From: Imran Khan <imran.f.khan@oracle.com>
To: tj@kernel.org, viro@zeniv.linux.org.uk,
gregkh@linuxfoundation.org, ebiederm@xmission.com
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH v8 01/10] kernfs: Remove reference counting for kernfs_open_node.
Date: Sun, 10 Apr 2022 12:37:10 +1000 [thread overview]
Message-ID: <20220410023719.1752460-2-imran.f.khan@oracle.com> (raw)
In-Reply-To: <20220410023719.1752460-1-imran.f.khan@oracle.com>
The decision to free kernfs_open_node object in kernfs_put_open_node can
be taken based on whether kernfs_open_node->files list is empty or not. As
far as kernfs_drain_open_files is concerned it can't overlap with
kernfs_fops_open and hence can check for ->attr.open optimistically
(if ->attr.open is NULL) or under kernfs_open_file_mutex (if it needs to
traverse the ->files list.) Thus kernfs_drain_open_files can work w/o ref
counting involved kernfs_open_node as well.
So remove ->refcnt and modify the above mentioned users accordingly.
Suggested by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
---
fs/kernfs/file.c | 23 +++++++++--------------
1 file changed, 9 insertions(+), 14 deletions(-)
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 88423069407c..aea6968c979e 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -33,7 +33,6 @@ static DEFINE_SPINLOCK(kernfs_open_node_lock);
static DEFINE_MUTEX(kernfs_open_file_mutex);
struct kernfs_open_node {
- atomic_t refcnt;
atomic_t event;
wait_queue_head_t poll;
struct list_head files; /* goes through kernfs_open_file.list */
@@ -530,10 +529,8 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
}
on = kn->attr.open;
- if (on) {
- atomic_inc(&on->refcnt);
+ if (on)
list_add_tail(&of->list, &on->files);
- }
spin_unlock_irq(&kernfs_open_node_lock);
mutex_unlock(&kernfs_open_file_mutex);
@@ -548,7 +545,6 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
if (!new_on)
return -ENOMEM;
- atomic_set(&new_on->refcnt, 0);
atomic_set(&new_on->event, 1);
init_waitqueue_head(&new_on->poll);
INIT_LIST_HEAD(&new_on->files);
@@ -557,11 +553,12 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
/**
* kernfs_put_open_node - put kernfs_open_node
- * @kn: target kernfs_nodet
+ * @kn: target kernfs_node
* @of: associated kernfs_open_file
*
* Put @kn->attr.open and unlink @of from the files list. If
- * reference count reaches zero, disassociate and free it.
+ * list of associated open files becomes empty, disassociate and
+ * free kernfs_open_node.
*
* LOCKING:
* None.
@@ -578,7 +575,7 @@ static void kernfs_put_open_node(struct kernfs_node *kn,
if (of)
list_del(&of->list);
- if (atomic_dec_and_test(&on->refcnt))
+ if (list_empty(&on->files))
kn->attr.open = NULL;
else
on = NULL;
@@ -768,15 +765,15 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
return;
- spin_lock_irq(&kernfs_open_node_lock);
on = kn->attr.open;
- if (on)
- atomic_inc(&on->refcnt);
- spin_unlock_irq(&kernfs_open_node_lock);
if (!on)
return;
mutex_lock(&kernfs_open_file_mutex);
+ if (!kn->attr.open) {
+ mutex_unlock(&kernfs_open_file_mutex);
+ return;
+ }
list_for_each_entry(of, &on->files, list) {
struct inode *inode = file_inode(of->file);
@@ -789,8 +786,6 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
}
mutex_unlock(&kernfs_open_file_mutex);
-
- kernfs_put_open_node(kn, NULL);
}
/*
--
2.30.2
next prev parent reply other threads:[~2022-04-10 2:37 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-10 2:37 [PATCH v8 00/10] kernfs: Remove reference counting for kernfs_open_node Imran Khan
2022-04-10 2:37 ` Imran Khan [this message]
2022-04-22 16:03 ` [PATCH v8 01/10] " Tejun Heo
2022-04-26 1:43 ` Imran Khan
2022-04-26 18:29 ` Tejun Heo
2022-04-26 20:13 ` Al Viro
2022-04-26 20:16 ` Tejun Heo
2022-04-10 2:37 ` [PATCH v8 02/10] kernfs: make ->attr.open RCU protected Imran Khan
2022-04-22 16:19 ` Tejun Heo
2022-04-26 1:54 ` Imran Khan
2022-04-26 18:37 ` Tejun Heo
2022-04-10 2:37 ` [PATCH v8 03/10] kernfs: Change kernfs_notify_list to llist Imran Khan
2022-04-22 16:41 ` Tejun Heo
2022-04-10 2:37 ` [PATCH v8 04/10] kernfs: Introduce interface to access global kernfs_open_file_mutex Imran Khan
2022-04-10 2:37 ` [PATCH v8 05/10] kernfs: Replace global kernfs_open_file_mutex with hashed mutexes Imran Khan
2022-04-22 17:00 ` Tejun Heo
2022-04-10 2:37 ` [PATCH v8 06/10] kernfs: Use a per-fs rwsem to protect per-fs list of kernfs_super_info Imran Khan
2022-04-10 2:37 ` [PATCH v8 07/10] kernfs: Change kernfs_rename_lock into a read-write lock Imran Khan
2022-04-10 2:37 ` [PATCH v8 08/10] kernfs: Introduce interface to access per-fs rwsem Imran Khan
2022-04-10 2:37 ` [PATCH v8 09/10] kernfs: Replace per-fs rwsem with hashed rwsems Imran Khan
2022-04-10 2:37 ` [PATCH v8 10/10] kernfs: Add a document to describe hashed locks used in kernfs Imran Khan
2022-04-22 17:03 ` [PATCH v8 00/10] kernfs: Remove reference counting for kernfs_open_node Tejun Heo
2022-04-23 8:49 ` Imran Khan
2022-04-25 17:21 ` Tejun Heo
2022-04-28 17:28 ` Imran Khan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220410023719.1752460-2-imran.f.khan@oracle.com \
--to=imran.f.khan@oracle.com \
--cc=ebiederm@xmission.com \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tj@kernel.org \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).