Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2326 insertions, 0 deletions

diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
new file mode 100644
index 000000000..1110bfa0a
--- /dev/null
+++ b/fs/ext4/fast_commit.c
@@ -0,0 +1,2326 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * fs/ext4/fast_commit.c
+ *
+ * Written by Harshad Shirwadkar <harshadshirwadkar@gmail.com>
+ *
+ * Ext4 fast commits routines.
+ */
+#include "ext4.h"
+#include "ext4_jbd2.h"
+#include "ext4_extents.h"
+#include "mballoc.h"
+
+/*
+ * Ext4 Fast Commits
+ * -----------------
+ *
+ * Ext4 fast commits implement fine grained journalling for Ext4.
+ *
+ * Fast commits are organized as a log of tag-length-value (TLV) structs. (See
+ * struct ext4_fc_tl). Each TLV contains some delta that is replayed TLV by
+ * TLV during the recovery phase. For the scenarios for which we currently
+ * don't have replay code, fast commit falls back to full commits.
+ * Fast commits record delta in one of the following three categories.
+ *
+ * (A) Directory entry updates:
+ *
+ * - EXT4_FC_TAG_UNLINK		- records directory entry unlink
+ * - EXT4_FC_TAG_LINK		- records directory entry link
+ * - EXT4_FC_TAG_CREAT		- records inode and directory entry creation
+ *
+ * (B) File specific data range updates:
+ *
+ * - EXT4_FC_TAG_ADD_RANGE	- records addition of new blocks to an inode
+ * - EXT4_FC_TAG_DEL_RANGE	- records deletion of blocks from an inode
+ *
+ * (C) Inode metadata (mtime / ctime etc):
+ *
+ * - EXT4_FC_TAG_INODE		- record the inode that should be replayed
+ *				  during recovery. Note that iblocks field is
+ *				  not replayed and instead derived during
+ *				  replay.
+ * Commit Operation
+ * ----------------
+ * With fast commits, we maintain all the directory entry operations in the
+ * order in which they are issued in an in-memory queue. This queue is flushed
+ * to disk during the commit operation. We also maintain a list of inodes
+ * that need to be committed during a fast commit in another in memory queue of
+ * inodes. During the commit operation, we commit in the following order:
+ *
+ * [1] Lock inodes for any further data updates by setting COMMITTING state
+ * [2] Submit data buffers of all the inodes
+ * [3] Wait for [2] to complete
+ * [4] Commit all the directory entry updates in the fast commit space
+ * [5] Commit all the changed inode structures
+ * [6] Write tail tag (this tag ensures the atomicity, please read the following
+ *     section for more details).
+ * [7] Wait for [4], [5] and [6] to complete.
+ *
+ * All the inode updates must call ext4_fc_start_update() before starting an
+ * update. If such an ongoing update is present, fast commit waits for it to
+ * complete. The completion of such an update is marked by
+ * ext4_fc_stop_update().
+ *
+ * Fast Commit Ineligibility
+ * -------------------------
+ *
+ * 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
+ * --------------------
+ * In order to guarantee atomicity during the commit operation, fast commit
+ * uses "EXT4_FC_TAG_TAIL" tag that marks a fast commit as complete. Tail
+ * tag contains CRC of the contents and TID of the transaction after which
+ * this fast commit should be applied. Recovery code replays fast commit
+ * logs only if there's at least 1 valid tail present. For every fast commit
+ * operation, there is 1 tail. This means, we may end up with multiple tails
+ * in the fast commit space. Here's an example:
+ *
+ * - Create a new file A and remove existing file B
+ * - fsync()
+ * - Append contents to file A
+ * - Truncate file A
+ * - fsync()
+ *
+ * The fast commit space at the end of above operations would look like this:
+ *      [HEAD] [CREAT A] [UNLINK B] [TAIL] [ADD_RANGE A] [DEL_RANGE A] [TAIL]
+ *             |<---  Fast Commit 1   --->|<---      Fast Commit 2     ---->|
+ *
+ * Replay code should thus check for all the valid tails in the FC area.
+ *
+ * Fast Commit Replay Idempotence
+ * ------------------------------
+ *
+ * Fast commits tags are idempotent in nature provided the recovery code follows
+ * certain rules. The guiding principle that the commit path follows while
+ * committing is that it stores the result of a particular operation instead of
+ * storing the procedure.
+ *
+ * Let's consider this rename operation: 'mv /a /b'. Let's assume dirent '/a'
+ * was associated with inode 10. During fast commit, instead of storing this
+ * operation as a procedure "rename a to b", we store the resulting file system
+ * state as a "series" of outcomes:
+ *
+ * - Link dirent b to inode 10
+ * - Unlink dirent a
+ * - Inode <10> with valid refcount
+ *
+ * Now when recovery code runs, it needs "enforce" this state on the file
+ * system. This is what guarantees idempotence of fast commit replay.
+ *
+ * Let's take an example of a procedure that is not idempotent and see how fast
+ * commits make it idempotent. Consider following sequence of operations:
+ *
+ *     rm A;    mv B A;    read A
+ *  (x)     (y)        (z)
+ *
+ * (x), (y) and (z) are the points at which we can crash. If we store this
+ * sequence of operations as is then the replay is not idempotent. Let's say
+ * while in replay, we crash at (z). During the second replay, file A (which was
+ * actually created as a result of "mv B A" operation) would get deleted. Thus,
+ * file named A would be absent when we try to read A. So, this sequence of
+ * operations is not idempotent. However, as mentioned above, instead of storing
+ * the procedure fast commits store the outcome of each procedure. Thus the fast
+ * commit log for above procedure would be as follows:
+ *
+ * (Let's assume dirent A was linked to inode 10 and dirent B was linked to
+ * inode 11 before the replay)
+ *
+ *    [Unlink A]   [Link A to inode 11]   [Unlink B]   [Inode 11]
+ * (w)          (x)                    (y)          (z)
+ *
+ * If we crash at (z), we will have file A linked to inode 11. During the second
+ * replay, we will remove file A (inode 11). But we will create it back and make
+ * it point to inode 11. We won't find B, so we'll just skip that step. At this
+ * point, the refcount for inode 11 is not reliable, but that gets fixed by the
+ * replay of last inode 11 tag. Crashes at points (w), (x) and (y) get handled
+ * similarly. Thus, by converting a non-idempotent procedure into a series of
+ * idempotent outcomes, fast commits ensured idempotence during the replay.
+ *
+ * TODOs
+ * -----
+ *
+ * 0) Fast commit replay path hardening: Fast commit replay code should use
+ *    journal handles to make sure all the updates it does during the replay
+ *    path are atomic. With that if we crash during fast commit replay, after
+ *    trying to do recovery again, we will find a file system where fast commit
+ *    area is invalid (because new full commit would be found). In order to deal
+ *    with that, fast commit replay code should ensure that the "FC_REPLAY"
+ *    superblock state is persisted before starting the replay, so that after
+ *    the crash, fast commit recovery code can look at that flag and perform
+ *    fast commit recovery even if that area is invalidated by later full
+ *    commits.
+ *
+ * 1) Fast commit's commit path locks the entire file system during fast
+ *    commit. This has significant performance penalty. Instead of that, we
+ *    should use ext4_fc_start/stop_update functions to start inode level
+ *    updates from ext4_journal_start/stop. Once we do that we can drop file
+ *    system locking during commit path.
+ *
+ * 2) Handle more ineligible cases.
+ */
+
+#include <trace/events/ext4.h>
+static struct kmem_cache *ext4_fc_dentry_cachep;
+
+static void ext4_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
+{
+	BUFFER_TRACE(bh, "");
+	if (uptodate) {
+		ext4_debug("%s: Block %lld up-to-date",
+			   __func__, bh->b_blocknr);
+		set_buffer_uptodate(bh);
+	} else {
+		ext4_debug("%s: Block %lld not up-to-date",
+			   __func__, bh->b_blocknr);
+		clear_buffer_uptodate(bh);
+	}
+
+	unlock_buffer(bh);
+}
+
+static inline void ext4_fc_reset_inode(struct inode *inode)
+{
+	struct ext4_inode_info *ei = EXT4_I(inode);
+
+	ei->i_fc_lblk_start = 0;
+	ei->i_fc_lblk_len = 0;
+}
+
+void ext4_fc_init_inode(struct inode *inode)
+{
+	struct ext4_inode_info *ei = EXT4_I(inode);
+
+	ext4_fc_reset_inode(inode);
+	ext4_clear_inode_state(inode, EXT4_STATE_FC_COMMITTING);
+	INIT_LIST_HEAD(&ei->i_fc_list);
+	INIT_LIST_HEAD(&ei->i_fc_dilist);
+	init_waitqueue_head(&ei->i_fc_wait);
+	atomic_set(&ei->i_fc_updates, 0);
+}
+
+/* This function must be called with sbi->s_fc_lock held. */
+static void ext4_fc_wait_committing_inode(struct inode *inode)
+__releases(&EXT4_SB(inode->i_sb)->s_fc_lock)
+{
+	wait_queue_head_t *wq;
+	struct ext4_inode_info *ei = EXT4_I(inode);
+
+#if (BITS_PER_LONG < 64)
+	DEFINE_WAIT_BIT(wait, &ei->i_state_flags,
+			EXT4_STATE_FC_COMMITTING);
+	wq = bit_waitqueue(&ei->i_state_flags,
+				EXT4_STATE_FC_COMMITTING);
+#else
+	DEFINE_WAIT_BIT(wait, &ei->i_flags,
+			EXT4_STATE_FC_COMMITTING);
+	wq = bit_waitqueue(&ei->i_flags,
+				EXT4_STATE_FC_COMMITTING);
+#endif
+	lockdep_assert_held(&EXT4_SB(inode->i_sb)->s_fc_lock);
+	prepare_to_wait(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
+	spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
+	schedule();
+	finish_wait(wq, &wait.wq_entry);
+}
+
+static bool ext4_fc_disabled(struct super_block *sb)
+{
+	return (!test_opt2(sb, JOURNAL_FAST_COMMIT) ||
+		(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY));
+}
+
+/*
+ * Inform Ext4's fast about start of an inode update
+ *
+ * This function is called by the high level call VFS callbacks before
+ * performing any inode update. This function blocks if there's an ongoing
+ * fast commit on the inode in question.
+ */
+void ext4_fc_start_update(struct inode *inode)
+{
+	struct ext4_inode_info *ei = EXT4_I(inode);
+
+	if (ext4_fc_disabled(inode->i_sb))
+		return;
+
+restart:
+	spin_lock(&EXT4_SB(inode->i_sb)->s_fc_lock);
+	if (list_empty(&ei->i_fc_list))
+		goto out;
+
+	if (ext4_test_inode_state(inode, EXT4_STATE_FC_COMMITTING)) {
+		ext4_fc_wait_committing_inode(inode);
+		goto restart;
+	}
+out:
+	atomic_inc(&ei->i_fc_updates);
+	spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
+}
+
+/*
+ * Stop inode update and wake up waiting fast commits if any.
+ */
+void ext4_fc_stop_update(struct inode *inode)
+{
+	struct ext4_inode_info *ei = EXT4_I(inode);
+
+	if (ext4_fc_disabled(inode->i_sb))
+		return;
+
+	if (atomic_dec_and_test(&ei->i_fc_updates))
+		wake_up_all(&ei->i_fc_wait);
+}
+
+/*
+ * Remove inode from fast commit list. If the inode is being committed
+ * we wait until inode commit is done.
+ */
+void ext4_fc_del(struct inode *inode)
+{
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+	struct ext4_fc_dentry_update *fc_dentry;
+
+	if (ext4_fc_disabled(inode->i_sb))
+		return;
+
+restart:
+	spin_lock(&EXT4_SB(inode->i_sb)->s_fc_lock);
+	if (list_empty(&ei->i_fc_list) && list_empty(&ei->i_fc_dilist)) {
+		spin_unlock(&EXT4_SB(inode->i_sb)->s_fc_lock);
+		return;
+	}
+
+	if (ext4_test_inode_state(inode, EXT4_STATE_FC_COMMITTING)) {
+		ext4_fc_wait_committing_inode(inode);
+		goto restart;
+	}
+
+	if (!list_empty(&ei->i_fc_list))
+		list_del_init(&ei->i_fc_list);
+
+	/*
+	 * Since this inode is getting removed, let's also remove all FC
+	 * dentry create references, since it is not needed to log it anyways.
+	 */
+	if (list_empty(&ei->i_fc_dilist)) {
+		spin_unlock(&sbi->s_fc_lock);
+		return;
+	}
+
+	fc_dentry = list_first_entry(&ei->i_fc_dilist, struct ext4_fc_dentry_update, fcd_dilist);
+	WARN_ON(fc_dentry->fcd_op != EXT4_FC_TAG_CREAT);
+	list_del_init(&fc_dentry->fcd_list);
+	list_del_init(&fc_dentry->fcd_dilist);
+
+	WARN_ON(!list_empty(&ei->i_fc_dilist));
+	spin_unlock(&sbi->s_fc_lock);
+
+	if (fc_dentry->fcd_name.name &&
+		fc_dentry->fcd_name.len > DNAME_INLINE_LEN)
+		kfree(fc_dentry->fcd_name.name);
+	kmem_cache_free(ext4_fc_dentry_cachep, fc_dentry);
+
+	return;
+}
+
+/*
+ * Mark file system as fast commit ineligible, and record latest
+ * ineligible transaction tid. This means until the recorded
+ * transaction, commit operation would result in a full jbd2 commit.
+ */
+void ext4_fc_mark_ineligible(struct super_block *sb, int reason, handle_t *handle)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	tid_t tid;
+
+	if (ext4_fc_disabled(sb))
+		return;
+
+	ext4_set_mount_flag(sb, EXT4_MF_FC_INELIGIBLE);
+	if (handle && !IS_ERR(handle))
+		tid = handle->h_transaction->t_tid;
+	else {
+		read_lock(&sbi->s_journal->j_state_lock);
+		tid = sbi->s_journal->j_running_transaction ?
+				sbi->s_journal->j_running_transaction->t_tid : 0;
+		read_unlock(&sbi->s_journal->j_state_lock);
+	}
+	spin_lock(&sbi->s_fc_lock);
+	if (sbi->s_fc_ineligible_tid < tid)
+		sbi->s_fc_ineligible_tid = tid;
+	spin_unlock(&sbi->s_fc_lock);
+	WARN_ON(reason >= EXT4_FC_REASON_MAX);
+	sbi->s_fc_stats.fc_ineligible_reason_count[reason]++;
+}
+
+/*
+ * 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
+ * __fc_track_fn() with update = 0. If we have already been called after a full
+ * commit, we pass update = 1. Based on that, the track function can determine
+ * if it needs to track a field for the first time or if it needs to just
+ * update the previously tracked value.
+ *
+ * If enqueue is set, this function enqueues the inode in fast commit list.
+ */
+static int ext4_fc_track_template(
+	handle_t *handle, struct inode *inode,
+	int (*__fc_track_fn)(struct inode *, void *, bool),
+	void *args, int enqueue)
+{
+	bool update = false;
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+	tid_t tid = 0;
+	int ret;
+
+	tid = handle->h_transaction->t_tid;
+	mutex_lock(&ei->i_fc_lock);
+	if (tid == ei->i_sync_tid) {
+		update = true;
+	} else {
+		ext4_fc_reset_inode(inode);
+		ei->i_sync_tid = tid;
+	}
+	ret = __fc_track_fn(inode, args, update);
+	mutex_unlock(&ei->i_fc_lock);
+
+	if (!enqueue)
+		return ret;
+
+	spin_lock(&sbi->s_fc_lock);
+	if (list_empty(&EXT4_I(inode)->i_fc_list))
+		list_add_tail(&EXT4_I(inode)->i_fc_list,
+				(sbi->s_journal->j_flags & JBD2_FULL_COMMIT_ONGOING ||
+				 sbi->s_journal->j_flags & JBD2_FAST_COMMIT_ONGOING) ?
+				&sbi->s_fc_q[FC_Q_STAGING] :
+				&sbi->s_fc_q[FC_Q_MAIN]);
+	spin_unlock(&sbi->s_fc_lock);
+
+	return ret;
+}
+
+struct __track_dentry_update_args {
+	struct dentry *dentry;
+	int op;
+};
+
+/* __track_fn for directory entry updates. Called with ei->i_fc_lock. */
+static int __track_dentry_update(struct inode *inode, void *arg, bool update)
+{
+	struct ext4_fc_dentry_update *node;
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	struct __track_dentry_update_args *dentry_update =
+		(struct __track_dentry_update_args *)arg;
+	struct dentry *dentry = dentry_update->dentry;
+	struct inode *dir = dentry->d_parent->d_inode;
+	struct super_block *sb = inode->i_sb;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+	mutex_unlock(&ei->i_fc_lock);
+
+	if (IS_ENCRYPTED(dir)) {
+		ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_ENCRYPTED_FILENAME,
+					NULL);
+		mutex_lock(&ei->i_fc_lock);
+		return -EOPNOTSUPP;
+	}
+
+	node = kmem_cache_alloc(ext4_fc_dentry_cachep, GFP_NOFS);
+	if (!node) {
+		ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_NOMEM, NULL);
+		mutex_lock(&ei->i_fc_lock);
+		return -ENOMEM;
+	}
+
+	node->fcd_op = dentry_update->op;
+	node->fcd_parent = dir->i_ino;
+	node->fcd_ino = inode->i_ino;
+	if (dentry->d_name.len > DNAME_INLINE_LEN) {
+		node->fcd_name.name = kmalloc(dentry->d_name.len, GFP_NOFS);
+		if (!node->fcd_name.name) {
+			kmem_cache_free(ext4_fc_dentry_cachep, node);
+			ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_NOMEM, NULL);
+			mutex_lock(&ei->i_fc_lock);
+			return -ENOMEM;
+		}
+		memcpy((u8 *)node->fcd_name.name, dentry->d_name.name,
+			dentry->d_name.len);
+	} else {
+		memcpy(node->fcd_iname, dentry->d_name.name,
+			dentry->d_name.len);
+		node->fcd_name.name = node->fcd_iname;
+	}
+	node->fcd_name.len = dentry->d_name.len;
+	INIT_LIST_HEAD(&node->fcd_dilist);
+	spin_lock(&sbi->s_fc_lock);
+	if (sbi->s_journal->j_flags & JBD2_FULL_COMMIT_ONGOING ||
+		sbi->s_journal->j_flags & JBD2_FAST_COMMIT_ONGOING)
+		list_add_tail(&node->fcd_list,
+				&sbi->s_fc_dentry_q[FC_Q_STAGING]);
+	else
+		list_add_tail(&node->fcd_list, &sbi->s_fc_dentry_q[FC_Q_MAIN]);
+
+	/*
+	 * This helps us keep a track of all fc_dentry updates which is part of
+	 * this ext4 inode. So in case the inode is getting unlinked, before
+	 * even we get a chance to fsync, we could remove all fc_dentry
+	 * references while evicting the inode in ext4_fc_del().
+	 * Also with this, we don't need to loop over all the inodes in
+	 * sbi->s_fc_q to get the corresponding inode in
+	 * ext4_fc_commit_dentry_updates().
+	 */
+	if (dentry_update->op == EXT4_FC_TAG_CREAT) {
+		WARN_ON(!list_empty(&ei->i_fc_dilist));
+		list_add_tail(&node->fcd_dilist, &ei->i_fc_dilist);
+	}
+	spin_unlock(&sbi->s_fc_lock);
+	mutex_lock(&ei->i_fc_lock);
+
+	return 0;
+}
+
+void __ext4_fc_track_unlink(handle_t *handle,
+		struct inode *inode, struct dentry *dentry)
+{
+	struct __track_dentry_update_args args;
+	int ret;
+
+	args.dentry = dentry;
+	args.op = EXT4_FC_TAG_UNLINK;
+
+	ret = ext4_fc_track_template(handle, inode, __track_dentry_update,
+					(void *)&args, 0);
+	trace_ext4_fc_track_unlink(handle, inode, dentry, ret);
+}
+
+void ext4_fc_track_unlink(handle_t *handle, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+
+	if (ext4_fc_disabled(inode->i_sb))
+		return;
+
+	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
+		return;
+
+	__ext4_fc_track_unlink(handle, inode, dentry);
+}
+
+void __ext4_fc_track_link(handle_t *handle,
+	struct inode *inode, struct dentry *dentry)
+{
+	struct __track_dentry_update_args args;
+	int ret;
+
+	args.dentry = dentry;
+	args.op = EXT4_FC_TAG_LINK;
+
+	ret = ext4_fc_track_template(handle, inode, __track_dentry_update,
+					(void *)&args, 0);
+	trace_ext4_fc_track_link(handle, inode, dentry, ret);
+}
+
+void ext4_fc_track_link(handle_t *handle, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+
+	if (ext4_fc_disabled(inode->i_sb))
+		return;
+
+	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
+		return;
+
+	__ext4_fc_track_link(handle, inode, dentry);
+}
+
+void __ext4_fc_track_create(handle_t *handle, struct inode *inode,
+			  struct dentry *dentry)
+{
+	struct __track_dentry_update_args args;
+	int ret;
+
+	args.dentry = dentry;
+	args.op = EXT4_FC_TAG_CREAT;
+
+	ret = ext4_fc_track_template(handle, inode, __track_dentry_update,
+					(void *)&args, 0);
+	trace_ext4_fc_track_create(handle, inode, dentry, ret);
+}
+
+void ext4_fc_track_create(handle_t *handle, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+
+	if (ext4_fc_disabled(inode->i_sb))
+		return;
+
+	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
+		return;
+
+	__ext4_fc_track_create(handle, inode, dentry);
+}
+
+/* __track_fn for inode tracking */
+static int __track_inode(struct inode *inode, void *arg, bool update)
+{
+	if (update)
+		return -EEXIST;
+
+	EXT4_I(inode)->i_fc_lblk_len = 0;
+
+	return 0;
+}
+
+void ext4_fc_track_inode(handle_t *handle, struct inode *inode)
+{
+	int ret;
+
+	if (S_ISDIR(inode->i_mode))
+		return;
+
+	if (ext4_fc_disabled(inode->i_sb))
+		return;
+
+	if (ext4_should_journal_data(inode)) {
+		ext4_fc_mark_ineligible(inode->i_sb,
+					EXT4_FC_REASON_INODE_JOURNAL_DATA, handle);
+		return;
+	}
+
+	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
+		return;
+
+	ret = ext4_fc_track_template(handle, inode, __track_inode, NULL, 1);
+	trace_ext4_fc_track_inode(handle, inode, ret);
+}
+
+struct __track_range_args {
+	ext4_lblk_t start, end;
+};
+
+/* __track_fn for tracking data updates */
+static int __track_range(struct inode *inode, void *arg, bool update)
+{
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	ext4_lblk_t oldstart;
+	struct __track_range_args *__arg =
+		(struct __track_range_args *)arg;
+
+	if (inode->i_ino < EXT4_FIRST_INO(inode->i_sb)) {
+		ext4_debug("Special inode %ld being modified\n", inode->i_ino);
+		return -ECANCELED;
+	}
+
+	oldstart = ei->i_fc_lblk_start;
+
+	if (update && ei->i_fc_lblk_len > 0) {
+		ei->i_fc_lblk_start = min(ei->i_fc_lblk_start, __arg->start);
+		ei->i_fc_lblk_len =
+			max(oldstart + ei->i_fc_lblk_len - 1, __arg->end) -
+				ei->i_fc_lblk_start + 1;
+	} else {
+		ei->i_fc_lblk_start = __arg->start;
+		ei->i_fc_lblk_len = __arg->end - __arg->start + 1;
+	}
+
+	return 0;
+}
+
+void ext4_fc_track_range(handle_t *handle, struct inode *inode, ext4_lblk_t start,
+			 ext4_lblk_t end)
+{
+	struct __track_range_args args;
+	int ret;
+
+	if (S_ISDIR(inode->i_mode))
+		return;
+
+	if (ext4_fc_disabled(inode->i_sb))
+		return;
+
+	if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FC_INELIGIBLE))
+		return;
+
+	args.start = start;
+	args.end = end;
+
+	ret = ext4_fc_track_template(handle, inode,  __track_range, &args, 1);
+
+	trace_ext4_fc_track_range(handle, inode, start, end, ret);
+}
+
+static void ext4_fc_submit_bh(struct super_block *sb, bool is_tail)
+{
+	blk_opf_t write_flags = REQ_SYNC;
+	struct buffer_head *bh = EXT4_SB(sb)->s_fc_bh;
+
+	/* Add REQ_FUA | REQ_PREFLUSH only its tail */
+	if (test_opt(sb, BARRIER) && is_tail)
+		write_flags |= REQ_FUA | REQ_PREFLUSH;
+	lock_buffer(bh);
+	set_buffer_dirty(bh);
+	set_buffer_uptodate(bh);
+	bh->b_end_io = ext4_end_buffer_io_sync;
+	submit_bh(REQ_OP_WRITE | write_flags, bh);
+	EXT4_SB(sb)->s_fc_bh = NULL;
+}
+
+/* Ext4 commit path routines */
+
+/* memcpy to fc reserved space and update CRC */
+static void *ext4_fc_memcpy(struct super_block *sb, void *dst, const void *src,
+				int len, u32 *crc)
+{
+	if (crc)
+		*crc = ext4_chksum(EXT4_SB(sb), *crc, src, len);
+	return memcpy(dst, src, len);
+}
+
+/* memzero and update CRC */
+static void *ext4_fc_memzero(struct super_block *sb, void *dst, int len,
+				u32 *crc)
+{
+	void *ret;
+
+	ret = memset(dst, 0, len);
+	if (crc)
+		*crc = ext4_chksum(EXT4_SB(sb), *crc, dst, len);
+	return ret;
+}
+
+/*
+ * Allocate len bytes on a fast commit buffer.
+ *
+ * During the commit time this function is used to manage fast commit
+ * block space. We don't split a fast commit log onto different
+ * blocks. So this function makes sure that if there's not enough space
+ * on the current block, the remaining space in the current block is
+ * marked as unused by adding EXT4_FC_TAG_PAD tag. In that case,
+ * new block is from jbd2 and CRC is updated to reflect the padding
+ * we added.
+ */
+static u8 *ext4_fc_reserve_space(struct super_block *sb, int len, u32 *crc)
+{
+	struct ext4_fc_tl tl;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct buffer_head *bh;
+	int bsize = sbi->s_journal->j_blocksize;
+	int ret, off = sbi->s_fc_bytes % bsize;
+	int remaining;
+	u8 *dst;
+
+	/*
+	 * If 'len' is too long to fit in any block alongside a PAD tlv, then we
+	 * cannot fulfill the request.
+	 */
+	if (len > bsize - EXT4_FC_TAG_BASE_LEN)
+		return NULL;
+
+	if (!sbi->s_fc_bh) {
+		ret = jbd2_fc_get_buf(EXT4_SB(sb)->s_journal, &bh);
+		if (ret)
+			return NULL;
+		sbi->s_fc_bh = bh;
+	}
+	dst = sbi->s_fc_bh->b_data + off;
+
+	/*
+	 * Allocate the bytes in the current block if we can do so while still
+	 * leaving enough space for a PAD tlv.
+	 */
+	remaining = bsize - EXT4_FC_TAG_BASE_LEN - off;
+	if (len <= remaining) {
+		sbi->s_fc_bytes += len;
+		return dst;
+	}
+
+	/*
+	 * Else, terminate the current block with a PAD tlv, then allocate a new
+	 * block and allocate the bytes at the start of that new block.
+	 */
+
+	tl.fc_tag = cpu_to_le16(EXT4_FC_TAG_PAD);
+	tl.fc_len = cpu_to_le16(remaining);
+	ext4_fc_memcpy(sb, dst, &tl, EXT4_FC_TAG_BASE_LEN, crc);
+	ext4_fc_memzero(sb, dst + EXT4_FC_TAG_BASE_LEN, remaining, crc);
+
+	ext4_fc_submit_bh(sb, false);
+
+	ret = jbd2_fc_get_buf(EXT4_SB(sb)->s_journal, &bh);
+	if (ret)
+		return NULL;
+	sbi->s_fc_bh = bh;
+	sbi->s_fc_bytes += bsize - off + len;
+	return sbi->s_fc_bh->b_data;
+}
+
+/*
+ * Complete a fast commit by writing tail tag.
+ *
+ * Writing tail tag marks the end of a fast commit. In order to guarantee
+ * atomicity, after writing tail tag, even if there's space remaining
+ * in the block, next commit shouldn't use it. That's why tail tag
+ * has the length as that of the remaining space on the block.
+ */
+static int ext4_fc_write_tail(struct super_block *sb, u32 crc)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_fc_tl tl;
+	struct ext4_fc_tail tail;
+	int off, bsize = sbi->s_journal->j_blocksize;
+	u8 *dst;
+
+	/*
+	 * ext4_fc_reserve_space takes care of allocating an extra block if
+	 * there's no enough space on this block for accommodating this tail.
+	 */
+	dst = ext4_fc_reserve_space(sb, EXT4_FC_TAG_BASE_LEN + sizeof(tail), &crc);
+	if (!dst)
+		return -ENOSPC;
+
+	off = sbi->s_fc_bytes % bsize;
+
+	tl.fc_tag = cpu_to_le16(EXT4_FC_TAG_TAIL);
+	tl.fc_len = cpu_to_le16(bsize - off + sizeof(struct ext4_fc_tail));
+	sbi->s_fc_bytes = round_up(sbi->s_fc_bytes, bsize);
+
+	ext4_fc_memcpy(sb, dst, &tl, EXT4_FC_TAG_BASE_LEN, &crc);
+	dst += EXT4_FC_TAG_BASE_LEN;
+	tail.fc_tid = cpu_to_le32(sbi->s_journal->j_running_transaction->t_tid);
+	ext4_fc_memcpy(sb, dst, &tail.fc_tid, sizeof(tail.fc_tid), &crc);
+	dst += sizeof(tail.fc_tid);
+	tail.fc_crc = cpu_to_le32(crc);
+	ext4_fc_memcpy(sb, dst, &tail.fc_crc, sizeof(tail.fc_crc), NULL);
+	dst += sizeof(tail.fc_crc);
+	memset(dst, 0, bsize - off); /* Don't leak uninitialized memory. */
+
+	ext4_fc_submit_bh(sb, true);
+
+	return 0;
+}
+
+/*
+ * Adds tag, length, value and updates CRC. Returns true if tlv was added.
+ * Returns false if there's not enough space.
+ */
+static bool ext4_fc_add_tlv(struct super_block *sb, u16 tag, u16 len, u8 *val,
+			   u32 *crc)
+{
+	struct ext4_fc_tl tl;
+	u8 *dst;
+
+	dst = ext4_fc_reserve_space(sb, EXT4_FC_TAG_BASE_LEN + len, crc);
+	if (!dst)
+		return false;
+
+	tl.fc_tag = cpu_to_le16(tag);
+	tl.fc_len = cpu_to_le16(len);
+
+	ext4_fc_memcpy(sb, dst, &tl, EXT4_FC_TAG_BASE_LEN, crc);
+	ext4_fc_memcpy(sb, dst + EXT4_FC_TAG_BASE_LEN, val, len, crc);
+
+	return true;
+}
+
+/* Same as above, but adds dentry tlv. */
+static bool ext4_fc_add_dentry_tlv(struct super_block *sb, u32 *crc,
+				   struct ext4_fc_dentry_update *fc_dentry)
+{
+	struct ext4_fc_dentry_info fcd;
+	struct ext4_fc_tl tl;
+	int dlen = fc_dentry->fcd_name.len;
+	u8 *dst = ext4_fc_reserve_space(sb,
+			EXT4_FC_TAG_BASE_LEN + sizeof(fcd) + dlen, crc);
+
+	if (!dst)
+		return false;
+
+	fcd.fc_parent_ino = cpu_to_le32(fc_dentry->fcd_parent);
+	fcd.fc_ino = cpu_to_le32(fc_dentry->fcd_ino);
+	tl.fc_tag = cpu_to_le16(fc_dentry->fcd_op);
+	tl.fc_len = cpu_to_le16(sizeof(fcd) + dlen);
+	ext4_fc_memcpy(sb, dst, &tl, EXT4_FC_TAG_BASE_LEN, crc);
+	dst += EXT4_FC_TAG_BASE_LEN;
+	ext4_fc_memcpy(sb, dst, &fcd, sizeof(fcd), crc);
+	dst += sizeof(fcd);
+	ext4_fc_memcpy(sb, dst, fc_dentry->fcd_name.name, dlen, crc);
+
+	return true;
+}
+
+/*
+ * Writes inode in the fast commit space under TLV with tag @tag.
+ * Returns 0 on success, error on failure.
+ */
+static int ext4_fc_write_inode(struct inode *inode, u32 *crc)
+{
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	int inode_len = EXT4_GOOD_OLD_INODE_SIZE;
+	int ret;
+	struct ext4_iloc iloc;
+	struct ext4_fc_inode fc_inode;
+	struct ext4_fc_tl tl;
+	u8 *dst;
+
+	ret = ext4_get_inode_loc(inode, &iloc);
+	if (ret)
+		return ret;
+
+	if (ext4_test_inode_flag(inode, EXT4_INODE_INLINE_DATA))
+		inode_len = EXT4_INODE_SIZE(inode->i_sb);
+	else if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE)
+		inode_len += ei->i_extra_isize;
+
+	fc_inode.fc_ino = cpu_to_le32(inode->i_ino);
+	tl.fc_tag = cpu_to_le16(EXT4_FC_TAG_INODE);
+	tl.fc_len = cpu_to_le16(inode_len + sizeof(fc_inode.fc_ino));
+
+	ret = -ECANCELED;
+	dst = ext4_fc_reserve_space(inode->i_sb,
+		EXT4_FC_TAG_BASE_LEN + inode_len + sizeof(fc_inode.fc_ino), crc);
+	if (!dst)
+		goto err;
+
+	if (!ext4_fc_memcpy(inode->i_sb, dst, &tl, EXT4_FC_TAG_BASE_LEN, crc))
+		goto err;
+	dst += EXT4_FC_TAG_BASE_LEN;
+	if (!ext4_fc_memcpy(inode->i_sb, dst, &fc_inode, sizeof(fc_inode), crc))
+		goto err;
+	dst += sizeof(fc_inode);
+	if (!ext4_fc_memcpy(inode->i_sb, dst, (u8 *)ext4_raw_inode(&iloc),
+					inode_len, crc))
+		goto err;
+	ret = 0;
+err:
+	brelse(iloc.bh);
+	return ret;
+}
+
+/*
+ * Writes updated data ranges for the inode in question. Updates CRC.
+ * Returns 0 on success, error otherwise.
+ */
+static int ext4_fc_write_inode_data(struct inode *inode, u32 *crc)
+{
+	ext4_lblk_t old_blk_size, cur_lblk_off, new_blk_size;
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	struct ext4_map_blocks map;
+	struct ext4_fc_add_range fc_ext;
+	struct ext4_fc_del_range lrange;
+	struct ext4_extent *ex;
+	int ret;
+
+	mutex_lock(&ei->i_fc_lock);
+	if (ei->i_fc_lblk_len == 0) {
+		mutex_unlock(&ei->i_fc_lock);
+		return 0;
+	}
+	old_blk_size = ei->i_fc_lblk_start;
+	new_blk_size = ei->i_fc_lblk_start + ei->i_fc_lblk_len - 1;
+	ei->i_fc_lblk_len = 0;
+	mutex_unlock(&ei->i_fc_lock);
+
+	cur_lblk_off = old_blk_size;
+	ext4_debug("will try writing %d to %d for inode %ld\n",
+		   cur_lblk_off, new_blk_size, inode->i_ino);
+
+	while (cur_lblk_off <= new_blk_size) {
+		map.m_lblk = cur_lblk_off;
+		map.m_len = new_blk_size - cur_lblk_off + 1;
+		ret = ext4_map_blocks(NULL, inode, &map, 0);
+		if (ret < 0)
+			return -ECANCELED;
+
+		if (map.m_len == 0) {
+			cur_lblk_off++;
+			continue;
+		}
+
+		if (ret == 0) {
+			lrange.fc_ino = cpu_to_le32(inode->i_ino);
+			lrange.fc_lblk = cpu_to_le32(map.m_lblk);
+			lrange.fc_len = cpu_to_le32(map.m_len);
+			if (!ext4_fc_add_tlv(inode->i_sb, EXT4_FC_TAG_DEL_RANGE,
+					    sizeof(lrange), (u8 *)&lrange, crc))
+				return -ENOSPC;
+		} else {
+			unsigned int max = (map.m_flags & EXT4_MAP_UNWRITTEN) ?
+				EXT_UNWRITTEN_MAX_LEN : EXT_INIT_MAX_LEN;
+
+			/* Limit the number of blocks in one extent */
+			map.m_len = min(max, map.m_len);
+
+			fc_ext.fc_ino = cpu_to_le32(inode->i_ino);
+			ex = (struct ext4_extent *)&fc_ext.fc_ex;
+			ex->ee_block = cpu_to_le32(map.m_lblk);
+			ex->ee_len = cpu_to_le16(map.m_len);
+			ext4_ext_store_pblock(ex, map.m_pblk);
+			if (map.m_flags & EXT4_MAP_UNWRITTEN)
+				ext4_ext_mark_unwritten(ex);
+			else
+				ext4_ext_mark_initialized(ex);
+			if (!ext4_fc_add_tlv(inode->i_sb, EXT4_FC_TAG_ADD_RANGE,
+					    sizeof(fc_ext), (u8 *)&fc_ext, crc))
+				return -ENOSPC;
+		}
+
+		cur_lblk_off += map.m_len;
+	}
+
+	return 0;
+}
+
+
+/* Submit data for all the fast commit inodes */
+static int ext4_fc_submit_inode_data_all(journal_t *journal)
+{
+	struct super_block *sb = journal->j_private;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_inode_info *ei;
+	int ret = 0;
+
+	spin_lock(&sbi->s_fc_lock);
+	list_for_each_entry(ei, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) {
+		ext4_set_inode_state(&ei->vfs_inode, EXT4_STATE_FC_COMMITTING);
+		while (atomic_read(&ei->i_fc_updates)) {
+			DEFINE_WAIT(wait);
+
+			prepare_to_wait(&ei->i_fc_wait, &wait,
+						TASK_UNINTERRUPTIBLE);
+			if (atomic_read(&ei->i_fc_updates)) {
+				spin_unlock(&sbi->s_fc_lock);
+				schedule();
+				spin_lock(&sbi->s_fc_lock);
+			}
+			finish_wait(&ei->i_fc_wait, &wait);
+		}
+		spin_unlock(&sbi->s_fc_lock);
+		ret = jbd2_submit_inode_data(ei->jinode);
+		if (ret)
+			return ret;
+		spin_lock(&sbi->s_fc_lock);
+	}
+	spin_unlock(&sbi->s_fc_lock);
+
+	return ret;
+}
+
+/* Wait for completion of data for all the fast commit inodes */
+static int ext4_fc_wait_inode_data_all(journal_t *journal)
+{
+	struct super_block *sb = journal->j_private;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_inode_info *pos, *n;
+	int ret = 0;
+
+	spin_lock(&sbi->s_fc_lock);
+	list_for_each_entry_safe(pos, n, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) {
+		if (!ext4_test_inode_state(&pos->vfs_inode,
+					   EXT4_STATE_FC_COMMITTING))
+			continue;
+		spin_unlock(&sbi->s_fc_lock);
+
+		ret = jbd2_wait_inode_data(journal, pos->jinode);
+		if (ret)
+			return ret;
+		spin_lock(&sbi->s_fc_lock);
+	}
+	spin_unlock(&sbi->s_fc_lock);
+
+	return 0;
+}
+
+/* Commit all the directory entry updates */
+static int ext4_fc_commit_dentry_updates(journal_t *journal, u32 *crc)
+__acquires(&sbi->s_fc_lock)
+__releases(&sbi->s_fc_lock)
+{
+	struct super_block *sb = journal->j_private;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_fc_dentry_update *fc_dentry, *fc_dentry_n;
+	struct inode *inode;
+	struct ext4_inode_info *ei;
+	int ret;
+
+	if (list_empty(&sbi->s_fc_dentry_q[FC_Q_MAIN]))
+		return 0;
+	list_for_each_entry_safe(fc_dentry, fc_dentry_n,
+				 &sbi->s_fc_dentry_q[FC_Q_MAIN], fcd_list) {
+		if (fc_dentry->fcd_op != EXT4_FC_TAG_CREAT) {
+			spin_unlock(&sbi->s_fc_lock);
+			if (!ext4_fc_add_dentry_tlv(sb, crc, fc_dentry)) {
+				ret = -ENOSPC;
+				goto lock_and_exit;
+			}
+			spin_lock(&sbi->s_fc_lock);
+			continue;
+		}
+		/*
+		 * With fcd_dilist we need not loop in sbi->s_fc_q to get the
+		 * corresponding inode pointer
+		 */
+		WARN_ON(list_empty(&fc_dentry->fcd_dilist));
+		ei = list_first_entry(&fc_dentry->fcd_dilist,
+				struct ext4_inode_info, i_fc_dilist);
+		inode = &ei->vfs_inode;
+		WARN_ON(inode->i_ino != fc_dentry->fcd_ino);
+
+		spin_unlock(&sbi->s_fc_lock);
+
+		/*
+		 * We first write the inode and then the create dirent. This
+		 * allows the recovery code to create an unnamed inode first
+		 * and then link it to a directory entry. This allows us
+		 * to use namei.c routines almost as is and simplifies
+		 * the recovery code.
+		 */
+		ret = ext4_fc_write_inode(inode, crc);
+		if (ret)
+			goto lock_and_exit;
+
+		ret = ext4_fc_write_inode_data(inode, crc);
+		if (ret)
+			goto lock_and_exit;
+
+		if (!ext4_fc_add_dentry_tlv(sb, crc, fc_dentry)) {
+			ret = -ENOSPC;
+			goto lock_and_exit;
+		}
+
+		spin_lock(&sbi->s_fc_lock);
+	}
+	return 0;
+lock_and_exit:
+	spin_lock(&sbi->s_fc_lock);
+	return ret;
+}
+
+static int ext4_fc_perform_commit(journal_t *journal)
+{
+	struct super_block *sb = journal->j_private;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_inode_info *iter;
+	struct ext4_fc_head head;
+	struct inode *inode;
+	struct blk_plug plug;
+	int ret = 0;
+	u32 crc = 0;
+
+	ret = ext4_fc_submit_inode_data_all(journal);
+	if (ret)
+		return ret;
+
+	ret = ext4_fc_wait_inode_data_all(journal);
+	if (ret)
+		return ret;
+
+	/*
+	 * If file system device is different from journal device, issue a cache
+	 * flush before we start writing fast commit blocks.
+	 */
+	if (journal->j_fs_dev != journal->j_dev)
+		blkdev_issue_flush(journal->j_fs_dev);
+
+	blk_start_plug(&plug);
+	if (sbi->s_fc_bytes == 0) {
+		/*
+		 * Add a head tag only if this is the first fast commit
+		 * in this TID.
+		 */
+		head.fc_features = cpu_to_le32(EXT4_FC_SUPPORTED_FEATURES);
+		head.fc_tid = cpu_to_le32(
+			sbi->s_journal->j_running_transaction->t_tid);
+		if (!ext4_fc_add_tlv(sb, EXT4_FC_TAG_HEAD, sizeof(head),
+			(u8 *)&head, &crc)) {
+			ret = -ENOSPC;
+			goto out;
+		}
+	}
+
+	spin_lock(&sbi->s_fc_lock);
+	ret = ext4_fc_commit_dentry_updates(journal, &crc);
+	if (ret) {
+		spin_unlock(&sbi->s_fc_lock);
+		goto out;
+	}
+
+	list_for_each_entry(iter, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) {
+		inode = &iter->vfs_inode;
+		if (!ext4_test_inode_state(inode, EXT4_STATE_FC_COMMITTING))
+			continue;
+
+		spin_unlock(&sbi->s_fc_lock);
+		ret = ext4_fc_write_inode_data(inode, &crc);
+		if (ret)
+			goto out;
+		ret = ext4_fc_write_inode(inode, &crc);
+		if (ret)
+			goto out;
+		spin_lock(&sbi->s_fc_lock);
+	}
+	spin_unlock(&sbi->s_fc_lock);
+
+	ret = ext4_fc_write_tail(sb, crc);
+
+out:
+	blk_finish_plug(&plug);
+	return ret;
+}
+
+static void ext4_fc_update_stats(struct super_block *sb, int status,
+				 u64 commit_time, int nblks, tid_t commit_tid)
+{
+	struct ext4_fc_stats *stats = &EXT4_SB(sb)->s_fc_stats;
+
+	ext4_debug("Fast commit ended with status = %d for tid %u",
+			status, commit_tid);
+	if (status == EXT4_FC_STATUS_OK) {
+		stats->fc_num_commits++;
+		stats->fc_numblks += nblks;
+		if (likely(stats->s_fc_avg_commit_time))
+			stats->s_fc_avg_commit_time =
+				(commit_time +
+				 stats->s_fc_avg_commit_time * 3) / 4;
+		else
+			stats->s_fc_avg_commit_time = commit_time;
+	} else if (status == EXT4_FC_STATUS_FAILED ||
+		   status == EXT4_FC_STATUS_INELIGIBLE) {
+		if (status == EXT4_FC_STATUS_FAILED)
+			stats->fc_failed_commits++;
+		stats->fc_ineligible_commits++;
+	} else {
+		stats->fc_skipped_commits++;
+	}
+	trace_ext4_fc_commit_stop(sb, nblks, status, commit_tid);
+}
+
+/*
+ * The main commit entry point. Performs a fast commit for transaction
+ * commit_tid if needed. If it's not possible to perform a fast commit
+ * due to various reasons, we fall back to full commit. Returns 0
+ * on success, error otherwise.
+ */
+int ext4_fc_commit(journal_t *journal, tid_t commit_tid)
+{
+	struct super_block *sb = journal->j_private;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	int nblks = 0, ret, bsize = journal->j_blocksize;
+	int subtid = atomic_read(&sbi->s_fc_subtid);
+	int status = EXT4_FC_STATUS_OK, fc_bufs_before = 0;
+	ktime_t start_time, commit_time;
+
+	if (!test_opt2(sb, JOURNAL_FAST_COMMIT))
+		return jbd2_complete_transaction(journal, commit_tid);
+
+	trace_ext4_fc_commit_start(sb, commit_tid);
+
+	start_time = ktime_get();
+
+restart_fc:
+	ret = jbd2_fc_begin_commit(journal, commit_tid);
+	if (ret == -EALREADY) {
+		/* There was an ongoing commit, check if we need to restart */
+		if (atomic_read(&sbi->s_fc_subtid) <= subtid &&
+			commit_tid > journal->j_commit_sequence)
+			goto restart_fc;
+		ext4_fc_update_stats(sb, EXT4_FC_STATUS_SKIPPED, 0, 0,
+				commit_tid);
+		return 0;
+	} else if (ret) {
+		/*
+		 * Commit couldn't start. Just update stats and perform a
+		 * full commit.
+		 */
+		ext4_fc_update_stats(sb, EXT4_FC_STATUS_FAILED, 0, 0,
+				commit_tid);
+		return jbd2_complete_transaction(journal, commit_tid);
+	}
+
+	/*
+	 * 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)) {
+		status = EXT4_FC_STATUS_INELIGIBLE;
+		goto fallback;
+	}
+
+	fc_bufs_before = (sbi->s_fc_bytes + bsize - 1) / bsize;
+	ret = ext4_fc_perform_commit(journal);
+	if (ret < 0) {
+		status = EXT4_FC_STATUS_FAILED;
+		goto fallback;
+	}
+	nblks = (sbi->s_fc_bytes + bsize - 1) / bsize - fc_bufs_before;
+	ret = jbd2_fc_wait_bufs(journal, nblks);
+	if (ret < 0) {
+		status = EXT4_FC_STATUS_FAILED;
+		goto fallback;
+	}
+	atomic_inc(&sbi->s_fc_subtid);
+	ret = jbd2_fc_end_commit(journal);
+	/*
+	 * weight the commit time higher than the average time so we
+	 * don't react too strongly to vast changes in the commit time
+	 */
+	commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
+	ext4_fc_update_stats(sb, status, commit_time, nblks, commit_tid);
+	return ret;
+
+fallback:
+	ret = jbd2_fc_end_commit_fallback(journal);
+	ext4_fc_update_stats(sb, status, 0, 0, commit_tid);
+	return ret;
+}
+
+/*
+ * Fast commit cleanup routine. This is called after every fast commit and
+ * full commit. full is true if we are called after a full commit.
+ */
+static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid)
+{
+	struct super_block *sb = journal->j_private;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_inode_info *iter, *iter_n;
+	struct ext4_fc_dentry_update *fc_dentry;
+
+	if (full && sbi->s_fc_bh)
+		sbi->s_fc_bh = NULL;
+
+	trace_ext4_fc_cleanup(journal, full, tid);
+	jbd2_fc_release_bufs(journal);
+
+	spin_lock(&sbi->s_fc_lock);
+	list_for_each_entry_safe(iter, iter_n, &sbi->s_fc_q[FC_Q_MAIN],
+				 i_fc_list) {
+		list_del_init(&iter->i_fc_list);
+		ext4_clear_inode_state(&iter->vfs_inode,
+				       EXT4_STATE_FC_COMMITTING);
+		if (iter->i_sync_tid <= tid)
+			ext4_fc_reset_inode(&iter->vfs_inode);
+		/* Make sure EXT4_STATE_FC_COMMITTING bit is clear */
+		smp_mb();
+#if (BITS_PER_LONG < 64)
+		wake_up_bit(&iter->i_state_flags, EXT4_STATE_FC_COMMITTING);
+#else
+		wake_up_bit(&iter->i_flags, EXT4_STATE_FC_COMMITTING);
+#endif
+	}
+
+	while (!list_empty(&sbi->s_fc_dentry_q[FC_Q_MAIN])) {
+		fc_dentry = list_first_entry(&sbi->s_fc_dentry_q[FC_Q_MAIN],
+					     struct ext4_fc_dentry_update,
+					     fcd_list);
+		list_del_init(&fc_dentry->fcd_list);
+		list_del_init(&fc_dentry->fcd_dilist);
+		spin_unlock(&sbi->s_fc_lock);
+
+		if (fc_dentry->fcd_name.name &&
+			fc_dentry->fcd_name.len > DNAME_INLINE_LEN)
+			kfree(fc_dentry->fcd_name.name);
+		kmem_cache_free(ext4_fc_dentry_cachep, fc_dentry);
+		spin_lock(&sbi->s_fc_lock);
+	}
+
+	list_splice_init(&sbi->s_fc_dentry_q[FC_Q_STAGING],
+				&sbi->s_fc_dentry_q[FC_Q_MAIN]);
+	list_splice_init(&sbi->s_fc_q[FC_Q_STAGING],
+				&sbi->s_fc_q[FC_Q_MAIN]);
+
+	if (tid >= sbi->s_fc_ineligible_tid) {
+		sbi->s_fc_ineligible_tid = 0;
+		ext4_clear_mount_flag(sb, EXT4_MF_FC_INELIGIBLE);
+	}
+
+	if (full)
+		sbi->s_fc_bytes = 0;
+	spin_unlock(&sbi->s_fc_lock);
+	trace_ext4_fc_stats(sb);
+}
+
+/* Ext4 Replay Path Routines */
+
+/* Helper struct for dentry replay routines */
+struct dentry_info_args {
+	int parent_ino, dname_len, ino, inode_len;
+	char *dname;
+};
+
+/* Same as struct ext4_fc_tl, but uses native endianness fields */
+struct ext4_fc_tl_mem {
+	u16 fc_tag;
+	u16 fc_len;
+};
+
+static inline void tl_to_darg(struct dentry_info_args *darg,
+			      struct ext4_fc_tl_mem *tl, u8 *val)
+{
+	struct ext4_fc_dentry_info fcd;
+
+	memcpy(&fcd, val, sizeof(fcd));
+
+	darg->parent_ino = le32_to_cpu(fcd.fc_parent_ino);
+	darg->ino = le32_to_cpu(fcd.fc_ino);
+	darg->dname = val + offsetof(struct ext4_fc_dentry_info, fc_dname);
+	darg->dname_len = tl->fc_len - sizeof(struct ext4_fc_dentry_info);
+}
+
+static inline void ext4_fc_get_tl(struct ext4_fc_tl_mem *tl, u8 *val)
+{
+	struct ext4_fc_tl tl_disk;
+
+	memcpy(&tl_disk, val, EXT4_FC_TAG_BASE_LEN);
+	tl->fc_len = le16_to_cpu(tl_disk.fc_len);
+	tl->fc_tag = le16_to_cpu(tl_disk.fc_tag);
+}
+
+/* Unlink replay function */
+static int ext4_fc_replay_unlink(struct super_block *sb,
+				 struct ext4_fc_tl_mem *tl, u8 *val)
+{
+	struct inode *inode, *old_parent;
+	struct qstr entry;
+	struct dentry_info_args darg;
+	int ret = 0;
+
+	tl_to_darg(&darg, tl, val);
+
+	trace_ext4_fc_replay(sb, EXT4_FC_TAG_UNLINK, darg.ino,
+			darg.parent_ino, darg.dname_len);
+
+	entry.name = darg.dname;
+	entry.len = darg.dname_len;
+	inode = ext4_iget(sb, darg.ino, EXT4_IGET_NORMAL);
+
+	if (IS_ERR(inode)) {
+		ext4_debug("Inode %d not found", darg.ino);
+		return 0;
+	}
+
+	old_parent = ext4_iget(sb, darg.parent_ino,
+				EXT4_IGET_NORMAL);
+	if (IS_ERR(old_parent)) {
+		ext4_debug("Dir with inode %d not found", darg.parent_ino);
+		iput(inode);
+		return 0;
+	}
+
+	ret = __ext4_unlink(old_parent, &entry, inode, NULL);
+	/* -ENOENT ok coz it might not exist anymore. */
+	if (ret == -ENOENT)
+		ret = 0;
+	iput(old_parent);
+	iput(inode);
+	return ret;
+}
+
+static int ext4_fc_replay_link_internal(struct super_block *sb,
+				struct dentry_info_args *darg,
+				struct inode *inode)
+{
+	struct inode *dir = NULL;
+	struct dentry *dentry_dir = NULL, *dentry_inode = NULL;
+	struct qstr qstr_dname = QSTR_INIT(darg->dname, darg->dname_len);
+	int ret = 0;
+
+	dir = ext4_iget(sb, darg->parent_ino, EXT4_IGET_NORMAL);
+	if (IS_ERR(dir)) {
+		ext4_debug("Dir with inode %d not found.", darg->parent_ino);
+		dir = NULL;
+		goto out;
+	}
+
+	dentry_dir = d_obtain_alias(dir);
+	if (IS_ERR(dentry_dir)) {
+		ext4_debug("Failed to obtain dentry");
+		dentry_dir = NULL;
+		goto out;
+	}
+
+	dentry_inode = d_alloc(dentry_dir, &qstr_dname);
+	if (!dentry_inode) {
+		ext4_debug("Inode dentry not created.");
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = __ext4_link(dir, inode, dentry_inode);
+	/*
+	 * It's possible that link already existed since data blocks
+	 * for the dir in question got persisted before we crashed OR
+	 * we replayed this tag and crashed before the entire replay
+	 * could complete.
+	 */
+	if (ret && ret != -EEXIST) {
+		ext4_debug("Failed to link\n");
+		goto out;
+	}
+
+	ret = 0;
+out:
+	if (dentry_dir) {
+		d_drop(dentry_dir);
+		dput(dentry_dir);
+	} else if (dir) {
+		iput(dir);
+	}
+	if (dentry_inode) {
+		d_drop(dentry_inode);
+		dput(dentry_inode);
+	}
+
+	return ret;
+}
+
+/* Link replay function */
+static int ext4_fc_replay_link(struct super_block *sb,
+			       struct ext4_fc_tl_mem *tl, u8 *val)
+{
+	struct inode *inode;
+	struct dentry_info_args darg;
+	int ret = 0;
+
+	tl_to_darg(&darg, tl, val);
+	trace_ext4_fc_replay(sb, EXT4_FC_TAG_LINK, darg.ino,
+			darg.parent_ino, darg.dname_len);
+
+	inode = ext4_iget(sb, darg.ino, EXT4_IGET_NORMAL);
+	if (IS_ERR(inode)) {
+		ext4_debug("Inode not found.");
+		return 0;
+	}
+
+	ret = ext4_fc_replay_link_internal(sb, &darg, inode);
+	iput(inode);
+	return ret;
+}
+
+/*
+ * Record all the modified inodes during replay. We use this later to setup
+ * block bitmaps correctly.
+ */
+static int ext4_fc_record_modified_inode(struct super_block *sb, int ino)
+{
+	struct ext4_fc_replay_state *state;
+	int i;
+
+	state = &EXT4_SB(sb)->s_fc_replay_state;
+	for (i = 0; i < state->fc_modified_inodes_used; i++)
+		if (state->fc_modified_inodes[i] == ino)
+			return 0;
+	if (state->fc_modified_inodes_used == state->fc_modified_inodes_size) {
+		int *fc_modified_inodes;
+
+		fc_modified_inodes = krealloc(state->fc_modified_inodes,
+				sizeof(int) * (state->fc_modified_inodes_size +
+				EXT4_FC_REPLAY_REALLOC_INCREMENT),
+				GFP_KERNEL);
+		if (!fc_modified_inodes)
+			return -ENOMEM;
+		state->fc_modified_inodes = fc_modified_inodes;
+		state->fc_modified_inodes_size +=
+			EXT4_FC_REPLAY_REALLOC_INCREMENT;
+	}
+	state->fc_modified_inodes[state->fc_modified_inodes_used++] = ino;
+	return 0;
+}
+
+/*
+ * Inode replay function
+ */
+static int ext4_fc_replay_inode(struct super_block *sb,
+				struct ext4_fc_tl_mem *tl, u8 *val)
+{
+	struct ext4_fc_inode fc_inode;
+	struct ext4_inode *raw_inode;
+	struct ext4_inode *raw_fc_inode;
+	struct inode *inode = NULL;
+	struct ext4_iloc iloc;
+	int inode_len, ino, ret, tag = tl->fc_tag;
+	struct ext4_extent_header *eh;
+	size_t off_gen = offsetof(struct ext4_inode, i_generation);
+
+	memcpy(&fc_inode, val, sizeof(fc_inode));
+
+	ino = le32_to_cpu(fc_inode.fc_ino);
+	trace_ext4_fc_replay(sb, tag, ino, 0, 0);
+
+	inode = ext4_iget(sb, ino, EXT4_IGET_NORMAL);
+	if (!IS_ERR(inode)) {
+		ext4_ext_clear_bb(inode);
+		iput(inode);
+	}
+	inode = NULL;
+
+	ret = ext4_fc_record_modified_inode(sb, ino);
+	if (ret)
+		goto out;
+
+	raw_fc_inode = (struct ext4_inode *)
+		(val + offsetof(struct ext4_fc_inode, fc_raw_inode));
+	ret = ext4_get_fc_inode_loc(sb, ino, &iloc);
+	if (ret)
+		goto out;
+
+	inode_len = tl->fc_len - sizeof(struct ext4_fc_inode);
+	raw_inode = ext4_raw_inode(&iloc);
+
+	memcpy(raw_inode, raw_fc_inode, offsetof(struct ext4_inode, i_block));
+	memcpy((u8 *)raw_inode + off_gen, (u8 *)raw_fc_inode + off_gen,
+	       inode_len - off_gen);
+	if (le32_to_cpu(raw_inode->i_flags) & EXT4_EXTENTS_FL) {
+		eh = (struct ext4_extent_header *)(&raw_inode->i_block[0]);
+		if (eh->eh_magic != EXT4_EXT_MAGIC) {
+			memset(eh, 0, sizeof(*eh));
+			eh->eh_magic = EXT4_EXT_MAGIC;
+			eh->eh_max = cpu_to_le16(
+				(sizeof(raw_inode->i_block) -
+				 sizeof(struct ext4_extent_header))
+				 / sizeof(struct ext4_extent));
+		}
+	} else if (le32_to_cpu(raw_inode->i_flags) & EXT4_INLINE_DATA_FL) {
+		memcpy(raw_inode->i_block, raw_fc_inode->i_block,
+			sizeof(raw_inode->i_block));
+	}
+
+	/* Immediately update the inode on disk. */
+	ret = ext4_handle_dirty_metadata(NULL, NULL, iloc.bh);
+	if (ret)
+		goto out;
+	ret = sync_dirty_buffer(iloc.bh);
+	if (ret)
+		goto out;
+	ret = ext4_mark_inode_used(sb, ino);
+	if (ret)
+		goto out;
+
+	/* Given that we just wrote the inode on disk, this SHOULD succeed. */
+	inode = ext4_iget(sb, ino, EXT4_IGET_NORMAL);
+	if (IS_ERR(inode)) {
+		ext4_debug("Inode not found.");
+		return -EFSCORRUPTED;
+	}
+
+	/*
+	 * Our allocator could have made different decisions than before
+	 * crashing. This should be fixed but until then, we calculate
+	 * the number of blocks the inode.
+	 */
+	if (!ext4_test_inode_flag(inode, EXT4_INODE_INLINE_DATA))
+		ext4_ext_replay_set_iblocks(inode);
+
+	inode->i_generation = le32_to_cpu(ext4_raw_inode(&iloc)->i_generation);
+	ext4_reset_inode_seed(inode);
+
+	ext4_inode_csum_set(inode, ext4_raw_inode(&iloc), EXT4_I(inode));
+	ret = ext4_handle_dirty_metadata(NULL, NULL, iloc.bh);
+	sync_dirty_buffer(iloc.bh);
+	brelse(iloc.bh);
+out:
+	iput(inode);
+	if (!ret)
+		blkdev_issue_flush(sb->s_bdev);
+
+	return 0;
+}
+
+/*
+ * Dentry create replay function.
+ *
+ * EXT4_FC_TAG_CREAT is preceded by EXT4_FC_TAG_INODE_FULL. Which means, the
+ * inode for which we are trying to create a dentry here, should already have
+ * been replayed before we start here.
+ */
+static int ext4_fc_replay_create(struct super_block *sb,
+				 struct ext4_fc_tl_mem *tl, u8 *val)
+{
+	int ret = 0;
+	struct inode *inode = NULL;
+	struct inode *dir = NULL;
+	struct dentry_info_args darg;
+
+	tl_to_darg(&darg, tl, val);
+
+	trace_ext4_fc_replay(sb, EXT4_FC_TAG_CREAT, darg.ino,
+			darg.parent_ino, darg.dname_len);
+
+	/* This takes care of update group descriptor and other metadata */
+	ret = ext4_mark_inode_used(sb, darg.ino);
+	if (ret)
+		goto out;
+
+	inode = ext4_iget(sb, darg.ino, EXT4_IGET_NORMAL);
+	if (IS_ERR(inode)) {
+		ext4_debug("inode %d not found.", darg.ino);
+		inode = NULL;
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (S_ISDIR(inode->i_mode)) {
+		/*
+		 * If we are creating a directory, we need to make sure that the
+		 * dot and dot dot dirents are setup properly.
+		 */
+		dir = ext4_iget(sb, darg.parent_ino, EXT4_IGET_NORMAL);
+		if (IS_ERR(dir)) {
+			ext4_debug("Dir %d not found.", darg.ino);
+			goto out;
+		}
+		ret = ext4_init_new_dir(NULL, dir, inode);
+		iput(dir);
+		if (ret) {
+			ret = 0;
+			goto out;
+		}
+	}
+	ret = ext4_fc_replay_link_internal(sb, &darg, inode);
+	if (ret)
+		goto out;
+	set_nlink(inode, 1);
+	ext4_mark_inode_dirty(NULL, inode);
+out:
+	iput(inode);
+	return ret;
+}
+
+/*
+ * Record physical disk regions which are in use as per fast commit area,
+ * and used by inodes during replay phase. Our simple replay phase
+ * allocator excludes these regions from allocation.
+ */
+int ext4_fc_record_regions(struct super_block *sb, int ino,
+		ext4_lblk_t lblk, ext4_fsblk_t pblk, int len, int replay)
+{
+	struct ext4_fc_replay_state *state;
+	struct ext4_fc_alloc_region *region;
+
+	state = &EXT4_SB(sb)->s_fc_replay_state;
+	/*
+	 * during replay phase, the fc_regions_valid may not same as
+	 * fc_regions_used, update it when do new additions.
+	 */
+	if (replay && state->fc_regions_used != state->fc_regions_valid)
+		state->fc_regions_used = state->fc_regions_valid;
+	if (state->fc_regions_used == state->fc_regions_size) {
+		struct ext4_fc_alloc_region *fc_regions;
+
+		fc_regions = krealloc(state->fc_regions,
+				      sizeof(struct ext4_fc_alloc_region) *
+				      (state->fc_regions_size +
+				       EXT4_FC_REPLAY_REALLOC_INCREMENT),
+				      GFP_KERNEL);
+		if (!fc_regions)
+			return -ENOMEM;
+		state->fc_regions_size +=
+			EXT4_FC_REPLAY_REALLOC_INCREMENT;
+		state->fc_regions = fc_regions;
+	}
+	region = &state->fc_regions[state->fc_regions_used++];
+	region->ino = ino;
+	region->lblk = lblk;
+	region->pblk = pblk;
+	region->len = len;
+
+	if (replay)
+		state->fc_regions_valid++;
+
+	return 0;
+}
+
+/* Replay add range tag */
+static int ext4_fc_replay_add_range(struct super_block *sb,
+				    struct ext4_fc_tl_mem *tl, u8 *val)
+{
+	struct ext4_fc_add_range fc_add_ex;
+	struct ext4_extent newex, *ex;
+	struct inode *inode;
+	ext4_lblk_t start, cur;
+	int remaining, len;
+	ext4_fsblk_t start_pblk;
+	struct ext4_map_blocks map;
+	struct ext4_ext_path *path = NULL;
+	int ret;
+
+	memcpy(&fc_add_ex, val, sizeof(fc_add_ex));
+	ex = (struct ext4_extent *)&fc_add_ex.fc_ex;
+
+	trace_ext4_fc_replay(sb, EXT4_FC_TAG_ADD_RANGE,
+		le32_to_cpu(fc_add_ex.fc_ino), le32_to_cpu(ex->ee_block),
+		ext4_ext_get_actual_len(ex));
+
+	inode = ext4_iget(sb, le32_to_cpu(fc_add_ex.fc_ino), EXT4_IGET_NORMAL);
+	if (IS_ERR(inode)) {
+		ext4_debug("Inode not found.");
+		return 0;
+	}
+
+	ret = ext4_fc_record_modified_inode(sb, inode->i_ino);
+	if (ret)
+		goto out;
+
+	start = le32_to_cpu(ex->ee_block);
+	start_pblk = ext4_ext_pblock(ex);
+	len = ext4_ext_get_actual_len(ex);
+
+	cur = start;
+	remaining = len;
+	ext4_debug("ADD_RANGE, lblk %d, pblk %lld, len %d, unwritten %d, inode %ld\n",
+		  start, start_pblk, len, ext4_ext_is_unwritten(ex),
+		  inode->i_ino);
+
+	while (remaining > 0) {
+		map.m_lblk = cur;
+		map.m_len = remaining;
+		map.m_pblk = 0;
+		ret = ext4_map_blocks(NULL, inode, &map, 0);
+
+		if (ret < 0)
+			goto out;
+
+		if (ret == 0) {
+			/* Range is not mapped */
+			path = ext4_find_extent(inode, cur, NULL, 0);
+			if (IS_ERR(path))
+				goto out;
+			memset(&newex, 0, sizeof(newex));
+			newex.ee_block = cpu_to_le32(cur);
+			ext4_ext_store_pblock(
+				&newex, start_pblk + cur - start);
+			newex.ee_len = cpu_to_le16(map.m_len);
+			if (ext4_ext_is_unwritten(ex))
+				ext4_ext_mark_unwritten(&newex);
+			down_write(&EXT4_I(inode)->i_data_sem);
+			ret = ext4_ext_insert_extent(
+				NULL, inode, &path, &newex, 0);
+			up_write((&EXT4_I(inode)->i_data_sem));
+			ext4_free_ext_path(path);
+			if (ret)
+				goto out;
+			goto next;
+		}
+
+		if (start_pblk + cur - start != map.m_pblk) {
+			/*
+			 * Logical to physical mapping changed. This can happen
+			 * if this range was removed and then reallocated to
+			 * map to new physical blocks during a fast commit.
+			 */
+			ret = ext4_ext_replay_update_ex(inode, cur, map.m_len,
+					ext4_ext_is_unwritten(ex),
+					start_pblk + cur - start);
+			if (ret)
+				goto out;
+			/*
+			 * Mark the old blocks as free since they aren't used
+			 * anymore. We maintain an array of all the modified
+			 * inodes. In case these blocks are still used at either
+			 * a different logical range in the same inode or in
+			 * some different inode, we will mark them as allocated
+			 * at the end of the FC replay using our array of
+			 * modified inodes.
+			 */
+			ext4_mb_mark_bb(inode->i_sb, map.m_pblk, map.m_len, 0);
+			goto next;
+		}
+
+		/* Range is mapped and needs a state change */
+		ext4_debug("Converting from %ld to %d %lld",
+				map.m_flags & EXT4_MAP_UNWRITTEN,
+			ext4_ext_is_unwritten(ex), map.m_pblk);
+		ret = ext4_ext_replay_update_ex(inode, cur, map.m_len,
+					ext4_ext_is_unwritten(ex), map.m_pblk);
+		if (ret)
+			goto out;
+		/*
+		 * We may have split the extent tree while toggling the state.
+		 * Try to shrink the extent tree now.
+		 */
+		ext4_ext_replay_shrink_inode(inode, start + len);
+next:
+		cur += map.m_len;
+		remaining -= map.m_len;
+	}
+	ext4_ext_replay_shrink_inode(inode, i_size_read(inode) >>
+					sb->s_blocksize_bits);
+out:
+	iput(inode);
+	return 0;
+}
+
+/* Replay DEL_RANGE tag */
+static int
+ext4_fc_replay_del_range(struct super_block *sb,
+			 struct ext4_fc_tl_mem *tl, u8 *val)
+{
+	struct inode *inode;
+	struct ext4_fc_del_range lrange;
+	struct ext4_map_blocks map;
+	ext4_lblk_t cur, remaining;
+	int ret;
+
+	memcpy(&lrange, val, sizeof(lrange));
+	cur = le32_to_cpu(lrange.fc_lblk);
+	remaining = le32_to_cpu(lrange.fc_len);
+
+	trace_ext4_fc_replay(sb, EXT4_FC_TAG_DEL_RANGE,
+		le32_to_cpu(lrange.fc_ino), cur, remaining);
+
+	inode = ext4_iget(sb, le32_to_cpu(lrange.fc_ino), EXT4_IGET_NORMAL);
+	if (IS_ERR(inode)) {
+		ext4_debug("Inode %d not found", le32_to_cpu(lrange.fc_ino));
+		return 0;
+	}
+
+	ret = ext4_fc_record_modified_inode(sb, inode->i_ino);
+	if (ret)
+		goto out;
+
+	ext4_debug("DEL_RANGE, inode %ld, lblk %d, len %d\n",
+			inode->i_ino, le32_to_cpu(lrange.fc_lblk),
+			le32_to_cpu(lrange.fc_len));
+	while (remaining > 0) {
+		map.m_lblk = cur;
+		map.m_len = remaining;
+
+		ret = ext4_map_blocks(NULL, inode, &map, 0);
+		if (ret < 0)
+			goto out;
+		if (ret > 0) {
+			remaining -= ret;
+			cur += ret;
+			ext4_mb_mark_bb(inode->i_sb, map.m_pblk, map.m_len, 0);
+		} else {
+			remaining -= map.m_len;
+			cur += map.m_len;
+		}
+	}
+
+	down_write(&EXT4_I(inode)->i_data_sem);
+	ret = ext4_ext_remove_space(inode, le32_to_cpu(lrange.fc_lblk),
+				le32_to_cpu(lrange.fc_lblk) +
+				le32_to_cpu(lrange.fc_len) - 1);
+	up_write(&EXT4_I(inode)->i_data_sem);
+	if (ret)
+		goto out;
+	ext4_ext_replay_shrink_inode(inode,
+		i_size_read(inode) >> sb->s_blocksize_bits);
+	ext4_mark_inode_dirty(NULL, inode);
+out:
+	iput(inode);
+	return 0;
+}
+
+static void ext4_fc_set_bitmaps_and_counters(struct super_block *sb)
+{
+	struct ext4_fc_replay_state *state;
+	struct inode *inode;
+	struct ext4_ext_path *path = NULL;
+	struct ext4_map_blocks map;
+	int i, ret, j;
+	ext4_lblk_t cur, end;
+
+	state = &EXT4_SB(sb)->s_fc_replay_state;
+	for (i = 0; i < state->fc_modified_inodes_used; i++) {
+		inode = ext4_iget(sb, state->fc_modified_inodes[i],
+			EXT4_IGET_NORMAL);
+		if (IS_ERR(inode)) {
+			ext4_debug("Inode %d not found.",
+				state->fc_modified_inodes[i]);
+			continue;
+		}
+		cur = 0;
+		end = EXT_MAX_BLOCKS;
+		if (ext4_test_inode_flag(inode, EXT4_INODE_INLINE_DATA)) {
+			iput(inode);
+			continue;
+		}
+		while (cur < end) {
+			map.m_lblk = cur;
+			map.m_len = end - cur;
+
+			ret = ext4_map_blocks(NULL, inode, &map, 0);
+			if (ret < 0)
+				break;
+
+			if (ret > 0) {
+				path = ext4_find_extent(inode, map.m_lblk, NULL, 0);
+				if (!IS_ERR(path)) {
+					for (j = 0; j < path->p_depth; j++)
+						ext4_mb_mark_bb(inode->i_sb,
+							path[j].p_block, 1, 1);
+					ext4_free_ext_path(path);
+				}
+				cur += ret;
+				ext4_mb_mark_bb(inode->i_sb, map.m_pblk,
+							map.m_len, 1);
+			} else {
+				cur = cur + (map.m_len ? map.m_len : 1);
+			}
+		}
+		iput(inode);
+	}
+}
+
+/*
+ * Check if block is in excluded regions for block allocation. The simple
+ * allocator that runs during replay phase is calls this function to see
+ * if it is okay to use a block.
+ */
+bool ext4_fc_replay_check_excluded(struct super_block *sb, ext4_fsblk_t blk)
+{
+	int i;
+	struct ext4_fc_replay_state *state;
+
+	state = &EXT4_SB(sb)->s_fc_replay_state;
+	for (i = 0; i < state->fc_regions_valid; i++) {
+		if (state->fc_regions[i].ino == 0 ||
+			state->fc_regions[i].len == 0)
+			continue;
+		if (in_range(blk, state->fc_regions[i].pblk,
+					state->fc_regions[i].len))
+			return true;
+	}
+	return false;
+}
+
+/* Cleanup function called after replay */
+void ext4_fc_replay_cleanup(struct super_block *sb)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+	sbi->s_mount_state &= ~EXT4_FC_REPLAY;
+	kfree(sbi->s_fc_replay_state.fc_regions);
+	kfree(sbi->s_fc_replay_state.fc_modified_inodes);
+}
+
+static bool ext4_fc_value_len_isvalid(struct ext4_sb_info *sbi,
+				      int tag, int len)
+{
+	switch (tag) {
+	case EXT4_FC_TAG_ADD_RANGE:
+		return len == sizeof(struct ext4_fc_add_range);
+	case EXT4_FC_TAG_DEL_RANGE:
+		return len == sizeof(struct ext4_fc_del_range);
+	case EXT4_FC_TAG_CREAT:
+	case EXT4_FC_TAG_LINK:
+	case EXT4_FC_TAG_UNLINK:
+		len -= sizeof(struct ext4_fc_dentry_info);
+		return len >= 1 && len <= EXT4_NAME_LEN;
+	case EXT4_FC_TAG_INODE:
+		len -= sizeof(struct ext4_fc_inode);
+		return len >= EXT4_GOOD_OLD_INODE_SIZE &&
+			len <= sbi->s_inode_size;
+	case EXT4_FC_TAG_PAD:
+		return true; /* padding can have any length */
+	case EXT4_FC_TAG_TAIL:
+		return len >= sizeof(struct ext4_fc_tail);
+	case EXT4_FC_TAG_HEAD:
+		return len == sizeof(struct ext4_fc_head);
+	}
+	return false;
+}
+
+/*
+ * Recovery Scan phase handler
+ *
+ * This function is called during the scan phase and is responsible
+ * for doing following things:
+ * - Make sure the fast commit area has valid tags for replay
+ * - Count number of tags that need to be replayed by the replay handler
+ * - Verify CRC
+ * - Create a list of excluded blocks for allocation during replay phase
+ *
+ * This function returns JBD2_FC_REPLAY_CONTINUE to indicate that SCAN is
+ * incomplete and JBD2 should send more blocks. It returns JBD2_FC_REPLAY_STOP
+ * to indicate that scan has finished and JBD2 can now start replay phase.
+ * It returns a negative error to indicate that there was an error. At the end
+ * of a successful scan phase, sbi->s_fc_replay_state.fc_replay_num_tags is set
+ * to indicate the number of tags that need to replayed during the replay phase.
+ */
+static int ext4_fc_replay_scan(journal_t *journal,
+				struct buffer_head *bh, int off,
+				tid_t expected_tid)
+{
+	struct super_block *sb = journal->j_private;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_fc_replay_state *state;
+	int ret = JBD2_FC_REPLAY_CONTINUE;
+	struct ext4_fc_add_range ext;
+	struct ext4_fc_tl_mem tl;
+	struct ext4_fc_tail tail;
+	__u8 *start, *end, *cur, *val;
+	struct ext4_fc_head head;
+	struct ext4_extent *ex;
+
+	state = &sbi->s_fc_replay_state;
+
+	start = (u8 *)bh->b_data;
+	end = start + journal->j_blocksize;
+
+	if (state->fc_replay_expected_off == 0) {
+		state->fc_cur_tag = 0;
+		state->fc_replay_num_tags = 0;
+		state->fc_crc = 0;
+		state->fc_regions = NULL;
+		state->fc_regions_valid = state->fc_regions_used =
+			state->fc_regions_size = 0;
+		/* Check if we can stop early */
+		if (le16_to_cpu(((struct ext4_fc_tl *)start)->fc_tag)
+			!= EXT4_FC_TAG_HEAD)
+			return 0;
+	}
+
+	if (off != state->fc_replay_expected_off) {
+		ret = -EFSCORRUPTED;
+		goto out_err;
+	}
+
+	state->fc_replay_expected_off++;
+	for (cur = start; cur <= end - EXT4_FC_TAG_BASE_LEN;
+	     cur = cur + EXT4_FC_TAG_BASE_LEN + tl.fc_len) {
+		ext4_fc_get_tl(&tl, cur);
+		val = cur + EXT4_FC_TAG_BASE_LEN;
+		if (tl.fc_len > end - val ||
+		    !ext4_fc_value_len_isvalid(sbi, tl.fc_tag, tl.fc_len)) {
+			ret = state->fc_replay_num_tags ?
+				JBD2_FC_REPLAY_STOP : -ECANCELED;
+			goto out_err;
+		}
+		ext4_debug("Scan phase, tag:%s, blk %lld\n",
+			   tag2str(tl.fc_tag), bh->b_blocknr);
+		switch (tl.fc_tag) {
+		case EXT4_FC_TAG_ADD_RANGE:
+			memcpy(&ext, val, sizeof(ext));
+			ex = (struct ext4_extent *)&ext.fc_ex;
+			ret = ext4_fc_record_regions(sb,
+				le32_to_cpu(ext.fc_ino),
+				le32_to_cpu(ex->ee_block), ext4_ext_pblock(ex),
+				ext4_ext_get_actual_len(ex), 0);
+			if (ret < 0)
+				break;
+			ret = JBD2_FC_REPLAY_CONTINUE;
+			fallthrough;
+		case EXT4_FC_TAG_DEL_RANGE:
+		case EXT4_FC_TAG_LINK:
+		case EXT4_FC_TAG_UNLINK:
+		case EXT4_FC_TAG_CREAT:
+		case EXT4_FC_TAG_INODE:
+		case EXT4_FC_TAG_PAD:
+			state->fc_cur_tag++;
+			state->fc_crc = ext4_chksum(sbi, state->fc_crc, cur,
+				EXT4_FC_TAG_BASE_LEN + tl.fc_len);
+			break;
+		case EXT4_FC_TAG_TAIL:
+			state->fc_cur_tag++;
+			memcpy(&tail, val, sizeof(tail));
+			state->fc_crc = ext4_chksum(sbi, state->fc_crc, cur,
+						EXT4_FC_TAG_BASE_LEN +
+						offsetof(struct ext4_fc_tail,
+						fc_crc));
+			if (le32_to_cpu(tail.fc_tid) == expected_tid &&
+				le32_to_cpu(tail.fc_crc) == state->fc_crc) {
+				state->fc_replay_num_tags = state->fc_cur_tag;
+				state->fc_regions_valid =
+					state->fc_regions_used;
+			} else {
+				ret = state->fc_replay_num_tags ?
+					JBD2_FC_REPLAY_STOP : -EFSBADCRC;
+			}
+			state->fc_crc = 0;
+			break;
+		case EXT4_FC_TAG_HEAD:
+			memcpy(&head, val, sizeof(head));
+			if (le32_to_cpu(head.fc_features) &
+				~EXT4_FC_SUPPORTED_FEATURES) {
+				ret = -EOPNOTSUPP;
+				break;
+			}
+			if (le32_to_cpu(head.fc_tid) != expected_tid) {
+				ret = JBD2_FC_REPLAY_STOP;
+				break;
+			}
+			state->fc_cur_tag++;
+			state->fc_crc = ext4_chksum(sbi, state->fc_crc, cur,
+				EXT4_FC_TAG_BASE_LEN + tl.fc_len);
+			break;
+		default:
+			ret = state->fc_replay_num_tags ?
+				JBD2_FC_REPLAY_STOP : -ECANCELED;
+		}
+		if (ret < 0 || ret == JBD2_FC_REPLAY_STOP)
+			break;
+	}
+
+out_err:
+	trace_ext4_fc_replay_scan(sb, ret, off);
+	return ret;
+}
+
+/*
+ * Main recovery path entry point.
+ * The meaning of return codes is similar as above.
+ */
+static int ext4_fc_replay(journal_t *journal, struct buffer_head *bh,
+				enum passtype pass, int off, tid_t expected_tid)
+{
+	struct super_block *sb = journal->j_private;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_fc_tl_mem tl;
+	__u8 *start, *end, *cur, *val;
+	int ret = JBD2_FC_REPLAY_CONTINUE;
+	struct ext4_fc_replay_state *state = &sbi->s_fc_replay_state;
+	struct ext4_fc_tail tail;
+
+	if (pass == PASS_SCAN) {
+		state->fc_current_pass = PASS_SCAN;
+		return ext4_fc_replay_scan(journal, bh, off, expected_tid);
+	}
+
+	if (state->fc_current_pass != pass) {
+		state->fc_current_pass = pass;
+		sbi->s_mount_state |= EXT4_FC_REPLAY;
+	}
+	if (!sbi->s_fc_replay_state.fc_replay_num_tags) {
+		ext4_debug("Replay stops\n");
+		ext4_fc_set_bitmaps_and_counters(sb);
+		return 0;
+	}
+
+#ifdef CONFIG_EXT4_DEBUG
+	if (sbi->s_fc_debug_max_replay && off >= sbi->s_fc_debug_max_replay) {
+		pr_warn("Dropping fc block %d because max_replay set\n", off);
+		return JBD2_FC_REPLAY_STOP;
+	}
+#endif
+
+	start = (u8 *)bh->b_data;
+	end = start + journal->j_blocksize;
+
+	for (cur = start; cur <= end - EXT4_FC_TAG_BASE_LEN;
+	     cur = cur + EXT4_FC_TAG_BASE_LEN + tl.fc_len) {
+		ext4_fc_get_tl(&tl, cur);
+		val = cur + EXT4_FC_TAG_BASE_LEN;
+
+		if (state->fc_replay_num_tags == 0) {
+			ret = JBD2_FC_REPLAY_STOP;
+			ext4_fc_set_bitmaps_and_counters(sb);
+			break;
+		}
+
+		ext4_debug("Replay phase, tag:%s\n", tag2str(tl.fc_tag));
+		state->fc_replay_num_tags--;
+		switch (tl.fc_tag) {
+		case EXT4_FC_TAG_LINK:
+			ret = ext4_fc_replay_link(sb, &tl, val);
+			break;
+		case EXT4_FC_TAG_UNLINK:
+			ret = ext4_fc_replay_unlink(sb, &tl, val);
+			break;
+		case EXT4_FC_TAG_ADD_RANGE:
+			ret = ext4_fc_replay_add_range(sb, &tl, val);
+			break;
+		case EXT4_FC_TAG_CREAT:
+			ret = ext4_fc_replay_create(sb, &tl, val);
+			break;
+		case EXT4_FC_TAG_DEL_RANGE:
+			ret = ext4_fc_replay_del_range(sb, &tl, val);
+			break;
+		case EXT4_FC_TAG_INODE:
+			ret = ext4_fc_replay_inode(sb, &tl, val);
+			break;
+		case EXT4_FC_TAG_PAD:
+			trace_ext4_fc_replay(sb, EXT4_FC_TAG_PAD, 0,
+					     tl.fc_len, 0);
+			break;
+		case EXT4_FC_TAG_TAIL:
+			trace_ext4_fc_replay(sb, EXT4_FC_TAG_TAIL,
+					     0, tl.fc_len, 0);
+			memcpy(&tail, val, sizeof(tail));
+			WARN_ON(le32_to_cpu(tail.fc_tid) != expected_tid);
+			break;
+		case EXT4_FC_TAG_HEAD:
+			break;
+		default:
+			trace_ext4_fc_replay(sb, tl.fc_tag, 0, tl.fc_len, 0);
+			ret = -ECANCELED;
+			break;
+		}
+		if (ret < 0)
+			break;
+		ret = JBD2_FC_REPLAY_CONTINUE;
+	}
+	return ret;
+}
+
+void ext4_fc_init(struct super_block *sb, journal_t *journal)
+{
+	/*
+	 * We set replay callback even if fast commit disabled because we may
+	 * could still have fast commit blocks that need to be replayed even if
+	 * fast commit has now been turned off.
+	 */
+	journal->j_fc_replay_callback = ext4_fc_replay;
+	if (!test_opt2(sb, JOURNAL_FAST_COMMIT))
+		return;
+	journal->j_fc_cleanup_callback = ext4_fc_cleanup;
+}
+
+static const char * const fc_ineligible_reasons[] = {
+	[EXT4_FC_REASON_XATTR] = "Extended attributes changed",
+	[EXT4_FC_REASON_CROSS_RENAME] = "Cross rename",
+	[EXT4_FC_REASON_JOURNAL_FLAG_CHANGE] = "Journal flag changed",
+	[EXT4_FC_REASON_NOMEM] = "Insufficient memory",
+	[EXT4_FC_REASON_SWAP_BOOT] = "Swap boot",
+	[EXT4_FC_REASON_RESIZE] = "Resize",
+	[EXT4_FC_REASON_RENAME_DIR] = "Dir renamed",
+	[EXT4_FC_REASON_FALLOC_RANGE] = "Falloc range op",
+	[EXT4_FC_REASON_INODE_JOURNAL_DATA] = "Data journalling",
+	[EXT4_FC_REASON_ENCRYPTED_FILENAME] = "Encrypted filename",
+};
+
+int ext4_fc_info_show(struct seq_file *seq, void *v)
+{
+	struct ext4_sb_info *sbi = EXT4_SB((struct super_block *)seq->private);
+	struct ext4_fc_stats *stats = &sbi->s_fc_stats;
+	int i;
+
+	if (v != SEQ_START_TOKEN)
+		return 0;
+
+	seq_printf(seq,
+		"fc stats:\n%ld commits\n%ld ineligible\n%ld numblks\n%lluus avg_commit_time\n",
+		   stats->fc_num_commits, stats->fc_ineligible_commits,
+		   stats->fc_numblks,
+		   div_u64(stats->s_fc_avg_commit_time, 1000));
+	seq_puts(seq, "Ineligible reasons:\n");
+	for (i = 0; i < EXT4_FC_REASON_MAX; i++)
+		seq_printf(seq, "\"%s\":\t%d\n", fc_ineligible_reasons[i],
+			stats->fc_ineligible_reason_count[i]);
+
+	return 0;
+}
+
+int __init ext4_fc_init_dentry_cache(void)
+{
+	ext4_fc_dentry_cachep = KMEM_CACHE(ext4_fc_dentry_update,
+					   SLAB_RECLAIM_ACCOUNT);
+
+	if (ext4_fc_dentry_cachep == NULL)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void ext4_fc_destroy_dentry_cache(void)
+{
+	kmem_cache_destroy(ext4_fc_dentry_cachep);
+}