[PATCH 2/5] quota: decouple fs reserved space from quota reservation. [V5]

[PATCH 2/5] quota: decouple fs reserved space from quota reservation. [V5]

[Dmitry Monakhov]

Currently inode_reservation is managed by fs itself and this
reservation is transfered on dquot_transfer(). This means what
inode_reservation must always be in sync with
dquot->dq_dqb.dqb_rsvspace. Otherwise dquot_transfer() will result
in incorrect quota(WARN_ON in dquot_claim_reserved_space() will be
triggered)
This is not easy because of complex locking order issues
for example http://bugzilla.kernel.org/show_bug.cgi?id=14739

The patch introduce quota reservation field for each fs-inode
(fs specific inode is used in order to prevent bloating generic
vfs inode). This reservation is managed by quota code internally
similar to i_blocks/i_bytes and may not be always in sync with
internal fs reservation.

Also perform some code rearrangement:
- Unify dquot_reserve_space() and dquot_reserve_space()
- Unify dquot_release_reserved_space() and dquot_free_space()
- Also this patch add missing warning update to release_rsv()
  dquot_release_reserved_space() must call flush_warnings() as
  dquot_free_space() does.

Changes from V4
 - fixes and cleanups according to Jan's comments.
Changes from V3:
 - fix deadlock in dquota_alloc_space in journalled mode with nodelalloc
Changes from V1:
 - move qutoa_reservation field from vfs_inode to fs_inode
 - account reservation in bytes instead of blocks.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 fs/quota/dquot.c      |  213 +++++++++++++++++++++++++++----------------------
 include/linux/quota.h |    5 +-
 2 files changed, 122 insertions(+), 96 deletions(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 39b49c4..942ea0b 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1388,6 +1388,67 @@ void vfs_dq_drop(struct inode *inode)
 EXPORT_SYMBOL(vfs_dq_drop);
 
 /*
+ * inode_reserved_space is managed internally by quota, and protected by
+ * i_lock similar to i_blocks+i_bytes.
+ */
+static qsize_t *inode_reserved_space(struct inode * inode)
+{
+	/* Filesystem must explicitly define it's own method in order to use
+	 * quota reservation interface */
+	BUG_ON(!inode->i_sb->dq_op->get_reserved_space);
+	return inode->i_sb->dq_op->get_reserved_space(inode);
+}
+
+static void inode_add_rsv_space(struct inode *inode, qsize_t number)
+{
+	spin_lock(&inode->i_lock);
+	*inode_reserved_space(inode) += number;
+	spin_unlock(&inode->i_lock);
+}
+
+
+static void inode_claim_rsv_space(struct inode *inode, qsize_t number)
+{
+	spin_lock(&inode->i_lock);
+	*inode_reserved_space(inode) -= number;
+	__inode_add_bytes(inode, number);
+	spin_unlock(&inode->i_lock);
+}
+
+static void inode_sub_rsv_space(struct inode *inode, qsize_t number)
+{
+	spin_lock(&inode->i_lock);
+	*inode_reserved_space(inode) -= number;
+	spin_unlock(&inode->i_lock);
+}
+
+static qsize_t inode_get_rsv_space(struct inode *inode)
+{
+	qsize_t ret;
+	spin_lock(&inode->i_lock);
+	ret = *inode_reserved_space(inode);
+	spin_unlock(&inode->i_lock);
+	return ret;
+}
+
+static void inode_incr_space(struct inode *inode, qsize_t number,
+				int reserve)
+{
+	if (reserve)
+		inode_add_rsv_space(inode, number);
+	else
+		inode_add_bytes(inode, number);
+}
+
+static void inode_decr_space(struct inode *inode, qsize_t number, int reserve)
+{
+	if (reserve)
+		inode_sub_rsv_space(inode, number);
+	else
+		inode_sub_bytes(inode, number);
+}
+
+/*
  * Following four functions update i_blocks+i_bytes fields and
  * quota information (together with appropriate checks)
  * NOTE: We absolutely rely on the fact that caller dirties
@@ -1405,6 +1466,21 @@ int __dquot_alloc_space(struct inode *inode, qsize_t number,
 	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)) {
+		inode_incr_space(inode, number, reserve);
+		goto out;
+	}
+
+	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
+	if (IS_NOQUOTA(inode)) {
+		inode_incr_space(inode, number, reserve);
+		goto out_unlock;
+	}
+
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
 		warntype[cnt] = QUOTA_NL_NOWARN;
 
@@ -1415,7 +1491,8 @@ int __dquot_alloc_space(struct inode *inode, qsize_t number,
 		if (check_bdq(inode->i_dquot[cnt], number, warn, warntype+cnt)
 		    == NO_QUOTA) {
 			ret = NO_QUOTA;
-			goto out_unlock;
+			spin_unlock(&dq_data_lock);
+			goto out_flush_warn;
 		}
 	}
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
@@ -1426,64 +1503,32 @@ int __dquot_alloc_space(struct inode *inode, qsize_t number,
 		else
 			dquot_incr_space(inode->i_dquot[cnt], number);
 	}
-	if (!reserve)
-		inode_add_bytes(inode, number);
-out_unlock:
+	inode_incr_space(inode, number, reserve);
 	spin_unlock(&dq_data_lock);
-	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)) {
-		inode_add_bytes(inode, number);
-		goto out;
-	}
-
-	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
-	if (IS_NOQUOTA(inode)) {
-		inode_add_bytes(inode, number);
-		goto out_unlock;
-	}
-
-	ret = __dquot_alloc_space(inode, number, warn, 0);
-	if (ret == NO_QUOTA)
-		goto out_unlock;
 
+	if (reserve)
+		goto out_flush_warn;
 	/* 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_flush_warn:
+	flush_warnings(inode->i_dquot, warntype);
 out_unlock:
 	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
 out:
 	return ret;
 }
+
+int dquot_alloc_space(struct inode *inode, qsize_t number, int warn)
+{
+	return __dquot_alloc_space(inode, number, warn, 0);
+}
 EXPORT_SYMBOL(dquot_alloc_space);
 
 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;
+	return __dquot_alloc_space(inode, number, warn, 1);
 }
 EXPORT_SYMBOL(dquot_reserve_space);
 
@@ -1540,14 +1585,14 @@ int dquot_claim_space(struct inode *inode, qsize_t number)
 	int ret = QUOTA_OK;
 
 	if (IS_NOQUOTA(inode)) {
-		inode_add_bytes(inode, number);
+		inode_claim_rsv_space(inode, number);
 		goto out;
 	}
 
 	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);
+		inode_claim_rsv_space(inode, number);
 		goto out;
 	}
 
@@ -1559,7 +1604,7 @@ int dquot_claim_space(struct inode *inode, qsize_t number)
 							number);
 	}
 	/* Update inode bytes */
-	inode_add_bytes(inode, number);
+	inode_claim_rsv_space(inode, number);
 	spin_unlock(&dq_data_lock);
 	/* Dirtify all the dquots - this can block when journalling */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
@@ -1572,38 +1617,9 @@ out:
 EXPORT_SYMBOL(dquot_claim_space);
 
 /*
- * Release reserved quota space
- */
-void dquot_release_reserved_space(struct inode *inode, qsize_t number)
-{
-	int cnt;
-
-	if (IS_NOQUOTA(inode))
-		goto out;
-
-	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
-	if (IS_NOQUOTA(inode))
-		goto out_unlock;
-
-	spin_lock(&dq_data_lock);
-	/* Release reserved dquots */
-	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		if (inode->i_dquot[cnt])
-			dquot_free_reserved_space(inode->i_dquot[cnt], number);
-	}
-	spin_unlock(&dq_data_lock);
-
-out_unlock:
-	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
-out:
-	return;
-}
-EXPORT_SYMBOL(dquot_release_reserved_space);
-
-/*
  * This operation can block, but only after everything is updated
  */
-int dquot_free_space(struct inode *inode, qsize_t number)
+int __dquot_free_space(struct inode *inode, qsize_t number, int reserve)
 {
 	unsigned int cnt;
 	char warntype[MAXQUOTAS];
@@ -1612,7 +1628,7 @@ int dquot_free_space(struct inode *inode, qsize_t number)
          * re-enter the quota code and are already holding the mutex */
 	if (IS_NOQUOTA(inode)) {
 out_sub:
-		inode_sub_bytes(inode, number);
+		inode_decr_space(inode, number, reserve);
 		return QUOTA_OK;
 	}
 
@@ -1627,21 +1643,43 @@ out_sub:
 		if (!inode->i_dquot[cnt])
 			continue;
 		warntype[cnt] = info_bdq_free(inode->i_dquot[cnt], number);
-		dquot_decr_space(inode->i_dquot[cnt], number);
+		if (reserve)
+			dquot_free_reserved_space(inode->i_dquot[cnt], number);
+		else
+			dquot_decr_space(inode->i_dquot[cnt], number);
 	}
-	inode_sub_bytes(inode, number);
+	inode_decr_space(inode, number, reserve);
 	spin_unlock(&dq_data_lock);
+
+	if (reserve)
+		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:
 	flush_warnings(inode->i_dquot, warntype);
 	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
 	return QUOTA_OK;
 }
+
+int dquot_free_space(struct inode *inode, qsize_t number)
+{
+	return  __dquot_free_space(inode, number, 0);
+}
 EXPORT_SYMBOL(dquot_free_space);
 
 /*
+ * Release reserved quota space
+ */
+void dquot_release_reserved_space(struct inode *inode, qsize_t number)
+{
+	return (void )__dquot_free_space(inode, number, 1);
+
+}
+EXPORT_SYMBOL(dquot_release_reserved_space);
+
+/*
  * This operation can block, but only after everything is updated
  */
 int dquot_free_inode(const struct inode *inode, qsize_t number)
@@ -1679,19 +1717,6 @@ int dquot_free_inode(const struct inode *inode, qsize_t number)
 EXPORT_SYMBOL(dquot_free_inode);
 
 /*
- * call back function, get reserved quota space from underlying fs
- */
-qsize_t dquot_get_reserved_space(struct inode *inode)
-{
-	qsize_t reserved_space = 0;
-
-	if (sb_any_quota_active(inode->i_sb) &&
-	    inode->i_sb->dq_op->get_reserved_space)
-		reserved_space = inode->i_sb->dq_op->get_reserved_space(inode);
-	return reserved_space;
-}
-
-/*
  * Transfer the number of inode and blocks from one diskquota to an other.
  *
  * This operation can block, but only after everything is updated
@@ -1734,7 +1759,7 @@ int dquot_transfer(struct inode *inode, struct iattr *iattr)
 	}
 	spin_lock(&dq_data_lock);
 	cur_space = inode_get_bytes(inode);
-	rsv_space = dquot_get_reserved_space(inode);
+	rsv_space = inode_get_rsv_space(inode);
 	space = cur_space + rsv_space;
 	/* Build the transfer_from list and check the limits */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
diff --git a/include/linux/quota.h b/include/linux/quota.h
index 78c4889..8fd8efc 100644
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -313,8 +313,9 @@ struct dquot_operations {
 	int (*claim_space) (struct inode *, qsize_t);
 	/* release rsved quota for delayed alloc */
 	void (*release_rsv) (struct inode *, qsize_t);
-	/* get reserved quota for delayed alloc */
-	qsize_t (*get_reserved_space) (struct inode *);
+	/* get reserved quota for delayed alloc, value returned is managed by
+	 * quota code only */
+	qsize_t *(*get_reserved_space) (struct inode *);
 };
 
 /* Operations handling requests from userspace */
-- 
1.6.0.4

[PATCH 3/5] ext4: Convert to generic reserved quota's space management. [V5]

[Dmitry Monakhov]

This patch fix write vs chown race condition.

Changes from V4
 - Coding style cleanup according to Jan's comment.
Changes from V2:
 - add missed i_reserved_quota iniatilization.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 fs/ext4/ext4.h  |    6 +++++-
 fs/ext4/inode.c |   16 +++++++---------
 fs/ext4/super.c |    3 +++
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 26d3cf8..708496f 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -705,6 +705,10 @@ struct ext4_inode_info {
 	struct list_head i_aio_dio_complete_list;
 	/* current io_end structure for async DIO write*/
 	ext4_io_end_t *cur_aio_dio;
+#ifdef CONFIG_QUOTA
+	/* quota space reservation, managed internally by quota code */
+	qsize_t i_reserved_quota;
+#endif
 };
 
 /*
@@ -1427,7 +1431,7 @@ extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
 extern int ext4_block_truncate_page(handle_t *handle,
 		struct address_space *mapping, loff_t from);
 extern int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf);
-extern qsize_t ext4_get_reserved_space(struct inode *inode);
+extern qsize_t *ext4_get_reserved_space(struct inode *inode);
 extern int flush_aio_dio_completed_IO(struct inode *inode);
 /* ioctl.c */
 extern long ext4_ioctl(struct file *, unsigned int, unsigned long);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d99173a..8254fe6 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1048,17 +1048,12 @@ out:
 	return err;
 }
 
-qsize_t ext4_get_reserved_space(struct inode *inode)
+#ifdef CONFIG_QUOTA
+qsize_t *ext4_get_reserved_space(struct inode *inode)
 {
-	unsigned long long total;
-
-	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
-	total = EXT4_I(inode)->i_reserved_data_blocks +
-		EXT4_I(inode)->i_reserved_meta_blocks;
-	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
-
-	return (total << inode->i_blkbits);
+	return &EXT4_I(inode)->i_reserved_quota;
 }
+#endif
 /*
  * Calculate the number of metadata blocks need to reserve
  * to allocate @blocks for non extent file based file
@@ -5048,6 +5043,9 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 			((__u64)le16_to_cpu(raw_inode->i_file_acl_high)) << 32;
 	inode->i_size = ext4_isize(raw_inode);
 	ei->i_disksize = inode->i_size;
+#ifdef CONFIG_QUOTA
+	ei->i_reserved_quota = 0;
+#endif
 	inode->i_generation = le32_to_cpu(raw_inode->i_generation);
 	ei->i_block_group = iloc.block_group;
 	ei->i_last_alloc_group = ~0;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 4c87d97..4697272 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -713,6 +713,9 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
 	spin_lock_init(&(ei->i_block_reservation_lock));
 	INIT_LIST_HEAD(&ei->i_aio_dio_complete_list);
 	ei->cur_aio_dio = NULL;
+#ifdef CONFIG_QUOTA
+	ei->i_reserved_quota = 0;
+#endif
 
 	return &ei->vfs_inode;
 }
-- 
1.6.0.4

Re: [PATCH 3/5] ext4: Convert to generic reserved quota's space management. [V5]

[tytso]

BTW, for some reason this patches never made it to the linux-ext4
list.  I'm not sure why; it's listed on the CC list, but it didn't
show up in the linux-ext4 archive, and it didn't show up in the
linux-ext4 patch queue.  Doesn't matter, since Jan will probably need
to push the patch since it's dependant on changes in the generic quota
tree.

						- Ted

Re: [PATCH 3/5] ext4: Convert to generic reserved quota's space management. [V5]

[tytso]

On Mon, Dec 14, 2009 at 03:21:14PM +0300, Dmitry Monakhov wrote:
> This patch fix write vs chown race condition.
> 
> Changes from V4
>  - Coding style cleanup according to Jan's comment.
> Changes from V2:
>  - add missed i_reserved_quota iniatilization.
> 
> Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>

Acked-by: "Theodore Ts'o" <tytso@mit.edu>

Jan, I assume you'll push this along with the other quota-related
changes out from your tree?  We have some ext4-related quota bugs that
I think may be related to this fix (and a bunch of distros are
planning on using 2.6.32), so if you could review this and get pushed
this patch series pushed out for 2.6.32 it would be appreciated,
thanks.

              	    	  	    	     - Ted

Re: [PATCH 3/5] ext4: Convert to generic reserved quota's space management. [V5]

[Jan Kara]

On Mon 14-12-09 09:35:51, tytso@mit.edu wrote:
> On Mon, Dec 14, 2009 at 03:21:14PM +0300, Dmitry Monakhov wrote:
> > This patch fix write vs chown race condition.
> > 
> > Changes from V4
> >  - Coding style cleanup according to Jan's comment.
> > Changes from V2:
> >  - add missed i_reserved_quota iniatilization.
> > 
> > Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
> 
> Acked-by: "Theodore Ts'o" <tytso@mit.edu>
> 
> Jan, I assume you'll push this along with the other quota-related
> changes out from your tree?  We have some ext4-related quota bugs that
> I think may be related to this fix (and a bunch of distros are
> planning on using 2.6.32), so if you could review this and get pushed
> this patch series pushed out for 2.6.32 it would be appreciated,
> thanks.
  Yes, I'll push it via my tree and take care of pushing into 2.6.32 stable
tree as well.

									Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR

Re: [PATCH 3/5] ext4: Convert to generic reserved quota's space management. [V5]

[Jan Kara]

On Mon 14-12-09 15:21:14, Dmitry Monakhov wrote:
> This patch fix write vs chown race condition.
> 
> Changes from V4
>  - Coding style cleanup according to Jan's comment.
> Changes from V2:
>  - add missed i_reserved_quota iniatilization.
  Looks good, merged into my tree.

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR

Re: [PATCH 2/5] quota: decouple fs reserved space from quota reservation. [V5]

[Jan Kara]

On Mon 14-12-09 15:21:13, Dmitry Monakhov wrote:
> Currently inode_reservation is managed by fs itself and this
> reservation is transfered on dquot_transfer(). This means what
> inode_reservation must always be in sync with
> dquot->dq_dqb.dqb_rsvspace. Otherwise dquot_transfer() will result
> in incorrect quota(WARN_ON in dquot_claim_reserved_space() will be
> triggered)
> This is not easy because of complex locking order issues
> for example http://bugzilla.kernel.org/show_bug.cgi?id=14739
> 
> The patch introduce quota reservation field for each fs-inode
> (fs specific inode is used in order to prevent bloating generic
> vfs inode). This reservation is managed by quota code internally
> similar to i_blocks/i_bytes and may not be always in sync with
> internal fs reservation.
> 
> Also perform some code rearrangement:
> - Unify dquot_reserve_space() and dquot_reserve_space()
> - Unify dquot_release_reserved_space() and dquot_free_space()
> - Also this patch add missing warning update to release_rsv()
>   dquot_release_reserved_space() must call flush_warnings() as
>   dquot_free_space() does.
> 
> Changes from V4
>  - fixes and cleanups according to Jan's comments.
> Changes from V3:
>  - fix deadlock in dquota_alloc_space in journalled mode with nodelalloc
> Changes from V1:
>  - move qutoa_reservation field from vfs_inode to fs_inode
>  - account reservation in bytes instead of blocks.
  Looks good. I've just slightly updated changelog and below
typecast (doing just __dquot_free_space(inode, number, 1)) and merged the
patch to my tree.

> +void dquot_release_reserved_space(struct inode *inode, qsize_t number)
> +{
> +	return (void )__dquot_free_space(inode, number, 1);
> +
> +}

									Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR