Btrfs: make fsync work after cloning into a file

Hello Filipe Manana,

The patch 7ffbb598a059: "Btrfs: make fsync work after cloning into a file" from Jun 9, 2014, leads to the following static checker warning:

	fs/btrfs/inode.c:6602 btrfs_get_extent()
	warn: we tested 'create' before and it was 'false'

fs/btrfs/inode.c
6589
6590 if (new_inline)

                            ^^^^^^^^^^

This implies that "create == 0".

6591 goto out;
6592

  6593                  size = btrfs_file_extent_inline_len(leaf, path->slots[0], item);
  6594                  extent_offset = page_offset(page) + pg_offset - extent_start;
  6595                  copy_size = min_t(u64, PAGE_CACHE_SIZE - pg_offset,
  6596                                  size - extent_offset);
  6597                  em->start = extent_start + extent_offset;
  6598                  em->len = ALIGN(copy_size, root->sectorsize);
  6599                  em->orig_block_len = em->len;
  6600                  em->orig_start = em->start;
  6601                  ptr = btrfs_file_extent_inline_start(item) + extent_offset;
  6602                  if (create == 0 && !PageUptodate(page)) {
                            ^^^^^^^^^^^

No need to check here.

6603 if (btrfs_file_extent_compression(leaf, item) !=
6604 BTRFS_COMPRESS_NONE) {
6605 ret = uncompress_inline(path, inode, page,
6606 pg_offset,
6607 extent_offset, item);
6608 if (ret) {
6609 err = ret;
6610 goto out;
6611 }
6612 } else {
6613 map = kmap(page);
6614 read_extent_buffer(leaf, map + pg_offset, ptr,
6615 copy_size);
6616 if (pg_offset + copy_size < PAGE_CACHE_SIZE) {
6617 memset(map + pg_offset + copy_size, 0,
6618 PAGE_CACHE_SIZE - pg_offset -
6619 copy_size);
6620 }
6621 kunmap(page);
6622 }
6623 flush_dcache_page(page);

  6624                  } else if (create && PageUptodate(page)) {
                                   ^^^^^^

Or here.

  6625                          BUG();
  6626                          if (!trans) {

regards,
dan carpenter

Hi,

Valid warning, but the change mentioned above didn't add or update that logic (only stored the result of "!page || create" into a local variable named "new_inline").
The logic with the unnecessary checks for "create" was added in 2007, commit 179e29e488cc (Btrfs: Fix a number of inline extent problems that Yan Zheng reported.).

thanks

Filipe David Manana,

"Reasonable men adapt themselves to the world.
 Unreasonable men adapt the world to themselves.
 That's why all progress depends on unreasonable men."