linux-kernel - [PATCH v2 2/3] xfs: always warn about deprecated mount options

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Message-ID: <20251015050342.GW6188@frogsfrogsfrogs>
Date: Tue, 14 Oct 2025 22:03:42 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Carlos Maiolino <cem@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
	Oleksandr Natalenko <oleksandr@...alenko.name>,
	Pavel Reichl <preichl@...hat.com>, Vlastimil Babka <vbabka@...e.cz>,
	Thorsten Leemhuis <linux@...mhuis.info>
Subject: [PATCH v2 2/3] xfs: always warn about deprecated mount options

From: Darrick J. Wong <djwong@...nel.org>

The deprecation of the 'attr2' mount option in 6.18 wasn't entirely
successful because nobody noticed that the kernel never printed a
warning about attr2 being set in fstab if the only xfs filesystem is the
root fs; the initramfs mounts the root fs with no mount options; and the
init scripts only conveyed the fstab options by remounting the root fs.

Fix this by making it complain all the time.

Cc: <stable@...r.kernel.org> # v5.13
Fixes: 92cf7d36384b99 ("xfs: Skip repetitive warnings about mount options")
Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 fs/xfs/xfs_super.c |   25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index e85a156dc17d16..ae9b17730eaf41 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1373,16 +1373,25 @@ suffix_kstrtoull(
 static inline void
 xfs_fs_warn_deprecated(
 	struct fs_context	*fc,
-	struct fs_parameter	*param,
-	uint64_t		flag,
-	bool			value)
+	struct fs_parameter	*param)
 {
-	/* Don't print the warning if reconfiguring and current mount point
-	 * already had the flag set
+	/*
+	 * Always warn about someone passing in a deprecated mount option.
+	 * Previously we wouldn't print the warning if we were reconfiguring
+	 * and current mount point already had the flag set, but that was not
+	 * the right thing to do.
+	 *
+	 * Many distributions mount the root filesystem with no options in the
+	 * initramfs and rely on mount -a to remount the root fs with the
+	 * options in fstab.  However, the old behavior meant that there would
+	 * never be a warning about deprecated mount options for the root fs in
+	 * /etc/fstab.  On a single-fs system, that means no warning at all.
+	 *
+	 * Compounding this problem are distribution scripts that copy
+	 * /proc/mounts to fstab, which means that we can't remove mount
+	 * options unless we're 100% sure they have only ever been advertised
+	 * in /proc/mounts in response to explicitly provided mount options.
 	 */
-	if ((fc->purpose & FS_CONTEXT_FOR_RECONFIGURE) &&
-            !!(XFS_M(fc->root->d_sb)->m_features & flag) == value)
-		return;
 	xfs_warn(fc->s_fs_info, "%s mount option is deprecated.", param->key);
 }