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, 21 insertions, 0 deletions

diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
index 0b35b3a1be05..3e3a0d2874d9 100644
--- a/include/linux/quotaops.h
+++ b/include/linux/quotaops.h
@@ -183,6 +183,16 @@ static inline int vfs_dq_alloc_space(struct inode *inode, qsize_t nr)
         return ret;
 }
 
+static inline int vfs_dq_reserve_space(struct inode *inode, qsize_t nr)
+{
+        if (sb_any_quota_active(inode->i_sb)) {
+                /* Used space is updated in alloc_space() */
+                if (inode->i_sb->dq_op->reserve_space(inode, nr, 0) == NO_QUOTA)
+                        return 1;
+        }
+        return 0;
+}
+
 static inline int vfs_dq_alloc_inode(struct inode *inode)
 {
         if (sb_any_quota_active(inode->i_sb)) {
@@ -339,6 +349,11 @@ static inline int vfs_dq_alloc_space(struct inode *inode, qsize_t nr)
         return 0;
 }
 
+static inline int vfs_dq_reserve_space(struct inode *inode, qsize_t nr)
+{
+        return 0;
+}
+
 static inline void vfs_dq_free_space_nodirty(struct inode *inode, qsize_t nr)
 {
         inode_sub_bytes(inode, nr);
@@ -376,6 +391,12 @@ static inline int vfs_dq_alloc_block(struct inode *inode, qsize_t nr)
                         nr << inode->i_sb->s_blocksize_bits);
 }
 
+static inline int vfs_dq_reserve_block(struct inode *inode, qsize_t nr)
+{
+        return vfs_dq_reserve_space(inode,
+                        nr << inode->i_blkbits);
+}
+
 static inline void vfs_dq_free_block_nodirty(struct inode *inode, qsize_t nr)
 {
         vfs_dq_free_space_nodirty(inode, nr << inode->i_sb->s_blocksize_bits);