Re: [PATCH v4 2/7] PCI: endpoint: Improve pci_epc_mem_alloc_addr()

[Niklas Cassel <cassel@kernel.org>]

On Mon, Oct 07, 2024 at 01:03:14PM +0900, Damien Le Moal wrote:
> There is no point in attempting to allocate memory from an endpoint
> controller memory window if the requested size is larger than the memory
> window size. Add a check to skip bitmap_find_free_region() calls for
> such case. This check can be done without the mem->lock mutex held as
> memory window sizes are constant and never modified at runtime.
> Also change the final return to return NULL to simplify the code.
> 
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>  drivers/pci/endpoint/pci-epc-mem.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/endpoint/pci-epc-mem.c b/drivers/pci/endpoint/pci-epc-mem.c
> index a9c028f58da1..218a60e945db 100644
> --- a/drivers/pci/endpoint/pci-epc-mem.c
> +++ b/drivers/pci/endpoint/pci-epc-mem.c
> @@ -178,7 +178,7 @@ EXPORT_SYMBOL_GPL(pci_epc_mem_exit);
>  void __iomem *pci_epc_mem_alloc_addr(struct pci_epc *epc,
>  				     phys_addr_t *phys_addr, size_t size)
>  {
> -	void __iomem *virt_addr = NULL;
> +	void __iomem *virt_addr;
>  	struct pci_epc_mem *mem;
>  	unsigned int page_shift;
>  	size_t align_size;
> @@ -188,10 +188,13 @@ void __iomem *pci_epc_mem_alloc_addr(struct pci_epc *epc,
>  
>  	for (i = 0; i < epc->num_windows; i++) {
>  		mem = epc->windows[i];
> -		mutex_lock(&mem->lock);
> +		if (size > mem->window.size)
> +			continue;
> +
>  		align_size = ALIGN(size, mem->window.page_size);
>  		order = pci_epc_mem_get_order(mem, align_size);
>  
> +		mutex_lock(&mem->lock);
>  		pageno = bitmap_find_free_region(mem->bitmap, mem->pages,
>  						 order);
>  		if (pageno >= 0) {
> @@ -211,7 +214,7 @@ void __iomem *pci_epc_mem_alloc_addr(struct pci_epc *epc,
>  		mutex_unlock(&mem->lock);
>  	}
>  
> -	return virt_addr;
> +	return NULL;
>  }
>  EXPORT_SYMBOL_GPL(pci_epc_mem_alloc_addr);
>  
> -- 
> 2.46.2
> 

Reviewed-by: Niklas Cassel <cassel@kernel.org>