jbd2: Avoid long replay times due to high number or revoke blocks

Some users are reporting journal replay takes a long time when there is
excessive number of revoke blocks in the journal. Reported times are
like:

1048576 records - 95 seconds
2097152 records - 580 seconds

The problem is that hash chains in the revoke table gets excessively
long in these cases. Fix the problem by sizing the revoke table
appropriately before the revoke pass.

Thanks to Alexey Zhuravlev <azhuravlev@ddn.com> for benchmarking the
patch with large numbers of revoke blocks [1].

[1] https://lore.kernel.org/all/20250113183107.7bfef7b6@x390.bzzz77.ru

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20250121140925.17231-2-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

2 files changed, 52 insertions, 14 deletions

diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
index 9192be7c19d8..7c23a8be673f 100644
--- a/fs/jbd2/recovery.c
+++ b/fs/jbd2/recovery.c
@@ -39,7 +39,7 @@ struct recovery_info
 
 static int do_one_pass(journal_t *journal,
 				struct recovery_info *info, enum passtype pass);
-static int scan_revoke_records(journal_t *, struct buffer_head *,
+static int scan_revoke_records(journal_t *, enum passtype, struct buffer_head *,
 				tid_t, struct recovery_info *);
 
 #ifdef __KERNEL__
@@ -327,6 +327,12 @@ int jbd2_journal_recover(journal_t *journal)
 		  journal->j_transaction_sequence, journal->j_head);
 
 	jbd2_journal_clear_revoke(journal);
+	/* Free revoke table allocated for replay */
+	if (journal->j_revoke != journal->j_revoke_table[0] &&
+	    journal->j_revoke != journal->j_revoke_table[1]) {
+		jbd2_journal_destroy_revoke_table(journal->j_revoke);
+		journal->j_revoke = journal->j_revoke_table[1];
+	}
 	err2 = sync_blockdev(journal->j_fs_dev);
 	if (!err)
 		err = err2;
@@ -612,6 +618,31 @@ static int do_one_pass(journal_t *journal,
 	first_commit_ID = next_commit_ID;
 	if (pass == PASS_SCAN)
 		info->start_transaction = first_commit_ID;
+	else if (pass == PASS_REVOKE) {
+		/*
+		 * Would the default revoke table have too long hash chains
+		 * during replay?
+		 */
+		if (info->nr_revokes > JOURNAL_REVOKE_DEFAULT_HASH * 16) {
+			unsigned int hash_size;
+
+			/*
+			 * Aim for average chain length of 8, limit at 1M
+			 * entries to avoid problems with malicious
+			 * filesystems.
+			 */
+			hash_size = min(roundup_pow_of_two(info->nr_revokes / 8),
+					1U << 20);
+			journal->j_revoke =
+				jbd2_journal_init_revoke_table(hash_size);
+			if (!journal->j_revoke) {
+				printk(KERN_ERR
+				       "JBD2: failed to allocate revoke table for replay with %u entries. "
+				       "Journal replay may be slow.\n", hash_size);
+				journal->j_revoke = journal->j_revoke_table[1];
+			}
+		}
+	}
 
 	jbd2_debug(1, "Starting recovery pass %d\n", pass);
 
@@ -852,6 +883,13 @@ chksum_ok:
 
 		case JBD2_REVOKE_BLOCK:
 			/*
+			 * If we aren't in the SCAN or REVOKE pass, then we can
+			 * just skip over this block.
+			 */
+			if (pass != PASS_REVOKE && pass != PASS_SCAN)
+				continue;
+
+			/*
 			 * Check revoke block crc in pass_scan, if csum verify
 			 * failed, check commit block time later.
 			 */
@@ -863,12 +901,7 @@ chksum_ok:
 				need_check_commit_time = true;
 			}
 
-			/* If we aren't in the REVOKE pass, then we can
-			 * just skip over this block. */
-			if (pass != PASS_REVOKE)
-				continue;
-
-			err = scan_revoke_records(journal, bh,
+			err = scan_revoke_records(journal, pass, bh,
 						  next_commit_ID, info);
 			if (err)
 				goto failed;
@@ -922,8 +955,9 @@ chksum_ok:
 
 /* Scan a revoke record, marking all blocks mentioned as revoked. */
 
-static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
-			       tid_t sequence, struct recovery_info *info)
+static int scan_revoke_records(journal_t *journal, enum passtype pass,
+			       struct buffer_head *bh, tid_t sequence,
+			       struct recovery_info *info)
 {
 	jbd2_journal_revoke_header_t *header;
 	int offset, max;
@@ -944,6 +978,11 @@ static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 	if (jbd2_has_feature_64bit(journal))
 		record_len = 8;
 
+	if (pass == PASS_SCAN) {
+		info->nr_revokes += (max - offset) / record_len;
+		return 0;
+	}
+
 	while (offset + record_len <= max) {
 		unsigned long long blocknr;
 		int err;
@@ -956,7 +995,6 @@ static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 		err = jbd2_journal_set_revoke(journal, blocknr, sequence);
 		if (err)
 			return err;
-		++info->nr_revokes;
 	}
 	return 0;
 }
diff --git a/fs/jbd2/revoke.c b/fs/jbd2/revoke.c
index ce63d5fde9c3..e157e890ff20 100644
--- a/fs/jbd2/revoke.c
+++ b/fs/jbd2/revoke.c
@@ -215,7 +215,7 @@ int __init jbd2_journal_init_revoke_table_cache(void)
 	return 0;
 }
 
-static struct jbd2_revoke_table_s *jbd2_journal_init_revoke_table(int hash_size)
+struct jbd2_revoke_table_s *jbd2_journal_init_revoke_table(int hash_size)
 {
 	int shift = 0;
 	int tmp = hash_size;
@@ -231,7 +231,7 @@ static struct jbd2_revoke_table_s *jbd2_journal_init_revoke_table(int hash_size)
 	table->hash_size = hash_size;
 	table->hash_shift = shift;
 	table->hash_table =
-		kmalloc_array(hash_size, sizeof(struct list_head), GFP_KERNEL);
+		kvmalloc_array(hash_size, sizeof(struct list_head), GFP_KERNEL);
 	if (!table->hash_table) {
 		kmem_cache_free(jbd2_revoke_table_cache, table);
 		table = NULL;
@@ -245,7 +245,7 @@ out:
 	return table;
 }
 
-static void jbd2_journal_destroy_revoke_table(struct jbd2_revoke_table_s *table)
+void jbd2_journal_destroy_revoke_table(struct jbd2_revoke_table_s *table)
 {
 	int i;
 	struct list_head *hash_list;
@@ -255,7 +255,7 @@ static void jbd2_journal_destroy_revoke_table(struct jbd2_revoke_table_s *table)
 		J_ASSERT(list_empty(hash_list));
 	}
 
-	kfree(table->hash_table);
+	kvfree(table->hash_table);
 	kmem_cache_free(jbd2_revoke_table_cache, table);
 }