linux-ext4 - Re: [PATCH V4 1/3] quota: Add reservation support for delayed block allocation

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Date:	Mon, 05 Jan 2009 20:32:24 -0800
From:	Mingming Cao <cmm@...ibm.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, tytso <tytso@....edu>,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH V4 1/3] quota: Add reservation support for delayed
	block allocation


在 2008-12-15一的 14:16 +0100，Jan Kara写道：
> Hi Minming,
> 
> On Fri 12-12-08 12:47:36, Mingming Cao wrote:
> > Quota: Add quota reservation support
> > 
> > Delayed allocation defers the block allocation at the dirty pages
> > flush-out time, doing quota charge/check at that time is too late.
> > But we can't charge the quota blocks until blocks are really allocated,
> > otherwise users could get overcharged after reboot from system crash.
> > 
> > This patch adds quota reservation for delayed llocation. Quota blocks
> > are reserved in memory, inode and quota won't gets dirtied until later
> > block allocation time.
> > 
> > Signed-off-by: Mingming Cao <cmm@...ibm.com>
> > 
> > 
> > ---
> >  fs/dquot.c               |  109 +++++++++++++++++++++++++++++++++--------------
> >  include/linux/quota.h    |    2 
> >  include/linux/quotaops.h |   22 +++++++++
> >  3 files changed, 102 insertions(+), 31 deletions(-)
> > 
> > Index: linux-2.6.28-rc2/fs/dquot.c
> > ===================================================================
> > --- linux-2.6.28-rc2.orig/fs/dquot.c	2008-11-06 13:36:21.000000000 -0800
> > +++ linux-2.6.28-rc2/fs/dquot.c	2008-12-12 12:20:45.000000000 -0800
> <snip>
> > @@ -1227,49 +1237,85 @@ void vfs_dq_drop(struct inode *inode)
> >  /*
> >   * This operation can block, but only after everything is updated
> >   */
> > -int dquot_alloc_space(struct inode *inode, qsize_t number, int warn)
> > +int __dquot_alloc_space(struct inode *inode, qsize_t number,
> > +			int warn, int reserve)
> >  {
> > -	int cnt, ret = NO_QUOTA;
> > +	int cnt, ret = QUOTA_OK;
> >  	char warntype[MAXQUOTAS];
> >  
> > -	/* First test before acquiring mutex - solves deadlocks when we
> > -         * re-enter the quota code and are already holding the mutex */
> > -	if (IS_NOQUOTA(inode)) {
> > -out_add:
> > -		inode_add_bytes(inode, number);
> > -		return QUOTA_OK;
> > -	}
> >  	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
> >  		warntype[cnt] = QUOTA_NL_NOWARN;
> >  
> > -	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > -	if (IS_NOQUOTA(inode)) {	/* Now we can do reliable test... */
> > -		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > -		goto out_add;
> > -	}
> >  	spin_lock(&dq_data_lock);
> >  	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
> >  		if (inode->i_dquot[cnt] == NODQUOT)
> >  			continue;
> > -		if (check_bdq(inode->i_dquot[cnt], number, warn, warntype+cnt) == NO_QUOTA)
> > -			goto warn_put_all;
> > +		if (check_bdq(inode->i_dquot[cnt], number, warn, warntype+cnt)
> > +		    == NO_QUOTA) {
> > +			ret = NO_QUOTA;
> > +			goto out_unlock;
> > +		}
> >  	}
> >  	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
> >  		if (inode->i_dquot[cnt] == NODQUOT)
> >  			continue;
> > -		dquot_incr_space(inode->i_dquot[cnt], number);
> > +		if (reserve)
> > +			dquot_resv_space(inode->i_dquot[cnt], number);
> > +		else{
>                     ^ here is missing space
> 

Okay, will fix that.
> > +			dquot_incr_space(inode->i_dquot[cnt], number);
> > +			inode_add_bytes(inode, number);
> > +		}
> >  	}
> > -	inode_add_bytes(inode, number);
> > -	ret = QUOTA_OK;
> > -warn_put_all:
> > -	spin_unlock(&dq_data_lock);
> > -	if (ret == QUOTA_OK)
> > -		/* Dirtify all the dquots - this can block when journalling */
> > -		for (cnt = 0; cnt < MAXQUOTAS; cnt++)
> > -			if (inode->i_dquot[cnt])
> > -				mark_dquot_dirty(inode->i_dquot[cnt]);
> > +out_unlock:
> >  	flush_warnings(inode->i_dquot, warntype);
> > +	spin_unlock(&dq_data_lock);
>   We can't do flush_warnings() inside the spinlock - that function can
> sleep. Please move the call outside the lock.
> 

Ok, Will do.

Mingming

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