[v1,2/2] exfat: do not zeroed the extended part

Commit Message

[e-mail] June 15, 2023, 3:29 a.m. UTC

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 <[e-mail]>
Reviewed-by: Andy Wu <[e-mail]>
Reviewed-by: Aoyama Wataru <[e-mail]>
---
 fs/exfat/file.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 78 insertions(+), 3 deletions(-)

Patch

diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 680597f3237d..3daf31a4b0ab 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -13,7 +13,7 @@ 
 #include "exfat_raw.h"
 #include "exfat_fs.h"
 
-static int exfat_cont_expand(struct inode *inode, loff_t size, bool sync)
+static int exfat_expand_and_zero(struct inode *inode, loff_t size, bool sync)
 {
 	struct address_space *mapping = inode->i_mapping;
 	loff_t start = i_size_read(inode), count = size - i_size_read(inode);
@@ -43,6 +43,81 @@  static int exfat_cont_expand(struct inode *inode, loff_t size, bool sync)
 	return filemap_fdatawait_range(mapping, start, start + count - 1);
 }
 
+static int exfat_expand(struct inode *inode, loff_t size)
+{
+	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;
+
+	ret = inode_newsize_ok(inode, size);
+	if (ret)
+		return ret;
+
+	num_clusters = EXFAT_B_TO_CLU_ROUND_UP(i_size_read(inode), 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->i_ctime = inode->i_mtime = current_time(inode);
+	/* Expanded range not zeroed, do not update valid_size */
+	i_size_write(inode, size);
+
+	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;
+
+	if (IS_DIRSYNC(inode))
+		return write_inode_now(inode, 1);
+
+	mark_inode_dirty(inode);
+
+	return 0;
+
+free_clu:
+	exfat_free_cluster(inode, &clu);
+	return -EIO;
+}
+
+static int exfat_cont_expand(struct inode *inode, loff_t size)
+{
+	if (mapping_writably_mapped(inode->i_mapping))
+		return exfat_expand_and_zero(inode, size, IS_SYNC(inode));
+
+	return exfat_expand(inode, size);
+}
+
 static bool exfat_allow_set_time(struct exfat_sb_info *sbi, struct inode *inode)
 {
 	mode_t allow_utime = sbi->options.allow_utime;
@@ -256,7 +331,7 @@  int exfat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 
 	if ((attr->ia_valid & ATTR_SIZE) &&
 	    attr->ia_size > i_size_read(inode)) {
-		error = exfat_cont_expand(inode, attr->ia_size, IS_SYNC(inode));
+		error = exfat_cont_expand(inode, attr->ia_size);
 		if (error || attr->ia_valid == ATTR_SIZE)
 			return error;
 		attr->ia_valid &= ~ATTR_SIZE;
@@ -444,7 +519,7 @@  static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 		goto unlock;
 
 	if (pos + count > size) {
-		ret = exfat_cont_expand(inode, pos + count, false);
+		ret = exfat_expand_and_zero(inode, pos + count, false);
 		if (ret < 0)
 			goto unlock;
 	}