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Message-ID: <492ac26f-5eb4-49bf-855a-11f021d9e937@suse.com>
Date: Fri, 14 Nov 2025 06:46:20 +1030
From: Qu Wenruo <wqu@...e.com>
To: Daniel Vacek <neelx@...e.com>
Cc: Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 3/8] btrfs: add a bio argument to btrfs_csum_one_bio
在 2025/11/14 05:37, Daniel Vacek 写道:
> On Wed, 12 Nov 2025 at 22:02, Qu Wenruo <wqu@...e.com> wrote:
>> 在 2025/11/13 06:06, Daniel Vacek 写道:
>>> From: Josef Bacik <josef@...icpanda.com>
>>>
>>> We only ever needed the bbio in btrfs_csum_one_bio, since that has the
>>> bio embedded in it. However with encryption we'll have a different bio
>>> with the encrypted data in it, and the original bbio. Update
>>> btrfs_csum_one_bio to take the bio we're going to csum as an argument,
>>> which will allow us to csum the encrypted bio and stuff the csums into
>>> the corresponding bbio to be used later when the IO completes.
>>
>> I'm wondering why we can not do it in a layered bio way.
>>
>> E.g. on device-mapper based solutions, the upper layer send out the bio
>> containing the plaintext data.
>> Then the dm-crypto send out a new bio, containing the encrypted data.
>
> This is similar but fscrypt works on FS level. It gets the original
> plaintext bio (the btrfs_bio::bio one) and gives us a callback with
> the encrypted bio to calculate the checksum of the encrypted data. No
> plaintext bio goes to the storage layer.
Then why put the original bio pointer into the super generic btrfs_bio?
I thought it's more common to put the original plaintext into the
encryption specific structure, like what we did for compression.
Thanks,
Qu
>
> --nX
>
>> The storage layer doesn't need to bother the plaintext bio at all, they
>> just write the encrypted one to disk.
>>
>> And it's the dm-crypto tracking the plaintext bio <-> encrypted bio mapping.
>>
>>
>> So why we can not just create a new bio for the final csum caculation,
>> just like compression?
>>
>> Thanks,
>> Qu
>>
>>>
>>> Signed-off-by: Josef Bacik <josef@...icpanda.com>
>>> Signed-off-by: Daniel Vacek <neelx@...e.com>
>>> ---
>>> Compared to v5 this needed to adapt to recent async csum changes.
>>> ---
>>> fs/btrfs/bio.c | 4 ++--
>>> fs/btrfs/bio.h | 1 +
>>> fs/btrfs/file-item.c | 17 ++++++++---------
>>> fs/btrfs/file-item.h | 2 +-
>>> 4 files changed, 12 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
>>> index a73652b8724a..a69174b2b6b6 100644
>>> --- a/fs/btrfs/bio.c
>>> +++ b/fs/btrfs/bio.c
>>> @@ -542,9 +542,9 @@ static int btrfs_bio_csum(struct btrfs_bio *bbio)
>>> if (bbio->bio.bi_opf & REQ_META)
>>> return btree_csum_one_bio(bbio);
>>> #ifdef CONFIG_BTRFS_EXPERIMENTAL
>>> - return btrfs_csum_one_bio(bbio, true);
>>> + return btrfs_csum_one_bio(bbio, &bbio->bio, true);
>>> #else
>>> - return btrfs_csum_one_bio(bbio, false);
>>> + return btrfs_csum_one_bio(bbio, &bbio->bio, false);
>>> #endif
>>> }
>>>
>>> diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h
>>> index deaeea3becf4..c5a6c66d51a0 100644
>>> --- a/fs/btrfs/bio.h
>>> +++ b/fs/btrfs/bio.h
>>> @@ -58,6 +58,7 @@ struct btrfs_bio {
>>> struct btrfs_ordered_sum *sums;
>>> struct work_struct csum_work;
>>> struct completion csum_done;
>>> + struct bio *csum_bio;
>>> struct bvec_iter csum_saved_iter;
>>> u64 orig_physical;
>>> };
>>> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
>>> index 72be3ede0edf..474949074da8 100644
>>> --- a/fs/btrfs/file-item.c
>>> +++ b/fs/btrfs/file-item.c
>>> @@ -765,21 +765,19 @@ int btrfs_lookup_csums_bitmap(struct btrfs_root *root, struct btrfs_path *path,
>>> return ret;
>>> }
>>>
>>> -static void csum_one_bio(struct btrfs_bio *bbio, struct bvec_iter *src)
>>> +static void csum_one_bio(struct btrfs_bio *bbio, struct bio *bio, struct bvec_iter *iter)
>>> {
>>> struct btrfs_inode *inode = bbio->inode;
>>> struct btrfs_fs_info *fs_info = inode->root->fs_info;
>>> SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
>>> - struct bio *bio = &bbio->bio;
>>> struct btrfs_ordered_sum *sums = bbio->sums;
>>> - struct bvec_iter iter = *src;
>>> phys_addr_t paddr;
>>> const u32 blocksize = fs_info->sectorsize;
>>> int index = 0;
>>>
>>> shash->tfm = fs_info->csum_shash;
>>>
>>> - btrfs_bio_for_each_block(paddr, bio, &iter, blocksize) {
>>> + btrfs_bio_for_each_block(paddr, bio, iter, blocksize) {
>>> btrfs_calculate_block_csum(fs_info, paddr, sums->sums + index);
>>> index += fs_info->csum_size;
>>> }
>>> @@ -791,19 +789,18 @@ static void csum_one_bio_work(struct work_struct *work)
>>>
>>> ASSERT(btrfs_op(&bbio->bio) == BTRFS_MAP_WRITE);
>>> ASSERT(bbio->async_csum == true);
>>> - csum_one_bio(bbio, &bbio->csum_saved_iter);
>>> + csum_one_bio(bbio, bbio->csum_bio, &bbio->csum_saved_iter);
>>> complete(&bbio->csum_done);
>>> }
>>>
>>> /*
>>> * Calculate checksums of the data contained inside a bio.
>>> */
>>> -int btrfs_csum_one_bio(struct btrfs_bio *bbio, bool async)
>>> +int btrfs_csum_one_bio(struct btrfs_bio *bbio, struct bio *bio, bool async)
>>> {
>>> struct btrfs_ordered_extent *ordered = bbio->ordered;
>>> struct btrfs_inode *inode = bbio->inode;
>>> struct btrfs_fs_info *fs_info = inode->root->fs_info;
>>> - struct bio *bio = &bbio->bio;
>>> struct btrfs_ordered_sum *sums;
>>> unsigned nofs_flag;
>>>
>>> @@ -822,12 +819,14 @@ int btrfs_csum_one_bio(struct btrfs_bio *bbio, bool async)
>>> btrfs_add_ordered_sum(ordered, sums);
>>>
>>> if (!async) {
>>> - csum_one_bio(bbio, &bbio->bio.bi_iter);
>>> + struct bvec_iter iter = bio->bi_iter;
>>> + csum_one_bio(bbio, bio, &iter);
>>> return 0;
>>> }
>>> init_completion(&bbio->csum_done);
>>> bbio->async_csum = true;
>>> - bbio->csum_saved_iter = bbio->bio.bi_iter;
>>> + bbio->csum_bio = bio;
>>> + bbio->csum_saved_iter = bio->bi_iter;
>>> INIT_WORK(&bbio->csum_work, csum_one_bio_work);
>>> schedule_work(&bbio->csum_work);
>>> return 0;
>>> diff --git a/fs/btrfs/file-item.h b/fs/btrfs/file-item.h
>>> index 5645c5e3abdb..d16fd2144552 100644
>>> --- a/fs/btrfs/file-item.h
>>> +++ b/fs/btrfs/file-item.h
>>> @@ -64,7 +64,7 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
>>> int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
>>> struct btrfs_root *root,
>>> struct btrfs_ordered_sum *sums);
>>> -int btrfs_csum_one_bio(struct btrfs_bio *bbio, bool async);
>>> +int btrfs_csum_one_bio(struct btrfs_bio *bbio, struct bio *bio, bool async);
>>> int btrfs_alloc_dummy_sum(struct btrfs_bio *bbio);
>>> int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
>>> struct list_head *list, int search_commit,
>>
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