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| author |   Al Viro <viro@zeniv.linux.org.uk> | 2023-10-30 01:09:50 -0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2023-11-25 02:33:56 -0500 |
| commit | 2f42f1eb9093834b635991c70d0273fbe249eabf (patch) | |
| tree | ce60831fa5018e50135b59e8d41d4ead48943638 /Documentation/filesystems | |
| parent | dentry_kill(): don't bother with retain_dentry() on slow path (diff) | |
| download | wireguard-linux-2f42f1eb9093834b635991c70d0273fbe249eabf.tar.xz wireguard-linux-2f42f1eb9093834b635991c70d0273fbe249eabf.zip | |
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.rst | 8 |
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... |