linux-kernel - [PATCH v2 33/47] jbd2,ext4: dynamically allocate the jbd2-journal shrinker

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Message-Id: <20230724094354.90817-34-zhengqi.arch@bytedance.com>
Date:   Mon, 24 Jul 2023 17:43:40 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     akpm@...ux-foundation.org, david@...morbit.com, tkhai@...ru,
        vbabka@...e.cz, roman.gushchin@...ux.dev, djwong@...nel.org,
        brauner@...nel.org, paulmck@...nel.org, tytso@....edu,
        steven.price@....com, cel@...nel.org, senozhatsky@...omium.org,
        yujie.liu@...el.com, gregkh@...uxfoundation.org,
        muchun.song@...ux.dev
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-erofs@...ts.ozlabs.org,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        linux-nfs@...r.kernel.org, linux-mtd@...ts.infradead.org,
        rcu@...r.kernel.org, netdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        dm-devel@...hat.com, linux-raid@...r.kernel.org,
        linux-bcache@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-btrfs@...r.kernel.org,
        Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH v2 33/47] jbd2,ext4: dynamically allocate the jbd2-journal shrinker

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the jbd2-journal shrinker, so that it can be freed
asynchronously using kfree_rcu(). Then it doesn't need to wait for RCU
read-side critical section when releasing the struct journal_s.

Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
---
 fs/jbd2/journal.c    | 27 +++++++++++++++++----------
 include/linux/jbd2.h |  2 +-
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index fbce16fedaa4..a7d555ea06e3 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1301,7 +1301,7 @@ static int jbd2_min_tag_size(void)
 static unsigned long jbd2_journal_shrink_scan(struct shrinker *shrink,
 					      struct shrink_control *sc)
 {
-	journal_t *journal = container_of(shrink, journal_t, j_shrinker);
+	journal_t *journal = shrink->private_data;
 	unsigned long nr_to_scan = sc->nr_to_scan;
 	unsigned long nr_shrunk;
 	unsigned long count;
@@ -1327,7 +1327,7 @@ static unsigned long jbd2_journal_shrink_scan(struct shrinker *shrink,
 static unsigned long jbd2_journal_shrink_count(struct shrinker *shrink,
 					       struct shrink_control *sc)
 {
-	journal_t *journal = container_of(shrink, journal_t, j_shrinker);
+	journal_t *journal = shrink->private_data;
 	unsigned long count;
 
 	count = percpu_counter_read_positive(&journal->j_checkpoint_jh_count);
@@ -1415,19 +1415,26 @@ static journal_t *journal_init_common(struct block_device *bdev,
 	journal->j_superblock = (journal_superblock_t *)bh->b_data;
 
 	journal->j_shrink_transaction = NULL;
-	journal->j_shrinker.scan_objects = jbd2_journal_shrink_scan;
-	journal->j_shrinker.count_objects = jbd2_journal_shrink_count;
-	journal->j_shrinker.seeks = DEFAULT_SEEKS;
-	journal->j_shrinker.batch = journal->j_max_transaction_buffers;
 
 	if (percpu_counter_init(&journal->j_checkpoint_jh_count, 0, GFP_KERNEL))
 		goto err_cleanup;
 
-	if (register_shrinker(&journal->j_shrinker, "jbd2-journal:(%u:%u)",
-			      MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev))) {
+	journal->j_shrinker = shrinker_alloc(0, "jbd2-journal:(%u:%u)",
+					     MAJOR(bdev->bd_dev),
+					     MINOR(bdev->bd_dev));
+	if (!journal->j_shrinker) {
 		percpu_counter_destroy(&journal->j_checkpoint_jh_count);
 		goto err_cleanup;
 	}
+
+	journal->j_shrinker->scan_objects = jbd2_journal_shrink_scan;
+	journal->j_shrinker->count_objects = jbd2_journal_shrink_count;
+	journal->j_shrinker->seeks = DEFAULT_SEEKS;
+	journal->j_shrinker->batch = journal->j_max_transaction_buffers;
+	journal->j_shrinker->private_data = journal;
+
+	shrinker_register(journal->j_shrinker);
+
 	return journal;
 
 err_cleanup:
@@ -2190,9 +2197,9 @@ int jbd2_journal_destroy(journal_t *journal)
 		brelse(journal->j_sb_buffer);
 	}
 
-	if (journal->j_shrinker.flags & SHRINKER_REGISTERED) {
+	if (journal->j_shrinker) {
 		percpu_counter_destroy(&journal->j_checkpoint_jh_count);
-		unregister_shrinker(&journal->j_shrinker);
+		shrinker_unregister(journal->j_shrinker);
 	}
 	if (journal->j_proc_entry)
 		jbd2_stats_proc_exit(journal);
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index d860499e15e4..9fdc02565c24 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -897,7 +897,7 @@ struct journal_s
 	 * Journal head shrinker, reclaim buffer's journal head which
 	 * has been written back.
 	 */
-	struct shrinker		j_shrinker;
+	struct shrinker		*j_shrinker;
 
 	/**
 	 * @j_checkpoint_jh_count:
-- 
2.30.2