exfat: change to get file size from DataLength

In stream extension directory entry, the ValidDataLength
field describes how far into the data stream user data has
been written, and the DataLength field describes the file
size.

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, 107 insertions, 17 deletions

diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index e7ff58b8e68c..b02677c9fd45 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -75,8 +75,8 @@ 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(on_disk_size);
-	ep2->dentry.stream.size = ep2->dentry.stream.valid_size;
+	ep2->dentry.stream.valid_size = cpu_to_le64(ei->valid_size);
+	ep2->dentry.stream.size = cpu_to_le64(on_disk_size);
 	if (on_disk_size) {
 		ep2->dentry.stream.flags = ei->flags;
 		ep2->dentry.stream.start_clu = cpu_to_le32(ei->start_clu);
@@ -278,6 +278,7 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
 	unsigned int cluster, sec_offset;
 	sector_t last_block;
 	sector_t phys = 0;
+	sector_t valid_blks;
 	loff_t pos;
 
 	mutex_lock(&sbi->s_lock);
@@ -306,17 +307,32 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
 	mapped_blocks = sbi->sect_per_clus - sec_offset;
 	max_blocks = min(mapped_blocks, max_blocks);
 
-	/* Treat newly added block / cluster */
-	if (iblock < last_block)
-		create = 0;
-
-	if (create || buffer_delay(bh_result)) {
-		pos = EXFAT_BLK_TO_B((iblock + 1), sb);
+	pos = EXFAT_BLK_TO_B((iblock + 1), sb);
+	if ((create && iblock >= last_block) || buffer_delay(bh_result)) {
 		if (ei->i_size_ondisk < pos)
 			ei->i_size_ondisk = pos;
 	}
 
+	map_bh(bh_result, sb, phys);
+	if (buffer_delay(bh_result))
+		clear_buffer_delay(bh_result);
+
 	if (create) {
+		valid_blks = EXFAT_B_TO_BLK_ROUND_UP(ei->valid_size, sb);
+
+		if (iblock + max_blocks < valid_blks) {
+			/* The range has been written, map it */
+			goto done;
+		} else if (iblock < valid_blks) {
+			/*
+			 * The range has been partially written,
+			 * map the written part.
+			 */
+			max_blocks = valid_blks - iblock;
+			goto done;
+		}
+
+		/* The area has not been written, map and mark as new. */
 		err = exfat_map_new_buffer(ei, bh_result, pos);
 		if (err) {
 			exfat_fs_error(sb,
@@ -324,11 +340,55 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
 					pos, ei->i_size_aligned);
 			goto unlock_ret;
 		}
+	} else {
+		valid_blks = EXFAT_B_TO_BLK(ei->valid_size, sb);
+
+		if (iblock + max_blocks < valid_blks) {
+			/* The range has been written, map it */
+			goto done;
+		} else if (iblock < valid_blks) {
+			/*
+			 * The area has been partially written,
+			 * map the written part.
+			 */
+			max_blocks = valid_blks - iblock;
+			goto done;
+		} else if (iblock == valid_blks &&
+			   (ei->valid_size & (sb->s_blocksize - 1))) {
+			/*
+			 * The block has been partially written,
+			 * zero the unwritten part and map the block.
+			 */
+			loff_t size, off;
+
+			max_blocks = 1;
+
+			/*
+			 * For direct read, the unwritten part will be zeroed in
+			 * exfat_direct_IO()
+			 */
+			if (!bh_result->b_folio)
+				goto done;
+
+			pos -= sb->s_blocksize;
+			size = ei->valid_size - pos;
+			off = pos & (PAGE_SIZE - 1);
+
+			folio_set_bh(bh_result, bh_result->b_folio, off);
+			err = bh_read(bh_result, 0);
+			if (err < 0)
+				goto unlock_ret;
+
+			folio_zero_segment(bh_result->b_folio, off + size,
+					off + sb->s_blocksize);
+		} else {
+			/*
+			 * The range has not been written, clear the mapped flag
+			 * to only zero the cache and do not read from disk.
+			 */
+			clear_buffer_mapped(bh_result);
+		}
 	}
-
-	if (buffer_delay(bh_result))
-		clear_buffer_delay(bh_result);
-	map_bh(bh_result, sb, phys);
 done:
 	bh_result->b_size = EXFAT_BLK_TO_B(max_blocks, sb);
 unlock_ret:
@@ -343,6 +403,17 @@ static int exfat_read_folio(struct file *file, struct folio *folio)
 
 static void exfat_readahead(struct readahead_control *rac)
 {
+	struct address_space *mapping = rac->mapping;
+	struct inode *inode = mapping->host;
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	loff_t pos = readahead_pos(rac);
+
+	/* Range cross valid_size, read it page by page. */
+	if (ei->valid_size < i_size_read(inode) &&
+	    pos <= ei->valid_size &&
+	    ei->valid_size < pos + readahead_length(rac))
+		return;
+
 	mpage_readahead(rac, exfat_get_block);
 }
 
@@ -370,9 +441,7 @@ static int exfat_write_begin(struct file *file, struct address_space *mapping,
 	int ret;
 
 	*pagep = NULL;
-	ret = cont_write_begin(file, mapping, pos, len, pagep, fsdata,
-			       exfat_get_block,
-			       &EXFAT_I(mapping->host)->i_size_ondisk);
+	ret = block_write_begin(mapping, pos, len, pagep, exfat_get_block);
 
 	if (ret < 0)
 		exfat_write_failed(mapping, pos+len);
@@ -400,6 +469,11 @@ static int exfat_write_end(struct file *file, struct address_space *mapping,
 	if (err < len)
 		exfat_write_failed(mapping, pos+len);
 
+	if (!(err < 0) && pos + err > ei->valid_size) {
+		ei->valid_size = pos + err;
+		mark_inode_dirty(inode);
+	}
+
 	if (!(err < 0) && !(ei->attr & EXFAT_ATTR_ARCHIVE)) {
 		inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
 		ei->attr |= EXFAT_ATTR_ARCHIVE;
@@ -413,6 +487,8 @@ static ssize_t exfat_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct address_space *mapping = iocb->ki_filp->f_mapping;
 	struct inode *inode = mapping->host;
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	loff_t pos = iocb->ki_pos;
 	loff_t size = iocb->ki_pos + iov_iter_count(iter);
 	int rw = iov_iter_rw(iter);
 	ssize_t ret;
@@ -436,8 +512,21 @@ static ssize_t exfat_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 	 * condition of exfat_get_block() and ->truncate().
 	 */
 	ret = blockdev_direct_IO(iocb, inode, iter, exfat_get_block);
-	if (ret < 0 && (rw & WRITE))
-		exfat_write_failed(mapping, size);
+	if (ret < 0) {
+		if (rw == WRITE)
+			exfat_write_failed(mapping, size);
+
+		if (ret != -EIOCBQUEUED)
+			return ret;
+	} else
+		size = pos + ret;
+
+	/* zero the unwritten part in the partially written block */
+	if (rw == READ && pos < ei->valid_size && ei->valid_size < size) {
+		iov_iter_revert(iter, size - ei->valid_size);
+		iov_iter_zero(size - ei->valid_size, iter);
+	}
+
 	return ret;
 }
 
@@ -537,6 +626,7 @@ static int exfat_fill_inode(struct inode *inode, struct exfat_dir_entry *info)
 	ei->start_clu = info->start_clu;
 	ei->flags = info->flags;
 	ei->type = info->type;
+	ei->valid_size = info->valid_size;
 
 	ei->version = 0;
 	ei->hint_stat.eidx = 0;