linux-kernel - Re: [PATCH v3] btrfs: handle bio

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Message-ID: <9eec1ccb-6e56-4701-83bf-3397d1bc5197@oracle.com>
Date: Wed, 13 Nov 2024 09:51:06 +0000
From: John Garry <john.g.garry@...cle.com>
To: Johannes Thumshirn <jth@...nel.org>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>,
        "open list:BTRFS FILE SYSTEM" <linux-btrfs@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Cc: linux-block@...r.kernel.org,
        Johannes Thumshirn <johannes.thumshirn@....com>
Subject: Re: [PATCH v3] btrfs: handle bio_split() error

On 04/11/2024 12:13, Johannes Thumshirn wrote:
> From: Johannes Thumshirn <johannes.thumshirn@....com>
> 
> Now that bio_split() can return errors, add error handling for it in
> btrfs_split_bio() and ultimately btrfs_submit_chunk().

I have a couple of comments, below; However, since I am not familiar 
with the code, maybe they are invalid.

> 
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
> ---
> 
> This is based on top of John Garry's series "bio_split() error handling
> rework" explicitly on the patch titled "block: Rework bio_split() return
> value", which are as of now (Tue Oct 29 10:02:16 2024) not yet merged into
> any tree.
> 
> Changes to v2:
> - assign the split bbio to a new variable, so we can keep the old error
>    paths and end the original bbio
> 
> Changes to v1:
> - convert ERR_PTR to blk_status_t
> - correctly fail already split bbios
> ---
>   fs/btrfs/bio.c | 15 +++++++++++++--
>   1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
> index 1f216d07eff6..7a0998d0abe3 100644
> --- a/fs/btrfs/bio.c
> +++ b/fs/btrfs/bio.c
> @@ -81,6 +81,9 @@ static struct btrfs_bio *btrfs_split_bio(struct btrfs_fs_info *fs_info,
>   
>   	bio = bio_split(&orig_bbio->bio, map_length >> SECTOR_SHIFT, GFP_NOFS,
>   			&btrfs_clone_bioset);
> +	if (IS_ERR(bio))
> +		return ERR_CAST(bio);
> +
>   	bbio = btrfs_bio(bio);
>   	btrfs_bio_init(bbio, fs_info, NULL, orig_bbio);
>   	bbio->inode = orig_bbio->inode;
> @@ -678,7 +681,7 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
>   				&bioc, &smap, &mirror_num);
>   	if (error) {
>   		ret = errno_to_blk_status(error);
> -		goto fail;
> +		goto end_bbio;

eh, I am not sure why this has changed (and we now skip the "fail" label 
actions)

>   	}
>   
>   	map_length = min(map_length, length);
> @@ -686,7 +689,14 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
>   		map_length = btrfs_append_map_length(bbio, map_length);
>   
>   	if (map_length < length) {
> -		bbio = btrfs_split_bio(fs_info, bbio, map_length);
> +		struct btrfs_bio *split;
> +
> +		split = btrfs_split_bio(fs_info, bbio, map_length);
> +		if (IS_ERR(split)) {
> +			ret = errno_to_blk_status(PTR_ERR(split));
> +			goto end_bbio;

Do we need to undo the btrfs_bio_counter_inc() (not shown)?

> +		}
> +		bbio = split;
>   		bio = &bbio->bio;
>   	}
>   
> @@ -760,6 +770,7 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
>   
>   		btrfs_bio_end_io(remaining, ret);
>   	}
> +end_bbio:
>   	btrfs_bio_end_io(bbio, ret);
>   	/* Do not submit another chunk */
>   	return true;