Commit 65995e97 authored by Naman Jain's avatar Naman Jain Committed by Greg Kroah-Hartman
Browse files

Drivers: hv: Make the sysfs node size for the ring buffer dynamic 



The ring buffer size varies across VMBus channels. The size of sysfs
node for the ring buffer is currently hardcoded to 4 MB. Userspace
clients either use fstat() or hardcode this size for doing mmap().
To address this, make the sysfs node size dynamic to reflect the
actual ring buffer size for each channel. This will ensure that
fstat() on ring sysfs node always returns the correct size of
ring buffer.

Reviewed-by: default avatarMichael Kelley <mhklinux@outlook.com>
Tested-by: default avatarMichael Kelley <mhklinux@outlook.com>
Reviewed-by: default avatarDexuan Cui <decui@microsoft.com>
Signed-off-by: default avatarNaman Jain <namjain@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250502074811.2022-3-namjain@linux.microsoft.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f31fe816

drivers/hv/vmbus_drv.c

+10 −1
Original line number Diff line number Diff line
@@ -1820,7 +1820,6 @@ static struct bin_attribute chan_attr_ring_buffer = { 
		.name = "ring",

		.mode = 0600,

	},

	.size = 2 * SZ_2M,

	.mmap = hv_mmap_ring_buffer_wrapper,

};

static struct attribute *vmbus_chan_attrs[] = {
@@ -1880,11 +1879,21 @@ static umode_t vmbus_chan_bin_attr_is_visible(struct kobject *kobj, 
	return attr->attr.mode;

}



static size_t vmbus_chan_bin_size(struct kobject *kobj,

				  const struct bin_attribute *bin_attr, int a)

{

	const struct vmbus_channel *channel =

		container_of(kobj, struct vmbus_channel, kobj);



	return channel->ringbuffer_pagecount << PAGE_SHIFT;

}



static const struct attribute_group vmbus_chan_group = {

	.attrs = vmbus_chan_attrs,

	.bin_attrs = vmbus_chan_bin_attrs,

	.is_visible = vmbus_chan_attr_is_visible,

	.is_bin_visible = vmbus_chan_bin_attr_is_visible,

	.bin_size = vmbus_chan_bin_size,

};



static const struct kobj_type vmbus_chan_ktype = {