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USB: make the usbfs memory limit configurable

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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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern 2011-11-17 16:41:35 -05:00 committed by Greg Kroah-Hartman
parent add1aaeabe
commit 3f5eb8d568
2 changed files with 26 additions and 4 deletions
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4
Documentation/kernel-parameters.txt
View file

@ -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).

26
drivers/usb/core/devio.c
View file

@ -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;
}