Re: [PATCH 11/13] btrfs: open code set_io_stripe for RAID56

Christoph Hellwig
2023-12-13T08:58:43Z

On Tue, Dec 12, 2023 at 04:38:09AM -0800, Johannes Thumshirn wrote:
> Open code set_io_stripe() for RAID56, as it a) uses a different method to
> calculate the stripe_index and b) doesn't need to go through raid-stripe-tree
> mapping code.

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

I think raid stripe tree handling also really should move out of
set_io_stripe. Below is the latest I have, although it probably won't
apply to your tree:

---
From ac208da48d7f9d11eef8a01ac0c6fbf9681665b5 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Thu, 22 Jun 2023 05:53:13 +0200
Subject: btrfs: move raid-stripe-tree handling out of set_io_stripe

set_io_stripe gets a little too complicated with the raid-stripe-tree
handling. Move it out into the only callers that actually needs it.

The only reads with more than a single stripe is the parity raid recovery
case thast will need very special handling anyway once implemented.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/btrfs/volumes.c | 61 ++++++++++++++++++++--------------------------
1 file changed, 27 insertions(+), 34 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 30ee5d1670d034..e32eefa242b0a4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6233,22 +6233,12 @@ static u64 btrfs_max_io_len(struct map_lookup *map, enum btrfs_map_op op,
return U64_MAX;
}

-static int set_io_stripe(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
- u64 logical, u64 *length, struct btrfs_io_stripe *dst,
- struct map_lookup *map, u32 stripe_index,
- u64 stripe_offset, u64 stripe_nr)
+static void set_io_stripe(struct btrfs_io_stripe *dst, const struct map_lookup *map,
+ u32 stripe_index, u64 stripe_offset, u32 stripe_nr)
{
dst->dev = map->stripes[stripe_index].dev;
-
- if (op == BTRFS_MAP_READ &&
- btrfs_use_raid_stripe_tree(fs_info, map->type))
- return btrfs_get_raid_extent_offset(fs_info, logical, length,
- map->type, stripe_index,
- dst);
-
dst->physical = map->stripes[stripe_index].physical +
stripe_offset + ((u64)stripe_nr << BTRFS_STRIPE_LEN_SHIFT);
- return 0;
}

int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
@@ -6423,15 +6413,24 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
* physical block information on the stack instead of allocating an
* I/O context structure.
*/
- if (smap && num_alloc_stripes == 1 &&
- !(btrfs_use_raid_stripe_tree(fs_info, map->type) &&
- op != BTRFS_MAP_READ) &&
- !((map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) && mirror_num > 1)) {
- ret = set_io_stripe(fs_info, op, logical, length, smap, map,
- stripe_index, stripe_offset, stripe_nr);
- *mirror_num_ret = mirror_num;
- *bioc_ret = NULL;
- goto out;
+ if (smap && num_alloc_stripes == 1) {
+ if (op == BTRFS_MAP_READ &&
+ btrfs_use_raid_stripe_tree(fs_info, map->type)) {
+ ret = btrfs_get_raid_extent_offset(fs_info, logical,
+ length, map->type,
+ stripe_index, smap);
+ *mirror_num_ret = mirror_num;
+ *bioc_ret = NULL;
+ goto out;
+ } else if (!(map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) ||
+ mirror_num == 0) {
+ set_io_stripe(smap, map, stripe_index, stripe_offset,
+ stripe_nr);
+ *mirror_num_ret = mirror_num;
+ *bioc_ret = NULL;
+ ret = 0;
+ goto out;
+ }
}

bioc = alloc_btrfs_io_context(fs_info, logical, num_alloc_stripes);
@@ -6448,6 +6447,8 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
*
* It's still mostly the same as other profiles, just with extra rotation.
*/
+ ASSERT(op != BTRFS_MAP_READ ||
+ btrfs_use_raid_stripe_tree(fs_info, map->type));
if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK && need_raid_map &&
(op != BTRFS_MAP_READ || mirror_num > 1)) {
/*
@@ -6461,29 +6462,21 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
bioc->full_stripe_logical = em->start +
((stripe_nr * data_stripes) << BTRFS_STRIPE_LEN_SHIFT);
for (i = 0; i < num_stripes; i++)
- ret = set_io_stripe(fs_info, op, logical, length,
- &bioc->stripes[i], map,
- (i + stripe_nr) % num_stripes,
- stripe_offset, stripe_nr);
+ set_io_stripe(&bioc->stripes[i], map,
+ (i + stripe_nr) % num_stripes,
+ stripe_offset, stripe_nr);
} else {
/*
* For all other non-RAID56 profiles, just copy the target
* stripe into the bioc.
*/
for (i = 0; i < num_stripes; i++) {
- ret = set_io_stripe(fs_info, op, logical, length,
- &bioc->stripes[i], map, stripe_index,
- stripe_offset, stripe_nr);
+ set_io_stripe(&bioc->stripes[i], map, stripe_index,
+ stripe_offset, stripe_nr);
stripe_index++;
}
}

- if (ret) {
- *bioc_ret = NULL;
- btrfs_put_bioc(bioc);
- goto out;
- }
-
if (op != BTRFS_MAP_READ)
max_errors = btrfs_chunk_max_errors(map);

--
2.39.2