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>

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index cd6bb9a33c131f3ab2ee5cb7d4654069777f3ad6..1cb8fa84300fb76954247e13a1f54b0a9f5e8a17 100644 (file)
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1318,6 +1318,67 @@ 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)
@@ -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++)
@@ -1502,39 +1547,10 @@ 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;
        }
 
@@ -1558,20 +1574,42 @@ 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
  */
@@ -1609,19 +1647,6 @@ 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.
  *
@@ -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++) {

diff --git a/include/linux/quota.h b/include/linux/quota.h
index e70e62194243f1a255b83cf930e9d69b9bc6f1fc..a6861f11748044d2c666c6f94edf463c8c47660a 100644 (file)
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -315,8 +315,9 @@ 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 */