git: hammer2 - Present hardlink solution, misc stability work
dillon at crater.dragonflybsd.org
Tue Nov 17 17:33:16 PST 2015
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date: Tue Nov 17 17:21:14 2015 -0800
hammer2 - Present hardlink solution, misc stability work
* The H2 design has had a long-standing problem of losing track of
hardlinks when intermediate directories are renamed, breaking the
common-parent-directory design for the inode target.
Fix this issue by placing the hardlink target in the first common
parent directory chflagged 'xlink' (or the root of the mount if
no parent is chflagged 'xlink'). Thus, by default, hardlink targets
for cross-directory situations will be placed in the root of the mount
and thus no confusion can ever occur if a mid-path directory is moved
within the hierarchy.
* This change does not modify the behavior of placing the hardlink target
in the same directory as the hardlink pointers when they are all in the
* installworld now chflags /*, /usr/*, /var/*, and /home/* 'xlink'.
* Note that hardlink and rename operations across 'xlink' boundaries
are disallowed (for obvious reasons), but system operators have very
rarely used hardlinks in major directory crossings. However, we might
be pushing it a bit much to automatically chflag /home/*.
In the past there have been a few minor situations where major-crossing
hardlinks are attempted. 'lpr' for example tries to hardlink a user
file into /var/spool, but will copy it if it cannot. Similarly there
have been situations in the past where hardlinks between home directories
have been used to save space, but franklyl softlinks can be used almost
as easily and such situations have fallen into disfavor.
* Stability improvements to the XOP FIFO mechanics, locking cleanups.
Summary of changes:
sys/sys/mutex2.h | 12 ++++++++
sys/vfs/hammer2/hammer2.h | 19 ++++---------
sys/vfs/hammer2/hammer2_chain.c | 60 ++++++++++++++++++++++++++--------------
sys/vfs/hammer2/hammer2_inode.c | 54 +++++++++++++++++++++++++++---------
sys/vfs/hammer2/hammer2_thread.c | 31 +++++++++++++++++++--
sys/vfs/hammer2/hammer2_vnops.c | 33 ++++++++++++++++------
sys/vfs/hammer2/hammer2_xops.c | 7 ++---
7 files changed, 153 insertions(+), 63 deletions(-)
DragonFly BSD source repository
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