linux-kernel - [PATCH] tmpfs: preserve SB_I

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Message-Id: <20250819061803.1496443-1-libaokun@huaweicloud.com>
Date: Tue, 19 Aug 2025 14:18:03 +0800
From: libaokun@...weicloud.com
To: linux-mm@...ck.org
Cc: hughd@...gle.com,
	baolin.wang@...ux.alibaba.com,
	akpm@...ux-foundation.org,
	jlayton@...nel.org,
	linux-kernel@...r.kernel.org,
	Baokun Li <libaokun1@...wei.com>
Subject: [PATCH] tmpfs: preserve SB_I_VERSION on remount

From: Baokun Li <libaokun1@...wei.com>

Now tmpfs enables i_version by default and tmpfs does not modify it. But
SB_I_VERSION can also be modified via sb_flags, and reconfigure_super()
always overwrites the existing flags with the latest ones. This means that
if tmpfs is remounted without specifying iversion, the default i_version
will be unexpectedly disabled.

To ensure iversion remains enabled, SB_I_VERSION is now always set for
fc->sb_flags in shmem_init_fs_context(), instead of for sb->s_flags in
shmem_fill_super().

Fixes: 36f05cab0a2c ("tmpfs: add support for an i_version counter")
Signed-off-by: Baokun Li <libaokun1@...wei.com>
---
 mm/shmem.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index e2c76a30802b..eebe12ff5bc6 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -5081,7 +5081,7 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
 		sb->s_flags |= SB_NOUSER;
 	}
 	sb->s_export_op = &shmem_export_ops;
-	sb->s_flags |= SB_NOSEC | SB_I_VERSION;
+	sb->s_flags |= SB_NOSEC;
 
 #if IS_ENABLED(CONFIG_UNICODE)
 	if (!ctx->encoding && ctx->strict_encoding) {
@@ -5385,6 +5385,9 @@ int shmem_init_fs_context(struct fs_context *fc)
 
 	fc->fs_private = ctx;
 	fc->ops = &shmem_fs_context_ops;
+#ifdef CONFIG_TMPFS
+	fc->sb_flags |= SB_I_VERSION;
+#endif
 	return 0;
 }
 
-- 
2.39.2