Subject: Re: linux-next: manual merge of the vfs-brauner tree with the btrfs tree

From: Stephen Rothwell <[email-masked]>
Date: Tue, 14 May 2024 11:38:47 +1000

Hi all,

On Fri, 3 May 2024 11:00:01 +1000 Stephen Rothwell <[email-masked]> wrote:
>
> Today's linux-next merge of the vfs-brauner tree got a conflict in:
> 
>   fs/btrfs/disk-io.c
> 
> between commits:
> 
>   4a63bd0ffbd2 ("btrfs: convert super block writes to folio in wait_dev_supers()")
>   545799bb1bb9 ("btrfs: count super block write errors in device instead of tracking folio error state")
> 
> from the btrfs tree and commit:
> 
>   db3102368e1b ("use ->bd_mapping instead of ->bd_inode->i_mapping")
> 
> from the vfs-brauner tree.
> 
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging.  You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
> 
> 
> diff --cc fs/btrfs/disk-io.c
> index e8aca9f0e692,f10e894b0bf5..000000000000
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@@ -3739,9 -3738,10 +3739,9 @@@ static int write_dev_supers(struct btrf
>   			    struct btrfs_super_block *sb, int max_mirrors)
>   {
>   	struct btrfs_fs_info *fs_info = device->fs_info;
> - 	struct address_space *mapping = device->bdev->bd_inode->i_mapping;
> + 	struct address_space *mapping = device->bdev->bd_mapping;
>   	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
>   	int i;
>  -	int errors = 0;
>   	int ret;
>   	u64 bytenr, bytenr_orig;
>   
> @@@ -3857,21 -3855,30 +3857,21 @@@ static int wait_dev_supers(struct btrfs
>   		    device->commit_total_bytes)
>   			break;
>   
> - 		folio = filemap_get_folio(device->bdev->bd_inode->i_mapping,
>  -		page = find_get_page(device->bdev->bd_mapping,
>  -				     bytenr >> PAGE_SHIFT);
>  -		if (!page) {
>  -			errors++;
>  -			if (i == 0)
>  -				primary_failed = true;
> ++		folio = filemap_get_folio(device->bdev->bd_mapping,
>  +					  bytenr >> PAGE_SHIFT);
>  +		/* If the folio has been removed, then we know it completed. */
>  +		if (IS_ERR(folio))
>   			continue;
>  -		}
>  -		/* Page is submitted locked and unlocked once the IO completes */
>  -		wait_on_page_locked(page);
>  -		if (PageError(page)) {
>  -			errors++;
>  -			if (i == 0)
>  -				primary_failed = true;
>  -		}
>  +		ASSERT(folio_order(folio) == 0);
>   
>  -		/* Drop our reference */
>  -		put_page(page);
>  -
>  -		/* Drop the reference from the writing run */
>  -		put_page(page);
>  +		/* Folio will be unlocked once the write completes. */
>  +		folio_wait_locked(folio);
>  +		folio_put(folio);
>   	}
>   
>  -	/* log error, force error return */
>  +	errors += atomic_read(&device->sb_write_errors);
>  +	if (errors >= BTRFS_SUPER_PRIMARY_WRITE_ERROR)
>  +		primary_failed = true;
>   	if (primary_failed) {
>   		btrfs_err(device->fs_info, "error writing primary super block to device %llu",
>   			  device->devid);

This is now a conflict between the vfs tree and the btrfs tree.

-- 
Cheers,
Stephen Rothwell