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Commit 3f5eb8d5 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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USB: make the usbfs memory limit configurable 



The 16-MB global limit on memory used by usbfs isn't suitable for all
people.  It's a reasonable default, but there are applications
(especially for SuperSpeed devices) that need a lot more.

This patch (as1498) creates a writable module parameter for usbcore to
control the global limit.  The default is still 16 MB, but users can
change it at runtime, even after usbcore has been loaded.  As a
special case, setting the value to 0 is treated the same as the hard
limit of 2047 MB.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent add1aaea

Documentation/kernel-parameters.txt

+4 −0
Original line number Diff line number Diff line
@@ -2632,6 +2632,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			[USB] Start with the old device initialization

			scheme (default 0 = off).



	usbcore.usbfs_memory_mb=

			[USB] Memory limit (in MB) for buffers allocated by

			usbfs (default = 16, 0 = max = 2047).



	usbcore.use_both_schemes=

			[USB] Try the other device initialization scheme

			if the first one fails (default 1 = enabled).

drivers/usb/core/devio.c

+22 −4
Original line number Diff line number Diff line
@@ -110,15 +110,33 @@ enum snoop_when { 
#define USB_DEVICE_DEV		MKDEV(USB_DEVICE_MAJOR, 0)



/* Limit on the total amount of memory we can allocate for transfers */

#define MAX_USBFS_MEMORY_USAGE	16777216	/* 16 MB */

static unsigned usbfs_memory_mb = 16;

module_param(usbfs_memory_mb, uint, 0644);

MODULE_PARM_DESC(usbfs_memory_mb,

		"maximum MB allowed for usbfs buffers (0 = no limit)");



/* Hard limit, necessary to avoid aithmetic overflow */

#define USBFS_XFER_MAX		(UINT_MAX / 2 - 1000000)



static atomic_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)

{

	unsigned lim;



	/*

	 * Convert usbfs_memory_mb to bytes, avoiding overflows.

	 * 0 means use the hard limit (effectively unlimited).

	 */

	lim = ACCESS_ONCE(usbfs_memory_mb);

	if (lim == 0 || lim > (USBFS_XFER_MAX >> 20))

		lim = USBFS_XFER_MAX;

	else

		lim <<= 20;



	atomic_add(amount, &usbfs_memory_usage);

	if (atomic_read(&usbfs_memory_usage) <= MAX_USBFS_MEMORY_USAGE)

	if (atomic_read(&usbfs_memory_usage) <= lim)

		return 0;

	atomic_sub(amount, &usbfs_memory_usage);

	return -ENOMEM;
@@ -907,7 +925,7 @@ static int proc_bulk(struct dev_state *ps, void __user *arg) 
	if (!usb_maxpacket(dev, pipe, !(bulk.ep & USB_DIR_IN)))

		return -EINVAL;

	len1 = bulk.len;

	if (len1 > MAX_USBFS_MEMORY_USAGE)

	if (len1 >= USBFS_XFER_MAX)

		return -EINVAL;

	ret = usbfs_increase_memory_usage(len1 + sizeof(struct urb));

	if (ret)
@@ -1227,7 +1245,7 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb, 
		return -EINVAL;

	}



	if (uurb->buffer_length > MAX_USBFS_MEMORY_USAGE) {

	if (uurb->buffer_length >= USBFS_XFER_MAX) {

		ret = -EINVAL;

		goto error;

	}