Re: [PATCH v3] btrfs: handle lack of space when cleaning up verity items

[Qu Wenruo]

在 2026/9/16 15:45, Daniel Linjama 写道:
> When enable_verity() hits the qgroup limit, rollback_verity() needs its
> own metadata reservation. When the qgroup limit or lack of space refuses
> the rollback, the whole filesystem is forced read-only even though the
> qgroup limit was for one subvolume only. Also orphan cleanup at the next
> mount fails the same way, so the leftover items are never removed: with
> -EDQUOT the subvolume stays unreachable, and with -ENOSPC on a full
> filesystem the next read-write mount fails.
>
> Start transactions with btrfs_start_transaction_fallback_global_rsv() in
> btrfs_orphan_cleanup(), drop_verity_items() and rollback_verity(). Those
> calls only delete items and free the space in the end, so they may use
> the global reserve and skip the qgroup limit, which avoids -ENOSPC and
> -EDQUOT.
>
> Fixes: 146054090b08 ("btrfs: initial fsverity support")
> Signed-off-by: Daniel Linjama <daniel@xxxxxxxxxxxxxxx>

Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>

Thanks,
Qu

> ---
> Changes since v2:
> - Explain in the commit message why the global reserve fallback and
>    skipping the qgroup limit are right here, as Qu Wenruo asked.
> - A helper in verity.c for the two verity call sites carries the one
>    comment, as Qu Wenruo suggested; the orphan cleanup call site only
>    notes what it does.
>
> v2: https://lore.kernel.org/linux-btrfs/20260915055109.311839-1-daniel@xxxxxxxxxxxxxxx/
> v1: https://lore.kernel.org/linux-btrfs/20260914062459.3889313-1-daniel@xxxxxxxxxxxxxxx/
>
>   fs/btrfs/inode.c  |  3 ++-
>   fs/btrfs/verity.c | 18 ++++++++++++++++--
>   2 files changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 93ef3cec191e..84dc44af17d7 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -3877,7 +3877,8 @@ int btrfs_orphan_cleanup(struct btrfs_root *root)
>   				if (ret)
>   					goto out;
>   			}
> -			trans = btrfs_start_transaction(root, 1);
> +			/* Only deletes the orphan */
> +			trans = btrfs_start_transaction_fallback_global_rsv(root, 1);
>   			if (IS_ERR(trans)) {
>   				ret = PTR_ERR(trans);
>   				goto out;
> diff --git a/fs/btrfs/verity.c b/fs/btrfs/verity.c
> index 4e0ab5842274..18b9d14f2e8c 100644
> --- a/fs/btrfs/verity.c
> +++ b/fs/btrfs/verity.c
> @@ -93,6 +93,20 @@ static loff_t merkle_file_pos(const struct inode *inode)
>   	return rounded;
>   }
>   
> +/*
> + * Start a transaction for removing verity items or the verity orphan.
> + *
> + * Like unlink, this only deletes items and frees space in the end, so the
> + * reservation may come from the global reserve when the filesystem is full
> + * (-ENOSPC) and is not subject to the qgroup limit (-EDQUOT). Otherwise a
> + * failed enable could never be cleaned up in either situation.
> + */
> +static struct btrfs_trans_handle *start_verity_cleanup_trans(struct btrfs_root *root,
> +							      unsigned int num_items)
> +{
> +	return btrfs_start_transaction_fallback_global_rsv(root, num_items);
> +}
> +
>   /*
>    * Drop all the items for this inode with this key_type.
>    *
> @@ -120,7 +134,7 @@ static int drop_verity_items(struct btrfs_inode *inode, u8 key_type)
>   
>   	while (1) {
>   		/* 1 for the item being dropped */
> -		trans = btrfs_start_transaction(root, 1);
> +		trans = start_verity_cleanup_trans(root, 1);
>   		if (IS_ERR(trans))
>   			return PTR_ERR(trans);
>   
> @@ -466,7 +480,7 @@ static int rollback_verity(struct btrfs_inode *inode)
>   	 * 1 for updating the inode flag
>   	 * 1 for deleting the orphan
>   	 */
> -	trans = btrfs_start_transaction(root, 2);
> +	trans = start_verity_cleanup_trans(root, 2);
>   	if (IS_ERR(trans)) {
>   		ret = PTR_ERR(trans);
>   		trans = NULL;
>
> base-commit: 08df884136f1c1197bab2a27814404fd329d9aac