On Thu, Aug 05, 2021 at 08:13:03AM +0800, Anand Jain wrote:

On 29/07/2021 00:56, David Sterba wrote:

quoted

We've hidden the zoned support in sysfs under debug config for the first
releases but now the stability is reasonable, though not all features
have been implemented.

As this depends on a config option, the per-filesystem feature won't
exist as such filesystem can't be mounted. The static feature will print
1 when the support is built-in, 0 otherwise.

Signed-off-by: David Sterba <dsterba@suse.com>
---

The merge target is not set, depends if everybody thinks it's the time
even though there are still known bugs. We're also waiting for
util-linux support (blkid, wipefs), so that needs to be synced too.

  fs/btrfs/sysfs.c | 12 +++++++++---
  1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index bfe5e27617b0..7ad8f802ab88 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c

@@ -263,8 +263,7 @@ BTRFS_FEAT_ATTR_INCOMPAT(no_holes, NO_HOLES);
  BTRFS_FEAT_ATTR_INCOMPAT(metadata_uuid, METADATA_UUID);
  BTRFS_FEAT_ATTR_COMPAT_RO(free_space_tree, FREE_SPACE_TREE);
  BTRFS_FEAT_ATTR_INCOMPAT(raid1c34, RAID1C34);
-/* Remove once support for zoned allocation is feature complete */
-#ifdef CONFIG_BTRFS_DEBUG
+#ifdef CONFIG_BLK_DEV_ZONED
  BTRFS_FEAT_ATTR_INCOMPAT(zoned, ZONED);
  #endif
  #ifdef CONFIG_FS_VERITY

@@ -285,7 +284,7 @@ static struct attribute *btrfs_supported_feature_attrs[] = {
  	BTRFS_FEAT_ATTR_PTR(metadata_uuid),
  	BTRFS_FEAT_ATTR_PTR(free_space_tree),
  	BTRFS_FEAT_ATTR_PTR(raid1c34),
-#ifdef CONFIG_BTRFS_DEBUG
+#ifdef CONFIG_BLK_DEV_ZONED
  	BTRFS_FEAT_ATTR_PTR(zoned),
  #endif
  #ifdef CONFIG_FS_VERITY

  Looks good until here.

quoted

@@ -384,12 +383,19 @@ static ssize_t supported_sectorsizes_show(struct kobject *kobj,
  BTRFS_ATTR(static_feature, supported_sectorsizes,
  	   supported_sectorsizes_show);
  
+static ssize_t zoned_show(struct kobject *kobj, struct kobj_attribute *a, char *buf)
+{
+	return scnprintf(buf, PAGE_SIZE, "%d\n", IS_ENABLED(CONFIG_BLK_DEV_ZONED));
+}
+BTRFS_ATTR(static_feature, zoned, zoned_show);
+
  static struct attribute *btrfs_supported_static_feature_attrs[] = {
  	BTRFS_ATTR_PTR(static_feature, rmdir_subvol),
  	BTRFS_ATTR_PTR(static_feature, supported_checksums),
  	BTRFS_ATTR_PTR(static_feature, send_stream_version),
  	BTRFS_ATTR_PTR(static_feature, supported_rescue_options),
  	BTRFS_ATTR_PTR(static_feature, supported_sectorsizes),
+	BTRFS_ATTR_PTR(static_feature, zoned),
  	NULL
  };

  We don't need this part. btrfs_supported_feature_attrs will
  take care of showing zoned if when enabled on the mounted btrfs.

The idea is to put zoned also to the static features so the zoned
support can be determined before mount.

  As of now, this patch fails with
     [ 44.464597] sysfs: cannot create duplicate filename 
'/fs/btrfs/features/zoned'

I'll have a look.