exfat: do not zero the extended part

Since the read operation beyond the ValidDataLength returns zero,
if we just extend the size of the file, we don't need to zero the
extended part, but only change the DataLength without changing
the ValidDataLength.

Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Reviewed-by: Andy Wu <Andy.Wu@sony.com>
Reviewed-by: Aoyama Wataru <wataru.aoyama@sony.com>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

1 files changed, 57 insertions, 20 deletions

diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 270e2f934124..d25a96a148af 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -18,32 +18,69 @@
 
 static int exfat_cont_expand(struct inode *inode, loff_t size)
 {
-	struct address_space *mapping = inode->i_mapping;
-	loff_t start = i_size_read(inode), count = size - i_size_read(inode);
-	int err, err2;
+	int ret;
+	unsigned int num_clusters, new_num_clusters, last_clu;
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	struct super_block *sb = inode->i_sb;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	struct exfat_chain clu;
 
-	err = generic_cont_expand_simple(inode, size);
-	if (err)
-		return err;
+	ret = inode_newsize_ok(inode, size);
+	if (ret)
+		return ret;
+
+	num_clusters = EXFAT_B_TO_CLU_ROUND_UP(ei->i_size_ondisk, sbi);
+	new_num_clusters = EXFAT_B_TO_CLU_ROUND_UP(size, sbi);
+
+	if (new_num_clusters == num_clusters)
+		goto out;
+
+	exfat_chain_set(&clu, ei->start_clu, num_clusters, ei->flags);
+	ret = exfat_find_last_cluster(sb, &clu, &last_clu);
+	if (ret)
+		return ret;
 
+	clu.dir = (last_clu == EXFAT_EOF_CLUSTER) ?
+			EXFAT_EOF_CLUSTER : last_clu + 1;
+	clu.size = 0;
+	clu.flags = ei->flags;
+
+	ret = exfat_alloc_cluster(inode, new_num_clusters - num_clusters,
+			&clu, IS_DIRSYNC(inode));
+	if (ret)
+		return ret;
+
+	/* Append new clusters to chain */
+	if (clu.flags != ei->flags) {
+		exfat_chain_cont_cluster(sb, ei->start_clu, num_clusters);
+		ei->flags = ALLOC_FAT_CHAIN;
+	}
+	if (clu.flags == ALLOC_FAT_CHAIN)
+		if (exfat_ent_set(sb, last_clu, clu.dir))
+			goto free_clu;
+
+	if (num_clusters == 0)
+		ei->start_clu = clu.dir;
+
+out:
 	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
-	EXFAT_I(inode)->valid_size = size;
-	mark_inode_dirty(inode);
+	/* Expanded range not zeroed, do not update valid_size */
+	i_size_write(inode, size);
 
-	if (!IS_SYNC(inode))
-		return 0;
+	ei->i_size_aligned = round_up(size, sb->s_blocksize);
+	ei->i_size_ondisk = ei->i_size_aligned;
+	inode->i_blocks = round_up(size, sbi->cluster_size) >> 9;
 
-	err = filemap_fdatawrite_range(mapping, start, start + count - 1);
-	err2 = sync_mapping_buffers(mapping);
-	if (!err)
-		err = err2;
-	err2 = write_inode_now(inode, 1);
-	if (!err)
-		err = err2;
-	if (err)
-		return err;
+	if (IS_DIRSYNC(inode))
+		return write_inode_now(inode, 1);
+
+	mark_inode_dirty(inode);
+
+	return 0;
 
-	return filemap_fdatawait_range(mapping, start, start + count - 1);
+free_clu:
+	exfat_free_cluster(inode, &clu);
+	return -EIO;
 }
 
 static bool exfat_allow_set_time(struct exfat_sb_info *sbi, struct inode *inode)