[PATCH v2] ext4: fix quota charging for shared xattr blocks

[Tahsin Erdogan]

ext4_xattr_block_set() calls dquot_alloc_block() to charge for an xattr
block when new references are made. However if dquot_initialize() hasn't
been called on an inode, request for charging is effectively ignored
because ext4_inode_info->i_dquot is not initialized yet.

Add dquot_initialize() to call paths that lead to ext4_xattr_block_set().

Signed-off-by: Tahsin Erdogan <tahsin@xxxxxxxxxx>
---
v2:
 - moved dquot_initialize() to outside the main transaction
 - added dquot_initialize_needed() function that is used by
   ext4_xattr_release_block() to warn about call paths that don't
   call dquot_initialize()

 fs/ext4/acl.c            |  4 ++++
 fs/ext4/super.c          |  3 +++
 fs/ext4/xattr.c          |  8 ++++++++
 fs/quota/dquot.c         | 16 ++++++++++++++++
 include/linux/quotaops.h |  6 ++++++
 5 files changed, 37 insertions(+)

diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index fd389935ecd1..3ec0e46de95f 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -4,6 +4,7 @@
  * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@xxxxxxx>
  */
 
+#include <linux/quotaops.h>
 #include "ext4_jbd2.h"
 #include "ext4.h"
 #include "xattr.h"
@@ -232,6 +233,9 @@ ext4_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 	handle_t *handle;
 	int error, retries = 0;
 
+	error = dquot_initialize(inode);
+	if (error)
+		return error;
 retry:
 	handle = ext4_journal_start(inode, EXT4_HT_XATTR,
 				    ext4_jbd2_credits_xattr(inode));
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 0b177da9ea82..e2e0eb7ac9a0 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1179,6 +1179,9 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
 		return res;
 	}
 
+	res = dquot_initialize(inode);
+	if (res)
+		return res;
 retry:
 	handle = ext4_journal_start(inode, EXT4_HT_MISC,
 			ext4_jbd2_credits_xattr(inode));
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 8fb7ce14e6eb..5d3c2536641c 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -888,6 +888,8 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 			else {
 				u32 ref;
 
+				WARN_ON_ONCE(dquot_initialize_needed(inode));
+
 				/* The old block is released after updating
 				   the inode. */
 				error = dquot_alloc_block(inode,
@@ -954,6 +956,8 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 			/* We need to allocate a new block */
 			ext4_fsblk_t goal, block;
 
+			WARN_ON_ONCE(dquot_initialize_needed(inode));
+
 			goal = ext4_group_first_block_no(sb,
 						EXT4_I(inode)->i_block_group);
 
@@ -1166,6 +1170,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
 		return -EINVAL;
 	if (strlen(name) > 255)
 		return -ERANGE;
+
 	ext4_write_lock_xattr(inode, &no_expand);
 
 	error = ext4_reserve_inode_write(handle, inode, &is.iloc);
@@ -1267,6 +1272,9 @@ ext4_xattr_set(struct inode *inode, int name_index, const char *name,
 	int error, retries = 0;
 	int credits = ext4_jbd2_credits_xattr(inode);
 
+	error = dquot_initialize(inode);
+	if (error)
+		return error;
 retry:
 	handle = ext4_journal_start(inode, EXT4_HT_XATTR, credits);
 	if (IS_ERR(handle)) {
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index ebf80c7739e1..48813aeaab80 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1512,6 +1512,22 @@ int dquot_initialize(struct inode *inode)
 }
 EXPORT_SYMBOL(dquot_initialize);
 
+bool dquot_initialize_needed(struct inode *inode)
+{
+	struct dquot **dquots;
+	int i;
+
+	if (!dquot_active(inode))
+		return false;
+
+	dquots = i_dquot(inode);
+	for (i = 0; i < MAXQUOTAS; i++)
+		if (!dquots[i] && sb_has_quota_active(inode->i_sb, i))
+			return true;
+	return false;
+}
+EXPORT_SYMBOL(dquot_initialize_needed);
+
 /*
  * Release all quotas referenced by inode.
  *
diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
index 9c6f768b7d32..dda22f45fc1b 100644
--- a/include/linux/quotaops.h
+++ b/include/linux/quotaops.h
@@ -44,6 +44,7 @@ void inode_sub_rsv_space(struct inode *inode, qsize_t number);
 void inode_reclaim_rsv_space(struct inode *inode, qsize_t number);
 
 int dquot_initialize(struct inode *inode);
+bool dquot_initialize_needed(struct inode *inode);
 void dquot_drop(struct inode *inode);
 struct dquot *dqget(struct super_block *sb, struct kqid qid);
 static inline struct dquot *dqgrab(struct dquot *dquot)
@@ -207,6 +208,11 @@ static inline int dquot_initialize(struct inode *inode)
 	return 0;
 }
 
+static inline bool dquot_initialize_needed(struct inode *inode)
+{
+	return false;
+}
+
 static inline void dquot_drop(struct inode *inode)
 {
 }
-- 
2.13.0.219.gdb65acc882-goog