Re: Btrfs: split up __extent_writepage to lower stack usage

[Chris Mason <clm@fb.com>]

On 06/09/2014 10:40 AM, Dan Carpenter wrote:
> Hello Chris Mason,
> 
> The patch 263524b4ac6b: "Btrfs: split up __extent_writepage to lower
> stack usage" from May 21, 2014, leads to the following static checker
> warning:
> 
> 	fs/btrfs/extent_io.c:4071 try_release_extent_state()
> 	warn: use 'mask' here instead of GFP_XXX?
> 
> fs/btrfs/extent_io.c
>   4053  static int try_release_extent_state(struct extent_map_tree *map,
>   4054                                      struct extent_io_tree *tree,
>   4055                                      struct page *page, gfp_t mask)
>   4056  {
>   4057          u64 start = page_offset(page);
>   4058          u64 end = start + PAGE_CACHE_SIZE - 1;
>   4059          int ret = 1;
>   4060  
>   4061          if (test_range_bit(tree, start, end,
>   4062                             EXTENT_IOBITS, 0, NULL))
>   4063                  ret = 0;
>   4064          else {
>   4065                  if ((mask & GFP_NOFS) == GFP_NOFS)
>   4066                          mask = GFP_NOFS;
>   4067                  /*
>   4068                   * at this point we can safely clear everything except the
>   4069                   * locked bit and the nodatasum bit
>   4070                   */
>   4071                  ret = clear_extent_bit(tree, start, end,
>   4072                                   ~(EXTENT_LOCKED | EXTENT_NODATASUM),
>   4073                                   0, 0, NULL, GFP_ATOMIC);
>                                                      ^^^^^^^^^^
> It upsets the static checkers to keep "mask" around when we don't use it
> anymore.

Thanks Dan, I'll switch this around to make it more clear.

-chris