The htree dir_index is perhaps one of the most characteristic
features of the linux ext3 implementation. It was removed
in r281670, due to repeated bug reports.
Damjan Jovanic detected and fixed three bugs and did some
stress testing by building Apache OpenOffice on top of it
so it is now in good shape to bring back.
Differential Revision: https://reviews.freebsd.org/D5007
Submitted by: Damjan Jovanovic
Reviewed by: pfg
Tested by: pho
Relnotes: Yes
MFC after: 2 months (only 10.x)
The htree directory index is a highly desirable feature for research
purposes and was meant to improve performance in our ext2/3 driver.
Unfortunately our implementation has two problems:
- It never really delivered any performance improvement.
- It appears to corrupt the filesystem in undetermined circumstances.
Strictly speaking dir_index is not required for read/write support in
ext2/3 and our limited ext4 support still works fine without it.
Regain stability in the ext2 driver by removing it. We may need it back
(fixed) if we want to support encrypted ext4 support but thanks to the
wonders of version control we can always revert this change and bring it
back.
PR: 191895
PR: 198731
PR: 199309
MFC after: 5 days
The htree implementation uses code derived from the
RSA Data Security, Inc. MD4 Message-Digest Algorithm.
Add a proper licensing statement for the code and clarify
the corresponding comments.
Approved by: core (hrs)
This is a port of NetBSD's GSoC 2012 Ext3 HTree directory indexing
by Vyacheslav Matyushin. It was cleaned up and enhanced for FreeBSD
by Zheng Liu (lz@).
This is an excellent example of work shared among different projects:
Vyacheslav was able to look at an early prototype from Zheng Liu who
was also able to check the code from Haiku (with permission).
As in linux, the feature is not available by default and must be
enabled explicitly with tune2fs. We still do not support the
workarounds required in readdir for NFS.
Submitted by: Zheng Liu
Tested by: Mike Ma
Sponsored by: Google Inc.
MFC after: 1 week
