ext2: Handle "zero" blocks

Any blocks with the value zero appear to indicate a region completly
filled to zeros.

I don't see this anywhere in the spec but it does make sense and the
behavior matches files that I have on my FreeBSD machine so I guess it
must be valid.

1 files changed, 7 insertions, 6 deletions

diff --git a/kernel/fs/ext2.c b/kernel/fs/ext2.c
index dc56ea1..948b0af 100644
--- a/kernel/fs/ext2.c
+++ b/kernel/fs/ext2.c
@@ -623,16 +623,17 @@ int read_inode(int inode_num, u8 *data, u64 size, u64 offset, u64 *file_size) {
 
   int bytes_read = 0;
   for (int i = block_start; size; i++) {
+    int read_len = ((size + block_offset) > block_byte_size)
+                       ? (block_byte_size - block_offset)
+                       : size;
+
     u32 block = get_block(inode, i);
     if (0 == block) {
-      klog(LOG_WARN, "Filesystem EXT2: Unable to find block");
-      return -1;
+      memset(data + bytes_read, 0, read_len);
+    } else {
+      ext2_read_block(block, data + bytes_read, read_len, block_offset);
     }
 
-    int read_len = ((size + block_offset) > block_byte_size)
-                       ? (block_byte_size - block_offset)
-                       : size;
-    ext2_read_block(block, data + bytes_read, read_len, block_offset);
     block_offset = 0;
     bytes_read += read_len;
     size -= read_len;