[v5,2/2] exfat: do not zero the extended part

Commit Message

[e-mail] Nov. 30, 2023, 3:09 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  | 77 +++++++++++++++++++++++++++++++++++-------------
 fs/exfat/inode.c | 14 ++++++++-
 2 files changed, 70 insertions(+), 21 deletions(-)

Patch

diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 154f39a03a69..3d01a4eefc11 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)
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index a7bb234c8bb1..9793c64f4ad6 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -75,8 +75,17 @@  int __exfat_write_inode(struct inode *inode, int sync)
 	if (ei->start_clu == EXFAT_EOF_CLUSTER)
 		on_disk_size = 0;
 
-	ep2->dentry.stream.valid_size = cpu_to_le64(ei->valid_size);
 	ep2->dentry.stream.size = cpu_to_le64(on_disk_size);
+	/*
+	 * mmap write does not use exfat_write_end(), valid_size may be
+	 * extended to the sector-aligned length in exfat_get_block().
+	 * So we need to fixup valid_size to the writren length.
+	 */
+	if (on_disk_size < ei->valid_size)
+		ep2->dentry.stream.valid_size = ep2->dentry.stream.size;
+	else
+		ep2->dentry.stream.valid_size = cpu_to_le64(ei->valid_size);
+
 	if (on_disk_size) {
 		ep2->dentry.stream.flags = ei->flags;
 		ep2->dentry.stream.start_clu = cpu_to_le32(ei->start_clu);
@@ -340,6 +349,9 @@  static int exfat_get_block(struct inode *inode, sector_t iblock,
 					pos, ei->i_size_aligned);
 			goto unlock_ret;
 		}
+
+		ei->valid_size = EXFAT_BLK_TO_B(iblock + max_blocks, sb);
+		mark_inode_dirty(inode);
 	} else {
 		valid_blks = EXFAT_B_TO_BLK(ei->valid_size, sb);