Re: [PATCH 12/17] btrfs: return proper mapped length for RAID56 profiles in __btrfs_map_block()

[Qu Wenruo <wqu@xxxxxxxx>]

On 2021/12/1 13:17, Qu Wenruo wrote:
> For profiles other than RAID56, __btrfs_map_block() returns @map_length
> as min(stripe_end, logical + *length), which is also the same result
> from btrfs_get_io_geometry().
>
> But for RAID56, __btrfs_map_block() returns @map_length as stripe_len.
>
> This strange behavior is going to hurt incoming bio split at
> btrfs_map_bio() time, as we will use @map_length as bio split size.
>
> Fix this behavior by:
>
> - Return @map_length by the same calculatioin as other profiles
>
> - Save stripe_len into btrfs_io_context
>
> - Pass btrfs_io_context::stripe_len to raid56_*() functions
>
> - Update raid56_*() functions to make its stripe_len parameter more
>    explicit
>
> - Add extra ASSERT()s to make sure the passed stripe_len is correct

There is another hidden call site, scrub_stripe_index_and_offset() that 
is abusing such stripe_len and mapped_length.

And this would cause crash at btrfs/158.

Will fix it in next update, and make this specific patch to do better 
check on stripe_len.

Thanks,
Qu
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> ---
>   fs/btrfs/raid56.c  | 12 ++++++++++--
>   fs/btrfs/raid56.h  |  2 +-
>   fs/btrfs/scrub.c   |  4 ++--
>   fs/btrfs/volumes.c | 13 ++++++++++---
>   fs/btrfs/volumes.h |  1 +
>   5 files changed, 24 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> index 13e726c88a81..d35cfd750b76 100644
> --- a/fs/btrfs/raid56.c
> +++ b/fs/btrfs/raid56.c
> @@ -969,6 +969,8 @@ static struct btrfs_raid_bio *alloc_rbio(struct btrfs_fs_info *fs_info,
>   	int stripe_npages = DIV_ROUND_UP(stripe_len, PAGE_SIZE);
>   	void *p;
>   
> +	ASSERT(stripe_len == BTRFS_STRIPE_LEN);
> +
>   	rbio = kzalloc(sizeof(*rbio) +
>   		       sizeof(*rbio->stripe_pages) * num_pages +
>   		       sizeof(*rbio->bio_pages) * num_pages +
> @@ -1725,6 +1727,9 @@ int raid56_parity_write(struct bio *bio, struct btrfs_io_context *bioc,
>   	struct blk_plug_cb *cb;
>   	int ret;
>   
> +	/* Currently we only support fixed stripe len */
> +	ASSERT(stripe_len == BTRFS_STRIPE_LEN);
> +
>   	rbio = alloc_rbio(fs_info, bioc, stripe_len);
>   	if (IS_ERR(rbio)) {
>   		btrfs_put_bioc(bioc);
> @@ -2122,6 +2127,9 @@ int raid56_parity_recover(struct bio *bio, struct btrfs_io_context *bioc,
>   	struct btrfs_raid_bio *rbio;
>   	int ret;
>   
> +	/* Currently we only support fixed stripe len */
> +	ASSERT(stripe_len == BTRFS_STRIPE_LEN);
> +
>   	if (generic_io) {
>   		ASSERT(bioc->mirror_num == mirror_num);
>   		btrfs_bio(bio)->mirror_num = mirror_num;
> @@ -2671,12 +2679,12 @@ void raid56_parity_submit_scrub_rbio(struct btrfs_raid_bio *rbio)
>   
>   struct btrfs_raid_bio *
>   raid56_alloc_missing_rbio(struct bio *bio, struct btrfs_io_context *bioc,
> -			  u64 length)
> +			  u64 stripe_len)
>   {
>   	struct btrfs_fs_info *fs_info = bioc->fs_info;
>   	struct btrfs_raid_bio *rbio;
>   
> -	rbio = alloc_rbio(fs_info, bioc, length);
> +	rbio = alloc_rbio(fs_info, bioc, stripe_len);
>   	if (IS_ERR(rbio))
>   		return NULL;
>   
> diff --git a/fs/btrfs/raid56.h b/fs/btrfs/raid56.h
> index 72c00fc284b5..7322dcae4498 100644
> --- a/fs/btrfs/raid56.h
> +++ b/fs/btrfs/raid56.h
> @@ -46,7 +46,7 @@ void raid56_parity_submit_scrub_rbio(struct btrfs_raid_bio *rbio);
>   
>   struct btrfs_raid_bio *
>   raid56_alloc_missing_rbio(struct bio *bio, struct btrfs_io_context *bioc,
> -			  u64 length);
> +			  u64 stripe_len);
>   void raid56_submit_missing_rbio(struct btrfs_raid_bio *rbio);
>   
>   int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info);
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 15a123e67108..58c7e8fcdeb1 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -2230,7 +2230,7 @@ static void scrub_missing_raid56_pages(struct scrub_block *sblock)
>   	bio->bi_private = sblock;
>   	bio->bi_end_io = scrub_missing_raid56_end_io;
>   
> -	rbio = raid56_alloc_missing_rbio(bio, bioc, length);
> +	rbio = raid56_alloc_missing_rbio(bio, bioc, bioc->stripe_len);
>   	if (!rbio)
>   		goto rbio_out;
>   
> @@ -2846,7 +2846,7 @@ static void scrub_parity_check_and_repair(struct scrub_parity *sparity)
>   	bio->bi_private = sparity;
>   	bio->bi_end_io = scrub_parity_bio_endio;
>   
> -	rbio = raid56_parity_alloc_scrub_rbio(bio, bioc, length,
> +	rbio = raid56_parity_alloc_scrub_rbio(bio, bioc, bioc->stripe_len,
>   					      sparity->scrub_dev,
>   					      sparity->dbitmap,
>   					      sparity->nsectors);
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index af01d54502ab..365e43bbfd14 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -6051,6 +6051,7 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
>   		ret = -ENOMEM;
>   		goto out;
>   	}
> +	bioc->stripe_len = map->stripe_len;
>   
>   	for (i = 0; i < num_stripes; i++) {
>   		bioc->stripes[i].physical =
> @@ -6406,6 +6407,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
>   {
>   	struct extent_map *em;
>   	struct map_lookup *map;
> +	const u64 orig_length = *length;
>   	u64 stripe_offset;
>   	u64 stripe_nr;
>   	u64 stripe_len;
> @@ -6427,6 +6429,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
>   
>   	ASSERT(bioc_ret);
>   	ASSERT(op != BTRFS_MAP_DISCARD);
> +	ASSERT(orig_length);
>   
>   	em = btrfs_get_chunk_map(fs_info, logical, *length);
>   	ASSERT(!IS_ERR(em));
> @@ -6522,7 +6525,10 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
>   			num_stripes = map->num_stripes;
>   			max_errors = nr_parity_stripes(map);
>   
> -			*length = map->stripe_len;
> +			/* Return the length to the full stripe end */
> +			*length = min(raid56_full_stripe_start + em->start +
> +				      data_stripes * stripe_len,
> +				      logical + orig_length) - logical;
>   			stripe_index = 0;
>   			stripe_offset = 0;
>   		} else {
> @@ -6574,6 +6580,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
>   		ret = -ENOMEM;
>   		goto out;
>   	}
> +	bioc->stripe_len = map->stripe_len;
>   
>   	for (i = 0; i < num_stripes; i++) {
>   		bioc->stripes[i].physical = map->stripes[stripe_index].physical +
> @@ -6824,9 +6831,9 @@ static int submit_one_mapped_range(struct btrfs_fs_info *fs_info, struct bio *bi
>   		/* In this case, map_length has been set to the length of
>   		   a single stripe; not the whole write */
>   		if (btrfs_op(bio) == BTRFS_MAP_WRITE) {
> -			ret = raid56_parity_write(bio, bioc, map_length);
> +			ret = raid56_parity_write(bio, bioc, bioc->stripe_len);
>   		} else {
> -			ret = raid56_parity_recover(bio, bioc, map_length,
> +			ret = raid56_parity_recover(bio, bioc, bioc->stripe_len,
>   						    mirror_num, 1);
>   		}
>   
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 8825a17d0620..b2dbf895b4e3 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -450,6 +450,7 @@ struct btrfs_io_context {
>   	struct bio *orig_bio;
>   	void *private;
>   	atomic_t error;
> +	u32 stripe_len;
>   	int max_errors;
>   	int num_stripes;
>   	int mirror_num;