1BFS - ToDo, May 26th, 2003
2-----
3
4BlockAllocator
5
6 - the BlockAllocator is only slightly optimized and probably slow
7 - the first free and the largest range are currently not correctly maintained (only efficiency suffers - it does work correctly)
8 - the allocation policies will have to stand against some real world tests
9 - the access to the block bitmap is currently managed using a global lock (doesn't matter as long as transactions are serialized)
10
11
12DataStream
13
14 - only files are trimmed back (in bfs_close()), but every inode has a preallocated stream...
15 - Inode::GrowStream(): merging of block_runs doesn't work between range/block boundaries
16 - check the array block size in BFS for different block sizes
17
18
19Queries
20
21 - There shouldn't be any cases where you can speed up a query with reordering the query expression - test it
22 - Check permissions of the parent directories
23 - Add protection against crashing applications which had a query open - at least the original BeOS kernel does not free the cookie (which throws some memory away *and* prevents unmounting the disk), but that won't be needed for OpenBeOS
24 - the query set for "!=" and last_modified/size is not the same as for "="; last_modified/size don't contain directories
25 - check if the query has to be checked for a live update
26 - accept hex values 0x...
27
28
29Journal
30
31 - Check if there are any standard and often-happening cases for a transaction to fail, and if so, start the transaction only when necessary
32 - if the system crashes between bfs_unlink() and bfs_remove_vnode(), the inode can be removed from the tree, but its memory is still allocated - this can happen if the inode is still in use by someone (and that's what the "chkbfs" utility is for, mainly).
33 - add delayed index updating (+ delete actions to solve the issue above)
34 - multiple log files, parallel transactions? (note that parallel transactions would require more locking to be done)
35 - variable sized log file
36 - as long as we have a fixed-sized log file, it should be possible to reserve space for a transaction to be able to decide if batching it is possible
37
38
39BPlusTree
40
41 - BPlusTree::Remove() could trigger CachedNode::Free() to go through the free nodes list and free all pages at the end of the data stream
42 - BPlusTree::Remove() could let the tree shrink (simple kind of reorganization)
43 - updating the TreeIterators doesn't work yet for duplicates (which may be a problem if a duplicate node will go away after a remove)
44 - BPlusTree::RemoveDuplicate() could merge the contents of duplicate node with only a few entries to save some space (right now, only empty nodes are freed)
45
46
47Inode
48
49 - exchange Inode::OldLastModified() with Inode::NewLastModified(), and don't change the last_modified field directly in Inode::WriteAt() for consistency in case of a crash
50 - the size is only updated in bfs_close() - but if the system crashes before, the entry in the size index doesn't match the one in the inode anymore - it would be better to let the data.size not reflect the real file size in this case (since the max_xxx_range entries are always correct)
51 - Inode::FillGapWithZeros() currently disabled; apart from being slow, it really shouldn't be executed while a transaction is running, because that stops all other threads from doing anything (which can be a long time for a 100 MB file)
52 - need better locking mechanism in combination with B+trees etc.!
53
54
55Indices
56
57 - consider Index::UpdateLastModified() writing back the updated inode
58 - clearing up Index::Update() and live query update (seems to be a bit confusing right now)
59 - investigate adding an index cache to improve performance
60
61Attributes
62
63 - Inode::WriteAttribute() doesn't check if the attribute data may fit into the small_data region if there already is that attribute as an attribute file
64 - for indices, we could get the old data from there when doing a query update
65
66
67Volume
68
69
70kernel_interface
71
72 - missing functions, maybe they are not really needed: bfs_rename_attr(), bfs_rename_index(), bfs_initialize(), bfs_link()
73 - bfs_rename() currently doesn't respect any permissions
74
75
76general stuff
77
78 - There are also some comments with a leading "ToDo:" directly in the code which may not be mentioned here.
79 - implement mkbfs (try to do it in OpenBeOS style directly - only write the superblock from user space)
80
81
82-----
83Axel D��rfler
84axeld@pinc-software.de
85