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Mercier" To: gregkh@linuxfoundation.org, tj@kernel.org, driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org, jack@suse.cz, amir73il@gmail.com, shuah@kernel.org, linux-kselftest@vger.kernel.org Cc: "T.J. Mercier" Content-Type: text/plain; charset="UTF-8" This series adds support for IN_DELETE_SELF and IN_IGNORED inotify events to kernfs files and directories. Currently, kernfs (used by cgroup and others) supports IN_MODIFY events but fails to notify watchers when the file is removed (e.g. during cgroup destruction). This forces userspace monitors to maintain resource intensive side-channels like pidfds, procfs polling, or redundant directory watches to detect when a cgroup dies and a watched file is removed. By generating IN_DELETE_SELF events on destruction, we allow watchers to rely on a single watch descriptor for the entire lifecycle of the monitored file, reducing resource usage (file descriptors, CPU cycles) and complexity in userspace. The series is structured as follows: Patch 1 preemptively addresses a race to set/clear i_nlink that would arise in patch 2. Patch 2 implements the logic to generate DELETE_SELF and IGNORED events on file / dir removal. Patch 3 adds selftests to verify the new behavior. --- Changes in v4: Clear inode i_nlink upon kernfs removal instead of calling fsnotify from kernfs per Jan. This adds support for directories. Abandon support for files removed from vfs_writes. Add selftest for directory watch per Amir. Add Amir's Ack to selftests. Changes in v3: Remove parent IN_DELETE notification per Amir. Refactored kernfs_notify_workfn to avoid grabbing parent when unnecessary for DELETE events as a result. Use notify_event for fsnotify_inode call per Amir Initialize memcg pointers to NULL in selftests Add Amir's Ack Add Tejun's Acks to the series Changes in v2: Remove unused variables from new selftests per kernel test robot Fix kernfs_type argument per Tejun Inline checks for FS_MODIFY, FS_DELETE in kernfs_notify_workfn per Tejun T.J. Mercier (3): kernfs: Don't set_nlink for directories being removed kernfs: Send IN_DELETE_SELF and IN_IGNORED selftests: memcg: Add tests for IN_DELETE_SELF and IN_IGNORED fs/kernfs/dir.c | 32 ++++- fs/kernfs/inode.c | 2 +- .../selftests/cgroup/test_memcontrol.c | 112 ++++++++++++++++++ 3 files changed, 144 insertions(+), 2 deletions(-) base-commit: ba268514ea14b44570030e8ed2aef92a38679e85 -- 2.53.0.414.gf7e9f6c205-goog