Re: [PATCH] Btrfs: fix BUG_ON in btrfs_orphan_add() when delete unused block group

[Forrest Liu <forrestl@synology.com>]

Kernel BUG_ON when running following script on kernel 3.19-rc7

mntpath=/btrfs
loopdev=/dev/loop0
filepath=/volume2/100g_image

umount $mntpath
losetup -d $loopdev
truncate --size 1000g $filepath
losetup $loopdev $filepath
mkfs.btrfs -f $loopdev
mount $loopdev $mntpath

for i in `seq 1 1 100`; do
        echo "round $i"
        for j in `seq 1 1 1000`; do
                fallocate -l 1g $mntpath/$j
        done
        rm $mntpath/*
done

[  613.093084] ------------[ cut here ]------------
[  613.097928] kernel BUG at fs/btrfs/inode.c:3142!
[  613.105855] invalid opcode: 0000 [#1] SMP
[  613.112702] Modules linked in: coretemp(E) crc32_pclmul(E)
ghash_clmulni_intel(E) aesni_intel(E) snd_ens1371(E) snd_ac97_codec(E)
aes_x86_64(E) lrw(E) gf128mul(E) glue_helper(E) ppdev(E) ac97_bus(E)
ablk_helper(E) gameport(E) cryptd(E) snd_rawmidi(E) snd_seq_device(E)
snd_pcm(E) vmw_balloon(E) snd_timer(E) snd(E) soundcore(E)
serio_raw(E) vmwgfx(E) ttm(E) drm_kms_helper(E) drm(E) vmw_vmci(E)
parport_pc(E) shpchp(E) i2c_piix4(E) mac_hid(E) lp(E) parport(E)
btrfs(E) xor(E) raid6_pq(E) hid_generic(E) usbhid(E) hid(E) psmouse(E)
ahci(E) libahci(E) e1000(E) mptspi(E) mptscsih(E) mptbase(E) floppy(E)
vmw_pvscsi(E) vmxnet3(E)
[  613.144196] CPU: 0 PID: 1480 Comm: btrfs-cleaner Tainted: G
   E  3.19.0-rc7-custom #2
[  613.148501] Hardware name: VMware, Inc. VMware Virtual
Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013
[  613.152694] task: ffff880035cdb1a0 ti: ffff880039cf4000 task.ti:
ffff880039cf4000
[  613.154969] RIP: 0010:[<ffffffffa01441c2>]  [<ffffffffa01441c2>]
btrfs_orphan_add+0x1d2/0x1e0 [btrfs]
[  613.157780] RSP: 0018:ffff880039cf7c48  EFLAGS: 00010286
[  613.159560] RAX: 00000000ffffffe4 RBX: ffff88003bd981a0 RCX: ffff88003c9e4000
[  613.161904] RDX: 0000000000002244 RSI: 0000000000040000 RDI: ffff88003c9e4138
[  613.164264] RBP: ffff880039cf7c88 R08: 000060ffc0000850 R09: 0000000000000000
[  613.166507] R10: ffff88003bc4b7a0 R11: ffffea0000eb6740 R12: ffff88003c9c0000
[  613.168681] R13: ffff88003c102160 R14: ffff88003c9c0458 R15: 0000000000000001
[  613.170932] FS:  0000000000000000(0000) GS:ffff88003f600000(0000)
knlGS:0000000000000000
[  613.173316] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  613.175227] CR2: 00007f6343537000 CR3: 0000000036329000 CR4: 00000000000407f0
[  613.177554] Stack:
[  613.178712]  ffff880039cf7c88 ffffffffa0182a54 ffff88003c9e4b04
ffff88003c9c7800
[  613.181297]  ffff88003bc4b7a0 ffff88003bd981a0 ffff88003c8db200
ffff88003c2fcc60
[  613.183782]  ffff880039cf7d18 ffffffffa012da97 ffff88003bc4b7a4
ffff88003bc4b7a0
[  613.186171] Call Trace:
[  613.187493]  [<ffffffffa0182a54>] ?
lookup_free_space_inode+0x44/0x100 [btrfs]
[  613.189801]  [<ffffffffa012da97>]
btrfs_remove_block_group+0x137/0x740 [btrfs]
[  613.192126]  [<ffffffffa0166912>] btrfs_remove_chunk+0x672/0x780 [btrfs]
[  613.194267]  [<ffffffffa012e2ff>] btrfs_delete_unused_bgs+0x25f/0x280 [btrfs]
[  613.196567]  [<ffffffffa0135e4c>] cleaner_kthread+0x12c/0x190 [btrfs]
[  613.198687]  [<ffffffffa0135d20>] ? check_leaf+0x350/0x350 [btrfs]
[  613.200758]  [<ffffffff8108f232>] kthread+0xd2/0xf0
[  613.202616]  [<ffffffff8108f160>] ? kthread_create_on_node+0x180/0x180
[  613.204738]  [<ffffffff8175dabc>] ret_from_fork+0x7c/0xb0
[  613.206652]  [<ffffffff8108f160>] ? kthread_create_on_node+0x180/0x180
[  613.208741] Code: ff ff 0f 1f 80 00 00 00 00 89 45 c8 3e 80 63 80
fd 48 89 df e8 d0 23 fe ff 8b 45 c8 e9 14 ff ff ff b8 f4 ff ff ff e9
12 ff ff ff <0f> 0b 66 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 66 66 90
55 48
[  613.216562] RIP  [<ffffffffa01441c2>] btrfs_orphan_add+0x1d2/0x1e0 [btrfs]
[  613.218828]  RSP <ffff880039cf7c48>
[  613.220382] ---[ end trace 71073106deb8a457 ]---

The patch fix problem of BUG_ON

Thanks,
Forrest

2015-02-02 16:08 GMT+08:00 Forrest Liu <forrestl@synology.com>:
> btrfs_orphan_reserve_metadata() will grab metadata reservation from
> transaction handle, and the transaction handle was passed from
> btrfs_delete_unused_bgs() when delete unused block group.
>
> Repace btrfs_join_transaction() with btrfs_start_transaction() in
> btrfs_delete_unused_bgs() to prevent BUG_ON() in btrfs_orphan_add()
>
> Signed-off-by: Forrest Liu <forrestl@synology.com>
> ---
>  fs/btrfs/extent-tree.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 53294da..61a3255 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -9548,7 +9548,8 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
>                  * Want to do this before we do anything else so we can recover
>                  * properly if we fail to join the transaction.
>                  */
> -               trans = btrfs_join_transaction(root);
> +               /* 1 for btrfs_orphan_reserve_metadata() */
> +               trans = btrfs_start_transaction(root, 1);
>                 if (IS_ERR(trans)) {
>                         btrfs_set_block_group_rw(root, block_group);
>                         ret = PTR_ERR(trans);
> --
> 1.9.1
>