[PATCH v2 00/18] fs/ceph: optimize struct layouts

[Max Kellermann <max.kellermann@ionos.com>]

This patch set aims to reduce the memory usage of the Ceph filesystems
by optimizing the layout of structs, most importantly struct
ceph_inode_info:

- use `bool` instead of `int` for booelans
- use `u32` instead of `u64` where possible
- reorder fields to eliminate padding holes
- eliminate redundant fields

Without this patch set, ceph_inode_info looks like this with pahole:

	/* size: 1456, cachelines: 23, members: 79 */
	/* sum members: 1424, holes: 8, sum holes: 32 */
	/* member types with holes: 3, total: 3 */

With this patch set, struct ceph_inode_info got smaller by 96 bytes:

	/* size: 1360, cachelines: 22, members: 76 */
	/* member types with holes: 1, total: 1 */

struct ceph_cap shrinks by 24 bytes:

	/* size: 120, cachelines: 2, members: 12 */

	/* size: 96, cachelines: 2, members: 10 */

struct ceph_snap_realm shrinks by 24 bytes, too:

	/* size: 232, cachelines: 4, members: 21 */
	/* sum members: 216, holes: 3, sum holes: 12 */

	/* size: 208, cachelines: 4, members: 20 */

---
v1->v2:
 - fix CONFIG_FS_ENCRYPTION check in "i_truncate_pagecache_size" patch
 - add patches to shrink ceph_cap and ceph_snap_realm

Max Kellermann (18):
  fs/ceph/super: remove unused field `i_cap_migration_resv`
  fs/ceph/super: make field `i_truncate_pagecache_size` optional
  include/ceph/ceph_fs.h: convert `pool_id` to u32
  fs/ceph/super.h: convert ceph_inode_xattr fields to `bool`
  fs/ceph/super.h: convert ceph_cap_snap.writing fields to `bool`
  fs/ceph: consistently use `u32` for `time_warp_seq`
  fs/ceph/super: reorder fields to eliminate padding holes
  fs/ceph: remove i_truncate_mutex, use i_fragtree_mutex for both
  fs/ceph/super.h: add `const` to helpers
  fs/ceph/super.h: add helper ceph_in_snap()
  fs/ceph: use ceph_vino() etc. instead of accessing i_vino directly
  fs/ceph: remove redundant inode number from ceph_inode_info
  fs/ceph: remove unused field `ceph_cap.last_used`
  fs/ceph: convert ceph_cap.queue_release to bool
  fs/ceph/super: move `ceph_cap.caps_item` into the union
  fs/ceph/snap: add a kmem_cache for struct ceph_snap_realm
  fs/ceph/super: reorder struct ceph_snap_realm fields
  fs/ceph/super: remove redundant field `ceph_snap_realm.parent_ino`

 fs/ceph/acl.c                |   2 +-
 fs/ceph/addr.c               |  23 ++++---
 fs/ceph/cache.c              |   4 +-
 fs/ceph/caps.c               |  14 ++--
 fs/ceph/dir.c                |  20 +++---
 fs/ceph/export.c             |   8 +--
 fs/ceph/file.c               |  28 ++++----
 fs/ceph/inode.c              |  38 +++++++----
 fs/ceph/mds_client.c         |  16 ++---
 fs/ceph/mds_client.h         |   2 +-
 fs/ceph/quota.c              |   6 +-
 fs/ceph/snap.c               |  17 +++--
 fs/ceph/super.c              |   9 +++
 fs/ceph/super.h              | 123 +++++++++++++++++++++++++----------
 fs/ceph/util.c               |   8 +--
 fs/ceph/xattr.c              |  18 ++---
 include/linux/ceph/ceph_fs.h |   2 +-
 include/linux/ceph/libceph.h |   1 +
 18 files changed, 204 insertions(+), 135 deletions(-)

-- 
2.47.3