linux-kernel - Re: [PATCH v2] btrfs: remove dead assignment in prepare_one

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Message-ID: <20251212032603.GQ4859@twin.jikos.cz>
Date: Fri, 12 Dec 2025 04:26:03 +0100
From: David Sterba <dsterba@...e.cz>
To: Massimiliano Pellizzer <mpellizzer.dev@...il.com>
Cc: clm@...com, dsterba@...e.com, linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] btrfs: remove dead assignment in prepare_one_folio()

On Thu, Dec 04, 2025 at 10:09:59PM +0100, Massimiliano Pellizzer wrote:
> In prepare_one_folio(), ret is initialized to 0 at declaration,
> and in an error path we assign ret = 0 before jumping to the
> again label to retry the operation. However, ret is immediately
> overwritten by ret = set_folio_extent_mapped(folio) after the
> again label.
> 
> Both assignments are never observed by any code path,
> therefore they can be safely removed.

Right, if 'ret' was the loop invariant such explicit settings are good
for readability but this is not the case.

> No functional change.
> 
> Signed-off-by: Massimiliano Pellizzer <mpellizzer.dev@...il.com>

Reviewed-by: David Sterba <dsterba@...e.com>

Added to for-next, thanks.

> ---
> v2: Remove also the initial ret = 0 assignment for consistency
> 
>  fs/btrfs/file.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 7a501e73d880..9e2c2f2cd03f 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -859,7 +859,7 @@ static noinline int prepare_one_folio(struct inode *inode, struct folio **folio_
>  	fgf_t fgp_flags = (nowait ? FGP_WRITEBEGIN | FGP_NOWAIT : FGP_WRITEBEGIN) |
>  			  fgf_set_order(write_bytes);
>  	struct folio *folio;
> -	int ret = 0;
> +	int ret;
>  
>  again:
>  	folio = __filemap_get_folio(inode->i_mapping, index, fgp_flags, mask);
> @@ -877,7 +877,6 @@ static noinline int prepare_one_folio(struct inode *inode, struct folio **folio_
>  		/* The folio is already unlocked. */
>  		folio_put(folio);
>  		if (!nowait && ret == -EAGAIN) {
> -			ret = 0;
>  			goto again;
>  		}

Minor thing fixed here, a single statement 'if' should not have the { }.