ext4: add a new spinlock i_raw_lock to protect the ext4's raw inode

To avoid potential data races, use a spinlock which protects the raw
(on-disk) inode.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

fs/ext4/ext4.h

@@ -875,6 +875,8 @@ struct ext4_inode_info {
 	struct inode vfs_inode;
 	struct jbd2_inode *jinode;
 
+	spinlock_t i_raw_lock;	/* protects updates to the raw inode */
+
 	/*
 	 * File creation time. Its function is same as that of
 	 * struct timespec i_{a,c,m}time in the generic inode.

fs/ext4/inode.c

@@ -4305,12 +4305,15 @@ static int ext4_do_update_inode(handle_t *handle,
 	struct ext4_inode *raw_inode = ext4_raw_inode(iloc);
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	struct buffer_head *bh = iloc->bh;
+	struct super_block *sb = inode->i_sb;
 	int err = 0, rc, block;
-	int need_datasync = 0;
+	int need_datasync = 0, set_large_file = 0;
 	uid_t i_uid;
 	gid_t i_gid;
 
-	/* For fields not not tracking in the in-memory inode,
+	spin_lock(&ei->i_raw_lock);
+
+	/* For fields not tracked in the in-memory inode,
 	 * initialise them to zero for new inodes. */
 	if (ext4_test_inode_state(inode, EXT4_STATE_NEW))
 		memset(raw_inode, 0, EXT4_SB(inode->i_sb)->s_inode_size);
@@ -4348,8 +4351,10 @@ static int ext4_do_update_inode(handle_t *handle,
 	EXT4_INODE_SET_XTIME(i_atime, inode, raw_inode);
 	EXT4_EINODE_SET_XTIME(i_crtime, ei, raw_inode);
 
-	if (ext4_inode_blocks_set(handle, raw_inode, ei))
+	if (ext4_inode_blocks_set(handle, raw_inode, ei)) {
+		spin_unlock(&ei->i_raw_lock);
 		goto out_brelse;
+	}
 	raw_inode->i_dtime = cpu_to_le32(ei->i_dtime);
 	raw_inode->i_flags = cpu_to_le32(ei->i_flags & 0xFFFFFFFF);
 	if (likely(!test_opt2(inode->i_sb, HURD_COMPAT)))
@@ -4361,24 +4366,11 @@ static int ext4_do_update_inode(handle_t *handle,
 		need_datasync = 1;
 	}
 	if (ei->i_disksize > 0x7fffffffULL) {
-		struct super_block *sb = inode->i_sb;
 		if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
 				EXT4_FEATURE_RO_COMPAT_LARGE_FILE) ||
 				EXT4_SB(sb)->s_es->s_rev_level ==
-				cpu_to_le32(EXT4_GOOD_OLD_REV)) {
-			/* If this is the first large file
-			 * created, add a flag to the superblock.
-			 */
-			err = ext4_journal_get_write_access(handle,
-					EXT4_SB(sb)->s_sbh);
-			if (err)
-				goto out_brelse;
-			ext4_update_dynamic_rev(sb);
-			EXT4_SET_RO_COMPAT_FEATURE(sb,
-					EXT4_FEATURE_RO_COMPAT_LARGE_FILE);
-			ext4_handle_sync(handle);
-			err = ext4_handle_dirty_super(handle, sb);
-		}
+		    cpu_to_le32(EXT4_GOOD_OLD_REV))
+			set_large_file = 1;
 	}
 	raw_inode->i_generation = cpu_to_le32(inode->i_generation);
 	if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
@@ -4410,12 +4402,23 @@ static int ext4_do_update_inode(handle_t *handle,
 
 	ext4_inode_csum_set(inode, raw_inode, ei);
 
+	spin_unlock(&ei->i_raw_lock);
+
 	BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
 	rc = ext4_handle_dirty_metadata(handle, NULL, bh);
 	if (!err)
 		err = rc;
 	ext4_clear_inode_state(inode, EXT4_STATE_NEW);
-
+	if (set_large_file) {
+		err = ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh);
+		if (err)
+			goto out_brelse;
+		ext4_update_dynamic_rev(sb);
+		EXT4_SET_RO_COMPAT_FEATURE(sb,
+					   EXT4_FEATURE_RO_COMPAT_LARGE_FILE);
+		ext4_handle_sync(handle);
+		err = ext4_handle_dirty_super(handle, sb);
+	}
 	ext4_update_inode_fsync_trans(handle, inode, need_datasync);
 out_brelse:
 	brelse(bh);

fs/ext4/super.c

@@ -879,6 +879,7 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
 		return NULL;
 
 	ei->vfs_inode.i_version = 1;
+	spin_lock_init(&ei->i_raw_lock);
 	INIT_LIST_HEAD(&ei->i_prealloc_list);
 	spin_lock_init(&ei->i_prealloc_lock);
 	ext4_es_init_tree(&ei->i_es_tree);