linux-kernel - [RFC PATCH v6 0/4] fuse: work queues to invalided dentries

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Message-ID: <20250916135310.51177-1-luis@igalia.com>
Date: Tue, 16 Sep 2025 14:53:06 +0100
From: Luis Henriques <luis@...lia.com>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: Bernd Schubert <bernd@...ernd.com>,
	Laura Promberger <laura.promberger@...n.ch>,
	Dave Chinner <david@...morbit.com>,
	Matt Harvey <mharvey@...ptrading.com>,
	linux-fsdevel@...r.kernel.org,
	kernel-dev@...lia.com,
	linux-kernel@...r.kernel.org,
	Luis Henriques <luis@...lia.com>
Subject: [RFC PATCH v6 0/4] fuse: work queues to invalided dentries

Hi Miklos,

Here's a new version of the patchset to invalidate expired dentries.  Most
of the changes (and there are a lot of them!) result from the v5 review.
See below for details.

Changes since v5:

- Changes to dcache: export shrink_dentry_list() and add new helper
  d_dispose_if_unused()
- Reduced hash lock array size
- Set 'inval_wq' max value to USHRT_MAX to prevent a potential overflow in
  secs_to_jiffies()
- Updated 'inval_wq' parameter description and comment
- Removed useless check in fuse_dentry_tree_del_node()
- Make fuse_dentry_tree_work() use dcache helpers d_dispose_if_unused() and
  shrink_dentry_list()
- Fix usage of need_resched() (replaced with cond_resched())
- fuse_dentry_tree_cleanup() now simply does a WARN_ON() if there are
  non-empty trees
- Removed TODO comment in fuse_conn_destroy() -- no need to prune trees
- Have fuse_epoch_work() use of shrink_dcache_sb() instead of going through
  all the trees
- Refactor fuse_conn_put() in a separate patch
- Fix bug in fuse_dentry_tree_add_node() for cases where dentries have the
  same timeout
- Reword some of the commits text

Changes since v4:
 
- Dropped extra check in fuse_dentry_tree_add_node() (Chunsheng)
- Make the dentries trees global instead of per fuse_conn (Miklos)
- Protect trees with hashed locking instead of a single lock (Miklos)
- Added new work queue (2nd patch) specifically to handle epoch (Miklos)
 
Changes since v3:
 
- Use of need_resched() instead of limiting the work queue to run for 5
  seconds
- Restore usage of union with rcu_head, in struct fuse_dentry
- Minor changes in comments (e.g. s/workqueue/work queue/)
 
Changes since v2:
 
- Major rework, the dentries tree nodes are now in fuse_dentry and they are
  tied to the actual dentry lifetime
- Mount option is now a module parameter
- workqueue now runs for at most 5 seconds before rescheduling

Luis Henriques (4):
  dcache: export shrink_dentry_list() and new helper
    d_dispose_if_unused()
  fuse: new work queue to periodically invalidate expired dentries
  fuse: new work queue to invalidate dentries from old epochs
  fuse: refactor fuse_conn_put() to remove negative logic.

 fs/dcache.c            |  18 ++--
 fs/fuse/dev.c          |   7 +-
 fs/fuse/dir.c          | 237 +++++++++++++++++++++++++++++++++++++----
 fs/fuse/fuse_i.h       |  14 +++
 fs/fuse/inode.c        |  44 ++++----
 include/linux/dcache.h |   2 +
 6 files changed, 273 insertions(+), 49 deletions(-)