git: kernel - Add trigger_syncer(), VFS_MODIFYING()

[Matthew Dillon]

commit 1c222faf36ea48e314d77b9f242ed1258f7717d5
Author: Matthew Dillon <***@apollo.backplane.com>
Date: Tue Dec 4 21:49:35 2018 -0800

kernel - Add trigger_syncer(), VFS_MODIFYING()

* Add trigger_syncer(). This function asynchronously triggers the
syncer vnode in the syncer thread for the mount. It is a NOP if
there is no syncer thread or syncer vnode.

Will be used by HAMMER2 to pipeline syncs when heavy filesystem
activity over-extends internal memory structures.

* Add VFS_MODIFYING(). This is a hook into the filesystem that
modifying filesystem ops in the kernel will call prior to locking
any vnodes. It allows the filesystem to moderate the over-allocation
of internal structures. Waiting until after the VOP is called is too
late, so we need kernel support for this. Numerous attempts to hack
moderation code into the H2 VOPs have all failed spectacularly.

In H2, over-allocation can occur because H2 must retain disconnected
inodes related to file creation and deletion until the next sync cycle.

Summary of changes:
sys/kern/vfs_default.c | 6 ++++++
sys/kern/vfs_init.c | 4 ++++
sys/kern/vfs_sync.c | 44 ++++++++++++++++++++++++++++++++++++++++----
sys/kern/vfs_syscalls.c | 1 +
sys/kern/vfs_vnops.c | 12 ++++++++++--
sys/sys/mount.h | 7 ++++++-
sys/sys/vnode.h | 1 +
7 files changed, 68 insertions(+), 7 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/1c222faf36ea48e314d77b9f242ed1258f7717d5