[Devel] Re: [PATCH 06/14] sysfs: Rewrite sysfs_get_dentry

[Eric W. Biederman]

Tejun Heo <htejun at gmail.com> writes:

> Hello, Eric.
>
> Eric W. Biederman wrote:
>> I will look a little more and see.  But right now it looks like the
>> real problem with locking is that we use sysfs_mutex to lock the
>> sysfs_dirent s_children list.
>> 
>> Instead it really looks like we should use i_mutex from the appropriate
>> inode.  Or is there a real performance problem with forcing the directory
>> inodes in core when we modify the directories?
>
> I don't think there is any performance problem.  Problems with using
> i_mutex were...
>
> * It was messy.  I don't remember all the details now but IIRC symlink
> walk code was pretty complex.
>
> * And more importantly, inodes are reclaimable and might or might not be
> there.

Yes.  But we can always force inodes into the cache when we need them.
When I complete it I will have to show you a patch using the inode lock
for locking directory modifications.  From what I can tell so far it allows
me to fix the weird lock order problems and generally simplify the locking.

Eric
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