ext4 / jbd2: add fast commit initialization

This patch adds fast commit area trackers in the journal_t
structure. These are initialized via the jbd2_fc_init() routine that
this patch adds. This patch also adds ext4/fast_commit.c and
ext4/fast_commit.h files for fast commit code that will be added in
subsequent patches in this series.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201015203802.3597742-4-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 48 insertions, 5 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index c0600405e7a2..4497bfbac527 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1181,6 +1181,14 @@ static journal_t *journal_init_common(struct block_device *bdev,
 	if (!journal->j_wbuf)
 		goto err_cleanup;
 
+	if (journal->j_fc_wbufsize > 0) {
+		journal->j_fc_wbuf = kmalloc_array(journal->j_fc_wbufsize,
+					sizeof(struct buffer_head *),
+					GFP_KERNEL);
+		if (!journal->j_fc_wbuf)
+			goto err_cleanup;
+	}
+
 	bh = getblk_unmovable(journal->j_dev, start, journal->j_blocksize);
 	if (!bh) {
 		pr_err("%s: Cannot get buffer for journal superblock\n",
@@ -1194,11 +1202,23 @@ static journal_t *journal_init_common(struct block_device *bdev,
 
 err_cleanup:
 	kfree(journal->j_wbuf);
+	kfree(journal->j_fc_wbuf);
 	jbd2_journal_destroy_revoke(journal);
 	kfree(journal);
 	return NULL;
 }
 
+int jbd2_fc_init(journal_t *journal, int num_fc_blks)
+{
+	journal->j_fc_wbufsize = num_fc_blks;
+	journal->j_fc_wbuf = kmalloc_array(journal->j_fc_wbufsize,
+				sizeof(struct buffer_head *), GFP_KERNEL);
+	if (!journal->j_fc_wbuf)
+		return -ENOMEM;
+	return 0;
+}
+EXPORT_SYMBOL(jbd2_fc_init);
+
 /* jbd2_journal_init_dev and jbd2_journal_init_inode:
  *
  * Create a journal structure assigned some fixed set of disk blocks to
@@ -1316,11 +1336,20 @@ static int journal_reset(journal_t *journal)
 	}
 
 	journal->j_first = first;
-	journal->j_last = last;
 
-	journal->j_head = first;
-	journal->j_tail = first;
-	journal->j_free = last - first;
+	if (jbd2_has_feature_fast_commit(journal) &&
+	    journal->j_fc_wbufsize > 0) {
+		journal->j_fc_last = last;
+		journal->j_last = last - journal->j_fc_wbufsize;
+		journal->j_fc_first = journal->j_last + 1;
+		journal->j_fc_off = 0;
+	} else {
+		journal->j_last = last;
+	}
+
+	journal->j_head = journal->j_first;
+	journal->j_tail = journal->j_first;
+	journal->j_free = journal->j_last - journal->j_first;
 
 	journal->j_tail_sequence = journal->j_transaction_sequence;
 	journal->j_commit_sequence = journal->j_transaction_sequence - 1;
@@ -1665,9 +1694,18 @@ static int load_superblock(journal_t *journal)
 	journal->j_tail_sequence = be32_to_cpu(sb->s_sequence);
 	journal->j_tail = be32_to_cpu(sb->s_start);
 	journal->j_first = be32_to_cpu(sb->s_first);
-	journal->j_last = be32_to_cpu(sb->s_maxlen);
 	journal->j_errno = be32_to_cpu(sb->s_errno);
 
+	if (jbd2_has_feature_fast_commit(journal) &&
+	    journal->j_fc_wbufsize > 0) {
+		journal->j_fc_last = be32_to_cpu(sb->s_maxlen);
+		journal->j_last = journal->j_fc_last - journal->j_fc_wbufsize;
+		journal->j_fc_first = journal->j_last + 1;
+		journal->j_fc_off = 0;
+	} else {
+		journal->j_last = be32_to_cpu(sb->s_maxlen);
+	}
+
 	return 0;
 }
 
@@ -1728,6 +1766,9 @@ int jbd2_journal_load(journal_t *journal)
 	 */
 	journal->j_flags &= ~JBD2_ABORT;
 
+	if (journal->j_fc_wbufsize > 0)
+		jbd2_journal_set_features(journal, 0, 0,
+					  JBD2_FEATURE_INCOMPAT_FAST_COMMIT);
 	/* OK, we've finished with the dynamic journal bits:
 	 * reinitialise the dynamic contents of the superblock in memory
 	 * and reset them on disk. */
@@ -1811,6 +1852,8 @@ int jbd2_journal_destroy(journal_t *journal)
 		jbd2_journal_destroy_revoke(journal);
 	if (journal->j_chksum_driver)
 		crypto_free_shash(journal->j_chksum_driver);
+	if (journal->j_fc_wbufsize > 0)
+		kfree(journal->j_fc_wbuf);
 	kfree(journal->j_wbuf);
 	kfree(journal);