From: Josef Bacik <josef@toxicpanda.com>
To: Anand Jain <anand.jain@oracle.com>, linux-btrfs@vger.kernel.org
Cc: dsterba@suse.com
Subject: Re: [PATCH 01/11] btrfs: initialize sysfs devid and device link for seed device
Date: Mon, 31 Aug 2020 12:21:52 -0400 [thread overview]
Message-ID: <1df53e43-2ec8-8e67-8a79-ec90782e9e3a@toxicpanda.com> (raw)
In-Reply-To: <2db650ec206db1cb3e68590951b59e222fb10116.1598792561.git.anand.jain@oracle.com>
On 8/30/20 10:40 AM, Anand Jain wrote:
> The following test case leads to null kobject-being-freed error.
>
> mount seed /mnt
> add sprout to /mnt
> umount /mnt
> mount sprout to /mnt
> delete seed
>
> kobject: '(null)' (00000000dd2b87e4): is not initialized, yet kobject_put() is being called.
> WARNING: CPU: 1 PID: 15784 at lib/kobject.c:736 kobject_put+0x80/0x350
> RIP: 0010:kobject_put+0x80/0x350
> ::
> Call Trace:
> btrfs_sysfs_remove_devices_dir+0x6e/0x160 [btrfs]
> btrfs_rm_device.cold+0xa8/0x298 [btrfs]
> btrfs_ioctl+0x206c/0x22a0 [btrfs]
> ksys_ioctl+0xe2/0x140
> __x64_sys_ioctl+0x1e/0x29
> do_syscall_64+0x96/0x150
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x7f4047c6288b
> ::
>
> This is because, at the end of the seed device-delete, we try to remove
> the seed's devid sysfs entry. But for the seed devices under the sprout
> fs, we don't initialize the devid kobject yet. So this patch initializes
> the seed device devid kobject and the device link in the sysfs. This takes
> care of the Warning.
>
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
Ok again, this will not work.
Mount a seed fs, you get fs_info->fs_devices pointed at the seed device, and
fs_info->fs_devices->devices_kobj is what is initialized.
Now you sprout.
This does clone_fs_devices(fs_info->fs_devices), which doesn't copy over
fs_fdevices->devices_kobj. Now we take this clone device, and set
fs_info->fsdevices to the cloned fs_devices, and we add the original fs_devices,
which had the sysfs objects init'ed already, to fs_devices->seed_list.
It appears to me you are completely ignoring this aspect of sprout. Maybe I'm
missing something, but I've gone through this code twice now to see if what I
think is happening is actually happening, and I'm convinced this is wrong.
If it's _not_ wrong, and I _am_ missing something, then you need to explain why
I'm wrong, and then go back and fix what needs to be fixed to make this whole
process more clear, and _then_ you can do this patch series. Thanks,
Josef
next prev parent reply other threads:[~2020-08-31 16:22 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-31 1:38 [PATCH 0/11] btrfs: seed fix null ptr, use only main device_list_mutex, and cleanups Anand Jain
2020-08-21 13:15 ` [PATCH RFC] btrfs/163: replace sprout instead of seed Anand Jain
2020-08-21 13:15 ` [PATCH 1/2] btrfs: initialize sysfs devid and device link for seed device Anand Jain
2020-08-21 13:15 ` [PATCH RFC 2/2] btrfs: fix replace of " Anand Jain
2020-08-21 14:38 ` Josef Bacik
2020-08-23 15:05 ` Anand Jain
2020-08-21 14:36 ` [PATCH 1/2] btrfs: initialize sysfs devid and device link for " Josef Bacik
2020-08-23 13:05 ` Anand Jain
2020-08-29 11:44 ` Anand Jain
2020-08-30 14:41 ` [PATCH] fstests: btrfs/163: replace sprout instead of seed Anand Jain
2020-08-30 14:40 ` Anand Jain
2020-08-30 14:40 ` [PATCH 01/11] btrfs: initialize sysfs devid and device link for seed device Anand Jain
2020-08-31 9:07 ` Nikolay Borisov
2020-08-31 12:00 ` Anand Jain
2020-08-31 16:21 ` Josef Bacik [this message]
2020-09-01 16:16 ` Anand Jain
2020-08-30 14:40 ` [PATCH 02/11] btrfs: refactor btrfs_sysfs_add_devices_dir Anand Jain
2020-08-30 14:40 ` [PATCH 03/11] btrfs: refactor btrfs_sysfs_remove_devices_dir Anand Jain
2020-08-31 8:58 ` Nikolay Borisov
2020-08-31 9:12 ` Anand Jain
2020-08-30 14:40 ` [PATCH 04/11] btrfs: reada: use sprout device_list_mutex Anand Jain
2020-08-31 8:54 ` Nikolay Borisov
2020-08-31 16:08 ` Josef Bacik
2020-09-01 9:02 ` Anand Jain
2020-08-30 14:41 ` [PATCH 05/11] btrfs: btrfs_init_devices_late: " Anand Jain
2020-08-31 8:37 ` Nikolay Borisov
2020-09-01 8:54 ` Anand Jain
2020-08-30 14:41 ` [PATCH 06/11] btrfs: open code list_head pointer in btrfs_init_dev_replace_tgtdev Anand Jain
2020-08-31 8:38 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 07/11] btrfs: cleanup btrfs_remove_chunk Anand Jain
2020-08-31 8:43 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 08/11] btrfs: cleanup btrfs_assign_next_active_device() Anand Jain
2020-08-31 8:44 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 09/11] btrfs: cleanup unnecessary goto in open_seed_device Anand Jain
2020-08-31 8:44 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 10/11] btrfs: btrfs_dev_replace_update_device_in_mapping_tree drop file global declare Anand Jain
2020-08-31 8:46 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 11/11] btrfs: fix replace of seed device Anand Jain
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