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authorAl Viro <viro@zeniv.linux.org.uk>2023-10-30 01:09:50 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2023-11-25 02:33:56 -0500
commit2f42f1eb9093834b635991c70d0273fbe249eabf (patch)
treece60831fa5018e50135b59e8d41d4ead48943638 /Documentation/filesystems
parentb06c684d3984ef64e792ec3e89889c96cab97b5e (diff)
Call retain_dentry() with refcount 0
Instead of bumping it from 0 to 1, calling retain_dentry(), then decrementing it back to 0 (with ->d_lock held all the way through), just leave refcount at 0 through all of that. It will have a visible effect for ->d_delete() - now it can be called with refcount 0 instead of 1 and it can no longer play silly buggers with dropping/regaining ->d_lock. Not that any in-tree instances tried to (it's pretty hard to get right). Any out-of-tree ones will have to adjust (assuming they need any changes). Note that we do not need to extend rcu-critical area here - we have verified that refcount is non-negative after having grabbed ->d_lock, so nobody will be able to free dentry until they get into __dentry_kill(), which won't happen until they manage to grab ->d_lock. Reviewed-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/porting.rst8
1 files changed, 8 insertions, 0 deletions
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 331405f4b29f..da8073b592ff 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1070,3 +1070,11 @@ The list of children anchored in parent dentry got turned into hlist now.
Field names got changed (->d_children/->d_sib instead of ->d_subdirs/->d_child
for anchor/entries resp.), so any affected places will be immediately caught
by compiler.
+
+---
+
+**mandatory**
+
+->d_delete() instances are now called for dentries with ->d_lock held
+and refcount equal to 0. They are not permitted to drop/regain ->d_lock.
+None of in-tree instances did anything of that sort. Make sure yours do not...