linux-kernel - [PATCH v8 8/9] tmpfs: Expose filesystem features via sysfs

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Message-Id: <20241021-tonyk-tmpfs-v8-8-f443d5814194@igalia.com>
Date: Mon, 21 Oct 2024 13:37:24 -0300
From: André Almeida <andrealmeid@...lia.com>
To: Gabriel Krisman Bertazi <krisman@...nel.org>, 
 Alexander Viro <viro@...iv.linux.org.uk>, 
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
 Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, 
 Hugh Dickins <hughd@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
 Jonathan Corbet <corbet@....net>, smcv@...labora.com
Cc: kernel-dev@...lia.com, linux-fsdevel@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org, 
 linux-mm@...ck.org, linux-doc@...r.kernel.org, 
 André Almeida <andrealmeid@...lia.com>, 
 Gabriel Krisman Bertazi <krisman@...e.de>
Subject: [PATCH v8 8/9] 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>
Reviewed-by: Gabriel Krisman Bertazi <krisman@...e.de>
---
 mm/shmem.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/mm/shmem.c b/mm/shmem.c
index ea01628e443423d82d44277e085b867ab9bf4b28..0739143d1419c732359d3a3c3457c3acb90c5b22 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -5546,3 +5546,40 @@ 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)
+static 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 */

-- 
2.47.0