From: Anand Jain <anand.jain@oracle.com>
To: dsterba@suse.cz, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 4/4] btrfs: sysfs, add devid/dev_state kobject and attribute
Date: Sat, 14 Dec 2019 08:26:24 +0800 [thread overview]
Message-ID: <1faa5860-130a-9f3c-3e44-724ce9a26adb@oracle.com> (raw)
In-Reply-To: <20191213170215.GB3929@twin.jikos.cz>
On 14/12/19 1:02 AM, David Sterba wrote:
> On Fri, Dec 13, 2019 at 05:43:32PM +0100, David Sterba wrote:
>>> Looked into this further, actually we don't need any lock here
>>> the device delete thread which calls kobject_put() makes sure
>>> sysfs read is closed. So an existing sysfs read thread will have
>>> to complete before device free.
>>>
>>>
>>> CPU1 CPU2
>>>
>>> btrfs_rm_device
>>> open file
>>> btrfs_sysfs_rm_device_link
>>> call read, access freed device
>>> sysfs waits for the open file
>>> to close.
>>
>> How exactly does sysfs wait for the device? Is it eg wait_event checking
>> number of references? If the file stays open by an evil process is it
>> going to block the device removal indefinitelly?
>
> Yeah, sysfs waits until the file is closed. Eg. umount can be stalled
> that way too.
>
And similar to umount, I don't think we should return EBUSY
for btrfs_rm_device if the device sysfs attribute is opened,
as sysfs show attributes are non blocking and would be completed
in the timely manner.
regards, Anand
next prev parent reply other threads:[~2019-12-14 0:26 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-05 11:27 [PATCH 0/4] btrfs, sysfs cleanup and add dev_state Anand Jain
2019-12-05 11:27 ` [PATCH 1/4] btrfs: sysfs, use btrfs_sysfs_remove_fsid in fail return in add_fsid Anand Jain
2019-12-05 11:27 ` [PATCH 2/4] btrfs: sysfs, add UUID/devinfo kobject Anand Jain
2020-01-14 18:32 ` David Sterba
2020-02-03 10:40 ` Anand Jain
2019-12-05 11:27 ` [PATCH v2 3/4] btrfs: sysfs, rename device_link add,remove functions Anand Jain
2019-12-05 11:27 ` [PATCH 4/4] btrfs: sysfs, add devid/dev_state kobject and attribute Anand Jain
2019-12-05 14:10 ` David Sterba
2019-12-05 14:38 ` Anand Jain
2019-12-05 14:21 ` David Sterba
2019-12-05 14:38 ` Anand Jain
2019-12-05 15:14 ` David Sterba
2019-12-06 13:49 ` Anand Jain
2019-12-09 14:05 ` Anand Jain
2019-12-09 18:31 ` David Sterba
2019-12-13 16:43 ` David Sterba
2019-12-13 17:02 ` David Sterba
2019-12-14 0:26 ` Anand Jain [this message]
2020-01-06 16:00 ` David Sterba
2019-12-09 14:06 ` [PATCH v2 " Anand Jain
2019-12-19 10:41 ` [PATCH v3 " Anand Jain
2020-01-06 11:38 ` [PATCH v4] " Anand Jain
2020-01-09 15:20 ` [PATCH v4 4/4] " David Sterba
2020-01-10 1:03 ` Anand Jain
2019-12-05 15:00 ` [PATCH 0/4] btrfs, sysfs cleanup and add dev_state David Sterba
2019-12-06 13:46 ` Anand Jain
2019-12-09 14:09 ` Anand Jain
2019-12-09 22:48 ` Anand Jain
2019-12-10 16:41 ` David Sterba
2020-01-14 18:39 ` David Sterba
2020-01-15 8:22 ` [PATCH] btrfs: update devid after replace Anand Jain
2020-01-15 16:17 ` David Sterba
2020-01-20 19:10 ` David Sterba
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