Summary is, existing btrfs fs is made into a seed device, mounting it mounts
read-only, add device to it, unmount, then mount again so it mounts rw, then
delete the seed device. I expect that everything on the seed device is moved to
the newly added device, while the seed device is unchanged (to later unmake it
a seed device). Idea is to make a fairly exactly copy of an existing device
including all subvolumes.
What actually happens is an oops upon device delete.
Setup:
kernel 3.15.0-0.rc5.git0.1.fc21.x86_64
btrfs-progs 3.14
/dev/sdb2 = existing btrfs fs
/dev/sdc3 = unformatted partition
Steps:
# btrfstune -S1 /dev/sdb2
# mount /dev/sdb2 /mnt
mount: /dev/sdb2 is write-protected, mounting read-only
# btrfs device add /dev/sdc3 /mnt
Performing full device TRIM (75.90GiB) ...
# btrfs fi show
Label: 'rawhide' uuid: d372e5d1-386f-460c-b036-611469e0155e
Total devices 1 FS bytes used 7.55GiB
devid 1 size 79.31GiB used 11.04GiB path /dev/sda3
btrfs: utils.c:1769: get_fs_info: Assertion `!(ndevs >= fi_args->num_devices)'
failed. ## previously reported subject "bug adding device to seed device,
btrfs fi show fails"
# umount /mnt
# mount /dev/sdc3 /mnt
# btrfs device delete /dev/sdb2 /mnt
[ 778.992693] BTRFS info (device sdb2): relocating block group 20464009216
flags 2
##mount rw occurs here
[ 1200.019460] BTRFS info (device sdc3): disk space caching is enabled
[ 1200.036656] BTRFS: checking UUID tree
[ 1200.037194] SELinux: initialized (dev sdc3, type btrfs), uses xattr
[ 1220.761243] BUG: unable to handle kernel NULL pointer dereference at
00000000000001e8
[ 1220.761433] IP: [<ffffffffa00d3883>] btrfs_shrink_device+0x33/0x420 [btrfs]
[ 1220.761614] PGD 7fe9e067 PUD 80379067 PMD 0
[ 1220.761758] Oops: 0000 [#1] SMP
[ 1220.761979] Modules linked in: fuse msdos xfs libcrc32c xt_CHECKSUM
ipt_MASQUERADE tun ip6t_rpfilter ip6t_REJECT xt_conntrack ebtable_nat
ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat
nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security
ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4
nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security
iptable_raw vfat fat ppdev sunrpc serio_raw microcode parport_pc parport
virtio_net i2c_piix4 i2c_core btrfs xor raid6_pq virtio_pci virtio virtio_ring
ata_generic pata_acpi
[ 1220.761979] CPU: 0 PID: 3469 Comm: btrfs Not tainted
3.15.0-0.rc5.git0.1.fc21.x86_64 #1
[ 1220.761979] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS
VirtualBox 12/01/2006
[ 1220.761979] task: ffff88007ff413a0 ti: ffff88009e376000 task.ti:
ffff88009e376000
[ 1220.761979] RIP: 0010:[<ffffffffa00d3883>] [<ffffffffa00d3883>]
btrfs_shrink_device+0x33/0x420 [btrfs]
[ 1220.761979] RSP: 0018:ffff88009e377c58 EFLAGS: 00010246
[ 1220.761979] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 1220.761979] RDX: 000000000000000f RSI: 0000000000000000 RDI: ffff88003e04fc00
[ 1220.761979] RBP: ffff88009e377ce8 R08: 0000000000000000 R09: 00000000000000c1
[ 1220.761979] R10: ffff88003e04fc00 R11: 0000000000000020 R12: ffff88009453ebc8
[ 1220.761979] R13: 0000000000000001 R14: 0000000000000000 R15: ffff88003e04fc00
[ 1220.761979] FS: 00007f18f112e880(0000) GS:ffff88009d400000(0000)
knlGS:0000000000000000
[ 1220.761979] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 1220.761979] CR2: 00000000000001e8 CR3: 000000007fd6b000 CR4: 00000000000006f0
[ 1220.761979] Stack:
[ 1220.761979] 00000000c3c73881 ffffffff812231fd ffff88009453ebc8
0000000000000082
[ 1220.761979] 0000000000000000 ffff88009e377d18 ffff88009e377cb8
ffffffffa00ce482
[ 1220.761979] ffff88009f3fa900 ffff8800853be020 ffff8800853be10b
0000000000000001
[ 1220.761979] Call Trace:
[ 1220.761979] [<ffffffff812231fd>] ? _submit_bh+0x15d/0x230
[ 1220.761979] [<ffffffffa00ce482>] ? __find_device+0x52/0x80 [btrfs]
[ 1220.761979] [<ffffffffa00d6784>] btrfs_rm_device+0x2e4/0x880 [btrfs]
[ 1220.761979] [<ffffffffa00e0db5>] btrfs_ioctl+0x1f95/0x2880 [btrfs]
[ 1220.761979] [<ffffffff811a57cf>] ? handle_mm_fault+0x6bf/0x10f0
[ 1220.761979] [<ffffffff811fa692>] ? final_putname+0x22/0x50
[ 1220.761979] [<ffffffff811fa949>] ? putname+0x29/0x40
[ 1220.761979] [<ffffffff81200f32>] ? user_path_at_empty+0x72/0xd0
[ 1220.761979] [<ffffffff8170c2fc>] ? __do_page_fault+0x26c/0x580
[ 1220.761979] [<ffffffff811f4427>] ? cp_new_stat+0x157/0x190
[ 1220.761979] [<ffffffff81203670>] do_vfs_ioctl+0x2d0/0x4b0
[ 1220.761979] [<ffffffff812038d1>] SyS_ioctl+0x81/0xa0
[ 1220.761979] [<ffffffff817119e9>] system_call_fastpath+0x16/0x1b
[ 1220.761979] Code: e5 41 57 41 56 41 55 41 54 49 89 ff 53 48 89 f3 48 83 ec
68 4c 8b 77 28 48 89 75 90 65 48 8b 04 25 28 00 00 00 48 89 45 d0 31 c0 <49> 8b
86 e8 01 00 00 48 8b 80 c0 02 00 00 48 89 85 78 ff ff ff
[ 1220.761979] RIP [<ffffffffa00d3883>] btrfs_shrink_device+0x33/0x420 [btrfs]
[ 1220.761979] RSP <ffff88009e377c58>
[ 1220.761979] CR2: 00000000000001e8
[ 1220.803856] ---[ end trace 8df409055cb58c83 ]---
Chris Murphy
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