Re: [PATCH v2 6/7] quota: simplify drop_dquot_ref()

[Baokun Li]

On 2023/6/29 19:08, Jan Kara wrote:
> On Wed 28-06-23 21:21:54, Baokun Li wrote:
> > Now when dqput() drops the last reference count, it will call
> > synchronize_srcu(&dquot_srcu) in quota_release_workfn() to ensure that
> > no other user will use the dquot after the last reference count is dropped,
> > so we don't need to call synchronize_srcu(&dquot_srcu) in drop_dquot_ref()
> > and remove the corresponding logic directly to simplify the code.
> Nice simplification!  It is also important that dqput() now cannot sleep
> which was another reason for the logic with tofree_head in
> remove_inode_dquot_ref().

I don't understand this sentence very well, so I would appreciate it

if you could explain it in detail. 🤔

> Probably this is good to mention in the
> changelog.
>
> > Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
> > ---
> >   fs/quota/dquot.c | 33 ++++++---------------------------
> >   1 file changed, 6 insertions(+), 27 deletions(-)
> >
> > diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> > index e8e702ac64e5..df028fb2ce72 100644
> > --- a/fs/quota/dquot.c
> > +++ b/fs/quota/dquot.c
> > @@ -1090,8 +1090,7 @@ static int add_dquot_ref(struct super_block *sb, int type)
> >    * Remove references to dquots from inode and add dquot to list for freeing
> >    * if we have the last reference to dquot
> >    */
> > -static void remove_inode_dquot_ref(struct inode *inode, int type,
> > -				   struct list_head *tofree_head)
> > +static void remove_inode_dquot_ref(struct inode *inode, int type)
> >   {
> >   	struct dquot **dquots = i_dquot(inode);
> >   	struct dquot *dquot = dquots[type];
> > @@ -1100,21 +1099,7 @@ static void remove_inode_dquot_ref(struct inode *inode, int type,
> >   		return;
> >   
> >   	dquots[type] = NULL;
> > -	if (list_empty(&dquot->dq_free)) {
> > -		/*
> > -		 * The inode still has reference to dquot so it can't be in the
> > -		 * free list
> > -		 */
> > -		spin_lock(&dq_list_lock);
> > -		list_add(&dquot->dq_free, tofree_head);
> > -		spin_unlock(&dq_list_lock);
> > -	} else {
> > -		/*
> > -		 * Dquot is already in a list to put so we won't drop the last
> > -		 * reference here.
> > -		 */
> > -		dqput(dquot);
> > -	}
> > +	dqput(dquot);
> >   }
> I think you can also just drop remove_inode_dquot_ref() as it is trivial
> now and inline it at its only callsite...
>
> 								Honza
Sure, I'll just remove it in the next version and inline the only 
remaining code
into remove_dquot_ref().

Thanks!
--
With Best Regards,
Baokun Li
.