates how this crash happens:

    RSB1 is inode metadata lock resource with LOCK_TYPE_USES_LVB;

    The 1st round:

    Node1 Node2
    RSB1: PR
    RSB1(master): NULL->EX
    ocfs2_downconvert_lock(PR->NULL, set_lvb==0)
    ocfs2_dlm_lock(no DLM_LKF_VALBLK)

    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    dlm_lock(no DLM_LKF_VALBLK)
    convert_lock(overwrite lkb->lkb_exflags
    with no DLM_LKF_VALBLK)

    RSB1: NULL RSB1: EX
    reset Node2
    dlm_recover_rsbs()
    recover_lvb()

    /* The LVB is not trustable if the node with EX fails and
    * no lock >= PR is left. We should set RSB_VALNOTVALID for RSB1.
    */

    if(!(kb_exflags & DLM_LKF_VALBLK)) /* This means we miss the chance to
    return; * to invalid the LVB here.
    */

    The 2nd round:

    Node 1 Node2
    RSB1(become master from recovery)

    ocfs2_setattr()
    ocfs2_inode_lock(NULL->EX)
    /* dlm_lock() return the stale lvb without setting DLM_SBF_VALNOTVALID */
    ocfs2_meta_lvb_is_trustable() return 1 /* so we don't refresh inode from disk */
    ocfs2_truncate_file()
    mlog_bug_on_msg(disk isize != i_size_read(inode)) /* crash! */

    The fix is quite straightforward. We keep to set DLM_LKF_VALBLK flag
    for dlm_lock() if the lock resource type needs LVB and the fsdlm plugin
    is uesed.

    Link: http://lkml.kernel.org/r/1481275846-6604-1-git-send-email-zren@suse.com
    Signed-off-by: Eric Ren <zren@suse.com>
    Reviewed-by: Joseph Qi <jiangqi903@gmail.com>
    Cc: Mark Fasheh <mfasheh@versity.com>
    Cc: Joel Becker <jlbec@evilplan.org>
    Cc: Junxiao Bi <junxiao.bi@oracle.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Willy Tarreau <w@1wt.eu>
    ---
    fs/ocfs2/dlmglue.c | 10 ++++++++++
    fs/ocfs2/stackglue.c | 6 ++++++
    fs/ocfs2/stackglue.h | 3 +++
    3 files changed, 19 insertions(+)

    diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
    index b294deb..cf88dd4 100644
    --- a/fs/ocfs2/dlmglue.c
    +++ b/fs/ocfs2/dlmglue.c
    @@ -3264,6 +3264,16 @@ static int ocfs2_downconvert_lock(struct ocfs2_super *osb,
    mlog(ML_BASTS, "lockres %s, level %d => %d\n", lockres->l_name,
    lockres->l_level, new_level);

    + /*
    + * On DLM_LKF_VALBLK, fsdlm behaves differently with o2cb. It always
    + * expects DLM_LKF_VALBLK being set if the LKB has LVB, so that
    + * we can recover correctly from node failure. Otherwise, we may get
    + * invalid LVB in LKB, but without DLM_SBF_VALNOTVALID being set.
    + */
    + if (!ocfs2_is_o2cb_active() &&
    + lockres->l_ops->flags & LOCK_TYPE_USES_LVB)
    + lvb = 1;
    +
    if (lvb)
    dlm_flags |= DLM_LKF_VALBLK;

    diff --git a/fs/ocfs2/stackglue.c b/fs/ocfs2/stackglue.c
    index 39abf89..88610b3 100644
    --- a/fs/ocfs2/stackglue.c
    +++ b/fs/ocfs2/stackglue.c
    @@ -48,6 +48,12 @@ static char ocfs2_hb_ctl_path[OCFS2_MAX_HB_CTL_PATH] = "/sbin/ocfs2_hb_ctl";
    */
    static struct ocfs2_stack_plugin *active_stack;

    +inline int ocfs2_is_o2cb_active(void)
    +{
    + return !strcmp(active_stack->sp_name, OCFS2_STACK_PLUGIN_O2CB);
    +}
    +EXPORT_SYMBOL_GPL(ocfs2_is_o2cb_active);
    +
    static struct ocfs2_stack_plugin *ocfs2_stack_lookup(const char *name)
    {
    struct ocfs2_stack_plugin *p;
    diff --git a/fs/ocfs2/stackglue.h b/fs/ocfs2/stackglue.h
    index 1ec56fd..fa49d8a 100644
    --- a/fs/ocfs2/stackglue.h
    +++ b/fs/ocfs2/stackglue.h
    @@ -289,4 +289,7 @@ void ocfs2_stack_glue_set_max_proto_version(struct ocfs2_protocol_version *max_p
    int ocfs2_stack_glue_register(struct ocfs2_stack_plugin *plugin);
    void ocfs2_stack_glue_unregister(struct ocfs2_stack_plugin *plugin);

    +/* In ocfs2_downconvert_lock(), we need to know which stack we are using */
    +int ocfs2_is_o2cb_active(void);
    +
    #endif /* STACKGLUE_H */
    --
    2.8.0.rc2.1.gbe9624a
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