From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
To: clm@fb.com, josef@toxicpanda.com, dsterba@suse.com
Cc: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>,
anand.jain@oracle.com, linux-btrfs@vger.kernel.org,
linux-kernel@vger.kernel.org, skhan@linuxfoundation.org,
gregkh@linuxfoundation.org,
linux-kernel-mentees@lists.linuxfoundation.org,
syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com
Subject: [PATCH v2] btrfs: fix rw device counting in __btrfs_free_extra_devids
Date: Tue, 27 Jul 2021 15:13:03 +0800 [thread overview]
Message-ID: <20210727071303.113876-1-desmondcheongzx@gmail.com> (raw)
When removing a writeable device in __btrfs_free_extra_devids, the rw
device count should be decremented.
This error was caught by Syzbot which reported a warning in
close_fs_devices because fs_devices->rw_devices was not 0 after
closing all devices. Here is the call trace that was observed:
btrfs_mount_root():
btrfs_scan_one_device():
device_list_add(); <---------------- device added
btrfs_open_devices():
open_fs_devices():
btrfs_open_one_device(); <-------- writable device opened,
rw device count ++
btrfs_fill_super():
open_ctree():
btrfs_free_extra_devids():
__btrfs_free_extra_devids(); <--- writable device removed,
rw device count not decremented
fail_tree_roots:
btrfs_close_devices():
close_fs_devices(); <------- rw device count off by 1
As a note, prior to commit cf89af146b7e ("btrfs: dev-replace: fail
mount if we don't have replace item with target device"), rw_devices
was decremented on removing a writable device in
__btrfs_free_extra_devids only if the BTRFS_DEV_STATE_REPLACE_TGT bit
was not set for the device. However, this check does not need to be
reinstated as it is now redundant and incorrect.
In __btrfs_free_extra_devids, we skip removing the device if it is the
target for replacement. This is done by checking whether device->devid
== BTRFS_DEV_REPLACE_DEVID. Since BTRFS_DEV_STATE_REPLACE_TGT is set
only on the device with devid BTRFS_DEV_REPLACE_DEVID, no devices
should have the BTRFS_DEV_STATE_REPLACE_TGT bit set after the check,
and so it's redundant to test for that bit.
Additionally, following commit 82372bc816d7 ("Btrfs: make
the logic of source device removing more clear"), rw_devices is
incremented whenever a writeable device is added to the alloc
list (including the target device in btrfs_dev_replace_finishing), so
all removals of writable devices from the alloc list should also be
accompanied by a decrement to rw_devices.
Fixes: cf89af146b7e ("btrfs: dev-replace: fail mount if we don't have replace item with target device")
Reported-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com
Tested-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
---
fs/btrfs/volumes.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 807502cd6510..916c25371658 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1078,6 +1078,7 @@ static void __btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices,
if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
list_del_init(&device->dev_alloc_list);
clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
+ fs_devices->rw_devices--;
}
list_del_init(&device->dev_list);
fs_devices->num_devices--;
--
2.25.1
next reply other threads:[~2021-07-27 7:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-27 7:13 Desmond Cheong Zhi Xi [this message]
2021-07-28 12:58 ` [PATCH v2] btrfs: fix rw device counting in __btrfs_free_extra_devids David Sterba
2021-08-12 10:38 ` David Sterba
2021-08-12 15:43 ` Desmond Cheong Zhi Xi
2021-08-12 15:50 ` David Sterba
2021-08-12 17:31 ` Desmond Cheong Zhi Xi
2021-08-13 8:51 ` David Sterba
2021-08-13 9:57 ` Desmond Cheong Zhi Xi
2021-08-13 10:30 ` David Sterba
2021-08-19 17:11 ` Desmond Cheong Zhi Xi
2021-08-19 17:34 ` David Sterba
2021-08-20 3:09 ` Desmond Cheong Zhi Xi
2021-08-20 10:58 ` David Sterba
2021-08-20 17:53 ` Desmond Cheong Zhi Xi
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