On Fri, 9 Dec 2016, Mateusz Berezecki wrote:
> This patch promotes a variable keeping track of USB transfer memory
> usage to a wider data type, allowing higher bandwidth transfers from a
> large number of USB devices connected to a single host.
>
> Signed-off-by: Mateusz Berezecki <mateuszb@xxxxxxxxxxx>
> ---
> drivers/usb/core/devio.c | 24 ++++++++++++------------
> 1 file changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
> index 4016dae..ca4c8581 100644
> --- a/drivers/usb/core/devio.c
> +++ b/drivers/usb/core/devio.c
> @@ -134,20 +134,20 @@ enum snoop_when {
> #define USB_DEVICE_DEV MKDEV(USB_DEVICE_MAJOR, 0)
>
> /* Limit on the total amount of memory we can allocate for transfers */
> -static unsigned usbfs_memory_mb = 16;
> -module_param(usbfs_memory_mb, uint, 0644);
> +static u64 usbfs_memory_mb = 16;
> +module_param(usbfs_memory_mb, ullong, 0644);
> MODULE_PARM_DESC(usbfs_memory_mb,
> "maximum MB allowed for usbfs buffers (0 = no limit)");
This parameter can remain a 32-bit quantity, since it gives the memory
limit in MB.
> -/* Hard limit, necessary to avoid arithmetic overflow */
> -#define USBFS_XFER_MAX (UINT_MAX / 2 - 1000000)
> +/* Hard limit */
> +#define USBFS_XFER_MAX (1ull << 32)
Only 4 GB? Why not allow a lot higher? This only doubles the existing
hard limit, roughly. In theory this could be as large as (1ull << 52)
-- that's about 4 billion MB, or if you prefer, 4 million GB.
The rest of the patch looks okay.
Alan Stern
> -static atomic_t usbfs_memory_usage; /* Total memory currently allocated */
> +static atomic64_t usbfs_memory_usage; /* Total memory currently allocated */
>
> /* Check whether it's okay to allocate more memory for a transfer */
> -static int usbfs_increase_memory_usage(unsigned amount)
> +static int usbfs_increase_memory_usage(u64 amount)
> {
> - unsigned lim;
> + u64 lim;
>
> /*
> * Convert usbfs_memory_mb to bytes, avoiding overflows.
> @@ -159,17 +159,17 @@ static int usbfs_increase_memory_usage(unsigned amount)
> else
> lim <<= 20;
>
> - atomic_add(amount, &usbfs_memory_usage);
> - if (atomic_read(&usbfs_memory_usage) <= lim)
> + atomic64_add(amount, &usbfs_memory_usage);
> + if (atomic64_read(&usbfs_memory_usage) <= lim)
> return 0;
> - atomic_sub(amount, &usbfs_memory_usage);
> + atomic64_sub(amount, &usbfs_memory_usage);
> return -ENOMEM;
> }
>
> /* Memory for a transfer is being deallocated */
> -static void usbfs_decrease_memory_usage(unsigned amount)
> +static void usbfs_decrease_memory_usage(u64 amount)
> {
> - atomic_sub(amount, &usbfs_memory_usage);
> + atomic64_sub(amount, &usbfs_memory_usage);
> }
>
> static int connected(struct usb_dev_state *ps)
--
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