linux-kernel - Re: [PATCH] btrfs: remove unused variable pages

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Date:   Thu, 1 Jun 2023 11:29:57 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Tom Rix <trix@...hat.com>
Cc:     clm@...com, josef@...icpanda.com, dsterba@...e.com,
        ndesaulniers@...gle.com, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] btrfs: remove unused variable pages_processed

On Tue, May 30, 2023 at 10:21:54AM -0400, Tom Rix wrote:
> clang with W=1 reports
> fs/btrfs/extent_io.c:230:16: error: variable
>   'pages_processed' set but not used [-Werror,-Wunused-but-set-variable]
>         unsigned long pages_processed = 0;
>                       ^
> This variable is not used so remove it.
> 
> Signed-off-by: Tom Rix <trix@...hat.com>

Caused by commit 6d6a31e7fc99 ("btrfs: split page locking out of
__process_pages_contig").

It is worth noting that while -Wunused-but-set-variable is normally
under W=1, btrfs explicitly enables it in their Makefile, so this
warning is visible during a normal build, which breaks the build with
CONFIG_WERROR.

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
>  fs/btrfs/extent_io.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 89e093ae1c33..6919409c1183 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -227,7 +227,6 @@ static void __process_pages_contig(struct address_space *mapping,
>  	pgoff_t start_index = start >> PAGE_SHIFT;
>  	pgoff_t end_index = end >> PAGE_SHIFT;
>  	pgoff_t index = start_index;
> -	unsigned long pages_processed = 0;
>  	struct folio_batch fbatch;
>  	int i;
>  
> @@ -242,7 +241,6 @@ static void __process_pages_contig(struct address_space *mapping,
>  
>  			process_one_page(fs_info, &folio->page, locked_page,
>  					 page_ops, start, end);
> -			pages_processed += folio_nr_pages(folio);
>  		}
>  		folio_batch_release(&fbatch);
>  		cond_resched();
> -- 
> 2.27.0
>