[PATCH 00/15] ceph: add binary logging (BLOG) for CephFS

[Alex Markuze]

This series adds a binary logging subsystem for the CephFS kernel
client.  On hot I/O paths every dout() call formats a printk-style
string even when nobody is reading the log.  BLOG sidesteps that cost
by storing compact binary records keyed by a source-ID; the records
are decoded offline or via debugfs.

All new code lives under fs/ceph/ and include/linux/ceph/.  There
are no changes outside the Ceph subsystem apart from the kselftests.

Design
------

Allocation.  A page-fragment allocator hands out buffer slices without
taking any global lock.  Freed fragments are recycled through per-CPU
magazine batches so the common-case log path is allocation-free.
Filesystem-reachable allocation uses GFP_NOFS to avoid reclaim
recursion.

Source-ID caching.  Each (file, func, line, fmt) tuple is registered
once in a per-logger rhashtable and assigned a u32 source-ID.  A
per-callsite cache with smp_store_release / smp_load_acquire avoids
the rhashtable lookup after the first hit.  A generation counter on
the logger prevents stale cache hits across mount/unmount cycles.

Per-superblock ownership.  Every mounted CephFS instance (including
-o noshare mounts) gets its own blog_module_context, so enable/disable
and debugfs are fully isolated between mounts.

Context propagation.  ceph_blog_enter() stashes the owning
ceph_fs_client and an optional mds_request pointer in a
ceph_journal_info that lives in current->journal_info.  Nested VFS
re-entry inherits the context only when the owning fsc matches,
preventing cross-mount leaks.  Task pointers used as hash keys are
not pinned; stale entries are retired lazily via PID-mismatch
detection on reuse.

debugfs.  Per-superblock files appear under
  /sys/kernel/debug/ceph/<fsid>/blog/{entries,stats,sources,clients}
plus a bool "enable" knob and a write-only "clear" trigger.

Logging macros.  bout() and boutc() are drop-in replacements for
dout() and doutc(), gated on fsc->blog_enabled.  The serializer
supports all kernel printf specifiers used by Ceph debug logs
including %o.

Patch breakdown
---------------

  01-06  BLOG infrastructure, one patch per compilation unit:
         headers, deserializer, pagefrag allocator, magazine batcher,
         logger core, per-module context manager.

  07     Ceph BLOG scaffolding -- ceph_blog.h, blog_client.c,
         super.h / libceph.h additions, Makefile wiring.

  08     bout/boutc macro definitions in ceph_debug.h.

  09     MDS request plumbing -- switch __do_request() to
         ceph_blog_enter() / ceph_blog_exit().

  10     debugfs interface -- blog_debugfs.c and lifecycle hooks.

  11-14  Callsite conversions -- dout/doutc -> bout/boutc, grouped
         by subsystem: inodes+dirs, data I/O, caps+snaps, helpers.

  15     Selftests and MAINTAINERS update.

Alex Markuze (15):
  ceph: add BLOG public headers
  ceph: add BLOG deserialization support
  ceph: add BLOG page-fragment allocator
  ceph: add BLOG magazine batch allocator
  ceph: add BLOG logger core
  ceph: add BLOG per-module context management
  ceph: add Ceph BLOG scaffolding
  ceph: add bout and boutc wrappers for BLOG
  ceph: switch MDS request plumbing to struct ceph_journal_info
  ceph: add BLOG debugfs interface
  ceph: convert VFS inode and directory paths to bout
  ceph: convert VFS data I/O paths to bout
  ceph: convert capability and snapshot paths to bout
  ceph: convert remaining helper paths to bout
  selftests: add Ceph BLOG smoke test and collection helpers

 MAINTAINERS                                   |   1 +
 fs/ceph/Makefile                              |   6 +
 fs/ceph/addr.c                                | 168 ++---
 fs/ceph/blog_batch.c                          | 312 ++++++++++
 fs/ceph/blog_client.c                         | 266 ++++++++
 fs/ceph/blog_core.c                           | 424 +++++++++++++
 fs/ceph/blog_debugfs.c                        | 434 +++++++++++++
 fs/ceph/blog_des.c                            | 342 ++++++++++
 fs/ceph/blog_module.c                         | 584 ++++++++++++++++++
 fs/ceph/blog_pagefrag.c                       |  95 +++
 fs/ceph/caps.c                                | 252 ++++----
 fs/ceph/crypto.c                              |  14 +-
 fs/ceph/debugfs.c                             |  23 +-
 fs/ceph/dir.c                                 | 290 ++++++---
 fs/ceph/export.c                              |  83 ++-
 fs/ceph/file.c                                | 274 +++++---
 fs/ceph/inode.c                               | 233 ++++---
 fs/ceph/ioctl.c                               |   6 +-
 fs/ceph/locks.c                               |  66 +-
 fs/ceph/mds_client.c                          | 293 ++++-----
 fs/ceph/mdsmap.c                              |   8 +-
 fs/ceph/quota.c                               |   2 +-
 fs/ceph/snap.c                                |  66 +-
 fs/ceph/super.c                               |  58 +-
 fs/ceph/super.h                               |   5 +
 fs/ceph/xattr.c                               |  88 ++-
 include/linux/ceph/blog.h                     |   0
 include/linux/ceph/blog_batch.h               |   0
 include/linux/ceph/blog_des.h                 |   0
 include/linux/ceph/blog_module.h              |   0
 include/linux/ceph/blog_pagefrag.h            |   0
 include/linux/ceph/blog_ser.h                 |   0
 include/linux/ceph/ceph_blog.h                | 284 +++++++++
 include/linux/ceph/ceph_debug.h               |  44 +-
 include/linux/ceph/libceph.h                  |   2 +
 tools/testing/selftests/Makefile              |   1 +
 tools/testing/selftests/ceph_blog/Makefile    |   7 +
 .../selftests/ceph_blog/blog_analyze.sh       | 124 ++++
 .../selftests/ceph_blog/blog_collect.sh       | 116 ++++
 .../selftests/ceph_blog/blog_smoke_test.sh    | 363 +++++++++++
 tools/testing/selftests/ceph_blog/config      |   2 +
 41 files changed, 4583 insertions(+), 753 deletions(-)
 create mode 100644 fs/ceph/blog_batch.c
 create mode 100644 fs/ceph/blog_client.c
 create mode 100644 fs/ceph/blog_core.c
 create mode 100644 fs/ceph/blog_debugfs.c
 create mode 100644 fs/ceph/blog_des.c
 create mode 100644 fs/ceph/blog_module.c
 create mode 100644 fs/ceph/blog_pagefrag.c
 create mode 100644 include/linux/ceph/blog.h
 create mode 100644 include/linux/ceph/blog_batch.h
 create mode 100644 include/linux/ceph/blog_des.h
 create mode 100644 include/linux/ceph/blog_module.h
 create mode 100644 include/linux/ceph/blog_pagefrag.h
 create mode 100644 include/linux/ceph/blog_ser.h
 create mode 100644 include/linux/ceph/ceph_blog.h
 create mode 100644 tools/testing/selftests/ceph_blog/Makefile
 create mode 100644 tools/testing/selftests/ceph_blog/blog_analyze.sh
 create mode 100644 tools/testing/selftests/ceph_blog/blog_collect.sh
 create mode 100644 tools/testing/selftests/ceph_blog/blog_smoke_test.sh
 create mode 100644 tools/testing/selftests/ceph_blog/config

-- 
2.34.1