ext4: drop ineligible txn start stop APIs

This patch drops ext4_fc_start_ineligible() and
ext4_fc_stop_ineligible() APIs. Fast commit ineligible transactions
should simply call ext4_fc_mark_ineligible() after starting the
trasaction.

Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20211223202140.2061101-3-harshads@google.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -1725,9 +1725,9 @@ struct ext4_sb_info {
 	 */
 	struct work_struct s_error_work;
 
-	/* Ext4 fast commit stuff */
+	/* Ext4 fast commit sub transaction ID */
 	atomic_t s_fc_subtid;
-	atomic_t s_fc_ineligible_updates;
+
 	/*
 	 * After commit starts, the main queue gets locked, and the further
 	 * updates get added in the staging queue.
@@ -2926,8 +2926,6 @@ void __ext4_fc_track_create(handle_t *handle, struct inode *inode,
 void ext4_fc_track_create(handle_t *handle, struct dentry *dentry);
 void ext4_fc_track_inode(handle_t *handle, struct inode *inode);
 void ext4_fc_mark_ineligible(struct super_block *sb, int reason);
-void ext4_fc_start_ineligible(struct super_block *sb, int reason);
-void ext4_fc_stop_ineligible(struct super_block *sb);
 void ext4_fc_start_update(struct inode *inode);
 void ext4_fc_stop_update(struct inode *inode);
 void ext4_fc_del(struct inode *inode);

fs/ext4/extents.c

@@ -5341,7 +5341,7 @@ static int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
 		ret = PTR_ERR(handle);
 		goto out_mmap;
 	}
-	ext4_fc_start_ineligible(sb, EXT4_FC_REASON_FALLOC_RANGE);
+	ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_FALLOC_RANGE);
 
 	down_write(&EXT4_I(inode)->i_data_sem);
 	ext4_discard_preallocations(inode, 0);
@@ -5380,7 +5380,6 @@ static int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
 
 out_stop:
 	ext4_journal_stop(handle);
-	ext4_fc_stop_ineligible(sb);
 out_mmap:
 	filemap_invalidate_unlock(mapping);
 out_mutex:
@@ -5482,7 +5481,7 @@ static int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
 		ret = PTR_ERR(handle);
 		goto out_mmap;
 	}
-	ext4_fc_start_ineligible(sb, EXT4_FC_REASON_FALLOC_RANGE);
+	ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_FALLOC_RANGE);
 
 	/* Expand file to avoid data loss if there is error while shifting */
 	inode->i_size += len;
@@ -5557,7 +5556,6 @@ static int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
 
 out_stop:
 	ext4_journal_stop(handle);
-	ext4_fc_stop_ineligible(sb);
 out_mmap:
 	filemap_invalidate_unlock(mapping);
 out_mutex:

fs/ext4/fast_commit.c

@@ -65,21 +65,11 @@
  *
  * Fast Commit Ineligibility
  * -------------------------
- * Not all operations are supported by fast commits today (e.g extended
- * attributes). Fast commit ineligibility is marked by calling one of the
- * two following functions:
- *
- * - ext4_fc_mark_ineligible(): This makes next fast commit operation to fall
- *   back to full commit. This is useful in case of transient errors.
  *
- * - ext4_fc_start_ineligible() and ext4_fc_stop_ineligible() - This makes all
- *   the fast commits happening between ext4_fc_start_ineligible() and
- *   ext4_fc_stop_ineligible() and one fast commit after the call to
- *   ext4_fc_stop_ineligible() to fall back to full commits. It is important to
- *   make one more fast commit to fall back to full commit after stop call so
- *   that it guaranteed that the fast commit ineligible operation contained
- *   within ext4_fc_start_ineligible() and ext4_fc_stop_ineligible() is
- *   followed by at least 1 full commit.
+ * Not all operations are supported by fast commits today (e.g extended
+ * attributes). Fast commit ineligibility is marked by calling
+ * ext4_fc_mark_ineligible(): This makes next fast commit operation to fall back
+ * to full commit.
  *
  * Atomicity of commits
  * --------------------
@@ -328,44 +318,6 @@ void ext4_fc_mark_ineligible(struct super_block *sb, int reason)
 	sbi->s_fc_stats.fc_ineligible_reason_count[reason]++;
 }
 
-/*
- * Start a fast commit ineligible update. Any commits that happen while
- * such an operation is in progress fall back to full commits.
- */
-void ext4_fc_start_ineligible(struct super_block *sb, int reason)
-{
-	struct ext4_sb_info *sbi = EXT4_SB(sb);
-
-	if (!test_opt2(sb, JOURNAL_FAST_COMMIT) ||
-	    (EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY))
-		return;
-
-	WARN_ON(reason >= EXT4_FC_REASON_MAX);
-	sbi->s_fc_stats.fc_ineligible_reason_count[reason]++;
-	atomic_inc(&sbi->s_fc_ineligible_updates);
-}
-
-/*
- * Stop a fast commit ineligible update. We set EXT4_MF_FC_INELIGIBLE flag here
- * to ensure that after stopping the ineligible update, at least one full
- * commit takes place.
- */
-void ext4_fc_stop_ineligible(struct super_block *sb)
-{
-	if (!test_opt2(sb, JOURNAL_FAST_COMMIT) ||
-	    (EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY))
-		return;
-
-	ext4_set_mount_flag(sb, EXT4_MF_FC_INELIGIBLE);
-	atomic_dec(&EXT4_SB(sb)->s_fc_ineligible_updates);
-}
-
-static inline int ext4_fc_is_ineligible(struct super_block *sb)
-{
-	return (ext4_test_mount_flag(sb, EXT4_MF_FC_INELIGIBLE) ||
-		atomic_read(&EXT4_SB(sb)->s_fc_ineligible_updates));
-}
-
 /*
  * Generic fast commit tracking function. If this is the first time this we are
  * called after a full commit, we initialize fast commit fields and then call
@@ -391,7 +343,7 @@ static int ext4_fc_track_template(
 	    (sbi->s_mount_state & EXT4_FC_REPLAY))
 		return -EOPNOTSUPP;
 
-	if (ext4_fc_is_ineligible(inode->i_sb))
+	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
 		return -EINVAL;
 
 	tid = handle->h_transaction->t_tid;
@@ -1142,11 +1094,8 @@ int ext4_fc_commit(journal_t *journal, tid_t commit_tid)
 
 	start_time = ktime_get();
 
-	if (!test_opt2(sb, JOURNAL_FAST_COMMIT) ||
-		(ext4_fc_is_ineligible(sb))) {
-		reason = EXT4_FC_REASON_INELIGIBLE;
-		goto out;
-	}
+	if (!test_opt2(sb, JOURNAL_FAST_COMMIT))
+		return jbd2_complete_transaction(journal, commit_tid);
 
 restart_fc:
 	ret = jbd2_fc_begin_commit(journal, commit_tid);
@@ -1162,6 +1111,14 @@ int ext4_fc_commit(journal_t *journal, tid_t commit_tid)
 		reason = EXT4_FC_REASON_FC_START_FAILED;
 		goto out;
 	}
+	/*
+	 * After establishing journal barrier via jbd2_fc_begin_commit(), check
+	 * if we are fast commit ineligible.
+	 */
+	if (ext4_test_mount_flag(sb, EXT4_MF_FC_INELIGIBLE)) {
+		reason = EXT4_FC_REASON_INELIGIBLE;
+		goto out;
+	}
 
 	fc_bufs_before = (sbi->s_fc_bytes + bsize - 1) / bsize;
 	ret = ext4_fc_perform_commit(journal);
@@ -1180,12 +1137,6 @@ int ext4_fc_commit(journal_t *journal, tid_t commit_tid)
 	atomic_inc(&sbi->s_fc_subtid);
 	jbd2_fc_end_commit(journal);
 out:
-	/* Has any ineligible update happened since we started? */
-	if (reason == EXT4_FC_REASON_OK && ext4_fc_is_ineligible(sb)) {
-		sbi->s_fc_stats.fc_ineligible_reason_count[EXT4_FC_COMMIT_FAILED]++;
-		reason = EXT4_FC_REASON_INELIGIBLE;
-	}
-
 	spin_lock(&sbi->s_fc_lock);
 	if (reason != EXT4_FC_REASON_OK &&
 		reason != EXT4_FC_REASON_ALREADY_COMMITTED) {

fs/ext4/ioctl.c

@@ -169,7 +169,7 @@ static long swap_inode_boot_loader(struct super_block *sb,
 		err = -EINVAL;
 		goto err_out;
 	}
-	ext4_fc_start_ineligible(sb, EXT4_FC_REASON_SWAP_BOOT);
+	ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_SWAP_BOOT);
 
 	/* Protect extent tree against block allocations via delalloc */
 	ext4_double_down_write_data_sem(inode, inode_bl);
@@ -252,7 +252,6 @@ static long swap_inode_boot_loader(struct super_block *sb,
 
 err_out1:
 	ext4_journal_stop(handle);
-	ext4_fc_stop_ineligible(sb);
 	ext4_double_up_write_data_sem(inode, inode_bl);
 
 err_out:

fs/ext4/super.c

@@ -5074,7 +5074,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 
 	/* Initialize fast commit stuff */
 	atomic_set(&sbi->s_fc_subtid, 0);
-	atomic_set(&sbi->s_fc_ineligible_updates, 0);
 	INIT_LIST_HEAD(&sbi->s_fc_q[FC_Q_MAIN]);
 	INIT_LIST_HEAD(&sbi->s_fc_q[FC_Q_STAGING]);
 	INIT_LIST_HEAD(&sbi->s_fc_dentry_q[FC_Q_MAIN]);