Directory index was introduced in ext3. We don't always use the
prefix to denote the ext2 variant they belong to but when we
do we should try to be accurate.
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
Consistently use a single tab after a #define as mentioned in style(9).
Use tabs instead of space for indenting.
Fix a typo: "hash_vesion".
No functional change.
MFC after: 3 days
The ext4 inode flags do not have equivalents for chflags (1)
and hold information that is private to the implementation.
The i_flag field in the inode is a better place to hold the Ext4
inode flags as it saves us from masking flags while setting or
getting attributes. It should also make things cleaner if we
implement write support for Ext4.
Suggested by: bde
Tested by: Mike Ma
MFC after: 3 days
The IN_* flags should be set in i_flag instead of corrupting
i_flags [1].
Re-enable HTree dirindex as the last series of bug fixes
seems to have fixed the issues.
Reported by: bde [1]
Tested by: kevlo
MFC after: 1 week
r260545 cleared the inode flags to fix corruption problems but
we still need to pass some EXT4 flags for the ext4 read-only
mode. None of these attributes has an equivalent in FreeBSD and
are uninteresting for the system utilities so they should be
innaccessible in ext2_getattrib().
Note: we also use EXT4_HUGE_FILE but we use it directly from the
dinode structure so it is not necessary to translate it,
Suggested by: bde
MFC after: 3 days
Our code does not consider yet the case of hash collisions. This
is a rather annoying situation where two or more files that
happen to have the same hash value will not appear accessible.
The situation is not difficult to work-around but given that things
will just work without enabling htree we will save possible
embarrassments for the next release.
Reported by: Kevin Lo
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
