On 03/31/2016 06:17 AM, Yauhen Kharuzhy wrote:
On Tue, Mar 29, 2016 at 10:40:40PM +0300, Yauhen Kharuzhy wrote:
Hi.
I am testing hotspare v2 on kernel v4.4.5 (I will try latest Chris' tree later)
now with lockdep debugging enabled. At starting of replacement, lockdep warning is displayed,
because kstrdup() is called with GFP_NOFS inside of rcu_read_lock/unlock()
block (GFP_NOFS can sleep).
Similar thing in the btrfs_auto_replace_start(): rcu_str_deref() without
rcu_read_lock():
int btrfs_auto_replace_start(struct btrfs_root *root,
struct btrfs_device *src_device)
{
int ret;
char *tgt_path;
if (btrfs_get_spare_device(&tgt_path)) {
btrfs_err(root->fs_info,
"No spare device found/configured in the kernel");
return -EINVAL;
}
ret = btrfs_dev_replace_start(root, tgt_path,
src_device->devid,
rcu_str_deref(src_device->name),
This is fixed in V3.
Thanks, Anand
BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID);
if (ret)
btrfs_put_spare_device(tgt_path);
kfree(tgt_path);
return 0;
}
[ 156.168133] ===============================
[ 156.168963] [ INFO: suspicious RCU usage. ]
[ 156.169822] 4.4.5-scst31x+ #20 Not tainted
[ 156.170656] -------------------------------
[ 156.171488] fs/btrfs/dev-replace.c:990 suspicious rcu_dereference_check() usage!
[ 156.172920]
[ 156.172920] other info that might help us debug this:
[ 156.172920]
[ 156.174825]
[ 156.174825] rcu_scheduler_active = 1, debug_locks = 0
[ 156.176152] 1 lock held by btrfs-casualty/4807:
[ 156.181917] #0: (&fs_info->casualty_mutex){+.+...}, at: [<ffffffffa0165364>] casualty_kthread+0x64/0x390 [btrfs]
[ 156.193511]
[ 156.193511] stack backtrace:
[ 156.194680] CPU: 0 PID: 4807 Comm: btrfs-casualty Not tainted 4.4.5-scst31x+ #20
[ 156.201650] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[ 156.219100] 0000000000000000 ffff88005d79fda0 ffffffff813529e3 ffff88005e19c600
[ 156.221216] 0000000000000001 ffff88005d79fdd0 ffffffff810d6407 0000000000000000
[ 156.224287] 0000000000000000 ffff88005f4a0c00 ffff88005da36000 ffff88005d79fe08
[ 156.226375] Call Trace:
[ 156.227078] [<ffffffff813529e3>] dump_stack+0x85/0xc2
[ 156.228152] [<ffffffff810d6407>] lockdep_rcu_suspicious+0xd7/0x110
[ 156.229418] [<ffffffffa01e6236>] btrfs_auto_replace_start+0xa6/0xd0 [btrfs]
[ 156.230714] [<ffffffffa01655c4>] casualty_kthread+0x2c4/0x390 [btrfs]
[ 156.231915] [<ffffffffa016549c>] ? casualty_kthread+0x19c/0x390 [btrfs]
[ 156.233105] [<ffffffffa0165300>] ? btrfs_check_devices+0x200/0x200 [btrfs]
[ 156.234339] [<ffffffff810a70df>] kthread+0xef/0x110
[ 156.235309] [<ffffffff810dc081>] ? __raw_callee_save___pv_queued_spin_unlock+0x11/0x20
[ 156.236940] [<ffffffff810a6ff0>] ? kthread_create_on_node+0x200/0x200
[ 156.239489] [<ffffffff81637c2f>] ret_from_fork+0x3f/0x70
[ 156.240533] [<ffffffff810a6ff0>] ? kthread_create_on_node+0x200/0x200
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