ext4: make sure blocks are not contaminated with data in block cache.

lwext4/ext4.c

@@ -1497,6 +1497,10 @@ int ext4_fwrite(ext4_file *f, const void *buf, size_t size, size_t *wcnt)
 		if (r != EOK)
 			goto Finish;
 
+		r = ext4_block_flush_lba(f->mp->fs.bdev, fblk);
+		if (r != EOK)
+			goto Finish;
+
 		off = fblk * block_size + unalg;
 		r = ext4_block_writebytes(f->mp->fs.bdev, off, u8_buf, len);
 		if (r != EOK)
@@ -1521,6 +1525,8 @@ int ext4_fwrite(ext4_file *f, const void *buf, size_t size, size_t *wcnt)
 	fblock_count = 0;
 	while (size >= block_size) {
 
+		uint32_t i;
+
 		while (iblk_idx < iblock_last) {
 			if (iblk_idx < ifile_blocks) {
 				r = ext4_fs_init_inode_dblk_idx(&ref, iblk_idx,
@@ -1550,6 +1556,13 @@ int ext4_fwrite(ext4_file *f, const void *buf, size_t size, size_t *wcnt)
 			fblock_count++;
 		}
 
+		for (i = 0;i < fblock_count;i++) {
+			r = ext4_block_flush_lba(f->mp->fs.bdev, fblock_start + i);
+			if (r != EOK)
+				goto Finish;
+
+		}
+
 		r = ext4_blocks_set_direct(f->mp->fs.bdev, u8_buf, fblock_start,
 					   fblock_count);
 		if (r != EOK)
@@ -1593,6 +1606,10 @@ int ext4_fwrite(ext4_file *f, const void *buf, size_t size, size_t *wcnt)
 				goto out_fsize;
 		}
 
+		r = ext4_block_flush_lba(f->mp->fs.bdev, fblk);
+		if (r != EOK)
+			goto Finish;
+
 		off = fblk * block_size;
 		r = ext4_block_writebytes(f->mp->fs.bdev, off, u8_buf, size);
 		if (r != EOK)