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 allocation. Quota blocks
are reserved in memory, inode and quota won't gets dirtied until later
block allocation time.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 86 insertions, 31 deletions

diff --git a/fs/dquot.c b/fs/dquot.c
index bca3cac..9b1c4d3 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -899,6 +899,11 @@ static inline void dquot_incr_space(struct dquot *dquot, qsize_t number)
 	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 ||
@@ -1068,7 +1073,11 @@ err_out:
 	kfree_skb(skb);
 }
 #endif
-
+/*
+ * Write warnings to the console and send warning messages over netlink.
+ *
+ * Note that this function can sleep.
+ */
 static inline void flush_warnings(struct dquot * const *dquots, char *warntype)
 {
 	int i;
@@ -1129,13 +1138,18 @@ static int check_idq(struct dquot *dquot, qsize_t inodes, char *warntype)
 /* 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;
@@ -1143,7 +1157,7 @@ static int check_bdq(struct dquot *dquot, qsize_t space, int prealloc, char *war
 	}
 
 	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)
@@ -1152,7 +1166,7 @@ static int check_bdq(struct dquot *dquot, qsize_t space, int prealloc, char *war
 	}
 
 	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;
@@ -1306,51 +1320,92 @@ 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);
-	ret = QUOTA_OK;
-warn_put_all:
+	if (!reserve)
+		inode_add_bytes(inode, number);
+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)) {
+		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;
+
+	/* 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
@@ -2057,7 +2112,7 @@ static void do_get_dqblk(struct dquot *dquot, struct if_dqblk *di)
 	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;
@@ -2097,7 +2152,7 @@ static int do_set_dqblk(struct dquot *dquot, struct if_dqblk *di)
 
 	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);
 	}