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btrfs: zoned: implement sequential extent allocation
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Implement a sequential extent allocator for zoned filesystems. This
allocator only needs to check if there is enough space in the block group
after the allocation pointer to satisfy the extent allocation request.
Therefore the allocator never manages bitmaps or clusters. Also, add
assertions to the corresponding functions.

As zone append writing is used, it would be unnecessary to track the
allocation offset, as the allocator only needs to check available space.
But by tracking and returning the offset as an allocated region, we can
skip modification of ordered extents and checksum information when there
is no IO reordering.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Naohiro Aota authored and David Sterba committed Feb 9, 2021
1 parent 169e0da commit 2eda570
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Showing 3 changed files with 94 additions and 6 deletions.
4 changes: 4 additions & 0 deletions fs/btrfs/block-group.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -725,6 +725,10 @@ int btrfs_cache_block_group(struct btrfs_block_group *cache, int load_cache_only
struct btrfs_caching_control *caching_ctl = NULL;
int ret = 0;

/* Allocator for zoned filesystems does not use the cache at all */
if (btrfs_is_zoned(fs_info))
return 0;

caching_ctl = kzalloc(sizeof(*caching_ctl), GFP_NOFS);
if (!caching_ctl)
return -ENOMEM;
Expand Down
90 changes: 84 additions & 6 deletions fs/btrfs/extent-tree.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3429,6 +3429,7 @@ btrfs_release_block_group(struct btrfs_block_group *cache,

enum btrfs_extent_allocation_policy {
BTRFS_EXTENT_ALLOC_CLUSTERED,
BTRFS_EXTENT_ALLOC_ZONED,
};

/*
Expand Down Expand Up @@ -3681,13 +3682,74 @@ static int do_allocation_clustered(struct btrfs_block_group *block_group,
return find_free_extent_unclustered(block_group, ffe_ctl);
}

/*
* Simple allocator for sequential-only block group. It only allows sequential
* allocation. No need to play with trees. This function also reserves the
* bytes as in btrfs_add_reserved_bytes.
*/
static int do_allocation_zoned(struct btrfs_block_group *block_group,
struct find_free_extent_ctl *ffe_ctl,
struct btrfs_block_group **bg_ret)
{
struct btrfs_space_info *space_info = block_group->space_info;
struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
u64 start = block_group->start;
u64 num_bytes = ffe_ctl->num_bytes;
u64 avail;
int ret = 0;

ASSERT(btrfs_is_zoned(block_group->fs_info));

spin_lock(&space_info->lock);
spin_lock(&block_group->lock);

if (block_group->ro) {
ret = 1;
goto out;
}

avail = block_group->length - block_group->alloc_offset;
if (avail < num_bytes) {
if (ffe_ctl->max_extent_size < avail) {
/*
* With sequential allocator, free space is always
* contiguous
*/
ffe_ctl->max_extent_size = avail;
ffe_ctl->total_free_space = avail;
}
ret = 1;
goto out;
}

ffe_ctl->found_offset = start + block_group->alloc_offset;
block_group->alloc_offset += num_bytes;
spin_lock(&ctl->tree_lock);
ctl->free_space -= num_bytes;
spin_unlock(&ctl->tree_lock);

/*
* We do not check if found_offset is aligned to stripesize. The
* address is anyway rewritten when using zone append writing.
*/

ffe_ctl->search_start = ffe_ctl->found_offset;

out:
spin_unlock(&block_group->lock);
spin_unlock(&space_info->lock);
return ret;
}

static int do_allocation(struct btrfs_block_group *block_group,
struct find_free_extent_ctl *ffe_ctl,
struct btrfs_block_group **bg_ret)
{
switch (ffe_ctl->policy) {
case BTRFS_EXTENT_ALLOC_CLUSTERED:
return do_allocation_clustered(block_group, ffe_ctl, bg_ret);
case BTRFS_EXTENT_ALLOC_ZONED:
return do_allocation_zoned(block_group, ffe_ctl, bg_ret);
default:
BUG();
}
Expand All @@ -3702,6 +3764,9 @@ static void release_block_group(struct btrfs_block_group *block_group,
ffe_ctl->retry_clustered = false;
ffe_ctl->retry_unclustered = false;
break;
case BTRFS_EXTENT_ALLOC_ZONED:
/* Nothing to do */
break;
default:
BUG();
}
Expand Down Expand Up @@ -3730,6 +3795,9 @@ static void found_extent(struct find_free_extent_ctl *ffe_ctl,
case BTRFS_EXTENT_ALLOC_CLUSTERED:
found_extent_clustered(ffe_ctl, ins);
break;
case BTRFS_EXTENT_ALLOC_ZONED:
/* Nothing to do */
break;
default:
BUG();
}
Expand All @@ -3745,6 +3813,9 @@ static int chunk_allocation_failed(struct find_free_extent_ctl *ffe_ctl)
*/
ffe_ctl->loop = LOOP_NO_EMPTY_SIZE;
return 0;
case BTRFS_EXTENT_ALLOC_ZONED:
/* Give up here */
return -ENOSPC;
default:
BUG();
}
Expand Down Expand Up @@ -3913,6 +3984,9 @@ static int prepare_allocation(struct btrfs_fs_info *fs_info,
case BTRFS_EXTENT_ALLOC_CLUSTERED:
return prepare_allocation_clustered(fs_info, ffe_ctl,
space_info, ins);
case BTRFS_EXTENT_ALLOC_ZONED:
/* Nothing to do */
return 0;
default:
BUG();
}
Expand Down Expand Up @@ -3976,6 +4050,9 @@ static noinline int find_free_extent(struct btrfs_root *root,
ffe_ctl.last_ptr = NULL;
ffe_ctl.use_cluster = true;

if (btrfs_is_zoned(fs_info))
ffe_ctl.policy = BTRFS_EXTENT_ALLOC_ZONED;

ins->type = BTRFS_EXTENT_ITEM_KEY;
ins->objectid = 0;
ins->offset = 0;
Expand Down Expand Up @@ -4118,20 +4195,21 @@ static noinline int find_free_extent(struct btrfs_root *root,
/* move on to the next group */
if (ffe_ctl.search_start + num_bytes >
block_group->start + block_group->length) {
btrfs_add_free_space(block_group, ffe_ctl.found_offset,
num_bytes);
btrfs_add_free_space_unused(block_group,
ffe_ctl.found_offset, num_bytes);
goto loop;
}

if (ffe_ctl.found_offset < ffe_ctl.search_start)
btrfs_add_free_space(block_group, ffe_ctl.found_offset,
ffe_ctl.search_start - ffe_ctl.found_offset);
btrfs_add_free_space_unused(block_group,
ffe_ctl.found_offset,
ffe_ctl.search_start - ffe_ctl.found_offset);

ret = btrfs_add_reserved_bytes(block_group, ram_bytes,
num_bytes, delalloc);
if (ret == -EAGAIN) {
btrfs_add_free_space(block_group, ffe_ctl.found_offset,
num_bytes);
btrfs_add_free_space_unused(block_group,
ffe_ctl.found_offset, num_bytes);
goto loop;
}
btrfs_inc_block_group_reservations(block_group);
Expand Down
6 changes: 6 additions & 0 deletions fs/btrfs/free-space-cache.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2928,6 +2928,8 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
u64 align_gap_len = 0;
enum btrfs_trim_state align_gap_trim_state = BTRFS_TRIM_STATE_UNTRIMMED;

ASSERT(!btrfs_is_zoned(block_group->fs_info));

spin_lock(&ctl->tree_lock);
entry = find_free_space(ctl, &offset, &bytes_search,
block_group->full_stripe_len, max_extent_size);
Expand Down Expand Up @@ -3059,6 +3061,8 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group *block_group,
struct rb_node *node;
u64 ret = 0;

ASSERT(!btrfs_is_zoned(block_group->fs_info));

spin_lock(&cluster->lock);
if (bytes > cluster->max_size)
goto out;
Expand Down Expand Up @@ -3835,6 +3839,8 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
int ret;
u64 rem = 0;

ASSERT(!btrfs_is_zoned(block_group->fs_info));

*trimmed = 0;

spin_lock(&block_group->lock);
Expand Down

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