linux-kernel - Re: [PATCH v8 08/11] btrfs: add raid stripe tree pretty printer

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Date:   Tue, 12 Sep 2023 22:42:39 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Johannes Thumshirn <johannes.thumshirn@....com>
Cc:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>,
        Christoph Hellwig <hch@....de>,
        Naohiro Aota <naohiro.aota@....com>, Qu Wenruo <wqu@...e.com>,
        Damien Le Moal <dlemoal@...nel.org>,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 08/11] btrfs: add raid stripe tree pretty printer

On Mon, Sep 11, 2023 at 05:52:09AM -0700, Johannes Thumshirn wrote:
> Decode raid-stripe-tree entries on btrfs_print_tree().
> 
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
> ---
>  fs/btrfs/print-tree.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
> 
> diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
> index 0c93439e929f..f01919e4bb37 100644
> --- a/fs/btrfs/print-tree.c
> +++ b/fs/btrfs/print-tree.c
> @@ -9,6 +9,7 @@
>  #include "print-tree.h"
>  #include "accessors.h"
>  #include "tree-checker.h"
> +#include "raid-stripe-tree.h"
>  
>  struct root_name_map {
>  	u64 id;
> @@ -28,6 +29,7 @@ static const struct root_name_map root_map[] = {
>  	{ BTRFS_FREE_SPACE_TREE_OBJECTID,	"FREE_SPACE_TREE"	},
>  	{ BTRFS_BLOCK_GROUP_TREE_OBJECTID,	"BLOCK_GROUP_TREE"	},
>  	{ BTRFS_DATA_RELOC_TREE_OBJECTID,	"DATA_RELOC_TREE"	},
> +	{ BTRFS_RAID_STRIPE_TREE_OBJECTID,	"RAID_STRIPE_TREE"	},
>  };
>  
>  const char *btrfs_root_name(const struct btrfs_key *key, char *buf)
> @@ -189,6 +191,48 @@ static void print_uuid_item(const struct extent_buffer *l, unsigned long offset,
>  	}
>  }
>  
> +struct raid_encoding_map {
> +	u8 encoding;
> +	char name[16];
> +};
> +
> +static const struct raid_encoding_map raid_map[] = {
> +	{ BTRFS_STRIPE_DUP,	"DUP" },
> +	{ BTRFS_STRIPE_RAID0,	"RAID0" },
> +	{ BTRFS_STRIPE_RAID1,	"RAID1" },
> +	{ BTRFS_STRIPE_RAID1C3,	"RAID1C3" },
> +	{ BTRFS_STRIPE_RAID1C4, "RAID1C4" },
> +	{ BTRFS_STRIPE_RAID5,	"RAID5" },
> +	{ BTRFS_STRIPE_RAID6,	"RAID6" },
> +	{ BTRFS_STRIPE_RAID10,	"RAID10" }
> +};

Instead of another table tranlating constants to raid names, can you
somehow utilize the btrfs_raid_array table? If the STRIPE values match
the RAID (the indexes to the table) you could add a simple wrapper.

> +
> +static const char *stripe_encoding_name(u8 encoding)
> +{
> +	for (int i = 0; i < ARRAY_SIZE(raid_map); i++) {
> +		if (raid_map[i].encoding == encoding)
> +			return raid_map[i].name;
> +	}
> +
> +	return "UNKNOWN";
> +}
> +
> +static void print_raid_stripe_key(const struct extent_buffer *eb, u32 item_size,
> +				  struct btrfs_stripe_extent *stripe)
> +{
> +	int num_stripes = btrfs_num_raid_stripes(item_size);
> +	u8 encoding = btrfs_stripe_extent_encoding(eb, stripe);
> +	int i;
> +
> +	pr_info("\t\t\tencoding: %s\n", stripe_encoding_name(encoding));
> +
> +	for (i = 0; i < num_stripes; i++)
> +		pr_info("\t\t\tstride %d devid %llu physical %llu length %llu\n",
> +			i, btrfs_raid_stride_devid(eb, &stripe->strides[i]),
> +			btrfs_raid_stride_physical(eb, &stripe->strides[i]),
> +			btrfs_raid_stride_length(eb, &stripe->strides[i]));
> +}
> +
>  /*
>   * Helper to output refs and locking status of extent buffer.  Useful to debug
>   * race condition related problems.
> @@ -349,6 +393,11 @@ void btrfs_print_leaf(const struct extent_buffer *l)
>  			print_uuid_item(l, btrfs_item_ptr_offset(l, i),
>  					btrfs_item_size(l, i));
>  			break;
> +		case BTRFS_RAID_STRIPE_KEY:
> +			print_raid_stripe_key(l, btrfs_item_size(l, i),
> +					      btrfs_item_ptr(l, i,
> +							     struct btrfs_stripe_extent));
> +			break;
>  		}
>  	}
>  }
> 
> -- 
> 2.41.0