Re: [PATCH v3 03/25] dcache: Enable lockless update of d_count indentry structure
From: Waiman Long
Date: Wed Jul 03 2013 - 16:53:13 EST
On 07/03/2013 04:37 PM, Linus Torvalds wrote:
This patch grew a lot, and that seems to be mainly because of bad reasons.
That is the main reason why I choose to implement it the way it was in
my previous version. As I add one more level to access d_lock and
d_count, I need to change a lot more files.
I'd suggest dropping the whole
"lockref_ret_count()"/"lockref_ret_lock()" helpers, which cause all
the annoyance, and just make people use the members directly.
Yes, I can do that. They are used in not that many places.
Then, just do
#define d_lock d_lockref.lockref_lock
or similar, so that all the existing code just continues to work,
without the need for the syntactic changes:
- spin_lock(&dentry->d_lock);
+ d_lock(dentry);
I had been thinking about that. The use of d_lock should be pretty safe
as I didn't see that variable name used in other places. I didn't do it
because I am afraid that people may say that using macro mapping like
this is not a good idea. By doing that, the patch should shrink
considerably.
For d_count, we probably do need to have the wrapper macro:
#define dentry_count(dentry) ((dentry)->d_lockref.lockref_count)
and change the existing users of "dentry->d_count" to use that, but
there are fewer of those than there are of people taking the dentry
lock. And most of them are in fs/dcache.c and would be affected by
this set of patches anyway.
The d_count name is not unique to the dentry structure. So files that
access d_count have to be modified explicitly.
I will see if there are more feedback and send an updated patchset by
the end of this week or early next week.
Regards,
Longman
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