linux-kernel - [PATCH 4/5] tmpfs: Expose filesystem features via sysfs

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Message-ID: <20240823173332.281211-5-andrealmeid@igalia.com>
Date: Fri, 23 Aug 2024 14:33:31 -0300
From: André Almeida <andrealmeid@...lia.com>
To: Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	kernel-dev@...lia.com,
	krisman@...nel.org,
	Daniel Rosenberg <drosen@...gle.com>,
	smcv@...labora.com,
	André Almeida <andrealmeid@...lia.com>
Subject: [PATCH 4/5] tmpfs: Expose filesystem features via sysfs

Expose filesystem features through sysfs, so userspace can query if
tmpfs support casefold.

This follows the same setup as defined by ext4 and f2fs to expose
casefold support to userspace.

Signed-off-by: André Almeida <andrealmeid@...lia.com>
---
 mm/shmem.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/mm/shmem.c b/mm/shmem.c
index 5c77b4e73204..f6e19b88d647 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -5384,3 +5384,40 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
 	return page;
 }
 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
+
+#if defined(CONFIG_SYSFS) && defined(CONFIG_TMPFS)
+#if IS_ENABLED(CONFIG_UNICODE)
+DEVICE_STRING_ATTR_RO(casefold, 0444, "supported");
+#endif
+
+static struct attribute *tmpfs_attributes[] = {
+#if IS_ENABLED(CONFIG_UNICODE)
+	&dev_attr_casefold.attr.attr,
+#endif
+	NULL
+};
+
+static const struct attribute_group tmpfs_attribute_group = {
+	.attrs = tmpfs_attributes,
+	.name = "features"
+};
+
+static struct kobject *tmpfs_kobj;
+
+static int __init tmpfs_sysfs_init(void)
+{
+	int ret;
+
+	tmpfs_kobj = kobject_create_and_add("tmpfs", fs_kobj);
+	if (!tmpfs_kobj)
+		return -ENOMEM;
+
+	ret = sysfs_create_group(tmpfs_kobj, &tmpfs_attribute_group);
+	if (ret)
+		kobject_put(tmpfs_kobj);
+
+	return ret;
+}
+
+fs_initcall(tmpfs_sysfs_init);
+#endif /* CONFIG_SYSFS && CONFIG_TMPFS */
-- 
2.46.0