Date:   Fri, 13 May 2022 09:02:17 +0100
From:   Martin Habets <habetsm.xilinx@...il.com>
To:     Íñigo Huguet <ihuguet@...hat.com>
Cc:     ecree.xilinx@...il.com, bhutchings@...arflare.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] sfc: simplify mtd partitions list handling

On Wed, May 11, 2022 at 12:36:04PM +0200, Íñigo Huguet wrote:
> efx_mtd_partitions are embedded inside efx_mcdi_mtd_partition structs.
> They contain a list entry that is appended to efx->mtd_list, which is
> traversed to perform add/remove/rename/etc operations over all
> efx_mtd_partitions.
> 
> However, almost all operations done on a efx_mtd_partition asume that it
> is actually embedded inside an efx_mcdi_mtd_partition, and the
> deallocation asume that the first member of the list is located at the
> beginning of the allocated memory.
> 
> Given all that asumptions, the possibility of having an
> efx_mtd_partition not embedded in an efx_mcdi_efx_partition doesn't
> exist. Neither it does the possibility of being in a memory position
> other the one allocated for the efx_mcdi_mtd_partition array. Also, they
> never need to be reordered.
> 
> Given all that, it is better to get rid of the list and use directly the
> efx_mcdi_mtd_partition array. This shows more clearly how they lay
> in memory, list traversal is more obvious and it save a small amount
> of memory on the list nodes.

I like this. Just 1 comment below.

> Signed-off-by: Íñigo Huguet <ihuguet@...hat.com>
> ---
>  drivers/net/ethernet/sfc/ef10.c       | 12 ++++++--
>  drivers/net/ethernet/sfc/efx.h        |  4 +--
>  drivers/net/ethernet/sfc/efx_common.c |  3 --
>  drivers/net/ethernet/sfc/mtd.c        | 42 ++++++++++-----------------
>  drivers/net/ethernet/sfc/net_driver.h |  9 ++++--
>  5 files changed, 33 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/net/ethernet/sfc/ef10.c b/drivers/net/ethernet/sfc/ef10.c
> index 15a229731296..b5284fa529b7 100644
> --- a/drivers/net/ethernet/sfc/ef10.c
> +++ b/drivers/net/ethernet/sfc/ef10.c
> @@ -3584,10 +3584,16 @@ static int efx_ef10_mtd_probe(struct efx_nic *efx)
>  		return 0;
>  	}
>  
> -	rc = efx_mtd_add(efx, &parts[0].common, n_parts, sizeof(*parts));
> -fail:
> +	rc = efx_mtd_add(efx, parts, n_parts);
>  	if (rc)
> -		kfree(parts);
> +		goto fail;
> +	efx->mcdi_mtd_parts = parts;
> +	efx->n_mcdi_mtd_parts = n_parts;
> +
> +	return 0;
> +
> +fail:
> +	kfree(parts);
>  	return rc;
>  }
>  
> diff --git a/drivers/net/ethernet/sfc/efx.h b/drivers/net/ethernet/sfc/efx.h
> index c05a83da9e44..2ab9ba691b0d 100644
> --- a/drivers/net/ethernet/sfc/efx.h
> +++ b/drivers/net/ethernet/sfc/efx.h
> @@ -181,8 +181,8 @@ void efx_update_sw_stats(struct efx_nic *efx, u64 *stats);
>  
>  /* MTD */
>  #ifdef CONFIG_SFC_MTD
> -int efx_mtd_add(struct efx_nic *efx, struct efx_mtd_partition *parts,
> -		size_t n_parts, size_t sizeof_part);
> +int efx_mtd_add(struct efx_nic *efx, struct efx_mcdi_mtd_partition *parts,
> +		size_t n_parts);
>  static inline int efx_mtd_probe(struct efx_nic *efx)
>  {
>  	return efx->type->mtd_probe(efx);
> diff --git a/drivers/net/ethernet/sfc/efx_common.c b/drivers/net/ethernet/sfc/efx_common.c
> index f6577e74d6e6..8802790403e9 100644
> --- a/drivers/net/ethernet/sfc/efx_common.c
> +++ b/drivers/net/ethernet/sfc/efx_common.c
> @@ -987,9 +987,6 @@ int efx_init_struct(struct efx_nic *efx,
>  	INIT_LIST_HEAD(&efx->node);
>  	INIT_LIST_HEAD(&efx->secondary_list);
>  	spin_lock_init(&efx->biu_lock);
> -#ifdef CONFIG_SFC_MTD
> -	INIT_LIST_HEAD(&efx->mtd_list);
> -#endif
>  	INIT_WORK(&efx->reset_work, efx_reset_work);
>  	INIT_DELAYED_WORK(&efx->monitor_work, efx_monitor);
>  	efx_selftest_async_init(efx);
> diff --git a/drivers/net/ethernet/sfc/mtd.c b/drivers/net/ethernet/sfc/mtd.c
> index 273c08e5455f..4d06e8a9a729 100644
> --- a/drivers/net/ethernet/sfc/mtd.c
> +++ b/drivers/net/ethernet/sfc/mtd.c
> @@ -12,6 +12,7 @@
>  
>  #include "net_driver.h"
>  #include "efx.h"
> +#include "mcdi.h"
>  
>  #define to_efx_mtd_partition(mtd)				\
>  	container_of(mtd, struct efx_mtd_partition, mtd)
> @@ -48,18 +49,16 @@ static void efx_mtd_remove_partition(struct efx_mtd_partition *part)
>  		ssleep(1);
>  	}
>  	WARN_ON(rc);
> -	list_del(&part->node);
>  }
>  
> -int efx_mtd_add(struct efx_nic *efx, struct efx_mtd_partition *parts,
> -		size_t n_parts, size_t sizeof_part)
> +int efx_mtd_add(struct efx_nic *efx, struct efx_mcdi_mtd_partition *parts,
> +		size_t n_parts)
>  {
>  	struct efx_mtd_partition *part;
>  	size_t i;
>  
>  	for (i = 0; i < n_parts; i++) {
> -		part = (struct efx_mtd_partition *)((char *)parts +
> -						    i * sizeof_part);
> +		part = &parts[i].common;
>  
>  		part->mtd.writesize = 1;
>  
> @@ -78,47 +77,38 @@ int efx_mtd_add(struct efx_nic *efx, struct efx_mtd_partition *parts,
>  
>  		if (mtd_device_register(&part->mtd, NULL, 0))
>  			goto fail;
> -
> -		/* Add to list in order - efx_mtd_remove() depends on this */
> -		list_add_tail(&part->node, &efx->mtd_list);
>  	}
>  
>  	return 0;
>  
>  fail:
> -	while (i--) {
> -		part = (struct efx_mtd_partition *)((char *)parts +
> -						    i * sizeof_part);
> -		efx_mtd_remove_partition(part);
> -	}
> +	while (i--)
> +		efx_mtd_remove_partition(&parts[i].common);
> +
>  	/* Failure is unlikely here, but probably means we're out of memory */
>  	return -ENOMEM;
>  }
>  
>  void efx_mtd_remove(struct efx_nic *efx)
>  {
> -	struct efx_mtd_partition *parts, *part, *next;
> +	int i;
>  
>  	WARN_ON(efx_dev_registered(efx));
>  
> -	if (list_empty(&efx->mtd_list))
> -		return;
> -
> -	parts = list_first_entry(&efx->mtd_list, struct efx_mtd_partition,
> -				 node);
> +	for (i = 0; i < efx->n_mcdi_mtd_parts; i++)
> +		efx_mtd_remove_partition(&efx->mcdi_mtd_parts[i].common);
>  
> -	list_for_each_entry_safe(part, next, &efx->mtd_list, node)
> -		efx_mtd_remove_partition(part);
> -
> -	kfree(parts);
> +	kfree(efx->mcdi_mtd_parts);
> +	efx->mcdi_mtd_parts = NULL;
> +	efx->n_mcdi_mtd_parts = 0;

It is safer to first set to NULL/0 before freeing the memory.
With this sequence bad things can happen if the thread gets descheduled
right after the kfree.

Martin

>  }
>  
>  void efx_mtd_rename(struct efx_nic *efx)
>  {
> -	struct efx_mtd_partition *part;
> +	int i;
>  
>  	ASSERT_RTNL();
>  
> -	list_for_each_entry(part, &efx->mtd_list, node)
> -		efx->type->mtd_rename(part);
> +	for (i = 0; i < efx->n_mcdi_mtd_parts; i++)
> +		efx->type->mtd_rename(&efx->mcdi_mtd_parts[i].common);
>  }
> diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
> index 318db906a154..5d20b25b0e82 100644
> --- a/drivers/net/ethernet/sfc/net_driver.h
> +++ b/drivers/net/ethernet/sfc/net_driver.h
> @@ -107,6 +107,8 @@ struct hwtstamp_config;
>  
>  struct efx_self_tests;
>  
> +struct efx_mcdi_mtd_partition;
> +
>  /**
>   * struct efx_buffer - A general-purpose DMA buffer
>   * @addr: host base address of the buffer
> @@ -865,7 +867,8 @@ enum efx_xdp_tx_queues_mode {
>   * @irq_zero_count: Number of legacy IRQs seen with queue flags == 0
>   * @irq_level: IRQ level/index for IRQs not triggered by an event queue
>   * @selftest_work: Work item for asynchronous self-test
> - * @mtd_list: List of MTDs attached to the NIC
> + * @mcdi_mtd_parts: Array of MTDs attached to the NIC
> + * @n_mcdi_mtd_parts: Number of MTDs attached to the NIC
>   * @nic_data: Hardware dependent state
>   * @mcdi: Management-Controller-to-Driver Interface state
>   * @mac_lock: MAC access lock. Protects @port_enabled, @phy_mode,
> @@ -1033,7 +1036,8 @@ struct efx_nic {
>  	struct delayed_work selftest_work;
>  
>  #ifdef CONFIG_SFC_MTD
> -	struct list_head mtd_list;
> +	struct efx_mcdi_mtd_partition *mcdi_mtd_parts;
> +	unsigned int n_mcdi_mtd_parts;
>  #endif
>  
>  	void *nic_data;
> @@ -1134,7 +1138,6 @@ static inline unsigned int efx_port_num(struct efx_nic *efx)
>  }
>  
>  struct efx_mtd_partition {
> -	struct list_head node;
>  	struct mtd_info mtd;
>  	const char *dev_type_name;
>  	const char *type_name;
> -- 
> 2.34.1

Powered by blists - more mailing lists