Re: [PATCH] ocfs2: fix crash caused by stale lvb with fsdlm plugin
From: Eric Ren
Date: Wed Dec 14 2016 - 21:29:10 EST
Hi,
On 12/15/2016 09:46 AM, Joseph Qi wrote:
In you description, this issue can only happen in case of stack user +
fsdlm.
Yes.
So I feel we'd better to make stack user and o2cb behaves the same,
other than treat it as a special case.
Yes, I agree. But, actually, there is nothing wrong with fsdlm. I think o2cb does some tricks
with DLM_LKF_VALBLK flag in such a special case where down conversion is PR->NULL.
I'd like to see this quick and small fix to be merged at this moment, because this issue is
little emergency for us.
Anyway, we can supersede this one easily if someone familiar with o2cb works out a patch for
o2cb in the future.
Does this sounds good to you?
Thanks,
Eric
Thanks,
Joseph
On 16/12/9 17:30, Eric Ren wrote:
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:
"
[ 245.197849] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover_grant 1 locks on 971
resources
[ 245.197859] dlm: C21CBDA5E0774F4BA5A9D4F317717495: dlm_recover 9 generation 5 done: 4 ms
[ 245.198379] ocfs2: Begin replay journal (node 318952601, slot 2) on device (253,18)
[ 247.272338] ocfs2: End replay journal (node 318952601, slot 2) on device (253,18)
[ 247.547084] ocfs2: Beginning quota recovery on device (253,18) for slot 2
[ 247.683263] ocfs2: Finishing quota recovery on device (253,18) for slot 2
[ 247.833022] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: bug expression:
le64_to_cpu(fe->i_size) != i_size_read(inode)
[ 247.833029] (truncate,30154,1):ocfs2_truncate_file:470 ERROR: Inode 290321, inode
i_size = 732 != di i_size = 937, i_flags = 0x1
[ 247.833074] ------------[ cut here ]------------
[ 247.833077] kernel BUG at /usr/src/linux/fs/ocfs2/file.c:470!
[ 247.833079] invalid opcode: 0000 [#1] SMP
[ 247.833081] 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
[ 247.833107] Supported: No, Unsupported modules are loaded
[ 247.833110] CPU: 1 PID: 30154 Comm: truncate Tainted: G OE N
4.4.21-69-default #1
[ 247.833111] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.8.1-0-g4adadbd-20151112_172657-sheep25 04/01/2014
[ 247.833112] task: ffff88004ff6d240 ti: ffff880074e68000 task.ti: ffff880074e68000
[ 247.833113] RIP: 0010:[<ffffffffa05c8c30>] [<ffffffffa05c8c30>]
ocfs2_truncate_file+0x640/0x6c0 [ocfs2]
[ 247.833151] RSP: 0018:ffff880074e6bd50 EFLAGS: 00010282
[ 247.833152] RAX: 0000000000000074 RBX: 000000000000029e RCX: 0000000000000000
[ 247.833153] RDX: 0000000000000001 RSI: 0000000000000246 RDI: 0000000000000246
[ 247.833154] RBP: ffff880074e6bda8 R08: 000000003675dc7a R09: ffffffff82013414
[ 247.833155] R10: 0000000000034c50 R11: 0000000000000000 R12: ffff88003aab3448
[ 247.833156] R13: 00000000000002dc R14: 0000000000046e11 R15: 0000000000000020
[ 247.833157] FS: 00007f839f965700(0000) GS:ffff88007fc80000(0000) knlGS:0000000000000000
[ 247.833158] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 247.833159] CR2: 00007f839f97e000 CR3: 0000000036723000 CR4: 00000000000006e0
[ 247.833164] Stack:
[ 247.833165] 00000000000003a9 0000000000000001 ffff880060554000 ffff88004fcaf000
[ 247.833167] ffff88003aa7b090 1000000000000000 ffff88003aab3448 ffff880074e6beb0
[ 247.833169] 0000000000000001 0000000000002068 0000000000000020 0000000000000000
[ 247.833171] Call Trace:
[ 247.833208] [<ffffffffa05cb1a8>] ocfs2_setattr+0x698/0xa90 [ocfs2]
[ 247.833225] [<ffffffff8121587e>] notify_change+0x1ae/0x380
[ 247.833242] [<ffffffff811f8bfe>] do_truncate+0x5e/0x90
[ 247.833246] [<ffffffff811f8f58>] do_sys_ftruncate.constprop.11+0x108/0x160
[ 247.833257] [<ffffffff815e142e>] entry_SYSCALL_64_fastpath+0x12/0x6d
[ 247.834724] DWARF2 unwinder stuck at entry_SYSCALL_64_fastpath+0x12/0x6d
[ 247.834725]
[ 247.834726] Leftover inexact backtrace:
[ 247.834728] 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
[ 247.834748] RIP [<ffffffffa05c8c30>] ocfs2_truncate_file+0x640/0x6c0 [ocfs2]
[ 247.834774] RSP <ffff880074e6bd50>
"
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.
Signed-off-by: Eric Ren <zren@xxxxxxxx>
---
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 83d576f..77d1632 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -3303,6 +3303,16 @@ 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 52c07346b..8203590 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 f2dce10..e3036e1 100644
--- a/fs/ocfs2/stackglue.h
+++ b/fs/ocfs2/stackglue.h
@@ -298,6 +298,9 @@ 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);
+
extern struct kset *ocfs2_kset;
#endif /* STACKGLUE_H */