quota: decouple fs reserved space from quota reservation

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.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 119 insertions, 94 deletions

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index cd6bb9a33c13..1cb8fa84300f 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1319,6 +1319,67 @@ 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
@@ -1336,6 +1397,21 @@ 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;
 
@@ -1346,7 +1422,8 @@ 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++) {
@@ -1357,64 +1434,32 @@ 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);
 
@@ -1471,14 +1516,14 @@ 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;
         }
 
@@ -1490,7 +1535,7 @@ 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++)
@@ -1503,38 +1548,9 @@ 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];
@@ -1543,7 +1559,7 @@ 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;
         }
 
@@ -1558,21 +1574,43 @@ 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)
+{
+        __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)
@@ -1610,19 +1648,6 @@ 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
@@ -1665,7 +1690,7 @@ 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++) {