ext4: main fast-commit commit path

This patch adds main fast commit commit path handlers. The overall
patch can be divided into two inter-related parts:

(A) Metadata updates tracking

    This part consists of helper functions to track changes that need
    to be committed during a commit operation. These updates are
    maintained by Ext4 in different in-memory queues. Following are
    the APIs and their short description that are implemented in this
    patch:

    - ext4_fc_track_link/unlink/creat() - Track unlink. link and creat
      operations
    - ext4_fc_track_range() - Track changed logical block offsets
      inodes
    - ext4_fc_track_inode() - Track inodes
    - ext4_fc_mark_ineligible() - Mark file system fast commit
      ineligible()
    - ext4_fc_start_update() / ext4_fc_stop_update() /
      ext4_fc_start_ineligible() / ext4_fc_stop_ineligible() These
      functions are useful for co-ordinating inode updates with
      commits.

(B) Main commit Path

    This part consists of functions to convert updates tracked in
    in-memory data structures into on-disk commits. Function
    ext4_fc_commit() is the main entry point to commit path.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201015203802.3597742-6-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/inode.c

@@ -729,6 +729,8 @@ out_sem:
 			if (ret)
 				return ret;
 		}
+		ext4_fc_track_range(inode, map->m_lblk,
+			    map->m_lblk + map->m_len - 1);
 	}
 
 	if (retval < 0)
@@ -3300,9 +3302,14 @@ static bool ext4_inode_datasync_dirty(struct inode *inode)
 {
 	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 
-	if (journal)
-		return !jbd2_transaction_committed(journal,
-					EXT4_I(inode)->i_datasync_tid);
+	if (journal) {
+		if (jbd2_transaction_committed(journal,
+					EXT4_I(inode)->i_datasync_tid))
+			return true;
+		return atomic_read(&EXT4_SB(inode->i_sb)->s_fc_subtid) >=
+			EXT4_I(inode)->i_fc_committed_subtid;
+	}
+
 	/* Any metadata buffers to write? */
 	if (!list_empty(&inode->i_mapping->private_list))
 		return true;
@@ -4097,6 +4104,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
 
 		up_write(&EXT4_I(inode)->i_data_sem);
 	}
+	ext4_fc_track_range(inode, first_block, stop_block);
 	if (IS_SYNC(inode))
 		ext4_handle_sync(handle);
 
@@ -4716,6 +4724,7 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
 	for (block = 0; block < EXT4_N_BLOCKS; block++)
 		ei->i_data[block] = raw_inode->i_block[block];
 	INIT_LIST_HEAD(&ei->i_orphan);
+	ext4_fc_init_inode(&ei->vfs_inode);
 
 	/*
 	 * Set transaction id's of transactions that have to be committed
@@ -5162,7 +5171,7 @@ int ext4_write_inode(struct inode *inode, struct writeback_control *wbc)
 		if (wbc->sync_mode != WB_SYNC_ALL || wbc->for_sync)
 			return 0;
 
-		err = jbd2_complete_transaction(EXT4_SB(inode->i_sb)->s_journal,
+		err = ext4_fc_commit(EXT4_SB(inode->i_sb)->s_journal,
 						EXT4_I(inode)->i_sync_tid);
 	} else {
 		struct ext4_iloc iloc;
@@ -5291,6 +5300,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
 		if (error)
 			return error;
 	}
+	ext4_fc_start_update(inode);
 	if ((ia_valid & ATTR_UID && !uid_eq(attr->ia_uid, inode->i_uid)) ||
 	    (ia_valid & ATTR_GID && !gid_eq(attr->ia_gid, inode->i_gid))) {
 		handle_t *handle;
@@ -5314,6 +5324,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
 
 		if (error) {
 			ext4_journal_stop(handle);
+			ext4_fc_stop_update(inode);
 			return error;
 		}
 		/* Update corresponding info in inode so that everything is in
@@ -5336,11 +5347,15 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
 		if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
 			struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 
-			if (attr->ia_size > sbi->s_bitmap_maxbytes)
+			if (attr->ia_size > sbi->s_bitmap_maxbytes) {
+				ext4_fc_stop_update(inode);
 				return -EFBIG;
+			}
 		}
-		if (!S_ISREG(inode->i_mode))
+		if (!S_ISREG(inode->i_mode)) {
+			ext4_fc_stop_update(inode);
 			return -EINVAL;
+		}
 
 		if (IS_I_VERSION(inode) && attr->ia_size != inode->i_size)
 			inode_inc_iversion(inode);
@@ -5364,7 +5379,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
 		rc = ext4_break_layouts(inode);
 		if (rc) {
 			up_write(&EXT4_I(inode)->i_mmap_sem);
-			return rc;
+			goto err_out;
 		}
 
 		if (attr->ia_size != inode->i_size) {
@@ -5385,6 +5400,21 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
 				inode->i_mtime = current_time(inode);
 				inode->i_ctime = inode->i_mtime;
 			}
+
+			if (shrink)
+				ext4_fc_track_range(inode,
+					(attr->ia_size > 0 ? attr->ia_size - 1 : 0) >>
+					inode->i_sb->s_blocksize_bits,
+					(oldsize > 0 ? oldsize - 1 : 0) >>
+					inode->i_sb->s_blocksize_bits);
+			else
+				ext4_fc_track_range(
+					inode,
+					(oldsize > 0 ? oldsize - 1 : oldsize) >>
+					inode->i_sb->s_blocksize_bits,
+					(attr->ia_size > 0 ? attr->ia_size - 1 : 0) >>
+					inode->i_sb->s_blocksize_bits);
+
 			down_write(&EXT4_I(inode)->i_data_sem);
 			EXT4_I(inode)->i_disksize = attr->ia_size;
 			rc = ext4_mark_inode_dirty(handle, inode);
@@ -5443,9 +5473,11 @@ out_mmap_sem:
 		rc = posix_acl_chmod(inode, inode->i_mode);
 
 err_out:
-	ext4_std_error(inode->i_sb, error);
+	if  (error)
+		ext4_std_error(inode->i_sb, error);
 	if (!error)
 		error = rc;
+	ext4_fc_stop_update(inode);
 	return error;
 }
 
@@ -5627,6 +5659,8 @@ int ext4_mark_iloc_dirty(handle_t *handle,
 		put_bh(iloc->bh);
 		return -EIO;
 	}
+	ext4_fc_track_inode(inode);
+
 	if (IS_I_VERSION(inode))
 		inode_inc_iversion(inode);
 
@@ -5950,6 +5984,8 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);
 
+	ext4_fc_mark_ineligible(inode->i_sb,
+		EXT4_FC_REASON_JOURNAL_FLAG_CHANGE);
 	err = ext4_mark_inode_dirty(handle, inode);
 	ext4_handle_sync(handle);
 	ext4_journal_stop(handle);