[PATCH v6 31/45] jbd2,ext4: dynamically allocate the jbd2-journal shrinker

Qi Zheng
2023-09-11T21:30:19Z

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the jbd2-journal shrinker, so that it can be freed
asynchronously via 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@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Jan Kara <jack@suse.cz>
CC: "Theodore Ts'o" <tytso@mit.edu>
CC: linux-ext4@vger.kernel.org
---
fs/jbd2/journal.c | 29 ++++++++++++++++++-----------
include/linux/jbd2.h | 2 +-
2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 768fa05bcbed..0ae19d527b22 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1290,7 +1290,7 @@ 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;
@@ -1316,7 +1316,7 @@ 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);
@@ -1588,14 +1588,21 @@ static journal_t *journal_init_common(struct block_device *bdev,
goto err_cleanup;

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;
- err = register_shrinker(&journal->j_shrinker, "jbd2-journal:(%u:%u)",
- MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
- if (err)
+
+ journal->j_shrinker = shrinker_alloc(0, "jbd2-journal:(%u:%u)",
+ MAJOR(bdev->bd_dev),
+ MINOR(bdev->bd_dev));
+ if (!journal->j_shrinker) {
+ err = -ENOMEM;
goto err_cleanup;
+ }
+
+ journal->j_shrinker->scan_objects = jbd2_journal_shrink_scan;
+ journal->j_shrinker->count_objects = jbd2_journal_shrink_count;
+ journal->j_shrinker->batch = journal->j_max_transaction_buffers;
+ journal->j_shrinker->private_data = journal;
+
+ shrinker_register(journal->j_shrinker);

return journal;

@@ -2170,9 +2177,9 @@ 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_free(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 52772c826c86..6dcbb4eb80fb 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -886,7 +886,7 @@ 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