On Fri, Mar 12, 2021 at 01:57:32PM +0800, Anand Jain wrote: > > > On 12/3/21 1:52 pm, Anand Jain wrote: > > On 12/3/21 12:23 am, Josef Bacik wrote: > >> Neal reported a panic trying to use -o rescue=all > >> > >> BUG: kernel NULL pointer dereference, address: 0000000000000030 > >> PGD 0 P4D 0 > >> Oops: 0000 [#1] SMP NOPTI > >> CPU: 0 PID: 696 Comm: mount Tainted: G W 5.12.0-rc2+ #296 > >> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 > >> 04/01/2014 > >> RIP: 0010:btrfs_device_init_dev_stats+0x1d/0x200 > >> RSP: 0018:ffffafaec1483bb8 EFLAGS: 00010286 > >> RAX: 0000000000000000 RBX: ffff9a5715bcb298 RCX: 0000000000000070 > >> RDX: ffff9a5703248000 RSI: ffff9a57052ea150 RDI: ffff9a5715bca400 > >> RBP: ffff9a57052ea150 R08: 0000000000000070 R09: ffff9a57052ea150 > >> R10: 000130faf0741c10 R11: 0000000000000000 R12: ffff9a5703700000 > >> R13: 0000000000000000 R14: ffff9a5715bcb278 R15: ffff9a57052ea150 > >> FS: 00007f600d122c40(0000) GS:ffff9a577bc00000(0000) > >> knlGS:0000000000000000 > >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >> CR2: 0000000000000030 CR3: 0000000112a46005 CR4: 0000000000370ef0 > >> Call Trace: > >> ? btrfs_init_dev_stats+0x1f/0xf0 > >> ? kmem_cache_alloc+0xef/0x1f0 > >> btrfs_init_dev_stats+0x5f/0xf0 > >> open_ctree+0x10cb/0x1720 > >> btrfs_mount_root.cold+0x12/0xea > >> legacy_get_tree+0x27/0x40 > >> vfs_get_tree+0x25/0xb0 > >> vfs_kern_mount.part.0+0x71/0xb0 > >> btrfs_mount+0x10d/0x380 > >> legacy_get_tree+0x27/0x40 > >> vfs_get_tree+0x25/0xb0 > >> path_mount+0x433/0xa00 > >> __x64_sys_mount+0xe3/0x120 > >> do_syscall_64+0x33/0x40 > >> entry_SYSCALL_64_after_hwframe+0x44/0xae > >> > >> This happens because when we call btrfs_init_dev_stats we do > >> device->fs_info->dev_root. However device->fs_info isn't init'ed > >> because we were only calling btrfs_init_devices_late() if we properly > >> read the device root. > > > > > >> However we don't actually need the device root to > >> init the devices, this function simply assigns the devices their > >> ->fs_info pointer properly, so this needs to be done unconditionally > >> always so that we can properly deref device->fs_info in rescue cases. > > > > btrfs_device_init_dev_stats() calls btrfs_search_slot() leading > > to btrfs_search_slot_get_root(), and does de-reference root (dev_root) > > to get fs_info. > > Never mind. patch 2/3 handles it. Spoke too early. > Maybe can reorder the patches during integration.
I think swapping the order makes sense, though all the patches fix some sort of crash, the number should be decreasing.
