linux-ext4 - Re: [PATCH 07/16] fsverity: don't issue readahead for non-ENOENT errors from __filemap_get

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Message-ID: <20260128005715.GB2127@quark>
Date: Tue, 27 Jan 2026 16:57:15 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: Christoph Hellwig <hch@....de>
Cc: "Darrick J. Wong" <djwong@...nel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	David Sterba <dsterba@...e.com>, Theodore Ts'o <tytso@....edu>,
	Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>,
	Andrey Albershteyn <aalbersh@...hat.com>,
	Matthew Wilcox <willy@...radead.org>, linux-fsdevel@...r.kernel.org,
	linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net, fsverity@...ts.linux.dev
Subject: Re: [PATCH 07/16] fsverity: don't issue readahead for non-ENOENT
 errors from __filemap_get_folio

On Tue, Jan 27, 2026 at 07:38:09AM +0100, Christoph Hellwig wrote:
> PTR_ERR(ptr) == -EFOO checks if ptr is an error pointer for the errno
> value -EFOO.

To reiterate (again): when ptr may or may not be an error pointer, it
should be written as ptr == ERR_PTR(-EFOO), as is normally done.
Otherwise an error code is being extracted from something that doesn't
have an error code, which is nonsense, even if it works by accident.

- Eric