[PATCH] [PATCH v2] erofs: fix missing folio_unlock causing lock imbalance

[Gao Xiang]

On 2026/3/31 11:46, Zhan Xusheng wrote:
> folio_trylock() in erofs_try_to_free_all_cached_folios() may
> successfully acquire the folio lock, but the subsequent check
> for erofs_folio_is_managed() can skip unlocking when the folio
> is not managed by EROFS.
> 
> As Gao Xiang pointed out, this condition should not happen in
> practice because compressed_bvecs[] only holds valid cached folios
> at this point — any non-managed folio would have already been
> detached by z_erofs_cache_release_folio() under folio lock.
> 
> Fix this by adding DBG_BUGON() to catch unexpected folios
> and ensure folio_unlock() is always called.
> 
> Suggested-by: Gao Xiang <hsiangkao at linux.alibaba.com>
> Signed-off-by: Zhan Xusheng <zhanxusheng at xiaomi.com>

emmm, the patch subject needs to be changed too, like:

[PATCH v3] erofs: ensure all folios are managed in erofs_try_to_free_all_cached_folios()

Thanks,
Gao Xiang

> ---
>   fs/erofs/zdata.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index fe8121df9ef2..b566996a0d1a 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -605,8 +605,7 @@ static int erofs_try_to_free_all_cached_folios(struct erofs_sb_info *sbi,
>   			if (!folio_trylock(folio))
>   				return -EBUSY;
>   
> -			if (!erofs_folio_is_managed(sbi, folio))
> -				continue;
> +			DBG_BUGON(!erofs_folio_is_managed(sbi, folio));
>   			pcl->compressed_bvecs[i].page = NULL;
>   			folio_detach_private(folio);
>   			folio_unlock(folio);