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btrfs: sysfs: show if ACL support has been compiled in

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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 <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Anand Jain 2023-06-20 16:55:09 +08:00 committed by David Sterba
parent 3a3c7a7f65
commit 070bb0011c
1 changed files with 7 additions and 0 deletions
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7
fs/btrfs/sysfs.c
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@ -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),