[PATCH] fs/ext4: get project quota from inode for mangling statfs results

[Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>]

Right now ext4_statfs_project() does quota lookup by id every time.
This is costly operation, especially if there is no inode who hold
reference to this quota and dqget() reads it from disk each time.

Function ext4_statfs_project() could be moved into generic quota code,
it is required for every filesystem which uses generic project quota.

Reported-by: Dmitry Monakhov <dmtrmonakhov@xxxxxxxxxxxxxx>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
 fs/ext4/super.c |   25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index dd654e53ba3d..f841c66aa499 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5532,18 +5532,23 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 }
 
 #ifdef CONFIG_QUOTA
-static int ext4_statfs_project(struct super_block *sb,
-			       kprojid_t projid, struct kstatfs *buf)
+static int ext4_statfs_project(struct inode *inode, struct kstatfs *buf)
 {
-	struct kqid qid;
+	struct super_block *sb = inode->i_sb;
 	struct dquot *dquot;
 	u64 limit;
 	u64 curblock;
+	int err;
+
+	err = dquot_initialize(inode);
+	if (err)
+		return err;
+
+	spin_lock(&inode->i_lock);
+	dquot = ext4_get_dquots(inode)[PRJQUOTA];
+	if (!dquot)
+		goto out_unlock;
 
-	qid = make_kqid_projid(projid);
-	dquot = dqget(sb, qid);
-	if (IS_ERR(dquot))
-		return PTR_ERR(dquot);
 	spin_lock(&dquot->dq_dqb_lock);
 
 	limit = (dquot->dq_dqb.dqb_bsoftlimit ?
@@ -5569,7 +5574,9 @@ static int ext4_statfs_project(struct super_block *sb,
 	}
 
 	spin_unlock(&dquot->dq_dqb_lock);
-	dqput(dquot);
+out_unlock:
+	spin_unlock(&inode->i_lock);
+
 	return 0;
 }
 #endif
@@ -5609,7 +5616,7 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
 #ifdef CONFIG_QUOTA
 	if (ext4_test_inode_flag(dentry->d_inode, EXT4_INODE_PROJINHERIT) &&
 	    sb_has_quota_limits_enabled(sb, PRJQUOTA))
-		ext4_statfs_project(sb, EXT4_I(dentry->d_inode)->i_projid, buf);
+		ext4_statfs_project(dentry->d_inode, buf);
 #endif
 	return 0;
 }