From 65995e97a1caacf0024bebda3332b8d1f0f443c4 Mon Sep 17 00:00:00 2001 From: Naman Jain Date: Fri, 2 May 2025 13:18:11 +0530 Subject: [PATCH] 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: Michael Kelley Tested-by: Michael Kelley Reviewed-by: Dexuan Cui Signed-off-by: Naman Jain Link: https://lore.kernel.org/r/20250502074811.2022-3-namjain@linux.microsoft.com Signed-off-by: Greg Kroah-Hartman --- drivers/hv/vmbus_drv.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 0f16a83cc2d6b..e3d51a3163163 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -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 = { -- 2.47.2