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Date: Sun, 5 Jul 2026 13:27:27 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: linux-fscrypt@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net, linux-block@vger.kernel.org,
	Christoph Hellwig <hch@lst.de>, Theodore Ts'o <tytso@mit.edu>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Baokun Li <libaokun@linux.alibaba.com>, Jan Kara <jack@suse.cz>,
	Ojaswin Mujoo <ojaswin@linux.ibm.com>,
	Ritesh Harjani <ritesh.list@gmail.com>,
	Zhang Yi <yi.zhang@huawei.com>, Jaegeuk Kim <jaegeuk@kernel.org>,
	Chao Yu <chao@kernel.org>
Subject: Re: [PATCH v2 08/17] ext4: Make ext4_bio_write_folio() return void
Message-ID: <20260705202727.GJ41916@quark>
References: <20260705194555.75030-1-ebiggers@kernel.org>
 <20260705194555.75030-9-ebiggers@kernel.org>
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In-Reply-To: <20260705194555.75030-9-ebiggers@kernel.org>

On Sun, Jul 05, 2026 at 12:45:45PM -0700, Eric Biggers wrote:
> @@ -2724,9 +2711,7 @@ static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
>  			 * through a pin.
>  			 */
>  			if (!mpd->can_map) {
> -				err = mpage_submit_folio(mpd, folio);
> -				if (err < 0)
> -					goto out;
> +				mpage_submit_folio(mpd, folio);
>  				/* Pending dirtying of journalled data? */
>  				if (folio_test_checked(folio)) {
>  					err = mpage_journal_page_buffers(handle,

Sashiko found a subtle bug here, where removing this assignment to 'err'
can leak a positive 'err' value of 1 from ext4_journal_ensure_credits()
into the caller of mpage_prepare_extent_to_map() in certain cases.

I'll fix that by leaving an assignment of 0 to 'err' here.

Really, positive values shouldn't be stored in a variable named 'err' in
the first place though.

- Eric