On 7/19/22 9:25 PM, Christophe JAILLET wrote:
> Le 19/07/2022 à 12:24, David Laight a écrit :
>> From: Christophe JAILLET
>>> Sent: 19 July 2022 11:02
>>>
>>> 'node_map_lock' is a spinlock only used to protect calls to set_bit(),
>>> clear_bit() and test_bit().
>>>
>>> {set|clear}_bit() are already atomic and don't need this extra spinlock.
>>> test_bit() only reads the bitmap for a given bit.
>>>
>>> Remove this useless spinlock.
>>
>> It looks to me like the calling code is racy
>> unless there is another lock in the callers.
>
> The call chains are:
> ocfs2_recover_orphans()
> ocfs2_mark_recovering_orphan_dir()
> spin_lock(&osb->osb_lock); <-- osb_lock spinlock
> ocfs2_node_map_set_bit() <-- uses node_map_lock
> ...
> spin_unlock(&osb->osb_lock);
> ...
> ocfs2_clear_recovering_orphan_dir()
> ocfs2_node_map_clear_bit() <-- uses node_map_lock
> osb_lock is NOT taken
>
>
> ocfs2_check_orphan_recovery_state()
> spin_lock(&osb->osb_lock); <-- osb_lock spinlock
> ...
> ocfs2_node_map_test_bit() <-- uses node_map_lock
> ...
> spin_unlock(&osb->osb_lock);
>
>
> So the code looks already protected by the 'osb_lock' spinlock, but I don't know this code and ocfs2_mark_recovering_orphan_dir() looks tricky to me. (so some other eyes are much welcome)
osb_lock is to protect osb filed such as 'osb_orphan_wipes', while
node_map_lock is to protect the node map 'osb_recovering_orphan_dirs'
specifically.
Thanks,
Joseph
