[PATCH 14/29] jbd2,ext4: dynamically allocate the jbd2-journal shrinker

Qi Zheng
2023-06-22T09:00:24Z

In preparation for implementing lockless slab shrink,
we need 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@bytedance.com>
---
fs/jbd2/journal.c | 32 +++++++++++++++++++-------------
include/linux/jbd2.h | 2 +-
2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index eee3c0ae349a..92a2f4360b5f 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);
@@ -1415,21 +1415,27 @@ 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))) {
- percpu_counter_destroy(&journal->j_checkpoint_jh_count);
- goto err_cleanup;
- }
+ journal->j_shrinker = shrinker_alloc_and_init(jbd2_journal_shrink_count,
+ jbd2_journal_shrink_scan,
+ journal->j_max_transaction_buffers,
+ DEFAULT_SEEKS, 0, journal);
+ if (!journal->j_shrinker)
+ goto err_shrinker;
+
+ if (register_shrinker(journal->j_shrinker, "jbd2-journal:(%u:%u)",
+ MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev)))
+ goto err_register;
+
return journal;

+err_register:
+ shrinker_free(journal->j_shrinker);
+err_shrinker:
+ percpu_counter_destroy(&journal->j_checkpoint_jh_count);
err_cleanup:
brelse(journal->j_sb_buffer);
kfree(journal->j_wbuf);
@@ -2190,9 +2196,9 @@ int jbd2_journal_destroy(journal_t *journal)
brelse(journal->j_sb_buffer);
}

- if (journal->j_shrinker.flags & SHRINKER_REGISTERED) {
+ if (journal->j_shrinker->flags & SHRINKER_REGISTERED) {
percpu_counter_destroy(&journal->j_checkpoint_jh_count);
- unregister_shrinker(&journal->j_shrinker);
+ unregister_and_free_shrinker(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 44c298aa58d4..beb4c4586320 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -891,7 +891,7 @@ 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