Hello all,
Background story to the current problem.
I first started with 3 drives and set up btrfs with builtin raid0.
Initially I started out with 3 drives.
Distro is Gentoo and I was using distcc. Then I started noticing that
gcc would hang during compiling. Eventually I tracked down the problem
to distcc. Disabling distcc would fix gcc getting stuck. Then I began
investigating in the distcc folder what was going on in there. If I
recall correct du would get stuck on distcc folder. Because disabling it
distcc was enough I left it alone and forget.
Until I got a new drive that I wanted to add to the raid0. I am not to
sure which of the two but re-balancing would either get stuck or
segfault. So I thought it had something to do with that damn distcc
folder. Then manually I began deleting one by one folders and files in
the distcc directory. Many times rm, ls and du would get stuck because I
didn't know which folder and file were causing it. After many tries and
reboots (due to hanged processes) in the end I removed EVERYTHING in
distcc except for the folder and that single file.
>From then on, at around kernel 2.6.38, certain operations resulted in
kernel panics, which in turn required cold power cycle. I guess that
made things worse.
By the way I was using many features of btrfs, subvolumes, some
subvolumes with compression enabled, etc.
Damn single file!
This is my most recent attempts at mounting read only since I read that
in certain cases is possible to mount a btrfs system.
Booting Gentoo in qemu with safe drive options like this for the btrfs disks:
-drive file=/dev/sdX,cache=none,if=virtio
Linux kernel 3.0.0-rc1
Btrfs v0.19-35-g1b444cd-dirty
Steps to reproduce current kernel bug.
1. Loglevel set to 9:
echo 9 > /proc/sysrq-trigger
2. Load module:
modprobe -v btrfs
insmod /lib/modules/3.0.0-rc1/kernel/lib/libcrc32c.ko
insmod /lib/modules/3.0.0-rc1/kernel/lib/lzo/lzo_compress.ko
insmod
/lib/modules/3.0.0-rc1/kernel/lib/zlib_deflate/zlib_deflate.ko
insmod /lib/modules/3.0.0-rc1/kernel/fs/btrfs/btrfs.ko
3. Scan for drives:
btrfs device scan
252.491295] Btrfs loaded
[ 268.978445] device fsid 48487393f515c9b8-be3d620d5899c184
devid 4 transid 906477 /dev/vdd
[ 268.981717] device fsid 48487393f515c9b8-be3d620d5899c184
devid 3 transid 906477 /dev/vdb
[ 268.984638] device fsid 48487393f515c9b8-be3d620d5899c184
devid 5 transid 906477 /dev/vde
[ 268.987513] device fsid 48487393f515c9b8-be3d620d5899c184
devid 2 transid 906475 /dev/vdc
[ 320.198357] device fsid 48487393f515c9b8-be3d620d5899c184
devid 3 transid 906477 /dev/vdb
4. fstab entry:
cat /etc/fstab
/dev/vdb /mnt/btrfs btrfs noauto,ro,atime 0 1
5. Mount read only:
mount -v -o ro -t btrfs /dev/vdb /mnt/btrfs/
Segmentation fault
6. dmesg output:
[ 236.556931] Loglevel set to 9
[ 252.491295] Btrfs loaded
[ 268.978445] device fsid 48487393f515c9b8-be3d620d5899c184 devid 4
transid 906477 /dev/vdd
[ 268.981717] device fsid 48487393f515c9b8-be3d620d5899c184 devid 3
transid 906477 /dev/vdb
[ 268.984638] device fsid 48487393f515c9b8-be3d620d5899c184 devid 5
transid 906477 /dev/vde
[ 268.987513] device fsid 48487393f515c9b8-be3d620d5899c184 devid 2
transid 906475 /dev/vdc
[ 320.198357] device fsid 48487393f515c9b8-be3d620d5899c184 devid 3
transid 906477 /dev/vdb
[ 320.251194] parent transid verify failed on 4517304938496 wanted
906477 found 852489
[ 320.252957] BUG: scheduling while atomic: mount/1608/0x00000002
[ 320.254318] Modules linked in: btrfs zlib_deflate lzo_compress crc32c
libcrc32c usbhid hid uhci_hcd ehci_hcd usbcore
[ 320.256779] Pid: 1608, comm: mount Tainted: G W 3.0.0-rc1 #8
[ 320.258216] Call Trace:
[ 320.258774] [<ffffffff81031331>] __schedule_bug+0x61/0x70
[ 320.259856] [<ffffffff8149c41e>] schedule+0x85e/0x900
[ 320.260973] [<ffffffff810a8450>] ? __lock_page+0x70/0x70
[ 320.262189] [<ffffffff8149c51b>] io_schedule+0x5b/0x80
[ 320.263316] [<ffffffff810a8459>] sleep_on_page+0x9/0x10
[ 320.264469] [<ffffffff8149cdd7>] __wait_on_bit+0x57/0x80
[ 320.265646] [<ffffffff810a85fe>] wait_on_page_bit+0x6e/0x80
[ 320.266880] [<ffffffff8105cd20>] ?
autoremove_wake_function+0x40/0x40
[ 320.268276] [<ffffffffa00d5d7c>] ? submit_one_bio+0x7c/0xa0 [btrfs]
[ 320.269690] [<ffffffffa00db1a2>]
read_extent_buffer_pages+0x422/0x4d0 [btrfs]
[ 320.271339] [<ffffffffa00af0e0>] ? run_one_async_free+0x10/0x10
[btrfs]
[ 320.272859] [<ffffffffa00b0799>]
btree_read_extent_buffer_pages.clone.65+0x89/0xc0 [btrfs]
[ 320.274745] [<ffffffffa00b1b8c>] read_tree_block+0x3c/0x60 [btrfs]
[ 320.276136] [<ffffffffa00962fb>]
read_block_for_search.clone.37+0x1eb/0x410 [btrfs]
[ 320.277842] [<ffffffffa00e9c55>] ? btrfs_tree_lock+0x65/0xe0 [btrfs]
[ 320.279282] [<ffffffffa00995c3>] btrfs_search_slot+0x313/0xa30
[btrfs]
[ 320.280737] [<ffffffff810a85fe>] ? wait_on_page_bit+0x6e/0x80
[ 320.282011] [<ffffffffa00aa84f>] btrfs_find_last_root+0x5f/0x150
[btrfs]
[ 320.283551] [<ffffffffa00b247c>] find_and_setup_root+0x5c/0x120
[btrfs]
[ 320.284932] [<ffffffffa00b4f42>] open_ctree+0x1002/0x17b0 [btrfs]
[ 320.286346] [<ffffffff81272259>] ? vsnprintf+0x1f9/0x5d0
[ 320.287613] [<ffffffff812695ab>] ? ida_get_new_above+0x15b/0x1d0
[ 320.288925] [<ffffffff8114ee92>] ? disk_name+0xb2/0xc0
[ 320.290122] [<ffffffffa008f6cf>] btrfs_mount+0x3ff/0x5b0 [btrfs]
[ 320.291487] [<ffffffff810f5f62>] mount_fs+0x42/0x1b0
[ 320.292603] [<ffffffff8110e9b6>] ? alloc_vfsmnt+0xb6/0x1b0
[ 320.293752] [<ffffffff8110eb40>] vfs_kern_mount+0x50/0xb0
[ 320.294875] [<ffffffff8110fbbf>] do_kern_mount+0x4f/0x100
[ 320.296092] [<ffffffff8111166a>] do_mount+0x4fa/0x7d0
[ 320.297212] [<ffffffff810c0af3>] ? strndup_user+0x53/0x70
[ 320.298440] [<ffffffff81111cf3>] sys_mount+0x93/0xe0
[ 320.299587] [<ffffffff8149f252>] system_call_fastpath+0x16/0x1b
[ 320.301943] parent transid verify failed on 4517304938496 wanted
906477 found 852489
[ 320.303759] parent transid verify failed on 4517304938496 wanted
906477 found 852489
[ 320.305664] ------------[ cut here ]------------
[ 320.306540] kernel BUG at fs/btrfs/disk-io.c:1106!
[ 320.306540] invalid opcode: 0000 [#1] PREEMPT SMP
[ 320.306540] CPU 0
[ 320.306540] Modules linked in: btrfs zlib_deflate lzo_compress crc32c
libcrc32c usbhid hid uhci_hcd ehci_hcd usbcore
[ 320.306540]
[ 320.306540] Pid: 1608, comm: mount Tainted: G W 3.0.0-rc1 #8
Bochs Bochs
[ 320.306540] RIP: 0010:[<ffffffffa00b252f>] [<ffffffffa00b252f>]
find_and_setup_root+0x10f/0x120 [btrfs]
[ 320.306540] RSP: 0018:ffff88003a0c5b78 EFLAGS: 00010282
[ 320.306540] RAX: 00000000fffffffe RBX: ffff88003a29e000 RCX:
0000000000000100
[ 320.306540] RDX: 00000000fffffffb RSI: 0000000000018b90 RDI:
ffffea0000ccd650
[ 320.306540] RBP: ffff88003a0c5ba8 R08: ffffffffa00925d5 R09:
0000000000000000
[ 320.306540] R10: 0000000000000000 R11: 0000000000000000 R12:
ffff88003a29c800
[ 320.306540] R13: 0000000000000002 R14: ffff88003a2d0000 R15:
ffff880039e17000
[ 320.306540] FS: 00007f3b19270740(0000) GS:ffff88003fc00000(0000)
knlGS:0000000000000000
[ 320.306540] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 320.306540] CR2: 00000000014a1018 CR3: 000000003a478000 CR4:
00000000000006b0
[ 320.306540] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[ 320.306540] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7:
0000000000000400
[ 320.306540] Process mount (pid: 1608, threadinfo ffff88003a0c4000,
task ffff88003a397680)
[ 320.306540] Stack:
[ 320.306540] 0000000000000002 ffff880039e17000 ffff88003a0c5ba8
ffff88003a410000
[ 320.306540] ffff88003a29e000 ffff880039e17800 ffff88003a0c5cd8
ffffffffa00b4f42
[ 320.306540] 0000000000000003 ffffffff81272259 ffff880000000000
0000100000000000
[ 320.306540] Call Trace:
[ 320.306540] [<ffffffffa00b4f42>] open_ctree+0x1002/0x17b0 [btrfs]
[ 320.306540] [<ffffffff81272259>] ? vsnprintf+0x1f9/0x5d0
[ 320.306540] [<ffffffff812695ab>] ? ida_get_new_above+0x15b/0x1d0
[ 320.306540] [<ffffffff8114ee92>] ? disk_name+0xb2/0xc0
[ 320.306540] [<ffffffffa008f6cf>] btrfs_mount+0x3ff/0x5b0 [btrfs]
[ 320.306540] [<ffffffff810f5f62>] mount_fs+0x42/0x1b0
[ 320.306540] [<ffffffff8110e9b6>] ? alloc_vfsmnt+0xb6/0x1b0
[ 320.306540] [<ffffffff8110eb40>] vfs_kern_mount+0x50/0xb0
[ 320.306540] [<ffffffff8110fbbf>] do_kern_mount+0x4f/0x100
[ 320.306540] [<ffffffff8111166a>] do_mount+0x4fa/0x7d0
[ 320.306540] [<ffffffff810c0af3>] ? strndup_user+0x53/0x70
[ 320.306540] [<ffffffff81111cf3>] sys_mount+0x93/0xe0
[ 320.306540] [<ffffffff8149f252>] system_call_fastpath+0x16/0x1b
[ 320.306540] Code: 00 00 00 00 41 8b 94 24 00 03 00 00 eb a7 66 0f 1f
44 00 00 49 8b 3c 24 e8 7f 82 02 00 b8 fb ff ff ff e9 5d ff ff ff 31 ff
eb ed <0f> 0b 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5
[ 320.306540] RIP [<ffffffffa00b252f>] find_and_setup_root+0x10f/0x120
[btrfs]
[ 320.306540] RSP <ffff88003a0c5b78>
[ 320.364923] ---[ end trace 508a31f69047c113 ]---
[ 907.168103] flush-254:0 used greatest stack depth: 2888 bytes left
7. Second attempt results in mount getting stuck:
mount -v -o ro -t btrfs /dev/vdb /mnt/btrfs/
8. dmesg output for the above command is just one line:
[17645.438073] device fsid 48487393f515c9b8-be3d620d5899c184
devid 3 transid 906477 /dev/vdb
9. Output of ps:
ps aux | grep mount
root 1656 0.0 0.0 8248 628 pts/1 D+ 13:59 0:00
mount -v -o ro -t btrfs /dev/vdb /mnt/btrfs/
10. proc info of the stuck mount process:
cat /proc/1656/stack
[<ffffffff81273c43>] call_rwsem_down_write_failed+0x13/0x20
[<ffffffff810f5330>] sget+0x2e0/0x430
[<ffffffffa008f4cd>] btrfs_mount+0x1fd/0x5b0 [btrfs]
[<ffffffff810f5f62>] mount_fs+0x42/0x1b0
[<ffffffff8110eb40>] vfs_kern_mount+0x50/0xb0
[<ffffffff8110fbbf>] do_kern_mount+0x4f/0x100
[<ffffffff8111166a>] do_mount+0x4fa/0x7d0
[<ffffffff81111cf3>] sys_mount+0x93/0xe0
[<ffffffff8149f252>] system_call_fastpath+0x16/0x1b
[<ffffffffffffffff>] 0xffffffffffffffff
The damn SINGLE file!!
☹
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