[PATCH] shmem: Report casefold setting in mount options

[Gabriel Krisman Bertazi]

For not device-backed filesystems, casefolding is a mount option.
Report the current encoding and casefolding flags in /proc/mounts so
userspace can easily check if casefolding is supported.

Reported-by: Daniel Tang <danielzgtg.opensource@xxxxxxxxx>
Link: https://lore.kernel.org/linux-fsdevel/5193732.31r3eYUQgx@daniel-desktop3/#R
Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxx>
---
 mm/shmem.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mm/shmem.c b/mm/shmem.c
index 897fa2b61346..2b93fcbf5127 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -4916,6 +4916,17 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root)
 	if (sbinfo->qlimits.grpquota_ihardlimit)
 		seq_printf(seq, ",grpquota_inode_hardlimit=%lld",
 			   sbinfo->qlimits.grpquota_ihardlimit);
+#endif
+#if IS_ENABLED(CONFIG_UNICODE)
+	if (root->d_sb->s_encoding) {
+		unsigned int version = root->d_sb->s_encoding->version;
+
+		seq_printf(seq, ",casefold=utf8-%u.%u.%u",
+			   unicode_major(version), unicode_minor(version),
+			   unicode_rev(version));
+		if (sb_has_strict_encoding(root->d_sb))
+			seq_puts(seq, ",strict_encoding");
+	}
 #endif
 	return 0;
 }
-- 
2.55.0


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