git: hammer2 - refactor filesystem sync 4/N

Matthew Dillon dillon at
Wed Dec 5 14:29:27 PST 2018

commit 6f445d15835c6677a0a79c8d168ef44d0b9b22c3
Author: Matthew Dillon <dillon at>
Date:   Tue Nov 13 13:32:33 2018 -0800

    hammer2 - refactor filesystem sync 4/N
    * Save synchronized iroot blockmaps for snapshot code, and use them
      in the snapshot code.
    * Improve dependency handling and syncq/sideq flagging for
      dependencies.  Also improve the hammer2_inode_t reordering
      code that allows the frontend to continue operating on dirty
      inodes simultaneous with a filesystem sync.
    * Move inode deletion into the filesystem sync code (in addition to
      creation), for the same reason.
    * Fix lost ref counts in the snapshot code which were causing umount
    * Stabilization pass on volume flush code.  Since flushes stop at
      inode boundaries, we must properly flush the superroot before
      flushing the volume header.  That is, the flush sequence is:
      - flush inodes for PFS  (flushes inode content)
      - flush PFS root inode  (flushes through to inodes)
      - flush superroot inode (flushes through to PFS root)
      - flush volume header   (flushes voulume header to superroot)
      Theoretically this allows the filesystem asynchronously write data
      and inodes flushed by the kernel's buffer cache and vnode code
      concurrent with a filesystem flush without messing up filesystem
      consistency, because these asynchronously flushed inodes are not
      included (or have already been flushed) in the filesystem flush that
      is already underway.
    * Filesystem consistency still not perfect (using snapshot-debug
      directive to test during heavy filesystem modification loads,
      directory entries are sometimes desynchronized from their inodes).

Summary of changes:
 sys/vfs/hammer2/hammer2.h        |   6 +-
 sys/vfs/hammer2/hammer2_flush.c  |  60 +++++--
 sys/vfs/hammer2/hammer2_inode.c  | 197 ++++++++-------------
 sys/vfs/hammer2/hammer2_ioctl.c  |  18 +-
 sys/vfs/hammer2/hammer2_vfsops.c | 358 ++++++++++++++++++++++++---------------
 sys/vfs/hammer2/hammer2_vnops.c  |  30 ++--
 6 files changed, 368 insertions(+), 301 deletions(-)

DragonFly BSD source repository

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