Re: client side "current->alloc_tag not set WARNING: ./include/linux/alloc_tag.h:161" at accessing CIFS share

[Erhard Furtner]

On 9/16/26 11:42, Hao Ge wrote:
> Right - and there's one more instance of the same pattern.
> Erhard's second warning (alloc_tag was not set on free) comes from
> netfs_folioq_alloc(), which does the same for the folio_queue:
> 	
> 	fq = netfs_folioq_pool.alloc(gfp, netfs_folioq_pool.pool_data);
>
> When I first saw the report I wondered why no other mempool user trips over this,
> so I had a look around the tree:
>
> Everyone else gets their elements through the mempool_alloc() macro, so the tag is
> set at their callsite and the callbacks see a valid current->alloc_tag.
>
> I went back to the commit that introduced the raw call, 1d78d56c43ef ("netfs: Fix folio_queue ENOMEM in
> writeback by adding a mempool") and OK, I think I roughly understand the story now.
>
> Here is my proposed fix patch. I don't have a test environment handy though. What do you think?
>
> diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
> index 420ee7b26580..373be970ec31 100644
> --- a/fs/netfs/internal.h
> +++ b/fs/netfs/internal.h
> @@ -45,6 +45,9 @@ extern mempool_t netfs_request_pool;
>   extern mempool_t netfs_subrequest_pool;
>   extern mempool_t netfs_folioq_pool;
>   
> +#define mempool_alloc_element(_pool, _gfp)				\
> +	alloc_hooks((_pool)->alloc(_gfp, (_pool)->pool_data))
> +
>   #ifdef CONFIG_PROC_FS
>   static inline void netfs_proc_add_rreq(struct netfs_io_request *rreq)
>   {
> diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
> index 01461a74642d..18f5c64d404e 100644
> --- a/fs/netfs/objects.c
> +++ b/fs/netfs/objects.c
> @@ -34,7 +34,7 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
>   
>   		rreq = mempool_alloc(mempool, gfp);
>   	} else {
> -		rreq = mempool->alloc(gfp, mempool->pool_data);
> +		rreq = mempool_alloc_element(mempool, gfp);
>   		if (!rreq)
>   			return ERR_PTR(-ENOMEM);
>   	}
> @@ -206,7 +206,7 @@ struct netfs_io_subrequest *netfs_alloc_subrequest(struct netfs_io_request *rreq
>   	struct kmem_cache *cache = mempool->pool_data;
>   
>   	if (rreq->gfp == GFP_KERNEL)
> -		subreq = mempool->alloc(rreq->gfp, mempool->pool_data);
> +		subreq = mempool_alloc_element(mempool, rreq->gfp);
>   	else
>   		subreq = mempool_alloc(mempool, rreq->gfp);
>   	if (!subreq)
> diff --git a/fs/netfs/rolling_buffer.c b/fs/netfs/rolling_buffer.c
> index 8c0026836f9c..d1ae6e081664 100644
> --- a/fs/netfs/rolling_buffer.c
> +++ b/fs/netfs/rolling_buffer.c
> @@ -29,7 +29,7 @@ struct folio_queue *netfs_folioq_alloc(unsigned int rreq_id, gfp_t gfp,
>   	struct folio_queue *fq;
>   
>   	if (gfp == GFP_KERNEL)
> -		fq = netfs_folioq_pool.alloc(gfp, netfs_folioq_pool.pool_data);
> +		fq = mempool_alloc_element(&netfs_folioq_pool, gfp);
>   	else
>   		fq = mempool_alloc(&netfs_folioq_pool, gfp);
>   	if (fq) {

Thanks for your patch Hao! On my side I can confirm it applies on 
v7.3-rc3 and fixes "the current->alloc_tag not set WARNING:"

Regards,
Erhard