Date:	Mon, 12 Jan 2009 16:19:06 -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 V5 1/5] quota: Add reservation support for delayed
	block allocation


Thanks for your review and suggestions. All points are taken. I have
updated the quota patches.I am attaching the updated patch here just for
your review.

I am waiting for the ext4 tree to updated to rebase the whole series
against 2.6.29-rc1 plus ext4 patch queue.  

在 2009-01-06二的 11:06 +0100，Jan Kara写道：
> On Mon 05-01-09 20:40:08, 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>
>   Just a few comments below:
> 
> > ---
> >  fs/dquot.c               |  111 +++++++++++++++++++++++++++++++++--------------
> >  include/linux/quota.h    |    3 +
> >  include/linux/quotaops.h |   22 +++++++++
> >  3 files changed, 105 insertions(+), 31 deletions(-)
> > 
> > Index: linux-2.6.28-git7/fs/dquot.c
> > ===================================================================
> > --- linux-2.6.28-git7.orig/fs/dquot.c	2009-01-05 17:09:50.000000000 -0800
> > +++ linux-2.6.28-git7/fs/dquot.c	2009-01-05 20:07:08.000000000 -0800
> > @@ -898,6 +898,11 @@ static inline void dquot_incr_space(stru
> >  	dquot->dq_dqb.dqb_curspace += number;
> >  }
> >  
> > +static inline void dquot_resv_space(struct dquot *dquot, qsize_t number)
> > +{
> > +	dquot->dq_dqb.dqb_rsvspace += number;
> > +}
> > +
> >  static inline void dquot_decr_inodes(struct dquot *dquot, qsize_t number)
> >  {
> >  	if (sb_dqopt(dquot->dq_sb)->flags & DQUOT_NEGATIVE_USAGE ||
> > @@ -1067,7 +1072,9 @@ err_out:
> >  	kfree_skb(skb);
> >  }
> >  #endif
> > -
> > +/*
> > + * Should called with dq_data_lock dropped, this function could sleep.
> > + */
>   If you want to add a comment here I'd add something like:
> /*
>  * Write warnings to the console and send warning messages over netlink.
>  *
>  * Note that this function can sleep.
>  */
> 
>   Because you cannot hold *any* spinlock when calling a function that can
> sleep...
> 
> >  static inline void flush_warnings(struct dquot * const *dquots, char *warntype)
> >  {
> >  	int i;
> > @@ -1128,13 +1135,18 @@ static int check_idq(struct dquot *dquot
> >  /* needs dq_data_lock */
> >  static int check_bdq(struct dquot *dquot, qsize_t space, int prealloc, char *warntype)
> >  {
> > +	qsize_t tspace;
> > +
> >  	*warntype = QUOTA_NL_NOWARN;
> >  	if (!sb_has_quota_limits_enabled(dquot->dq_sb, dquot->dq_type) ||
> >  	    test_bit(DQ_FAKE_B, &dquot->dq_flags))
> >  		return QUOTA_OK;
> >  
> > +	tspace = dquot->dq_dqb.dqb_curspace + dquot->dq_dqb.dqb_rsvspace
> > +		+ space;
> > +
> >  	if (dquot->dq_dqb.dqb_bhardlimit &&
> > -	    dquot->dq_dqb.dqb_curspace + space > dquot->dq_dqb.dqb_bhardlimit &&
> > +	    tspace > dquot->dq_dqb.dqb_bhardlimit &&
> >              !ignore_hardlimit(dquot)) {
> >  		if (!prealloc)
> >  			*warntype = QUOTA_NL_BHARDWARN;
> > @@ -1142,7 +1154,7 @@ static int check_bdq(struct dquot *dquot
> >  	}
> >  
> >  	if (dquot->dq_dqb.dqb_bsoftlimit &&
> > -	    dquot->dq_dqb.dqb_curspace + space > dquot->dq_dqb.dqb_bsoftlimit &&
> > +	    tspace > dquot->dq_dqb.dqb_bsoftlimit &&
> >  	    dquot->dq_dqb.dqb_btime && get_seconds() >= dquot->dq_dqb.dqb_btime &&
> >              !ignore_hardlimit(dquot)) {
> >  		if (!prealloc)
> > @@ -1151,7 +1163,7 @@ static int check_bdq(struct dquot *dquot
> >  	}
> >  
> >  	if (dquot->dq_dqb.dqb_bsoftlimit &&
> > -	    dquot->dq_dqb.dqb_curspace + space > dquot->dq_dqb.dqb_bsoftlimit &&
> > +	    tspace > dquot->dq_dqb.dqb_bsoftlimit &&
> >  	    dquot->dq_dqb.dqb_btime == 0) {
> >  		if (!prealloc) {
> >  			*warntype = QUOTA_NL_BSOFTWARN;
> > @@ -1292,51 +1304,88 @@ 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 {
> > +			dquot_incr_space(inode->i_dquot[cnt], number);
> > +			inode_add_bytes(inode, number);
> > +		}
> >  	}
> > -	inode_add_bytes(inode, number);
> > -	ret = QUOTA_OK;
> > -warn_put_all:
> > +out_unlock:
> >  	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]);
> >  	flush_warnings(inode->i_dquot, warntype);
> > +	return ret;
> > +}
> > +
> > +int dquot_alloc_space(struct inode *inode, qsize_t number, int warn)
> > +{
> > +	int cnt, ret = QUOTA_OK;
> > +
> > +	/*
> > +	 * First test before acquiring mutex - solves deadlocks when we
> > +	 * re-enter the quota code and are already holding the mutex
> > +	 */
> > +	if (IS_NOQUOTA(inode))
> > +		goto out;
> > +
> > +	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +	if (IS_NOQUOTA(inode))
> > +		goto out_unlock;
>     We need to call inode_add_bytes(inode, number) even for IS_NOQUOTA()
> inodes (but we don't have to hold dq_data_lock for such inodes). Your
> rewrite has removed this call...
> 

> > +
> > +	ret = __dquot_alloc_space(inode, number, warn, 0);
> > +	if (ret == NO_QUOTA)
> > +		goto out_unlock;
> > +
> > +	/* 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:
> >  	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +out:
> > +	return ret;
> > +}
> > +
> > +int dquot_reserve_space(struct inode *inode, qsize_t number, int warn)
> > +{
> > +	int ret = QUOTA_OK;
> > +
> > +	if (IS_NOQUOTA(inode))
> > +		goto out;
> > +
> > +	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +	if (IS_NOQUOTA(inode))
> > +		goto out_unlock;
> > +
> > +	ret = __dquot_alloc_space(inode, number, warn, 1);
> > +out_unlock:
> > +	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +out:
> >  	return ret;
> >  }
> > +EXPORT_SYMBOL(dquot_reserve_space);
> >  
> >  /*
> >   * This operation can block, but only after everything is updated
> > @@ -2025,7 +2074,7 @@ static void do_get_dqblk(struct dquot *d
> >  	spin_lock(&dq_data_lock);
> >  	di->dqb_bhardlimit = stoqb(dm->dqb_bhardlimit);
> >  	di->dqb_bsoftlimit = stoqb(dm->dqb_bsoftlimit);
> > -	di->dqb_curspace = dm->dqb_curspace;
> > +	di->dqb_curspace = dm->dqb_curspace + dm->dqb_rsvspace;
> >  	di->dqb_ihardlimit = dm->dqb_ihardlimit;
> >  	di->dqb_isoftlimit = dm->dqb_isoftlimit;
> >  	di->dqb_curinodes = dm->dqb_curinodes;
> > @@ -2067,7 +2116,7 @@ static int do_set_dqblk(struct dquot *dq
> >  
> >  	spin_lock(&dq_data_lock);
> >  	if (di->dqb_valid & QIF_SPACE) {
> > -		dm->dqb_curspace = di->dqb_curspace;
> > +		dm->dqb_curspace = di->dqb_curspace - dm->dqb_rsvspace;
> >  		check_blim = 1;
> >  		__set_bit(DQ_LASTSET_B + QIF_SPACE_B, &dquot->dq_flags);
> >  	}
> > Index: linux-2.6.28-git7/include/linux/quota.h
> > ===================================================================
> > --- linux-2.6.28-git7.orig/include/linux/quota.h	2009-01-05 17:09:37.000000000 -0800
> > +++ linux-2.6.28-git7/include/linux/quota.h	2009-01-05 20:07:08.000000000 -0800
> > @@ -198,6 +198,7 @@ struct mem_dqblk {
> >  	qsize_t dqb_bhardlimit;	/* absolute limit on disk blks alloc */
> >  	qsize_t dqb_bsoftlimit;	/* preferred limit on disk blks */
> >  	qsize_t dqb_curspace;	/* current used space */
> > +	qsize_t dqb_rsvspace;   /* current reserved space for delalloc*/
> >  	qsize_t dqb_ihardlimit;	/* absolute limit on allocated inodes */
> >  	qsize_t dqb_isoftlimit;	/* preferred inode limit */
> >  	qsize_t dqb_curinodes;	/* current # allocated inodes */
> > @@ -308,6 +309,8 @@ struct dquot_operations {
> >  	int (*release_dquot) (struct dquot *);		/* Quota is going to be deleted from disk */
> >  	int (*mark_dirty) (struct dquot *);		/* Dquot is marked dirty */
> >  	int (*write_info) (struct super_block *, int);	/* Write of quota "superblock" */
> > +	/* reserve quota for delayed block allocation */
> > +	int (*reserve_space) (struct inode *, qsize_t, int);
> >  };
> >  
> >  /* Operations handling requests from userspace */
> > Index: linux-2.6.28-git7/include/linux/quotaops.h
> > ===================================================================
> > --- linux-2.6.28-git7.orig/include/linux/quotaops.h	2009-01-05 17:09:37.000000000 -0800
> > +++ linux-2.6.28-git7/include/linux/quotaops.h	2009-01-05 20:07:08.000000000 -0800
> > @@ -185,6 +185,16 @@ static inline int vfs_dq_alloc_space(str
> >  	return ret;
> >  }
> >  
> > +static inline int vfs_dq_reserve_space(struct inode *inode, qsize_t nr)
> > +{
> > +	if (sb_any_quota_active(inode->i_sb)) {
> > +		/* Used space is updated in alloc_space() */
> > +		if (inode->i_sb->dq_op->reserve_space(inode, nr, 0) == NO_QUOTA)
> > +			return 1;
> > +	}
> > +	return 0;
> > +}
> > +
> >  static inline int vfs_dq_alloc_inode(struct inode *inode)
> >  {
> >  	if (sb_any_quota_active(inode->i_sb)) {
> > @@ -341,6 +351,11 @@ static inline int vfs_dq_alloc_space(str
> >  	return 0;
> >  }
> >  
> > +static inline int vfs_dq_reserve_space(struct inode *inode, qsize_t nr)
> > +{
> > +	return 0;
> > +}
> > +
> >  static inline void vfs_dq_free_space_nodirty(struct inode *inode, qsize_t nr)
> >  {
> >  	inode_sub_bytes(inode, nr);
> > @@ -372,12 +387,19 @@ static inline int vfs_dq_alloc_block_nod
> >  			nr << inode->i_sb->s_blocksize_bits);
> >  }
> >  
> > +
>   ^^ This empty line was added by accident I guess...
> 
> 
> 
> >  static inline int vfs_dq_alloc_block(struct inode *inode, qsize_t nr)
> >  {
> >  	return vfs_dq_alloc_space(inode,
> >  			nr << inode->i_sb->s_blocksize_bits);
> >  }
> >  
> > +static inline int vfs_dq_reserve_block(struct inode *inode, qsize_t nr)
> > +{
> > +	return vfs_dq_reserve_space(inode,
> > +			nr << inode->i_blkbits);
> > +}
> > +
> >  static inline void vfs_dq_free_block_nodirty(struct inode *inode, qsize_t nr)
> >  {
> >  	vfs_dq_free_space_nodirty(inode, nr << inode->i_sb->s_blocksize_bits);
> > 
> > 

View attachment "quota-make-reservation-vfs.patch" of type "text/x-patch" (9621 bytes)

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