[PATCH v5 0/5] vfs: Use dlock list for SB's s_inodes list

[Waiman Long]

v4->v5:
 - Rebased the patch to 4.8-rc1 (changes to fs/fs-writeback.c was
   dropped).
 - Use kcalloc() instead of percpu_alloc() to allocate the dlock list
   heads structure as suggested by Christoph Lameter.
 - Replaced patch 5 by another one that made sibling CPUs use the same
   dlock list head thus reducing the number of list heads that needed
   to be maintained.

v3->v4:
 - As suggested by Al, encapsulate the dlock list mechanism into
   the dlist_for_each_entry() and dlist_for_each_entry_safe()
   which are the equivalent of list_for_each_entry() and
   list_for_each_entry_safe() for regular linked list. That simplifies
   the changes in the call sites that perform dlock list iterations.
 - Add a new patch to make the percpu head structure cacheline aligned
   to prevent cacheline contention from disrupting the performance
   of nearby percpu variables.

v2->v3:
 - Remove the 2 persubnode API patches.
 - Merge __percpu tag patch 2 into patch 1.
 - As suggested by Tejun Heo, restructure the dlock_list_head data
   structure to hide the __percpu tag and rename some of the functions
   and structures.
 - Move most of the code from dlock_list.h to dlock_list.c and export
   the symbols.

v1->v2:
 - Add a set of simple per-subnode APIs that is between percpu and
   per-node in granularity.
 - Make dlock list to use the per-subnode APIs so as to reduce the
   total number of separate linked list that needs to be managed
   and iterated.
 - There is no change in patches 1-5.

This is a follow up of the following patchset:

  [PATCH v7 0/4] vfs: Use per-cpu list for SB's s_inodes list
  https://lkml.org/lkml/2016/4/12/1009

Patch 1 introduces the dlock list. The list heads are allocated
by kcalloc() instead of percpu_alloc(). This may slightly increase
cacheline contention when multiple CPUs are accessing dlock list,
but improve performance when the whole dlock list needs to be iterated.

Patch 2 cleans up the fsnotify_unmount_inodes() function by making
the code simpler and more standard.

Patch 3 replaces the use of list_for_each_entry_safe() in
evict_inodes() and invalidate_inodes() by list_for_each_entry().

Patch 4 modifies the superblock and inode structures to use the dlock
list. The corresponding functions that reference those structures
are modified.

Patch 5 makes the sibling CPUs use the same dlock list head to reduce
the number of list heads that need to be iterated.

Jan Kara (2):
  fsnotify: Simplify inode iteration on umount
  vfs: Remove unnecessary list_for_each_entry_safe() variants

Waiman Long (3):
  lib/dlock-list: Distributed and lock-protected lists
  vfs: Use dlock list for superblock's inode list
  lib/dlock-list: Make sibling CPUs share the same linked list

 fs/block_dev.c             |    9 +-
 fs/drop_caches.c           |    9 +-
 fs/inode.c                 |   38 +++----
 fs/notify/inode_mark.c     |   52 ++-------
 fs/quota/dquot.c           |   14 +--
 fs/super.c                 |    7 +-
 include/linux/dlock-list.h |  230 +++++++++++++++++++++++++++++++++++++
 include/linux/fs.h         |    8 +-
 lib/Makefile               |    2 +-
 lib/dlock-list.c           |  268 ++++++++++++++++++++++++++++++++++++++++++++
 10 files changed, 548 insertions(+), 89 deletions(-)
 create mode 100644 include/linux/dlock-list.h
 create mode 100644 lib/dlock-list.c