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Message-ID: <ca55e159-3ce0-491f-9fc3-fdcbab2bcb05@gmx.com>
Date:   Fri, 15 Sep 2023 10:25:09 +0930
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User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v9 03/11] btrfs: add support for inserting raid stripe
 extents
Content-Language: en-US
To:     Johannes Thumshirn <johannes.thumshirn@wdc.com>,
        Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Naohiro Aota <naohiro.aota@wdc.com>, Qu Wenruo <wqu@suse.com>,
        Damien Le Moal <dlemoal@kernel.org>,
        linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20230914-raid-stripe-tree-v9-0-15d423829637@wdc.com>
 <20230914-raid-stripe-tree-v9-3-15d423829637@wdc.com>
From:   Qu Wenruo <quwenruo.btrfs@gmx.com>
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In-Reply-To: <20230914-raid-stripe-tree-v9-3-15d423829637@wdc.com>
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Precedence: bulk


On 2023/9/15 01:36, Johannes Thumshirn wrote:
> Add support for inserting stripe extents into the raid stripe tree on
> completion of every write that needs an extra logical-to-physical
> translation when using RAID.
>
> Inserting the stripe extents happens after the data I/O has completed,
> this is done to a) support zone-append and b) rule out the possibility o=
f
> a RAID-write-hole.
>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
>   fs/btrfs/Makefile           |   2 +-
>   fs/btrfs/bio.c              |  23 +++++
>   fs/btrfs/extent-tree.c      |   1 +
>   fs/btrfs/inode.c            |   8 +-
>   fs/btrfs/ordered-data.c     |   1 +
>   fs/btrfs/ordered-data.h     |   2 +
>   fs/btrfs/raid-stripe-tree.c | 245 ++++++++++++++++++++++++++++++++++++=
++++++++
>   fs/btrfs/raid-stripe-tree.h |  34 ++++++
>   fs/btrfs/volumes.c          |   4 +-
>   fs/btrfs/volumes.h          |  15 +--
>   10 files changed, 326 insertions(+), 9 deletions(-)
>
> diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
> index c57d80729d4f..525af975f61c 100644
> --- a/fs/btrfs/Makefile
> +++ b/fs/btrfs/Makefile
> @@ -33,7 +33,7 @@ btrfs-y +=3D super.o ctree.o extent-tree.o print-tree.=
o root-tree.o dir-item.o \
>   	   uuid-tree.o props.o free-space-tree.o tree-checker.o space-info.o =
\
>   	   block-rsv.o delalloc-space.o block-group.o discard.o reflink.o \
>   	   subpage.o tree-mod-log.o extent-io-tree.o fs.o messages.o bio.o \
> -	   lru_cache.o
> +	   lru_cache.o raid-stripe-tree.o
>
>   btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) +=3D acl.o
>   btrfs-$(CONFIG_BTRFS_FS_REF_VERIFY) +=3D ref-verify.o
> diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
> index 31ff36990404..ddbe6f8d4ea2 100644
> --- a/fs/btrfs/bio.c
> +++ b/fs/btrfs/bio.c
> @@ -14,6 +14,7 @@
>   #include "rcu-string.h"
>   #include "zoned.h"
>   #include "file-item.h"
> +#include "raid-stripe-tree.h"
>
>   static struct bio_set btrfs_bioset;
>   static struct bio_set btrfs_clone_bioset;
> @@ -415,6 +416,9 @@ static void btrfs_orig_write_end_io(struct bio *bio)
>   	else
>   		bio->bi_status =3D BLK_STS_OK;
>
> +	if (bio_op(bio) =3D=3D REQ_OP_ZONE_APPEND && !bio->bi_status)
> +		stripe->physical =3D bio->bi_iter.bi_sector << SECTOR_SHIFT;
> +
>   	btrfs_orig_bbio_end_io(bbio);
>   	btrfs_put_bioc(bioc);
>   }
> @@ -426,6 +430,8 @@ static void btrfs_clone_write_end_io(struct bio *bio=
)
>   	if (bio->bi_status) {
>   		atomic_inc(&stripe->bioc->error);
>   		btrfs_log_dev_io_error(bio, stripe->dev);
> +	} else if (bio_op(bio) =3D=3D REQ_OP_ZONE_APPEND) {
> +		stripe->physical =3D bio->bi_iter.bi_sector << SECTOR_SHIFT;
>   	}
>
>   	/* Pass on control to the original bio this one was cloned from */
> @@ -487,6 +493,7 @@ static void btrfs_submit_mirrored_bio(struct btrfs_i=
o_context *bioc, int dev_nr)
>   	bio->bi_private =3D &bioc->stripes[dev_nr];
>   	bio->bi_iter.bi_sector =3D bioc->stripes[dev_nr].physical >> SECTOR_S=
HIFT;
>   	bioc->stripes[dev_nr].bioc =3D bioc;
> +	bioc->size =3D bio->bi_iter.bi_size;
>   	btrfs_submit_dev_bio(bioc->stripes[dev_nr].dev, bio);
>   }
>
> @@ -496,6 +503,8 @@ static void __btrfs_submit_bio(struct bio *bio, stru=
ct btrfs_io_context *bioc,
>   	if (!bioc) {
>   		/* Single mirror read/write fast path. */
>   		btrfs_bio(bio)->mirror_num =3D mirror_num;
> +		if (bio_op(bio) !=3D REQ_OP_READ)
> +			btrfs_bio(bio)->orig_physical =3D smap->physical;
>   		bio->bi_iter.bi_sector =3D smap->physical >> SECTOR_SHIFT;
>   		if (bio_op(bio) !=3D REQ_OP_READ)
>   			btrfs_bio(bio)->orig_physical =3D smap->physical;
> @@ -688,6 +697,20 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bb=
io, int mirror_num)
>   			bio->bi_opf |=3D REQ_OP_ZONE_APPEND;
>   		}
>
> +		if (is_data_bbio(bbio) && bioc &&
> +		    btrfs_need_stripe_tree_update(bioc->fs_info,
> +						  bioc->map_type)) {
> +			/*
> +			 * No locking for the list update, as we only add to
> +			 * the list in the I/O submission path, and list
> +			 * iteration only happens in the completion path,
> +			 * which can't happen until after the last submission.
> +			 */
> +			btrfs_get_bioc(bioc);
> +			list_add_tail(&bioc->ordered_entry,
> +				      &bbio->ordered->bioc_list);
> +		}
> +
>   		/*
>   		 * Csum items for reloc roots have already been cloned at this
>   		 * point, so they are handled as part of the no-checksum case.
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index cb12bfb047e7..959d7449ea0d 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -42,6 +42,7 @@
>   #include "file-item.h"
>   #include "orphan.h"
>   #include "tree-checker.h"
> +#include "raid-stripe-tree.h"
>
>   #undef SCRAMBLE_DELAYED_REFS
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index e02a5ba5b533..b5e0ed3a36f7 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -71,6 +71,7 @@
>   #include "super.h"
>   #include "orphan.h"
>   #include "backref.h"
> +#include "raid-stripe-tree.h"
>
>   struct btrfs_iget_args {
>   	u64 ino;
> @@ -3091,6 +3092,10 @@ int btrfs_finish_one_ordered(struct btrfs_ordered=
_extent *ordered_extent)
>
>   	trans->block_rsv =3D &inode->block_rsv;
>
> +	ret =3D btrfs_insert_raid_extent(trans, ordered_extent);
> +	if (ret)
> +		goto out;
> +
>   	if (test_bit(BTRFS_ORDERED_COMPRESSED, &ordered_extent->flags))
>   		compress_type =3D ordered_extent->compress_type;
>   	if (test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
> @@ -3224,7 +3229,8 @@ int btrfs_finish_one_ordered(struct btrfs_ordered_=
extent *ordered_extent)
>   int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered)
>   {
>   	if (btrfs_is_zoned(btrfs_sb(ordered->inode->i_sb)) &&
> -	    !test_bit(BTRFS_ORDERED_IOERR, &ordered->flags))
> +	    !test_bit(BTRFS_ORDERED_IOERR, &ordered->flags) &&
> +	    list_empty(&ordered->bioc_list))
>   		btrfs_finish_ordered_zoned(ordered);
>   	return btrfs_finish_one_ordered(ordered);
>   }
> diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
> index 345c449d588c..55c7d5543265 100644
> --- a/fs/btrfs/ordered-data.c
> +++ b/fs/btrfs/ordered-data.c
> @@ -191,6 +191,7 @@ static struct btrfs_ordered_extent *alloc_ordered_ex=
tent(
>   	INIT_LIST_HEAD(&entry->log_list);
>   	INIT_LIST_HEAD(&entry->root_extent_list);
>   	INIT_LIST_HEAD(&entry->work_list);
> +	INIT_LIST_HEAD(&entry->bioc_list);
>   	init_completion(&entry->completion);
>
>   	/*
> diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
> index 173bd5c5df26..1c51ac57e5df 100644
> --- a/fs/btrfs/ordered-data.h
> +++ b/fs/btrfs/ordered-data.h
> @@ -151,6 +151,8 @@ struct btrfs_ordered_extent {
>   	struct completion completion;
>   	struct btrfs_work flush_work;
>   	struct list_head work_list;
> +
> +	struct list_head bioc_list;
>   };
>
>   static inline void
> diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c
> new file mode 100644
> index 000000000000..7cdcc45a8796
> --- /dev/null
> +++ b/fs/btrfs/raid-stripe-tree.c
> @@ -0,0 +1,245 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2023 Western Digital Corporation or its affiliates.
> + */
> +
> +#include <linux/btrfs_tree.h>
> +
> +#include "ctree.h"
> +#include "fs.h"
> +#include "accessors.h"
> +#include "transaction.h"
> +#include "disk-io.h"
> +#include "raid-stripe-tree.h"
> +#include "volumes.h"
> +#include "misc.h"
> +#include "print-tree.h"
> +
> +static int btrfs_insert_one_raid_extent(struct btrfs_trans_handle *tran=
s,
> +				 int num_stripes,
> +				 struct btrfs_io_context *bioc)
> +{
> +	struct btrfs_fs_info *fs_info =3D trans->fs_info;
> +	struct btrfs_key stripe_key;
> +	struct btrfs_root *stripe_root =3D fs_info->stripe_root;
> +	u8 encoding =3D btrfs_bg_flags_to_raid_index(bioc->map_type);
> +	struct btrfs_stripe_extent *stripe_extent;
> +	const size_t item_size =3D struct_size(stripe_extent, strides, num_str=
ipes);
> +	int ret;
> +
> +	stripe_extent =3D kzalloc(item_size, GFP_NOFS);
> +	if (!stripe_extent) {
> +		btrfs_abort_transaction(trans, -ENOMEM);
> +		btrfs_end_transaction(trans);
> +		return -ENOMEM;
> +	}
> +
> +	btrfs_set_stack_stripe_extent_encoding(stripe_extent, encoding);
> +	for (int i =3D 0; i < num_stripes; i++) {
> +		u64 devid =3D bioc->stripes[i].dev->devid;
> +		u64 physical =3D bioc->stripes[i].physical;
> +		u64 length =3D bioc->stripes[i].length;
> +		struct btrfs_raid_stride *raid_stride =3D
> +						&stripe_extent->strides[i];
> +
> +		if (length =3D=3D 0)
> +			length =3D bioc->size;
> +
> +		btrfs_set_stack_raid_stride_devid(raid_stride, devid);
> +		btrfs_set_stack_raid_stride_physical(raid_stride, physical);
> +		btrfs_set_stack_raid_stride_length(raid_stride, length);
> +	}
> +
> +	stripe_key.objectid =3D bioc->logical;
> +	stripe_key.type =3D BTRFS_RAID_STRIPE_KEY;
> +	stripe_key.offset =3D bioc->size;
> +
> +	ret =3D btrfs_insert_item(trans, stripe_root, &stripe_key, stripe_exte=
nt,
> +				item_size);
> +	if (ret)
> +		btrfs_abort_transaction(trans, ret);
> +
> +	kfree(stripe_extent);
> +
> +	return ret;
> +}
> +
> +static int btrfs_insert_mirrored_raid_extents(struct btrfs_trans_handle=
 *trans,
> +				      struct btrfs_ordered_extent *ordered,
> +				      u64 map_type)
> +{
> +	int num_stripes =3D btrfs_bg_type_to_factor(map_type);
> +	struct btrfs_io_context *bioc;
> +	int ret;
> +
> +	list_for_each_entry(bioc, &ordered->bioc_list, ordered_entry) {
> +		ret =3D btrfs_insert_one_raid_extent(trans, num_stripes, bioc);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int btrfs_insert_striped_mirrored_raid_extents(
> +				      struct btrfs_trans_handle *trans,
> +				      struct btrfs_ordered_extent *ordered,
> +				      u64 map_type)
> +{
> +	struct btrfs_io_context *bioc;
> +	struct btrfs_io_context *rbioc;
> +	const int nstripes =3D list_count_nodes(&ordered->bioc_list);
> +	const int index =3D btrfs_bg_flags_to_raid_index(map_type);
> +	const int substripes =3D btrfs_raid_array[index].sub_stripes;
> +	const int max_stripes =3D
> +		trans->fs_info->fs_devices->rw_devices / substripes;
> +	int left =3D nstripes;
> +	int i;
> +	int ret =3D 0;
> +	u64 stripe_end;
> +	u64 prev_end;
> +
> +	if (nstripes =3D=3D 1)
> +		return btrfs_insert_mirrored_raid_extents(trans, ordered, map_type);
> +
> +	rbioc =3D kzalloc(struct_size(rbioc, stripes, nstripes * substripes),
> +			GFP_NOFS);
> +	if (!rbioc)
> +		return -ENOMEM;
> +
> +	rbioc->map_type =3D map_type;
> +	rbioc->logical =3D list_first_entry(&ordered->bioc_list, typeof(*rbioc=
),
> +					   ordered_entry)->logical;
> +
> +	stripe_end =3D rbioc->logical;
> +	prev_end =3D stripe_end;
> +	i =3D 0;
> +	list_for_each_entry(bioc, &ordered->bioc_list, ordered_entry) {
> +
> +		rbioc->size +=3D bioc->size;
> +		for (int j =3D 0; j < substripes; j++) {
> +			int stripe =3D i + j;
> +			rbioc->stripes[stripe].dev =3D bioc->stripes[j].dev;
> +			rbioc->stripes[stripe].physical =3D bioc->stripes[j].physical;
> +			rbioc->stripes[stripe].length =3D bioc->size;
> +		}
> +
> +		stripe_end +=3D rbioc->size;
> +		if (i >=3D nstripes ||
> +		    (stripe_end - prev_end >=3D max_stripes * BTRFS_STRIPE_LEN)) {
> +			ret =3D btrfs_insert_one_raid_extent(trans,
> +							   nstripes * substripes,
> +							   rbioc);
> +			if (ret)
> +				goto out;
> +
> +			left -=3D nstripes;
> +			i =3D 0;
> +			rbioc->logical +=3D rbioc->size;
> +			rbioc->size =3D 0;
> +		} else {
> +			i +=3D substripes;
> +			prev_end =3D stripe_end;
> +		}
> +	}
> +
> +	if (left) {
> +		bioc =3D list_prev_entry(bioc, ordered_entry);
> +		ret =3D btrfs_insert_one_raid_extent(trans, substripes, bioc);
> +	}
> +
> +out:
> +	kfree(rbioc);
> +	return ret;
> +}
> +
> +static int btrfs_insert_striped_raid_extents(struct btrfs_trans_handle =
*trans,
> +				     struct btrfs_ordered_extent *ordered,
> +				     u64 map_type)
> +{
> +	struct btrfs_io_context *bioc;
> +	struct btrfs_io_context *rbioc;
> +	const int nstripes =3D list_count_nodes(&ordered->bioc_list);
> +	int i;
> +	int ret =3D 0;
> +
> +	rbioc =3D kzalloc(struct_size(rbioc, stripes, nstripes), GFP_NOFS);
> +	if (!rbioc)
> +		return -ENOMEM;
> +	rbioc->map_type =3D map_type;
> +	rbioc->logical =3D list_first_entry(&ordered->bioc_list, typeof(*rbioc=
),
> +					   ordered_entry)->logical;
> +
> +	i =3D 0;
> +	list_for_each_entry(bioc, &ordered->bioc_list, ordered_entry) {
> +		rbioc->size +=3D bioc->size;
> +		rbioc->stripes[i].dev =3D bioc->stripes[0].dev;
> +		rbioc->stripes[i].physical =3D bioc->stripes[0].physical;
> +		rbioc->stripes[i].length =3D bioc->size;
> +
> +		if (i =3D=3D nstripes - 1) {
> +			ret =3D btrfs_insert_one_raid_extent(trans, nstripes, rbioc);
> +			if (ret)
> +				goto out;
> +
> +			i =3D 0;
> +			rbioc->logical +=3D rbioc->size;
> +			rbioc->size =3D 0;
> +		} else {
> +			i++;
> +		}
> +	}
> +
> +	if (i && i < nstripes - 1)
> +		ret =3D btrfs_insert_one_raid_extent(trans, i, rbioc);
> +
> +out:
> +	kfree(rbioc);
> +	return ret;
> +}
> +
> +int btrfs_insert_raid_extent(struct btrfs_trans_handle *trans,
> +			     struct btrfs_ordered_extent *ordered_extent)
> +{
> +	struct btrfs_io_context *bioc;
> +	u64 map_type;
> +	int ret;
> +
> +	if (!trans->fs_info->stripe_root)
> +		return 0;
> +
> +	map_type =3D list_first_entry(&ordered_extent->bioc_list, typeof(*bioc=
),
> +				    ordered_entry)->map_type;
> +
> +	switch (map_type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
> +	case BTRFS_BLOCK_GROUP_DUP:
> +	case BTRFS_BLOCK_GROUP_RAID1:
> +	case BTRFS_BLOCK_GROUP_RAID1C3:
> +	case BTRFS_BLOCK_GROUP_RAID1C4:
> +		ret =3D btrfs_insert_mirrored_raid_extents(trans, ordered_extent,
> +							 map_type);
> +		break;
> +	case BTRFS_BLOCK_GROUP_RAID0:
> +		ret =3D btrfs_insert_striped_raid_extents(trans, ordered_extent,
> +							map_type);
> +		break;
> +	case BTRFS_BLOCK_GROUP_RAID10:
> +		ret =3D btrfs_insert_striped_mirrored_raid_extents(trans, ordered_ext=
ent, map_type);
> +		break;
> +	default:
> +		btrfs_err(trans->fs_info, "unknown block-group profile %lld",
> +			  map_type & BTRFS_BLOCK_GROUP_PROFILE_MASK);
> +		ASSERT(0);
> +		ret =3D -EINVAL;
> +		break;
> +	}
> +
> +	while (!list_empty(&ordered_extent->bioc_list)) {
> +		bioc =3D list_first_entry(&ordered_extent->bioc_list,
> +					typeof(*bioc), ordered_entry);
> +		list_del(&bioc->ordered_entry);
> +		btrfs_put_bioc(bioc);
> +	}
> +
> +	return ret;
> +}
> diff --git a/fs/btrfs/raid-stripe-tree.h b/fs/btrfs/raid-stripe-tree.h
> new file mode 100644
> index 000000000000..884f0e99d5e8
> --- /dev/null
> +++ b/fs/btrfs/raid-stripe-tree.h
> @@ -0,0 +1,34 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2023 Western Digital Corporation or its affiliates.
> + */
> +
> +#ifndef BTRFS_RAID_STRIPE_TREE_H
> +#define BTRFS_RAID_STRIPE_TREE_H
> +
> +struct btrfs_io_context;
> +struct btrfs_io_stripe;
> +struct btrfs_ordered_extent;
> +struct btrfs_trans_handle;
> +
> +int btrfs_insert_raid_extent(struct btrfs_trans_handle *trans,
> +			     struct btrfs_ordered_extent *ordered_extent);
> +
> +static inline bool btrfs_need_stripe_tree_update(struct btrfs_fs_info *=
fs_info,
> +						 u64 map_type)
> +{
> +	u64 type =3D map_type & BTRFS_BLOCK_GROUP_TYPE_MASK;
> +	u64 profile =3D map_type & BTRFS_BLOCK_GROUP_PROFILE_MASK;
> +
> +	if (!fs_info->stripe_root)
> +		return false;

I found a corncer case that this can be problematic.

If we have a fs with RST root tree node/leaf corrupted, mounted with
rescue=3Dibadroots, then fs_info->stripe_root would be NULL, and in the
5th patch inside set_io_stripe() we just fall back to regular non-RST path=
.
This would bring us mostly incorrect data (and can be very problematic
for nodatacsum files).

Thus stripe_root itself is not a reliable way to determine if we're at
RST routine, I'd say only super incompat flags is reliable.

And fs_info->stripe_root should only be checked for functions that do
RST tree operations, and return -EIO properly if it's not initialized.

> +
> +	if (type !=3D BTRFS_BLOCK_GROUP_DATA)
> +		return false;
> +
> +	if (profile & BTRFS_BLOCK_GROUP_RAID1_MASK)
> +		return true;

Just a stupid quest, RAID0 DATA doesn't need RST purely because they are
  the same as SINGLE, thus we only update the file items to the real
written logical address, and no need for the extra mapping?

Thus only profiles with duplication relies on RST, right?
If so, then I guess DUP should also be covered by RST.

> +
> +	return false;
> +}
> +#endif
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index a1eae8b5b412..c2bac87912c7 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -5984,6 +5984,7 @@ static int find_live_mirror(struct btrfs_fs_info *=
fs_info,
>   }
>
>   static struct btrfs_io_context *alloc_btrfs_io_context(struct btrfs_fs=
_info *fs_info,
> +						       u64 logical,
>   						       u16 total_stripes)
>   {
>   	struct btrfs_io_context *bioc;
> @@ -6003,6 +6004,7 @@ static struct btrfs_io_context *alloc_btrfs_io_con=
text(struct btrfs_fs_info *fs_
>   	bioc->fs_info =3D fs_info;
>   	bioc->replace_stripe_src =3D -1;
>   	bioc->full_stripe_logical =3D (u64)-1;
> +	bioc->logical =3D logical;
>
>   	return bioc;
>   }
> @@ -6537,7 +6539,7 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info,=
 enum btrfs_map_op op,
>   		goto out;
>   	}
>
> -	bioc =3D alloc_btrfs_io_context(fs_info, num_alloc_stripes);
> +	bioc =3D alloc_btrfs_io_context(fs_info, logical, num_alloc_stripes);
>   	if (!bioc) {
>   		ret =3D -ENOMEM;
>   		goto out;
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 26397adc8706..2043aff6e966 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -390,12 +390,11 @@ struct btrfs_fs_devices {
>
>   struct btrfs_io_stripe {
>   	struct btrfs_device *dev;
> -	union {
> -		/* Block mapping */
> -		u64 physical;
> -		/* For the endio handler */
> -		struct btrfs_io_context *bioc;
> -	};
> +	/* Block mapping */
> +	u64 physical;
> +	u64 length;
> +	/* For the endio handler */
> +	struct btrfs_io_context *bioc;
>   };
>
>   struct btrfs_discard_stripe {
> @@ -428,6 +427,10 @@ struct btrfs_io_context {
>   	atomic_t error;
>   	u16 max_errors;
>
> +	u64 logical;
> +	u64 size;
> +	struct list_head ordered_entry;

Considering this is only utlized by RST, can we rename it to be more
specific?
Like rst_ordered_entry?

Or I'm pretty sure just weeks later I would need to dig to see what this
list is used for.

Thanks,
Qu
> +
>   	/*
>   	 * The total number of stripes, including the extra duplicated
>   	 * stripe for replace.
>