Re: [PATCH 05/15] btrfs: clarify btrfs_lookup_bio_sums documentation

From: Josef Bacik <josef@toxicpanda.com>
To: Omar Sandoval <osandov@osandov.com>
Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 05/15] btrfs: clarify btrfs_lookup_bio_sums documentation
Date: Wed, 11 Mar 2020 14:34:07 -0400	[thread overview]
Message-ID: <5b647dbd-ba6a-4428-1780-6045b13821e1@toxicpanda.com> (raw)
In-Reply-To: <20200311182325.GA296369@vader>

On 3/11/20 2:23 PM, Omar Sandoval wrote:
> On Wed, Mar 11, 2020 at 01:56:44PM -0400, Josef Bacik wrote:
>> On 3/9/20 5:32 PM, Omar Sandoval wrote:
>>> From: Omar Sandoval <osandov@fb.com>
>>>
>>> Fix a couple of issues in the btrfs_lookup_bio_sums documentation:
>>>
>>> * The bio doesn't need to be a btrfs_io_bio if dst was provided. Move
>>>     the declaration in the code to make that clear, too.
>>> * dst must be large enough to hold nblocks * csum_size, not just
>>>     csum_size.
>>>
>>> Signed-off-by: Omar Sandoval <osandov@fb.com>
>>> ---
>>>    fs/btrfs/file-item.c | 11 +++++++----
>>>    1 file changed, 7 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
>>> index 6c849e8fd5a1..fa9f4a92f74d 100644
>>> --- a/fs/btrfs/file-item.c
>>> +++ b/fs/btrfs/file-item.c
>>> @@ -242,11 +242,13 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
>>>    /**
>>>     * btrfs_lookup_bio_sums - Look up checksums for a bio.
>>>     * @inode: inode that the bio is for.
>>> - * @bio: bio embedded in btrfs_io_bio.
>>> + * @bio: bio to look up.
>>>     * @offset: Unless (u64)-1, look up checksums for this offset in the file.
>>>     *          If (u64)-1, use the page offsets from the bio instead.
>>> - * @dst: Buffer of size btrfs_super_csum_size() used to return checksum. If
>>> - *       NULL, the checksum is returned in btrfs_io_bio(bio)->csum instead.
>>> + * @dst: Buffer of size nblocks * btrfs_super_csum_size() used to return
>>> + *       checksum (nblocks = bio->bi_iter.bi_size / sectorsize). If NULL, the
>>> + *       checksum buffer is allocated and returned in btrfs_io_bio(bio)->csum
>>> + *       instead.
>>>     *
>>>     * Return: BLK_STS_RESOURCE if allocating memory fails, BLK_STS_OK otherwise.
>>>     */
>>> @@ -256,7 +258,6 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
>>>    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
>>>    	struct bio_vec bvec;
>>>    	struct bvec_iter iter;
>>> -	struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);
>>>    	struct btrfs_csum_item *item = NULL;
>>>    	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
>>>    	struct btrfs_path *path;
>>> @@ -277,6 +278,8 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
>>>    	nblocks = bio->bi_iter.bi_size >> inode->i_sb->s_blocksize_bits;
>>>    	if (!dst) {
>>> +		struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);
>>> +
>>
>> Looks like you have some extra changes in here?
> 
> I mentioned it in the commit message: "Move the declaration in the code
> to make that clear". It looks weird to document that the bio only needs
> to be a btrfs_io_bio if dst == NULL and then always get the btrfs_bio,
> even if we don't use it.
> 

Apparently I can't read multi-sentence bullet points.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef