On Fri, 2012-10-26 at 08:16 -0400, Jeff Layton wrote: > On Sat, 20 Oct 2012 20:44:42 -0400 > Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > > The following oops was reported by Vit Zahradka. The BUG is this in > > __d_rehash(): > > > > BUG_ON(!d_unhashed(entry)); > > > > :kernel BUG at fs/dcache.c:2138! > > :invalid opcode: 0000 [#1] SMP > > :Modules linked in: fuse ebtable_nat ebtables ipt_MASQUERADE iptable_nat > > nf_nat des_generic xt_CHECKSUM iptable_mangle md4 bridge stp llc nls_utf8 > > cifs dns_resolver fscache lockd sunrpc rfcomm bnep be2iscsi > > iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i cxgb3 mdio libcxgbi > > ib_iser rdma_cm ib_addr iw_cm ib_cm ib_sa ib_mad ib_core iscsi_tcp > > libiscsi_tcp libiscsi scsi_transport_iscsi ip6t_REJECT nf_conntrack_ipv6 > > nf_defrag_ipv6 ip6table_filter ip6_tables nf_conntrack_ipv4 nf_defrag_ipv4 > > xt_state nf_conntrack snd_hda_codec_conexant btusb bluetooth snd_hda_intel > > snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm thinkpad_acpi > > snd_page_alloc arc4 snd_timer iwldvm mac80211 iwlwifi cfg80211 uvcvideo > > videobuf2_vmalloc videobuf2_memops videobuf2_core videodev snd media rfkill > > soundcore i2c_i801 mei r592 memstick iTCO_wdt iTCO_vendor_support lpc_ich > > tg3 coretemp microcode ppdev parport_pc parport vhost_net tun macvtap > > macvlan kvm_intel kvm uinput binfmt_misc firewire_oh > > :ci firewire_core crc_itu_t sdhci_pci sdhci mmc_core yenta_socket wmi video > > radeon i2c_algo_bit drm_kms_helper ttm drm i2c_core > > :Pid: 2219, comm: eclipse Not tainted 3.6.1-1.fc17.i686 #1 LENOVO > > 27326FG/27326FG > > :EIP: 0060:[<c0557577>] EFLAGS: 00010282 CPU: 1 > > :EIP is at __d_rehash+0x57/0x60 > > :EAX: ee641c80 EBX: 0000096a ECX: f7338208 EDX: f7338208 > > :ESI: fffffffe EDI: f6339f60 EBP: f0481d84 ESP: f0481d80 > > : DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 > > :CR0: 8005003b CR2: 06567f84 CR3: 30710000 CR4: 000027d0 > > :DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 > > :DR6: ffff0ff0 DR7: 00000400 > > :Process eclipse (pid: 2219, ti=f0480000 task=f0490c90 task.ti=f0480000) > > :Stack: > > : 0000096a f0481d90 c05575b2 ee641c80 f0481d9c c05575da 00000000 f0481dd8 > > : f9c01e32 f0734000 00004213 00000000 f0734000 f0481df4 f11ce600 00004213 > > : f6b07c60 00000000 00000000 f0481ef8 ee641c80 ef1781e0 f0481e20 f9c01f52 > > :Call Trace: > > : [<c05575b2>] _d_rehash+0x32/0x40 > > : [<c05575da>] d_rehash+0x1a/0x30 > > : [<f9c01e32>] cifs_lookup+0x212/0x300 [cifs] > > : [<f9c01f52>] cifs_atomic_open+0x32/0x200 [cifs] > > : [<c05584bf>] ? d_lookup+0x2f/0x50 > > : [<c055074c>] do_last+0x42c/0xbd0 > > : [<c054dd8c>] ? link_path_walk+0x1dc/0x750 > > : [<c0550f8d>] path_openat+0x9d/0x3b0 > > : [<c046d47f>] ? wake_up_state+0xf/0x20 > > : [<c0490ed2>] ? wake_futex+0x32/0x50 > > : [<c046fcb5>] ? __dequeue_entity+0x25/0x40 > > : [<c0551481>] do_filp_open+0x31/0x80 > > : [<c055bdfc>] ? alloc_fd+0x3c/0xe0 > > : [<c054c970>] ? getname_flags+0x40/0xd0 > > : [<c0542885>] do_sys_open+0xe5/0x1c0 > > : [<c05429d0>] sys_openat+0x30/0x40 > > : [<c095addf>] sysenter_do_call+0x12/0x28 > > :Code: 48 08 74 03 89 59 04 f6 c3 01 89 50 0c 75 20 f6 02 01 74 19 83 cb 01 > > 89 1a 0f ba 32 00 5b 5d c3 f3 90 8b 0a 80 e1 01 75 f7 eb b9 <0f> 0b 0f 0b > > 0f 0b 8d 76 00 55 89 e5 53 66 66 66 66 90 8b 0d fc > > :EIP: [<c0557577>] __d_rehash+0x57/0x60 SS:ESP 0068:f0481d80 > > > > I think what happened is something like the following: > > > > openat() was called on the file without O_CREAT. A negative dentry was > > already in the cache, and was successfully revalidated. At that point a > > hashed, negative dentry was passed to cifs_atomic_open. Since O_CREAT > > wasn't set, it punted it over to cifs_lookup which did a lookup and then > > tried to rehash the result and tripped over the bug. > > > > Fix this by simply returning -ENOENT in this case instead of calling > > cifs_lookup. For the longer term, I think cifs_atomic_open could use > > some cleanup. There is probably no reason to limit atomic opens to the > > O_CREAT case. > > > > Cc: <stable@xxxxxxxxxx> # 3.6.x > > Reported-and-Tested-by: Vit Zahradka <vit.zahradka@xxxxxxxxxx> > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > > --- > > Steve, > > It turns out that Marcus has hit an issue with this patch in place that > we don't fully understand yet: > > https://bugzilla.redhat.com/show_bug.cgi?id=867344#c25 > > I've asked Sachin to take a look, but it might be best to hold off on > pushing this to Linus until we understand the problem there. The problem here is that we will always receive a dentry without an associated inode. The difference is that some of these dentries are hashed ie. a negative lookup and some of these aren't hashed ie. cifs_lookup() is expected to lookup the inode details, update the dentry and hash it. This patch ends up returning -ENOENT for every open called which doesn't have the O_CREAT flag set and whose dentry hasn't been cached yet. I will be sending another patch which fixes this problem shortly. Sachin Prabhu -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
