ext4: delayed allocation ENOSPC handling

This patch does block reservation for delayed
allocation, to avoid ENOSPC later at page flush time.

Blocks(data and metadata) are reserved at da_write_begin()
time, the freeblocks counter is updated by then, and the number of
reserved blocks is store in per inode counter.
        
At the writepage time, the unused reserved meta blocks are returned
back. At unlink/truncate time, reserved blocks are properly released.

Updated fix from  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
to fix the oldallocator block reservation accounting with delalloc, added
lock to guard the counters and also fix the reservation for meta blocks.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index de9d3d0eb203..25e2f2488cd2 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -574,6 +574,11 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
         INIT_LIST_HEAD(&ei->i_prealloc_list);
         spin_lock_init(&ei->i_prealloc_lock);
         jbd2_journal_init_jbd_inode(&ei->jinode, &ei->vfs_inode);
+        ei->i_reserved_data_blocks = 0;
+        ei->i_reserved_meta_blocks = 0;
+        ei->i_allocated_meta_blocks = 0;
+        ei->i_delalloc_reserved_flag = 0;
+        spin_lock_init(&(ei->i_block_reservation_lock));
         return &ei->vfs_inode;
 }