From 070bb0011ccfd00c7de25dce2489fbe9cce5ba44 Mon Sep 17 00:00:00 2001 From: Anand Jain Date: Tue, 20 Jun 2023 16:55:09 +0800 Subject: [PATCH] btrfs: sysfs: show if ACL support has been compiled in ACL support depends on the compile-time configuration option CONFIG_BTRFS_FS_POSIX_ACL. Prior to mounting a btrfs filesystem, it is not possible to determine whether ACL support has been compiled in. To address this, add a sysfs interface, /sys/fs/btrfs/features/acl, and check for ACL support in the system's btrfs. To determine ACL support: Return 0 indicates ACL is not supported: $ cat /sys/fs/btrfs/features/acl 0 Return 1 indicates ACL is supported: $ cat /sys/fs/btrfs/features/acl 1 IMO, this is a better approach, so that we also know if kernel is older. On an older kernel $ ls /sys/fs/btrfs/features/acl ls: cannot access '/sys/fs/btrfs/features/acl': No such file or directory mount a btrfs filesystem $ cat /proc/self/mounts | grep btrfs | grep -q noacl $ echo $? 0 Signed-off-by: Anand Jain Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/sysfs.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 25294e6..b1d1ac2 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -414,6 +414,12 @@ static ssize_t supported_sectorsizes_show(struct kobject *kobj, BTRFS_ATTR(static_feature, supported_sectorsizes, supported_sectorsizes_show); +static ssize_t acl_show(struct kobject *kobj, struct kobj_attribute *a, char *buf) +{ + return sysfs_emit(buf, "%d\n", !!IS_ENABLED(CONFIG_BTRFS_FS_POSIX_ACL)); +} +BTRFS_ATTR(static_feature, acl, acl_show); + /* * Features which only depend on kernel version. * @@ -421,6 +427,7 @@ BTRFS_ATTR(static_feature, supported_sectorsizes, * btrfs_supported_feature_attrs. */ static struct attribute *btrfs_supported_static_feature_attrs[] = { + BTRFS_ATTR_PTR(static_feature, acl), BTRFS_ATTR_PTR(static_feature, rmdir_subvol), BTRFS_ATTR_PTR(static_feature, supported_checksums), BTRFS_ATTR_PTR(static_feature, send_stream_version), -- 2.7.4