Date:	Thu, 06 Nov 2008 15:28:20 -0800
From:	Mingming Cao <cmm@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	jack@...e.cz, tytso@....edu, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH V2 2/3] quota: Add quota claim and release reserved
	quota blocks operations


On Tue, 2008-11-04 at 17:23 -0800, Andrew Morton wrote:
> On Fri, 31 Oct 2008 14:27:26 -0700
> Mingming Cao <cmm@...ibm.com> wrote:
> 
> > quota: Add quota reservation claim and released operations
> > 
> > Reserved quota will be claimed at the block allocation time. Over-booked
> > quota could be returned back with the release callback function.
> > 
> > --- linux-2.6.28-rc2.orig/include/linux/quotaops.h	2008-10-30 14:41:35.000000000 -0700
> > +++ linux-2.6.28-rc2/include/linux/quotaops.h	2008-10-30 14:42:00.000000000 -0700
> > @@ -28,6 +28,11 @@ int dquot_drop(struct inode *inode);
> >  int dquot_alloc_space(struct inode *inode, qsize_t number, int prealloc);
> >  int dquot_alloc_inode(const struct inode *inode, qsize_t number);
> >  
> > +int dquot_reserve_space(struct inode *inode, qsize_t number, int prealloc);
> > +int dquot_claim_space(struct inode *inode, qsize_t number);
> > +void dquot_release_reserved_space(struct inode *inode, qsize_t number);
> > +
> > +
> >  int dquot_free_space(struct inode *inode, qsize_t number);
> >  int dquot_free_inode(const struct inode *inode, qsize_t number);
> >  
> > @@ -196,6 +201,31 @@ static inline int vfs_dq_alloc_inode(str
> >  	return 0;
> >  }
> >  
> > +/*
> > + * Convert in-memory reserved quotas to real consumed quotas
> > + */
> > +static inline int vfs_dq_claim_space(struct inode *inode, qsize_t nr)
> > +{
> > +	if (sb_any_quota_active(inode->i_sb)){
> > +		if (inode->i_sb->dq_op->claim_space(inode, nr) == NO_QUOTA)
> > +			return 1;
> > +	}
> > +	else
> > +		inode_add_bytes(inode, nr);
> > +
> > +	mark_inode_dirty(inode);
> > +	return 0;
> > +}
> 
> The amount of inlining in this code is, umm, suboptimal.
> 
> Thankfully there only appears to be a single DQUOT_CLAIM_BLOCK()
> callsite at this stage.
> 
> I blame Jan ;)
> 
> > +/*
> > + * Release reserved (in-memory) quotas
> > + */
> > +static inline void vfs_dq_release_reservation_space(struct inode *inode, qsize_t nr)
> > +{
> > +	if (sb_any_quota_active(inode->i_sb))
> > +		inode->i_sb->dq_op->release_rsv(inode, nr);
> > +}
> > +
> >  static inline void vfs_dq_free_space_nodirty(struct inode *inode, qsize_t nr)
> >  {
> >  	if (sb_any_quota_active(inode->i_sb))
> > @@ -342,6 +372,16 @@ static inline int vfs_dq_reserve_space(s
> >  	return 0;
> >  }
> >  
> > +static inline int vfs_dq_claim_space(struct inode *inode, qsize_t nr)
> > +{
> > +	return vfs_dq_alloc_space(inode, nr);
> > +}
> > +
> > +static inline int vfs_dq_release_reservation_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);
> > @@ -386,6 +426,17 @@ static inline int vfs_dq_reserve_block(s
> >  			nr << inode->i_sb->s_blocksize_bits);
> >  }
> >  
> > +static inline int vfs_dq_claim_block(struct inode *inode, qsize_t nr)
> > +{
> > +	return vfs_dq_claim_space(inode,
> > +			nr << inode->i_sb->s_blocksize_bits);
> > +}
> > +
> > +static inline void vfs_dq_release_reservation(struct inode *inode, qsize_t nr)
> > +{
> > +	vfs_dq_release_reservation_space(inode, nr << inode->i_sb->s_blocksize_bits);
> 
> I think you'll find that inode->i_blkbits contains the same
> information.  Accessing that is faster and will emit less code.
> 

Agree. I will make the change.
> It appears that this optimisation can be made in several places in the
> quota code.
> 
That is true. I will create a seperate patch to cleanup this in quota
code.

> 
> > +}
> > +
> >  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);
> > @@ -415,6 +466,8 @@ static inline void vfs_dq_free_block(str
> >  				vfs_dq_alloc_block_nodirty(inode, nr)
> >  #define DQUOT_ALLOC_BLOCK(inode, nr) vfs_dq_alloc_block(inode, nr)
> >  #define DQUOT_RESERVE_BLOCK(inode, nr) vfs_dq_reserve_block(inode, nr)
> > +#define DQUOT_CLAIM_BLOCK(inode, nr) vfs_dq_claim_block(inode, nr)
> > +#define DQUOT_RELEASE_RSV_BLOCK(inode, nr) vfs_dq_release_reservation(inode, nr)
> 
> erk.  I blame him for this too.
> 

>>From the comments it seems the DQUOT_XX_XXX micros will be phase out
soon, so I assume it is expecting the filesystem to use vfs_dq_xxx()
functions? 

> >  #define DQUOT_ALLOC_INODE(inode) vfs_dq_alloc_inode(inode)
> >  #define DQUOT_FREE_SPACE_NODIRTY(inode, nr) \
> >  				vfs_dq_free_space_nodirty(inode, nr)
> > Index: linux-2.6.28-rc2/fs/dquot.c
> > ===================================================================
> > --- linux-2.6.28-rc2.orig/fs/dquot.c	2008-10-30 14:41:50.000000000 -0700
> > +++ linux-2.6.28-rc2/fs/dquot.c	2008-10-31 13:27:20.000000000 -0700
> > @@ -846,6 +846,24 @@ static inline void dquot_resv_space(stru
> >  	dquot->dq_dqb.dqb_rsvspace += number;
> >  }
> >  
> > +/*
> > + * Claim reserved quota space
> > + */
> > +static int dquot_claim_reserved_space(struct dquot *dquot,
> > +						qsize_t number)
> > +{
> > +	if (dquot->dq_dqb.dqb_rsvspace < number) {
> > +		printk("WARNING: reserved quota %llu is not enough for"
> > +			"request %llu bytes\n",
> > +			dquot->dq_dqb.dqb_rsvspace, number);
> 
> Nope.
> 
> You cannot print a u64 - you do not know what type it has.  It must be
> typecast to a known type for printing purposes.
> 
> This mistake seems to be happening a lot in ext4 world.  People, please
> remember this!  You might want to have a think about your compilation
> test coverage also.  powerpc and sparc64 are good ones to use.
> 

Ok, thanks for point this out. I tested on amd64.

> > +		return 1;
> > +	}
> > +
> > +	dquot->dq_dqb.dqb_curspace += number;
> > +	dquot->dq_dqb.dqb_rsvspace -= number;
> > +	return 0;
> > +}
> > +
> >  static inline void dquot_decr_inodes(struct dquot *dquot, qsize_t number)
> >  {
> >  	if (dquot->dq_dqb.dqb_curinodes > number)
> > @@ -1325,6 +1343,71 @@ int dquot_reserve_space(struct inode *in
> >  	return ret;
> >  }
> >  
> > +int dquot_claim_space(struct inode *inode, qsize_t number)
> > +{
> > +	int cnt;
> > +	int ret = QUOTA_OK;
> > +
> > +	if (IS_NOQUOTA(inode)) {
> > +		inode_add_bytes(inode, number);
> > +		return ret;
> > +	}
> > +
> > +	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +	if (IS_NOQUOTA(inode))	{
> > +		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +		inode_add_bytes(inode, number);
> > +		return ret;
> > +	}
> > +
> > +	/* Claim reserved quotas to allocated quotas */
> > +	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
> > +		if (inode->i_dquot[cnt] != NODQUOT)
> > +			ret = dquot_claim_reserved_space(inode->i_dquot[cnt],
> > +							number);
> > +	}
> > +	if (ret == NO_QUOTA) {
> > +		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +		return ret;
> > +	}
> > +	/* 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]);
> > +	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +
> > +	/* Update inode bytes */
> > +	inode_add_bytes(inode, number);
> > +	return ret;
> > +}
> 
> Didn't I just review that function?  I might have got my patches confused.
> 
> 

The one got you confused is dquot_alloc_space(). They are very similar,
but have a few subtle differences. Sharing the common code is possible,
I tried, the code becomes less readable. I was not sure if it worth the
effort so give up.

> > +/*
> > + * Release reserved quota space
> > + */
> > +void dquot_release_reserved_space(struct inode *inode, qsize_t number)
> > +{
> > +	int cnt;
> > +	struct dquot *dquot;
> > +
> > +	if (IS_NOQUOTA(inode))
> > +		return;
> > +
> > +	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +	if (IS_NOQUOTA(inode))	{
> > +		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +		return;
> > +	}
> 
> again, `goto out' will yield more maintainable and perhaps more
> efficient code here.
> 
OK.

> > +	/* Release reserved dquots */
> > +	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
> > +		if (inode->i_dquot[cnt] != NODQUOT) {
> > +			dquot = inode->i_dquot[cnt];
> > +			dquot->dq_dqb.dqb_rsvspace -= number;
> > +		}
> > +	}
> > +	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
> > +}
> > +
> >  /*
> >   * This operation can block, but only after everything is updated
> >   */
> > @@ -2350,6 +2433,8 @@ EXPORT_SYMBOL(dquot_alloc_inode);
> >  EXPORT_SYMBOL(dquot_free_space);
> >  EXPORT_SYMBOL(dquot_free_inode);
> >  EXPORT_SYMBOL(dquot_reserve_space);
> > +EXPORT_SYMBOL(dquot_claim_space);
> > +EXPORT_SYMBOL(dquot_release_reserved_space);
> 
> I blame him for that too.
> 

OK, I think I will just follow Jan's style here now in this series. I
will make a seperate cleanup patch to move all the quota exported
symbols next to their functions.

> >  EXPORT_SYMBOL(dquot_transfer);
> >  EXPORT_SYMBOL(vfs_dq_transfer);
> >  EXPORT_SYMBOL(vfs_dq_quota_on_remount);
> > 


Attached incremental fix below, please check if I missed any thing,

Thanks,

Mingming
---
 fs/dquot.c               |   16 +++++++++-------
 include/linux/quota.h    |    6 +++---
 include/linux/quotaops.h |   18 ++++++++++--------
 3 files changed, 22 insertions(+), 18 deletions(-)

Index: linux-2.6.28-rc2/fs/dquot.c
===================================================================
--- linux-2.6.28-rc2.orig/fs/dquot.c	2008-11-06 13:37:06.000000000 -0800
+++ linux-2.6.28-rc2/fs/dquot.c	2008-11-06 13:37:08.000000000 -0800
@@ -853,9 +853,9 @@ static int dquot_claim_reserved_space(st
 						qsize_t number)
 {
 	if (dquot->dq_dqb.dqb_rsvspace < number) {
-		printk("WARNING: reserved quota %llu is not enough for"
+		printk(KERN_WARNING "Reserved quota %llu is not enough for"
 			"request %llu bytes\n",
-			dquot->dq_dqb.dqb_rsvspace, number);
+			(unsigned long long)dquot->dq_dqb.dqb_rsvspace, number);
 		return 1;
 	}
 
@@ -1384,13 +1384,11 @@ void dquot_release_reserved_space(struct
 	struct dquot *dquot;
 
 	if (IS_NOQUOTA(inode))
-		return;
+		goto out;
 
 	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
-	if (IS_NOQUOTA(inode))	{
-		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
-		return;
-	}
+	if (IS_NOQUOTA(inode))
+		goto out_unlock;
 
 	/* Release reserved dquots */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
@@ -1399,7 +1397,11 @@ void dquot_release_reserved_space(struct
 			dquot->dq_dqb.dqb_rsvspace -= number;
 		}
 	}
+
+out_unlock:
 	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
+out:
+	return;
 }
 
 /*
Index: linux-2.6.28-rc2/include/linux/quotaops.h
===================================================================
--- linux-2.6.28-rc2.orig/include/linux/quotaops.h	2008-11-06 13:37:06.000000000 -0800
+++ linux-2.6.28-rc2/include/linux/quotaops.h	2008-11-06 14:00:32.000000000 -0800
@@ -206,11 +206,10 @@ static inline int vfs_dq_alloc_inode(str
  */
 static inline int vfs_dq_claim_space(struct inode *inode, qsize_t nr)
 {
-	if (sb_any_quota_active(inode->i_sb)){
+	if (sb_any_quota_active(inode->i_sb)) {
 		if (inode->i_sb->dq_op->claim_space(inode, nr) == NO_QUOTA)
 			return 1;
-	}
-	else
+	} else
 		inode_add_bytes(inode, nr);
 
 	mark_inode_dirty(inode);
@@ -220,7 +219,8 @@ static inline int vfs_dq_claim_space(str
 /*
  * Release reserved (in-memory) quotas
  */
-static inline void vfs_dq_release_reservation_space(struct inode *inode, qsize_t nr)
+static inline
+void vfs_dq_release_reservation_space(struct inode *inode, qsize_t nr)
 {
 	if (sb_any_quota_active(inode->i_sb))
 		inode->i_sb->dq_op->release_rsv(inode, nr);
@@ -377,7 +377,8 @@ static inline int vfs_dq_claim_space(str
 	return vfs_dq_alloc_space(inode, nr);
 }
 
-static inline int vfs_dq_release_reservation_space(struct inode *inode, qsize_t nr)
+static inline
+int vfs_dq_release_reservation_space(struct inode *inode, qsize_t nr)
 {
 	return 0;
 }
@@ -429,12 +430,13 @@ static inline int vfs_dq_reserve_block(s
 static inline int vfs_dq_claim_block(struct inode *inode, qsize_t nr)
 {
 	return vfs_dq_claim_space(inode,
-			nr << inode->i_sb->s_blocksize_bits);
+			nr << inode->i_blkbits);
 }
 
-static inline void vfs_dq_release_reservation(struct inode *inode, qsize_t nr)
+static inline
+void vfs_dq_release_reservation(struct inode *inode, qsize_t nr)
 {
-	vfs_dq_release_reservation_space(inode, nr << inode->i_sb->s_blocksize_bits);
+	vfs_dq_release_reservation_space(inode, nr << inode->i_blkbits);
 }
 
 static inline void vfs_dq_free_block_nodirty(struct inode *inode, qsize_t nr)
Index: linux-2.6.28-rc2/include/linux/quota.h
===================================================================
--- linux-2.6.28-rc2.orig/include/linux/quota.h	2008-11-06 13:37:06.000000000 -0800
+++ linux-2.6.28-rc2/include/linux/quota.h	2008-11-06 13:37:08.000000000 -0800
@@ -292,9 +292,9 @@ 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" */
-	int (*reserve_space) (struct inode *, qsize_t, int); /* reserve quota for delayed block allocation */
-	int (*claim_space) (struct inode *, qsize_t); /* claim reserved quota for delayed block allocation */
-	void (*release_rsv) (struct inode *, qsize_t); /* release reserved quota for delayed block allocation */
+	int (*reserve_space) (struct inode *, qsize_t, int); /* reserve quota for delayed alloc */
+	int (*claim_space) (struct inode *, qsize_t); /* claim reserved quota for delayed alloc */
+	void (*release_rsv) (struct inode *, qsize_t); /* release rsved quota for delayed alloc */
 };
 
 /* Operations handling requests from userspace */


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