Re: [PATCH 1/5] btrfs: make the bg_reclaim_threshold per-space info

[Josef Bacik <josef@toxicpanda.com>]

On Mon, Mar 21, 2022 at 09:14:10AM -0700, Johannes Thumshirn wrote:
> From: Josef Bacik <josef@toxicpanda.com>
> 
> For !zoned file systems it's useful to have the auto reclaim feature,
> however there are different use cases for !zoned, for example we may not
> want to reclaim metadata chunks ever, only data chunks.  Move this sysfs
> flag to per-space_info.  This won't affect current users because this
> tunable only ever did anything for zoned, and that is currently hidden
> behind BTRFS_CONFIG_DEBUG.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> [ jth restore global bg_reclaim_threshold ]
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
>  fs/btrfs/free-space-cache.c |  7 +++++--
>  fs/btrfs/space-info.c       |  9 +++++++++
>  fs/btrfs/space-info.h       |  6 ++++++
>  fs/btrfs/sysfs.c            | 37 +++++++++++++++++++++++++++++++++++++
>  fs/btrfs/zoned.h            |  6 +-----
>  5 files changed, 58 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index 01a408db5683..ef84bc5030cd 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -2630,16 +2630,19 @@ int __btrfs_add_free_space(struct btrfs_block_group *block_group,
>  static int __btrfs_add_free_space_zoned(struct btrfs_block_group *block_group,
>  					u64 bytenr, u64 size, bool used)
>  {
> -	struct btrfs_fs_info *fs_info = block_group->fs_info;
> +	struct btrfs_space_info *sinfo = block_group->space_info;
>  	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
>  	u64 offset = bytenr - block_group->start;
>  	u64 to_free, to_unusable;
> -	const int bg_reclaim_threshold = READ_ONCE(fs_info->bg_reclaim_threshold);
> +	int bg_reclaim_threshold = 0;
>  	bool initial = (size == block_group->length);
>  	u64 reclaimable_unusable;
>  
>  	WARN_ON(!initial && offset + size > block_group->zone_capacity);
>  
> +	if (!initial)
> +		bg_reclaim_threshold = READ_ONCE(sinfo->bg_reclaim_threshold);
> +
>  	spin_lock(&ctl->tree_lock);
>  	if (!used)
>  		to_free = size;
> diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
> index b87931a458eb..60d0a58c4644 100644
> --- a/fs/btrfs/space-info.c
> +++ b/fs/btrfs/space-info.c
> @@ -181,6 +181,12 @@ void btrfs_clear_space_info_full(struct btrfs_fs_info *info)
>  		found->full = 0;
>  }
>  
> +/*
> + * Block groups with more than this value (percents) of unusable space will be
> + * scheduled for background reclaim.
> + */
> +#define BTRFS_DEFAULT_ZONED_RECLAIM_THRESH	75
> +
>  static int create_space_info(struct btrfs_fs_info *info, u64 flags)
>  {
>  
> @@ -203,6 +209,9 @@ static int create_space_info(struct btrfs_fs_info *info, u64 flags)
>  	INIT_LIST_HEAD(&space_info->priority_tickets);
>  	space_info->clamp = 1;
>  
> +	if (btrfs_is_zoned(info))
> +		space_info->bg_reclaim_threshold = BTRFS_DEFAULT_ZONED_RECLAIM_THRESH;
> +
>  	ret = btrfs_sysfs_add_space_info_type(info, space_info);
>  	if (ret)
>  		return ret;
> diff --git a/fs/btrfs/space-info.h b/fs/btrfs/space-info.h
> index d841fed73492..0c45f539e3cf 100644
> --- a/fs/btrfs/space-info.h
> +++ b/fs/btrfs/space-info.h
> @@ -24,6 +24,12 @@ struct btrfs_space_info {
>  				   the space info if we had an ENOSPC in the
>  				   allocator. */
>  
> +	/*
> +	 * Once a block group drops below this threshold we'll schedule it for
> +	 * reclaim.
> +	 */
> +	int bg_reclaim_threshold;
> +
>  	int clamp;		/* Used to scale our threshold for preemptive
>  				   flushing. The value is >> clamp, so turns
>  				   out to be a 2^clamp divisor. */
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index 17389a42a3ab..90da1ea0cae0 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -722,6 +722,42 @@ SPACE_INFO_ATTR(bytes_zone_unusable);
>  SPACE_INFO_ATTR(disk_used);
>  SPACE_INFO_ATTR(disk_total);
>  
> +static ssize_t btrfs_sinfo_bg_reclaim_threshold_show(struct kobject *kobj,
> +						     struct kobj_attribute *a,
> +						     char *buf)
> +{
> +	struct btrfs_space_info *space_info = to_space_info(kobj);
> +	ssize_t ret;
> +
> +	ret = sysfs_emit(buf, "%d\n", READ_ONCE(space_info->bg_reclaim_threshold));
> +
> +	return ret;
> +}
> +
> +static ssize_t btrfs_sinfo_bg_reclaim_threshold_store(struct kobject *kobj,
> +						      struct kobj_attribute *a,
> +						      const char *buf, size_t len)
> +{
> +	struct btrfs_space_info *space_info = to_space_info(kobj);
> +	int thresh;
> +	int ret;
> +
> +	ret = kstrtoint(buf, 10, &thresh);
> +	if (ret)
> +		return ret;
> +
> +	if (thresh != 0 && (thresh <= 50 || thresh > 100))
> +		return -EINVAL;
> +
> +	WRITE_ONCE(space_info->bg_reclaim_threshold, thresh);
> +
> +	return len;
> +}
> +
> +BTRFS_ATTR_RW(space_info, bg_reclaim_threshold,
> +	      btrfs_sinfo_bg_reclaim_threshold_show,
> +	      btrfs_sinfo_bg_reclaim_threshold_store);
> +
>  /*
>   * Allocation information about block group types.
>   *
> @@ -738,6 +774,7 @@ static struct attribute *space_info_attrs[] = {
>  	BTRFS_ATTR_PTR(space_info, bytes_zone_unusable),
>  	BTRFS_ATTR_PTR(space_info, disk_used),
>  	BTRFS_ATTR_PTR(space_info, disk_total),
> +	BTRFS_ATTR_PTR(space_info, bg_reclaim_threshold),
>  	NULL,
>  };
>  ATTRIBUTE_GROUPS(space_info);
> diff --git a/fs/btrfs/zoned.h b/fs/btrfs/zoned.h
> index cbf016a7bb5d..c489c08d7fd5 100644
> --- a/fs/btrfs/zoned.h
> +++ b/fs/btrfs/zoned.h
> @@ -10,11 +10,7 @@
>  #include "block-group.h"
>  #include "btrfs_inode.h"
>  
> -/*
> - * Block groups with more than this value (percents) of unusable space will be
> - * scheduled for background reclaim.
> - */
> -#define BTRFS_DEFAULT_RECLAIM_THRESH		75
> +#define BTRFS_DEFAULT_RECLAIM_THRESH           75
> 

Looks like you added this back by accident?

Josef