On 9 Dec 2016, at 12:37, Alan Stern wrote:
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.
Good call.
-/* 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.
Agreed. I’ll revise and re-submit.
Thanks!
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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