From a26d60dedf9af81df7aeaef66353eb391f85e7a9 Mon Sep 17 00:00:00 2001 From: Anand Jain Date: Thu, 21 Oct 2021 23:31:17 +0800 Subject: [PATCH] btrfs: sysfs: add devinfo/fsid to retrieve actual fsid from the device In the case of the seed device, the fsid can be different from the mounted sprout fsid. The userland has to read the device superblock to know the fsid but, that idea fails if the device is missing. So add a sysfs interface devinfo//fsid to show the fsid of the device. For example: $ cd /sys/fs/btrfs/b10b02a5-f9de-4276-b9e8-2bfd09a578a8 $ cat devinfo/1/fsid c44d771f-639d-4df3-99ec-5bc7ad2af93b $ cat devinfo/3/fsid b10b02a5-f9de-4276-b9e8-2bfd09a578a8 Though it's related to seeding, the name of the sysfs file is plain fsid as it matches what blkid says. A path to the device's fsid will aid scripting. Reviewed-by: Josef Bacik Signed-off-by: Anand Jain Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/sysfs.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index f9eff3b..beb7f72 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -1537,6 +1537,16 @@ static ssize_t btrfs_devinfo_writeable_show(struct kobject *kobj, } BTRFS_ATTR(devid, writeable, btrfs_devinfo_writeable_show); +static ssize_t btrfs_devinfo_fsid_show(struct kobject *kobj, + struct kobj_attribute *a, char *buf) +{ + struct btrfs_device *device = container_of(kobj, struct btrfs_device, + devid_kobj); + + return sysfs_emit(buf, "%pU\n", device->fs_devices->fsid); +} +BTRFS_ATTR(devid, fsid, btrfs_devinfo_fsid_show); + static ssize_t btrfs_devinfo_error_stats_show(struct kobject *kobj, struct kobj_attribute *a, char *buf) { @@ -1572,6 +1582,7 @@ BTRFS_ATTR(devid, error_stats, btrfs_devinfo_error_stats_show); */ static struct attribute *devid_attrs[] = { BTRFS_ATTR_PTR(devid, error_stats), + BTRFS_ATTR_PTR(devid, fsid), BTRFS_ATTR_PTR(devid, in_fs_metadata), BTRFS_ATTR_PTR(devid, missing), BTRFS_ATTR_PTR(devid, replace_target), -- 2.7.4