Hi there, while playing with snapshots for btrfs send, I also encountered seemingly duplicate inodes, which are multiple BTRFS_EMPTY_SUBVOL_DIR_OBJECTID objects within the same directory. I can imagine software that feels uncomfortable, here. Such objects are created by btrfs_lookup_dentry() in fs/btrfs/inode.c when ENOENT is encountered. The main purpose for this email is to ask: Is this going to stay like that? David Sterba sent a related issue some days ago with effects seen on dcache level (subject: "WARNING: at fs/dcache.c:1256 d_set_d_op+0xaa/0xc0() , nested snapshots"). I hit a bug when trying to rename(2) one of those objects, and I'm still hitting it reproducably on 3.1-rc5. However, I cannot reproduce it with the current for-linus branch (3.1-rc6). I don't see a commit I'd expect to fix this, but it may be fixed: -- Oct 17 13:28:26 oglaroon kernel: [266945.208573] btrfs failed to delete reference to snap2, inode 257 parent 256 Oct 17 13:28:26 oglaroon kernel: [266945.208586] ------------[ cut here ]------------ Oct 17 13:28:26 oglaroon kernel: [266945.264688] kernel BUG at fs/btrfs/inode.c:6907! Oct 17 13:28:26 oglaroon kernel: [266945.320807] invalid opcode: 0000 [#1] SMP Oct 17 13:28:26 oglaroon kernel: [266945.370907] CPU 2 Oct 17 13:28:26 oglaroon kernel: [266945.393831] Modules linked in: btrfs mpt2sas scsi_transport_sas raid_class [last unloaded: btrfs] Oct 17 13:28:26 oglaroon kernel: [266945.503578] Oct 17 13:28:26 oglaroon kernel: [266945.522353] Pid: 29567, comm: mv Not tainted 3.1.0-rc4+ #5 Supermicro X8SIL/X8SIL Oct 17 13:28:26 oglaroon kernel: [266945.613011] RIP: 0010:[<ffffffffa06d906a>] [<ffffffffa06d906a>] btrfs_rename+0x42a/0x770 [btrfs] Oct 17 13:28:26 oglaroon kernel: [266945.720059] RSP: 0018:ffff88022f933c78 EFLAGS: 00010282 Oct 17 13:28:26 oglaroon kernel: [266945.784476] RAX: 00000000fffffffe RBX: 000000003b2456a4 RCX: 0000000000000054 Oct 17 13:28:26 oglaroon kernel: [266945.870675] RDX: 0000000000000053 RSI: 000060fdc00042c0 RDI: ffff880234330000 Oct 17 13:28:26 oglaroon kernel: [266945.956874] RBP: ffff88022f933d48 R08: 0000000000000000 R09: 0000000000000001 Oct 17 13:28:26 oglaroon kernel: [266946.043072] R10: 0000000000000006 R11: 0000000000000000 R12: 000000004e9c1157 Oct 17 13:28:26 oglaroon kernel: [266946.129270] R13: ffff880234468368 R14: 0000000000000000 R15: ffff880234446d58 Oct 17 13:28:26 oglaroon kernel: [266946.215471] FS: 00007f3bf0b96700(0000) GS:ffff88023fc80000(0000) knlGS:0000000000000000 Oct 17 13:28:26 oglaroon kernel: [266946.313080] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Oct 17 13:28:26 oglaroon kernel: [266946.382681] CR2: 00007f3bf0072110 CR3: 000000015c05f000 CR4: 00000000000006e0 Oct 17 13:28:26 oglaroon kernel: [266946.468880] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 Oct 17 13:28:26 oglaroon kernel: [266946.555079] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Oct 17 13:28:26 oglaroon kernel: [266946.641278] Process mv (pid: 29567, threadinfo ffff88022f932000, task ffff880234330000) Oct 17 13:28:26 oglaroon kernel: [266946.737849] Stack: Oct 17 13:28:26 oglaroon kernel: [266946.762849] 000000000000000a 0000000000000006 00000000000000d0 0000000000000000 Oct 17 13:28:26 oglaroon kernel: [266946.852574] ffff88022f933c01 0000000000000101 00ff8802346b4158 ffff8802349b81b8 Oct 17 13:28:26 oglaroon kernel: [266946.942299] 0000000000000000 ffff88022f9e7000 ffff88022f9e7000 ffff88019d4b6aa8 Oct 17 13:28:26 oglaroon kernel: [266947.032025] Call Trace: Oct 17 13:28:26 oglaroon kernel: [266947.062215] [<ffffffff81189ea2>] vfs_rename+0x162/0x3e0 Oct 17 13:28:26 oglaroon kernel: [266947.126629] [<ffffffff8118bfb9>] sys_renameat+0x239/0x270 Oct 17 13:28:26 oglaroon kernel: [266947.193120] [<ffffffff8187568c>] ? do_page_fault+0x20c/0x450 Oct 17 13:28:26 oglaroon kernel: [266947.262722] [<ffffffff818723ca>] ? retint_swapgs+0xe/0x13 Oct 17 13:28:26 oglaroon kernel: [266947.329214] [<ffffffff810c84dd>] ? trace_hardirqs_on_caller+0xfd/0x190 Oct 17 13:28:26 oglaroon kernel: [266947.409185] [<ffffffff8118c006>] sys_rename+0x16/0x20 Oct 17 13:28:26 oglaroon kernel: [266947.471527] [<ffffffff8187983b>] system_call_fastpath+0x16/0x1b Oct 17 13:28:26 oglaroon kernel: [266947.544240] Code: 68 ff ff ff 48 8b 4a 30 44 8b 4a 24 4c 8b 42 28 48 8b 55 90 4c 89 95 58 ff ff ff 44 88 9d 50 ff ff ff e8 ba c0 ff ff 85 c0 74 4a <0f> 0b eb fe 48 8b 45 80 48 8b b8 20 01 00 00 88 95 48 ff ff ff Oct 17 13:28:26 oglaroon kernel: [266947.777216] RIP [<ffffffffa06d906a>] btrfs_rename+0x42a/0x770 [btrfs] Oct 17 13:28:26 oglaroon kernel: [266947.856259] RSP <ffff88022f933c78> Oct 17 13:28:26 oglaroon kernel: [266947.899234] ---[ end trace fd19520e3af48c17 ]--- -- Reproducer for the curious: # mkfs.btrfs /dev/sdv2 # mount /dev/sdv2 /mnt # btrfs subvol snap /mnt /mnt/snap1 # btrfs subvol snap /mnt /mnt/snap2 # btrfs subvol snap /mnt /mnt/snap3 When snap2 was created, there was a dir item for snap1, so this is no surprise: # ls -lai /mnt/snap2 total 8 256 dr-xr-xr-x 1 root root 20 Jan 1 1970 . 256 dr-xr-xr-x 1 root root 30 Jan 1 1970 .. 2 drwxr-xr-x 1 root root 0 Oct 18 16:25 snap1 Inode 2 seems a bit strange, but stay tuned. When snap3 was created, there were dir items for snap1 and snap2, so ... *drumroll* # ls -lai /mnt/snap3 total 8 256 dr-xr-xr-x 1 root root 30 Jan 1 1970 . 256 dr-xr-xr-x 1 root root 30 Jan 1 1970 .. 2 drwxr-xr-x 1 root root 0 Oct 18 16:26 snap1 2 drwxr-xr-x 1 root root 0 Oct 18 16:26 snap2 -Jan -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
