ext4: inline jbd2_journal_[un]register_shrinker()

The function jbd2_journal_unregister_shrinker() was getting called
twice when the file system was getting unmounted.  On Power and ARM
platforms this was causing kernel crash when unmounting the file
system, when a percpu_counter was destroyed twice.

Fix this by removing jbd2_journal_[un]register_shrinker() functions,
and inlining the shrinker setup and teardown into
journal_init_common() and jbd2_journal_destroy().  This means that
ext4 and ocfs2 now no longer need to know about registering and
unregistering jbd2's shrinker.

Also, while we're at it, rename the percpu counter from
j_jh_shrink_count to j_checkpoint_jh_count, since this makes it
clearer what this counter is intended to track.

Link: https://lore.kernel.org/r/20210705145025.3363130-1-tytso@mit.edu
Fixes: 4ba3fcdde7e3 ("jbd2,ext4: add a shrinker to release checkpointed buffers")
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b8ff0399e171d19ae3b07c743099d7a88dc16446..dfa09a277b56fb4a1add7b5c28d8e75030c65023 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1184,7 +1184,6 @@ static void ext4_put_super(struct super_block *sb)
        ext4_unregister_sysfs(sb);
 
        if (sbi->s_journal) {
-               jbd2_journal_unregister_shrinker(sbi->s_journal);
                aborted = is_journal_aborted(sbi->s_journal);
                err = jbd2_journal_destroy(sbi->s_journal);
                sbi->s_journal = NULL;
@@ -5176,7 +5175,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
        sbi->s_ea_block_cache = NULL;
 
        if (sbi->s_journal) {
-               jbd2_journal_unregister_shrinker(sbi->s_journal);
                jbd2_journal_destroy(sbi->s_journal);
                sbi->s_journal = NULL;
        }
@@ -5502,12 +5500,6 @@ static int ext4_load_journal(struct super_block *sb,
                ext4_commit_super(sb);
        }
 
-       err = jbd2_journal_register_shrinker(journal);
-       if (err) {
-               EXT4_SB(sb)->s_journal = NULL;
-               goto err_out;
-       }
-
        return 0;
 
 err_out:

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 51d1eb2ffeb95069f1c1529f3233980040c63cde..746132998c577fe2fc2a955a378ecc3cd8078e74 100644 (file)
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -701,7 +701,7 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 
        __buffer_unlink(jh);
        jh->b_cp_transaction = NULL;
-       percpu_counter_dec(&journal->j_jh_shrink_count);
+       percpu_counter_dec(&journal->j_checkpoint_jh_count);
        jbd2_journal_put_journal_head(jh);
 
        /* Is this transaction empty? */
@@ -764,7 +764,7 @@ void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
                jh->b_cpnext->b_cpprev = jh;
        }
        transaction->t_checkpoint_list = jh;
-       percpu_counter_inc(&transaction->t_journal->j_jh_shrink_count);
+       percpu_counter_inc(&transaction->t_journal->j_checkpoint_jh_count);
 }
 
 /*

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 152880c298cab61ebfbba10d7cd29dd55e54e21e..35302bc192eb933e44fb30fb491e512800547e0c 100644 (file)
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1283,6 +1283,48 @@ static int jbd2_min_tag_size(void)
        return sizeof(journal_block_tag_t) - 4;
 }
 
+/**
+ * jbd2_journal_shrink_scan()
+ *
+ * Scan the checkpointed buffer on the checkpoint list and release the
+ * journal_head.
+ */
+static unsigned long jbd2_journal_shrink_scan(struct shrinker *shrink,
+                                             struct shrink_control *sc)
+{
+       journal_t *journal = container_of(shrink, journal_t, j_shrinker);
+       unsigned long nr_to_scan = sc->nr_to_scan;
+       unsigned long nr_shrunk;
+       unsigned long count;
+
+       count = percpu_counter_read_positive(&journal->j_checkpoint_jh_count);
+       trace_jbd2_shrink_scan_enter(journal, sc->nr_to_scan, count);
+
+       nr_shrunk = jbd2_journal_shrink_checkpoint_list(journal, &nr_to_scan);
+
+       count = percpu_counter_read_positive(&journal->j_checkpoint_jh_count);
+       trace_jbd2_shrink_scan_exit(journal, nr_to_scan, nr_shrunk, count);
+
+       return nr_shrunk;
+}
+
+/**
+ * jbd2_journal_shrink_count()
+ *
+ * Count the number of checkpoint buffers on the checkpoint list.
+ */
+static unsigned long jbd2_journal_shrink_count(struct shrinker *shrink,
+                                              struct shrink_control *sc)
+{
+       journal_t *journal = container_of(shrink, journal_t, j_shrinker);
+       unsigned long count;
+
+       count = percpu_counter_read_positive(&journal->j_checkpoint_jh_count);
+       trace_jbd2_shrink_count(journal, sc->nr_to_scan, count);
+
+       return count;
+}
+
 /*
  * Management for journal control blocks: functions to create and
  * destroy journal_t structures, and to initialise and read existing
@@ -1361,9 +1403,23 @@ static journal_t *journal_init_common(struct block_device *bdev,
        journal->j_sb_buffer = bh;
        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)) {
+               percpu_counter_destroy(&journal->j_checkpoint_jh_count);
+               goto err_cleanup;
+       }
        return journal;
 
 err_cleanup:
+       brelse(journal->j_sb_buffer);
        kfree(journal->j_wbuf);
        jbd2_journal_destroy_revoke(journal);
        kfree(journal);
@@ -2050,93 +2106,6 @@ int jbd2_journal_load(journal_t *journal)
        return -EIO;
 }
 
-/**
- * jbd2_journal_shrink_scan()
- *
- * Scan the checkpointed buffer on the checkpoint list and release the
- * journal_head.
- */
-static unsigned long jbd2_journal_shrink_scan(struct shrinker *shrink,
-                                             struct shrink_control *sc)
-{
-       journal_t *journal = container_of(shrink, journal_t, j_shrinker);
-       unsigned long nr_to_scan = sc->nr_to_scan;
-       unsigned long nr_shrunk;
-       unsigned long count;
-
-       count = percpu_counter_read_positive(&journal->j_jh_shrink_count);
-       trace_jbd2_shrink_scan_enter(journal, sc->nr_to_scan, count);
-
-       nr_shrunk = jbd2_journal_shrink_checkpoint_list(journal, &nr_to_scan);
-
-       count = percpu_counter_read_positive(&journal->j_jh_shrink_count);
-       trace_jbd2_shrink_scan_exit(journal, nr_to_scan, nr_shrunk, count);
-
-       return nr_shrunk;
-}
-
-/**
- * jbd2_journal_shrink_count()
- *
- * Count the number of checkpoint buffers on the checkpoint list.
- */
-static unsigned long jbd2_journal_shrink_count(struct shrinker *shrink,
-                                              struct shrink_control *sc)
-{
-       journal_t *journal = container_of(shrink, journal_t, j_shrinker);
-       unsigned long count;
-
-       count = percpu_counter_read_positive(&journal->j_jh_shrink_count);
-       trace_jbd2_shrink_count(journal, sc->nr_to_scan, count);
-
-       return count;
-}
-
-/**
- * jbd2_journal_register_shrinker()
- * @journal: Journal to act on.
- *
- * Init a percpu counter to record the checkpointed buffers on the checkpoint
- * list and register a shrinker to release their journal_head.
- */
-int jbd2_journal_register_shrinker(journal_t *journal)
-{
-       int err;
-
-       journal->j_shrink_transaction = NULL;
-
-       err = percpu_counter_init(&journal->j_jh_shrink_count, 0, GFP_KERNEL);
-       if (err)
-               return err;
-
-       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);
-       if (err) {
-               percpu_counter_destroy(&journal->j_jh_shrink_count);
-               return err;
-       }
-
-       return 0;
-}
-EXPORT_SYMBOL(jbd2_journal_register_shrinker);
-
-/**
- * jbd2_journal_unregister_shrinker()
- * @journal: Journal to act on.
- *
- * Unregister the checkpointed buffer shrinker and destroy the percpu counter.
- */
-void jbd2_journal_unregister_shrinker(journal_t *journal)
-{
-       percpu_counter_destroy(&journal->j_jh_shrink_count);
-       unregister_shrinker(&journal->j_shrinker);
-}
-EXPORT_SYMBOL(jbd2_journal_unregister_shrinker);
-
 /**
  * jbd2_journal_destroy() - Release a journal_t structure.
  * @journal: Journal to act on.
@@ -2209,8 +2178,10 @@ int jbd2_journal_destroy(journal_t *journal)
                brelse(journal->j_sb_buffer);
        }
 
-       jbd2_journal_unregister_shrinker(journal);
-
+       if (journal->j_shrinker.flags & SHRINKER_REGISTERED) {
+               percpu_counter_destroy(&journal->j_checkpoint_jh_count);
+               unregister_shrinker(&journal->j_shrinker);
+       }
        if (journal->j_proc_entry)
                jbd2_stats_proc_exit(journal);
        iput(journal->j_inode);

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 6cc03532156276fdd40ba814c2b5c40a51b9b982..fd933c45281af84c8391e3845021c70518c6b164 100644 (file)
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -918,11 +918,11 @@ struct journal_s
        struct shrinker         j_shrinker;
 
        /**
-        * @j_jh_shrink_count:
+        * @j_checkpoint_jh_count:
         *
         * Number of journal buffers on the checkpoint list. [j_list_lock]
         */
-       struct percpu_counter   j_jh_shrink_count;
+       struct percpu_counter   j_checkpoint_jh_count;
 
        /**
         * @j_shrink_transaction:
@@ -1556,8 +1556,6 @@ extern int           jbd2_journal_set_features
                   (journal_t *, unsigned long, unsigned long, unsigned long);
 extern void       jbd2_journal_clear_features
                   (journal_t *, unsigned long, unsigned long, unsigned long);
-extern int        jbd2_journal_register_shrinker(journal_t *journal);
-extern void       jbd2_journal_unregister_shrinker(journal_t *journal);
 extern int        jbd2_journal_load       (journal_t *journal);
 extern int        jbd2_journal_destroy    (journal_t *);
 extern int        jbd2_journal_recover    (journal_t *journal);