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Message-Id: <20250610-reftrack-dbgfs-v14-0-efb532861428@kernel.org>
Date: Tue, 10 Jun 2025 10:59:20 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Tvrtko Ursulin <tursulin@...ulin.net>
Cc: Krzysztof Karas <krzysztof.karas@...el.com>,
Kuniyuki Iwashima <kuniyu@...zon.com>, Qasim Ijaz <qasdev00@...il.com>,
Nathan Chancellor <nathan@...nel.org>, Andrew Lunn <andrew@...n.ch>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
Jeff Layton <jlayton@...nel.org>,
Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH v14 0/9] ref_tracker: add ability to register a debugfs
file for a ref_tracker_dir
For those just joining in, this series adds a new top-level
"ref_tracker" debugfs directory, and has each ref_tracker_dir register a
file in there as part of its initialization. It also adds the ability to
register a symlink with a more human-usable name that points to the
file, and does some general cleanup of how the ref_tracker object names
are handled.
The big change in this set is in how debugfs entries get removed:
With the last set, Jakub pointed out a warning that showed it calling
debugfs_remove() from RCU callback [1].
While ref_tracker_dir_init is generally safe for sleeping operations,
the same can't be said for ref_tracker_dir_exit(). It can be called from
any context, so it's not safe to sleep in that function. The removal of
debugfs dentries has to be deferred.
This set revamps how the dentries are tracked. Instead of pointers in
the ref_tracker_dir, they are tracked in xarrays from the time they are
instantiated. ref_tracker_dir_exit() will mark the appropriate xarray
entries for deletion and kick off a workqueue job to clean them up
asynchronously.
This unfortunately necessitates some complex locking for
ref_tracker_debugfs_show(), since the debugfs dentries can now outlive
their corresponding ref_tracker_dir. It's not pretty, but it should
work.
[1]: https://netdev-3.bots.linux.dev/vmksft-packetdrill-dbg/results/149560/2-tcp-slow-start-slow-start-app-limited-pkt/stderr
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
Changes in v14:
- Clean up dentries asynchronously after ref_tracker_dir_exit()
- Link to v13: https://lore.kernel.org/r/20250603-reftrack-dbgfs-v13-0-7b2a425019d8@kernel.org
Changes in v13:
- drop i915 patch
- Link to v12: https://lore.kernel.org/r/20250529-reftrack-dbgfs-v12-0-11b93c0c0b6e@kernel.org
Changes in v12:
- drop redundant pr_warn() calls. Debugfs already warns when these ops fail
- Link to v11: https://lore.kernel.org/r/20250528-reftrack-dbgfs-v11-0-94ae0b165841@kernel.org
Changes in v11:
- don't call ref_tracker_dir_init() more than once for same i915 objects
- use %llx in format for net_cookie in symlink name
- Link to v10: https://lore.kernel.org/r/20250527-reftrack-dbgfs-v10-0-dc55f7705691@kernel.org
Changes in v10:
- drop the i915 symlink patch
- Link to v9: https://lore.kernel.org/r/20250509-reftrack-dbgfs-v9-0-8ab888a4524d@kernel.org
Changes in v9:
- fix typo in ref_tracker_dir_init() kerneldoc header
- Link to v8: https://lore.kernel.org/r/20250507-reftrack-dbgfs-v8-0-607717d3bb98@kernel.org
Changes in v8:
- fix up compiler warnings that the KTR warned about
- ensure builds with CONFIG_DEBUG_FS=n and CONFIG_REF_TRACKER=y work
- Link to v7: https://lore.kernel.org/r/20250505-reftrack-dbgfs-v7-0-f78c5d97bcca@kernel.org
Changes in v7:
- include net->net_cookie in netns symlink name
- add __ostream_printf to ref_tracker_dir_symlink() stub function
- remove unneeded #include of seq_file.h
- Link to v6: https://lore.kernel.org/r/20250430-reftrack-dbgfs-v6-0-867c29aff03a@kernel.org
Changes in v6:
- clean up kerneldoc comment for ref_tracker_dir_debugfs()
- add missing stub function for ref_tracker_dir_symlink()
- temporary __maybe_unused on ref_tracker_dir_seq_print() to silence compiler warning
- Link to v5: https://lore.kernel.org/r/20250428-reftrack-dbgfs-v5-0-1cbbdf2038bd@kernel.org
Changes in v5:
- add class string to each ref_tracker_dir
- auto-register debugfs file for every tracker in ref_tracker_dir_init
- add function to allow adding a symlink for each tracker
- add patches to create symlinks for netns's and i915 entries
- change output format to print class@%p instead of name@%p
- eliminate the name field in ref_tracker_dir
- fix off-by-one bug when NULL terminating name string
- Link to v4: https://lore.kernel.org/r/20250418-reftrack-dbgfs-v4-0-5ca5c7899544@kernel.org
Changes in v4:
- Drop patch to widen ref_tracker_dir_.name, use NAME_MAX+1 (256) instead since this only affects dentry name
- Link to v3: https://lore.kernel.org/r/20250417-reftrack-dbgfs-v3-0-c3159428c8fb@kernel.org
Changes in v3:
- don't overwrite dir->name in ref_tracker_dir_debugfs
- define REF_TRACKER_NAMESZ and use it when setting name
- Link to v2: https://lore.kernel.org/r/20250415-reftrack-dbgfs-v2-0-b18c4abd122f@kernel.org
Changes in v2:
- Add patch to do %pK -> %p conversion in ref_tracker.c
- Pass in output function to pr_ostream() instead of if statement
- Widen ref_tracker_dir.name to 64 bytes to accomodate unique names
- Eliminate error handling with debugfs manipulation
- Incorporate pointer value into netdev name
- Link to v1: https://lore.kernel.org/r/20250414-reftrack-dbgfs-v1-0-f03585832203@kernel.org
---
Jeff Layton (9):
ref_tracker: don't use %pK in pr_ostream() output
ref_tracker: add a top level debugfs directory for ref_tracker
ref_tracker: have callers pass output function to pr_ostream()
ref_tracker: add a static classname string to each ref_tracker_dir
ref_tracker: allow pr_ostream() to print directly to a seq_file
ref_tracker: automatically register a file in debugfs for a ref_tracker_dir
ref_tracker: add a way to create a symlink to the ref_tracker_dir debugfs file
net: add symlinks to ref_tracker_dir for netns
ref_tracker: eliminate the ref_tracker_dir name field
drivers/gpu/drm/display/drm_dp_tunnel.c | 2 +-
drivers/gpu/drm/i915/intel_runtime_pm.c | 4 +-
drivers/gpu/drm/i915/intel_wakeref.c | 3 +-
include/linux/ref_tracker.h | 50 +++++-
lib/ref_tracker.c | 275 ++++++++++++++++++++++++++++++--
net/core/dev.c | 2 +-
net/core/net_namespace.c | 34 +++-
7 files changed, 344 insertions(+), 26 deletions(-)
---
base-commit: 8630c59e99363c4b655788fd01134aef9bcd9264
change-id: 20250413-reftrack-dbgfs-3767b303e2fa
Best regards,
--
Jeff Layton <jlayton@...nel.org>
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