linux-kernel - Re: [PATCH 8/8] gfs2: use lockref_init for qd

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Message-ID: <20250117160352.1881139-1-agruenba@redhat.com>
Date: Fri, 17 Jan 2025 17:03:51 +0100
From: Andreas Gruenbacher <agruenba@...hat.com>
To: Christoph Hellwig <hch@....de>
Cc: Andreas Gruenbacher <agruenba@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Gao Xiang <xiang@...nel.org>,
	Chao Yu <chao@...nel.org>,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-erofs@...ts.ozlabs.org,
	gfs2@...ts.linux.dev
Subject: Re: [PATCH 8/8] gfs2: use lockref_init for qd_lockref

On Thu, 16 Jan 2025 05:32:26 +0100, Christoph Hellwig <hch@....de> wrote:
> Well, if you can fix it to start with 1 we could start out with 1
> as the default.  FYI, I also didn't touch the other gfs2 lockref
> because it initialize the lock in the slab init_once callback and
> the count on every initialization.

Sure, can you add the below patch before the lockref_init conversion?

Thanks,
Andreas

--

gfs2: Prepare for converting to lockref_init

First, move initializing the glock lockref spin lock from
gfs2_init_glock_once() to gfs2_glock_get().

Second, in qd_alloc(), initialize the lockref count to 1 to cover the
common case.  Compensate for that in gfs2_quota_init() by adjusting the
count back down to 0; this case occurs only when mounting the filesystem
rw.

Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
---
 fs/gfs2/glock.c | 3 ++-
 fs/gfs2/main.c  | 1 -
 fs/gfs2/quota.c | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 8c4c1f871a88..22ff77cdd827 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1201,8 +1201,9 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
 	if (glops->go_instantiate)
 		gl->gl_flags |= BIT(GLF_INSTANTIATE_NEEDED);
 	gl->gl_name = name;
-	lockdep_set_subclass(&gl->gl_lockref.lock, glops->go_subclass);
 	gl->gl_lockref.count = 1;
+	spin_lock_init(&gl->gl_lockref.lock);
+	lockdep_set_subclass(&gl->gl_lockref.lock, glops->go_subclass);
 	gl->gl_state = LM_ST_UNLOCKED;
 	gl->gl_target = LM_ST_UNLOCKED;
 	gl->gl_demote_state = LM_ST_EXCLUSIVE;
diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
index 04cadc02e5a6..0727f60ad028 100644
--- a/fs/gfs2/main.c
+++ b/fs/gfs2/main.c
@@ -51,7 +51,6 @@ static void gfs2_init_glock_once(void *foo)
 {
 	struct gfs2_glock *gl = foo;
 
-	spin_lock_init(&gl->gl_lockref.lock);
 	INIT_LIST_HEAD(&gl->gl_holders);
 	INIT_LIST_HEAD(&gl->gl_lru);
 	INIT_LIST_HEAD(&gl->gl_ail_list);
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index 72b48f6f5561..df78eb8f35f9 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -236,7 +236,7 @@ static struct gfs2_quota_data *qd_alloc(unsigned hash, struct gfs2_sbd *sdp, str
 		return NULL;
 
 	qd->qd_sbd = sdp;
-	qd->qd_lockref.count = 0;
+	qd->qd_lockref.count = 1;
 	spin_lock_init(&qd->qd_lockref.lock);
 	qd->qd_id = qid;
 	qd->qd_slot = -1;
@@ -298,7 +298,6 @@ static int qd_get(struct gfs2_sbd *sdp, struct kqid qid,
 	spin_lock_bucket(hash);
 	*qdp = qd = gfs2_qd_search_bucket(hash, sdp, qid);
 	if (qd == NULL) {
-		new_qd->qd_lockref.count++;
 		*qdp = new_qd;
 		list_add(&new_qd->qd_list, &sdp->sd_quota_list);
 		hlist_bl_add_head_rcu(&new_qd->qd_hlist, &qd_hash_table[hash]);
@@ -1451,6 +1450,7 @@ int gfs2_quota_init(struct gfs2_sbd *sdp)
 			if (qd == NULL)
 				goto fail_brelse;
 
+			qd->qd_lockref.count = 0;
 			set_bit(QDF_CHANGE, &qd->qd_flags);
 			qd->qd_change = qc_change;
 			qd->qd_slot = slot;
-- 
2.47.1