On Mon, Oct 16, 2017 at 9:44 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> On Mon, 2017-10-16 at 08:15 +0800, Yan, Zheng wrote:
>> > On 14 Oct 2017, at 19:40, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>> >
>> > (re-cc'ing ceph-devel list)
>> >
>> > Not right offhand, but I do have some comments about this code for the
>> > maintainers. See below:
>> >
>> > On Fri, 2017-10-13 at 23:11 +0000, Anish Gupta wrote:
>> > > Hello Jeff,
>> > >
>> > >
>> > > I did not see the issue with 4.4.14-rc4.
>> > >
>> > >
>> > > Would you or Zheng know which set of changes from 4.4 onwards might have helped fix this?
>> > > PS: I worked with Zheng on chage-id: 62a65f36d016fff32179acdbfcb8b2d8d9e54757
>> > >
>> > > thanks,
>> > > Anish
>> > >
>> > >
>> > > On Monday, October 9, 2017, 9:12:54 AM PDT, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>> > >
>> > >
>> > > On Mon, 2017-10-09 at 16:09 +0000, Anish Gupta wrote:
>> > >
>> > > >
>> > > >
>> > > > Hello Ceph gurus,
>> > > >
>> > > > I was running a script in a loop that was doing the following:
>> > > >
>> > > > > Loop:
>> > > > > mount 2 different ceph "clients" using their own shares and secret keys and FSCache
>> > > > > write data into a sub-directory of client1
>> > > > > let i=0; while (($i<10)); do sudo dd if=/dev/urandom of=data_file_$i bs=10M count=1; let i=$i+1; done
>> > > > > write data into client 2 using same as previous step.
>> > > > > read data from client 1
>> > > > > cp -r /client1/data/ /tmp/scratch1_dir
>> > > > > read data from client 2
>> > > > > cp -r /client2/data/ /tmp/scratch2_dir
>> > > > > unmount the 2 clients
>> > > > >
>> > > > >
>> > > > >
>> > > >
>> > > > Linux Kernel: 4.4.0-81-generic
>> > > > $ ceph --version
>> > > > ceph version 10.2.7 (50e863e0f4bc8f4b9e31156de690d765af245185)
>> > > >
>> > > > Only one script of above loop was running and after 4th iteration ran into this bug:
>> > > >
>> > > > Back trace looks like this:
>> > > > [2183922.263463] ------------[ cut here ]------------
>> > > > [2183922.264771] kernel BUG at /root/ubuntu-xenial/fs/ceph/mds_client.c:1258!
>> > > > [2183922.264771] invalid opcode: 0000 [#1] SMP
>> > > > [2183922.264771] Modules linked in: nfs lockd grace xt_nat ceph(OE) libceph libcrc32c veth ip6t_REJECT nf_reject_ipv6 nf_log_ipv6 xt_recent ipt_MASQUERADE nf_nat_masquerade_ipv4 xfrm_user xfrm_algo iptable_nat nf_nat_ipv4 br_netfilter bridge stp llc overlay binfmt_misc cachefiles(OE) fscache(OE) xt_multiport xenfs xen_privcmd ppdev nls_utf8 isofs intel_rapl crct10dif_pclmul crc32_pclmul ghash_clmulni_intel nvidia_uvm(POE) aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd input_leds joydev serio_raw i2c_piix4 8250_fintek parport_pc parport mac_hid xt_hl ip6t_rt nf_conntrack_ipv6 nf_defrag_ipv6 ipt_REJECT nf_reject_ipv4 nf_log_ipv4 nf_log_common xt_LOG xt_limit xt_tcpudp xt_addrtype nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack ip6table_filter ip6_tables nf_conntrack_netbios_ns nf_conntrack_broadcast
>> > > > [2183922.264771] nf_nat_ftp nf_nat nf_conntrack_ftp nf_conntrack iptable_filter ip_tables x_tables sunrpc autofs4 hid_generic usbhid hid nvidia_drm(POE) nvidia_modeset(POE) nvidia(POE) drm_kms_helper syscopyarea sysfillrect sysimgblt psmouse fb_sys_fops drm pata_acpi floppy fjes
>> > > > [2183922.264771] CPU: 0 PID: 19728 Comm: umount Tainted: P OE 4.4.0-81-generic #104-Ubuntu
>> > > > [2183922.264771] Hardware name: Xen HVM domU, BIOS 4.6.1-xs137595 03/23/2017
>> > > > [2183922.264771] task: ffff880d3aa12a00 ti: ffff880f321a0000 task.ti: ffff880f321a0000
>> > > > [2183922.264771] RIP: 0010:[<ffffffffc12218ac>] [<ffffffffc12218ac>] remove_session_caps+0x13c/0x150 [ceph]
>> > > > [2183922.264771] RSP: 0018:ffff880f321a3d38 EFLAGS: 00010202
>> > > > [2183922.264771] RAX: 0000000000000001 RBX: ffff8809976b7000 RCX: ffff8807c1ee5028
>> > > > [2183922.264771] RDX: 0000000000000039 RSI: ffff880f321a3d00 RDI: ffff880f3978a608
>> > > > [2183922.264771] RBP: ffff880f321a3d78 R08: ffff880f321a0000 R09: 0000000000000000
>> > > > [2183922.264771] R10: 0000000000032800 R11: 0000000000000000 R12: ffff8809976b7540
>> > > > [2183922.264771] R13: ffff8807c1ee5168 R14: ffff8809976b7548 R15: ffff8809976b2800
>> > > > [2183922.264771] FS: 00007f4fb7e28840(0000) GS:ffff880f42a00000(0000) knlGS:0000000000000000
>> > > > [2183922.264771] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> > > > [2183922.264771] CR2: 00007f4fb7656170 CR3: 0000000f34af2000 CR4: 00000000003406f0
>> > > > [2183922.264771] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> > > > [2183922.264771] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> > > > [2183922.264771] Stack:
>> > > > [2183922.264771] 0000010007dee895 fffffffffffffffe 0000000039d663f2 ffff880f3978a400
>> > > > [2183922.264771] 0000000000000000 ffff8809976b7000 ffff880f3978a408 ffff8809976b7020
>> > > > [2183922.264771] ffff880f321a3df0 ffffffffc12268f8 ffff88007bb9d200 00000001976b2e08
>> > > > [2183922.264771] Call Trace:
>> > > > [2183922.264771] [<ffffffffc12268f8>] ceph_mdsc_close_sessions+0x1d8/0x2e0 [ceph]
>> > > > [2183922.264771] [<ffffffff8122bf27>] ? evict_inodes+0x177/0x1a0
>> > > > [2183922.264771] [<ffffffffc12031b3>] ceph_put_super+0x23/0x50 [ceph]
>> > > > [2183922.264771] [<ffffffff812115df>] generic_shutdown_super+0x6f/0x100
>> > > > [2183922.264771] [<ffffffffc1203136>] ceph_kill_sb+0x36/0x90 [ceph]
>> > > > [2183922.264771] [<ffffffff81211ac3>] deactivate_locked_super+0x43/0x70
>> > > > [2183922.264771] [<ffffffff81211f9c>] deactivate_super+0x5c/0x60
>> > > > [2183922.264771] [<ffffffff8123000f>] cleanup_mnt+0x3f/0x90
>> > > > [2183922.264771] [<ffffffff812300a2>] __cleanup_mnt+0x12/0x20
>> > > > [2183922.264771] [<ffffffff8109f031>] task_work_run+0x81/0xa0
>> > > > [2183922.264771] [<ffffffff81003242>] exit_to_usermode_loop+0xc2/0xd0
>> > > > [2183922.264771] [<ffffffff81003c6e>] syscall_return_slowpath+0x4e/0x60
>> > > > [2183922.264771] [<ffffffff81840bd0>] int_ret_from_sys_call+0x25/0x8f
>> > > > [2183922.264771] Code: 2e 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 89 fa 48 c7 c6 80 79 23 c1 48 c7 c7 40 4d 24 c1 e8 59 2c 20 c0 e9 f9 fe ff ff <0f> 0b 0f 0b e8 4b f8 e5 bf 90 66 2e 0f 1f 84 00 00 00 00 00 0f
>> > > > [2183922.264771] RIP [<ffffffffc12218ac>] remove_session_caps+0x13c/0x150 [ceph]
>> > > > [2183922.264771] RSP <ffff880f321a3d38>
>> > > > [2183922.307469] ---[ end trace e6fc86f4c2c986fd ]---
>> > > > [2183922.263463] ------------[ cut here ]------------
>> > > > [2183922.264771] kernel BUG at /root/ubuntu-xenial/fs/ceph/mds_client.c:1258!
>> > > > [2183922.264771] invalid opcode: 0000 [#1] SMP
>> > > > [2183922.264771] Modules linked in: nfs lockd grace xt_nat ceph(OE) libceph libcrc32c veth ip6t_REJECT nf_reject_ipv6 nf_log_ipv6 xt_recent ipt_MASQUERADE nf_nat_masquerade_ipv4 xfrm_user xfrm_algo iptable_nat nf_nat_ipv4 br_netfilter bridge stp llc overlay binfmt_misc cachefiles(OE) fscache(OE) xt_multiport xenfs xen_privcmd ppdev nls_utf8 isofs intel_rapl crct10dif_pclmul crc32_pclmul ghash_clmulni_intel nvidia_uvm(POE) aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd input_leds joydev serio_raw i2c_piix4 8250_fintek parport_pc parport mac_hid xt_hl ip6t_rt nf_conntrack_ipv6 nf_defrag_ipv6 ipt_REJECT nf_reject_ipv4 nf_log_ipv4 nf_log_common xt_LOG xt_limit xt_tcpudp xt_addrtype nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack ip6table_filter ip6_tables nf_conntrack_netbios_ns nf_conntrack_broadcast
>> > > > [2183922.264771] nf_nat_ftp nf_nat nf_conntrack_ftp nf_conntrack iptable_filter ip_tables x_tables sunrpc autofs4 hid_generic usbhid hid nvidia_drm(POE) nvidia_modeset(POE) nvidia(POE) drm_kms_helper syscopyarea sysfillrect sysimgblt psmouse fb_sys_fops drm pata_acpi floppy fjes
>> > > > [2183922.264771] CPU: 0 PID: 19728 Comm: umount Tainted: P OE 4.4.0-81-generic #104-Ubuntu
>> > > > [2183922.264771] Hardware name: Xen HVM domU, BIOS 4.6.1-xs137595 03/23/2017
>> > > > [2183922.264771] task: ffff880d3aa12a00 ti: ffff880f321a0000 task.ti: ffff880f321a0000
>> > > > [2183922.264771] RIP: 0010:[<ffffffffc12218ac>] [<ffffffffc12218ac>] remove_session_caps+0x13c/0x150 [ceph]
>> > > > [2183922.264771] RSP: 0018:ffff880f321a3d38 EFLAGS: 00010202
>> > > > [2183922.264771] RAX: 0000000000000001 RBX: ffff8809976b7000 RCX: ffff8807c1ee5028
>> > > > [2183922.264771] RDX: 0000000000000039 RSI: ffff880f321a3d00 RDI: ffff880f3978a608
>> > > > [2183922.264771] RBP: ffff880f321a3d78 R08: ffff880f321a0000 R09: 0000000000000000
>> > > > [2183922.264771] R10: 0000000000032800 R11: 0000000000000000 R12: ffff8809976b7540
>> > > > [2183922.264771] R13: ffff8807c1ee5168 R14: ffff8809976b7548 R15: ffff8809976b2800
>> > > > [2183922.264771] FS: 00007f4fb7e28840(0000) GS:ffff880f42a00000(0000) knlGS:0000000000000000
>> > > > [2183922.264771] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> > > > [2183922.264771] CR2: 00007f4fb7656170 CR3: 0000000f34af2000 CR4: 00000000003406f0
>> > > > [2183922.264771] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> > > > [2183922.264771] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> > > > [2183922.264771] Stack:
>> > > > [2183922.264771] 0000010007dee895 fffffffffffffffe 0000000039d663f2 ffff880f3978a400
>> > > > [2183922.264771] 0000000000000000 ffff8809976b7000 ffff880f3978a408 ffff8809976b7020
>> > > > [2183922.264771] ffff880f321a3df0 ffffffffc12268f8 ffff88007bb9d200 00000001976b2e08
>> > > > [2183922.264771] Call Trace:
>> > > > [2183922.264771] [<ffffffffc12268f8>] ceph_mdsc_close_sessions+0x1d8/0x2e0 [ceph]
>> > > > [2183922.264771] [<ffffffff8122bf27>] ? evict_inodes+0x177/0x1a0
>> > > > [2183922.264771] [<ffffffffc12031b3>] ceph_put_super+0x23/0x50 [ceph]
>> > > > [2183922.264771] [<ffffffff812115df>] generic_shutdown_super+0x6f/0x100
>> > > > [2183922.264771] [<ffffffffc1203136>] ceph_kill_sb+0x36/0x90 [ceph]
>> > > > [2183922.264771] [<ffffffff81211ac3>] deactivate_locked_super+0x43/0x70
>> > > > [2183922.264771] [<ffffffff81211f9c>] deactivate_super+0x5c/0x60
>> > > > [2183922.264771] [<ffffffff8123000f>] cleanup_mnt+0x3f/0x90
>> > > > [2183922.264771] [<ffffffff812300a2>] __cleanup_mnt+0x12/0x20
>> > > > [2183922.264771] [<ffffffff8109f031>] task_work_run+0x81/0xa0
>> > > > [2183922.264771] [<ffffffff81003242>] exit_to_usermode_loop+0xc2/0xd0
>> > > > [2183922.264771] [<ffffffff81003c6e>] syscall_return_slowpath+0x4e/0x60
>> > > > [2183922.264771] [<ffffffff81840bd0>] int_ret_from_sys_call+0x25/0x8f
>> > > > [2183922.264771] Code: 2e 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 89 fa 48 c7 c6 80 79 23 c1 48 c7 c7 40 4d 24 c1 e8 59 2c 20 c0 e9 f9 fe ff ff <0f> 0b 0f 0b e8 4b f8 e5 bf 90 66 2e 0f 1f 84 00 00 00 00 00 0f
>> > > > [2183922.264771] RIP [<ffffffffc12218ac>] remove_session_caps+0x13c/0x150 [ceph]
>> > > > [2183922.264771] RSP <ffff880f321a3d38>
>> > > > [2183922.307469] ---[ end trace e6fc86f4c2c986fd ]---
>> > > >
>> > > > This is different from a previous one that Zheng had looked into few months back as it seems to
>> > > > point that s_nr_caps still remains > 0 ?
>> > > >
>> > > > 1
>> > > > 1218 /*
>> > > > 1219 * caller must hold session s_mutex
>> > > > 1220 */
>> > > > 1221 static void remove_session_caps(struct ceph_mds_session *session)
>> > > > 1222 {
>> > > > 1223 dout("remove_session_caps on %p\n", session);
>> > > > 1224 iterate_session_caps(session, remove_session_caps_cb, NULL);
>> > > > 1225
>> > > > 1226 spin_lock(&session->s_cap_lock);
>> > > > 1227 if (session->s_nr_caps > 0) {
>> > > > 1228 struct super_block *sb = session->s_mdsc->fsc->sb;
>> > > > 1229 struct inode *inode;
>> > > > 1230 struct ceph_cap *cap, *prev = NULL;
>> > > > 1231 struct ceph_vino vino;
>> > > > 1232 /*
>> > > > 1233 * iterate_session_caps() skips inodes that are being
>> > > > 1234 * deleted, we need to wait until deletions are complete.
>> > > > 1235 * __wait_on_freeing_inode() is designed for the job,
>> > > > 1236 * but it is not exported, so use lookup inode function
>> > > > 1237 * to access it.
>> > > > 1238 */
>> > > > 1239 while (!list_empty(&session->s_caps)) {
>> > > > 1240 cap = list_entry(session->s_caps.next,
>> > > > 1241 struct ceph_cap, session_caps);
>> > > > 1242 if (cap == prev)
>> > > > 1243 break;
>> > > > 1244 prev = cap;
>> > > > 1245 vino = cap->ci->i_vino;
>> > > > 1246 spin_unlock(&session->s_cap_lock);
>> > > > 1247
>> > > > 1248 inode = ceph_find_inode(sb, vino);
>> > > > 1249 iput(inode);
>> > > > 1250
>> > > > 1251 spin_lock(&session->s_cap_lock);
>> > > > 1252 }
>> > > > 1253 }
>> > > > 1254
>> > > > 1255 // drop cap expires and unlock s_cap_lock
>> > > > 1256 cleanup_cap_releases(session->s_mdsc, session);
>> > > > 1257
>> > > > 1258 BUG_ON(session->s_nr_caps > 0);
>> > > > 1259 BUG_ON(!list_empty(&session->s_cap_flushing));
>> > > > 1260 }
>> > > > 1261
>> > > >
>> > > > Easily reproducible multiple times.
>> >
>> > FWIW, the locking in this function looks really wrong.
>> >
>> > Both s_caps list and s_nr_caps are protected by the s_cap_lock. That
>> > function drops that lock in the middle of walking the list to call
>> > ceph_find_inode. What prevents concurrent alterations to that list?
>> >
>>
>> when remove_session_caps() is being called, no one should add caps to the session. It’s only
>> possible that there are concurrent freeing inodes. what’s the problem here?
>>
>
> It looks like Anish's box hit this:
>
> BUG_ON(session->s_nr_caps > 0);
>
> I get that we're tearing down the session and that no new caps should be
> added, but what is the mechanism that prevents it?
>
> For instance, fill_inode is not done under the session->s_mutex,
> AFAICT.
>
> I don't see what would prevent fill_inode running concurrently on
> another CPU racing in and adding caps to the session after
> cleanup_cap_releases drops the spinlock here.
>
I think this race can happen in theory. But it's likely to cause the
oops. because if there were pending request replies, umounting should
return -EBUSY,
Regads
Yan, Zheng
> --
> Jeff Layton <jlayton@xxxxxxxxxx>
> --
> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
