On Fri, Mar 20, 2015 at 2:38 PM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> 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) {
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
>
> regards,
> dan carpenter
--
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."
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