doing copy-on-write.
- Change VFS_SNAPSHOT() to return the snapshot vnode locked.
- Make the IO path for copy-on-write and snapshot-read more lightweight.
Avoids deadlocks where vn_rdwr(...READ...) has a shared lock and needs
to copy-on-write.
Avoids deadlocks/panics where to clean pages the copy-on-write needs
to allocate pages for its VOP_PUTPAGES().
L_COWINPROGRESS part approved by: Jason R. Thorpe <thorpej@netbsd.org>
- Not enabled by default. Needs kernel option FFS_SNAPSHOT.
- Change parameters of ffs_blkfree.
- Let the copy-on-write functions return an error so spec_strategy
may fail if the copy-on-write fails.
- Change genfs_*lock*() to use vp->v_vnlock instead of &vp->v_lock.
- Add flag B_METAONLY to VOP_BALLOC to return indirect block buffer.
- Add a function ffs_checkfreefile needed for snapshot creation.
- Add special handling of snapshot files:
Snapshots may not be opened for writing and the attributes are read-only.
Use the mtime as the time this snapshot was taken.
Deny mtime updates for snapshot files.
- Add function transferlockers to transfer any waiting processes from
one lock to another.
- Add vfsop VFS_SNAPSHOT to take a snapshot and make it accessible through
a vnode.
- Add snapshot support to ls, fsck_ffs and dump.
Welcome to 2.0F.
Approved by: Jason R. Thorpe <thorpej@netbsd.org>
