Re: [Linux-kernel-mentees] [PATCH v2] PCI: sysfs: Change bus_rescan and dev_rescan to rescan

From: Bjorn Helgaas
Date: Sat Mar 28 2020 - 16:06:38 EST


On Thu, Mar 26, 2020 at 07:35:24AM +0100, Greg KH wrote:
> On Wed, Mar 25, 2020 at 05:10:33PM -0500, Bjorn Helgaas wrote:
> > -static DEVICE_ATTR_WO(dev_rescan);
> > +static struct device_attribute dev_attr_dev_rescan = __ATTR(rescan, 0200, NULL,
> > + dev_rescan_store);
>
> Oops, this should just be DEVICE_ATTR(), no need for __ATTR() as this
> isn't a kobject-only file.
>
> So how about:
>
> static DEVICE_ATTR(rescan, 0200, NULL, dev_rescan_store);

I don' think DEVICE_ATTR() works in this case because it uses the
first argument ("rescan") to build both the C symbol for the
device_attribute struct and the sysfs filename.

There are two instances in this file. The two sysfs "rescan" files
are not a problem, but the two "dev_attr_rescan_name" C symbols *are*.
We could resolve that by putting the bus attributes in a different
source file than the dev attributes, but it doesn't seem worth it now.

I tentatively have the patch below on pci/misc. I dropped the
tested-by and reviewed-by because I didn't want to put words in your
mouths :)

Bjorn

commit bce34ce1806e ("PCI: sysfs: Revert "rescan" file renames")
Author: Kelsey Skunberg <kelsey.skunberg@xxxxxxxxx>
Date: Wed Mar 25 09:17:08 2020 -0600

PCI: sysfs: Revert "rescan" file renames

We changed these sysfs filenames:

.../pci_bus/<domain:bus>/rescan -> .../pci_bus/<domain:bus>/bus_rescan
.../<domain:bus:dev.fn>/rescan -> .../<domain:bus:dev.fn>/dev_rescan

and Ruslan reported [1] that this broke a userspace application.

Revert these name changes so both files are named "rescan" again.

Note that we have to use __ATTR() to assign custom C symbols, i.e.,
"struct device_attribute <symbol>".

[1] https://lore.kernel.org/r/CAB=otbSYozS-ZfxB0nCiNnxcbqxwrHOSYxJJtDKa63KzXbXgpw@xxxxxxxxxxxxxx

[bhelgaas: commit log, use __ATTR() both places so we don't have to rename
the attributes]
Fixes: 8bdfa145f582 ("PCI: sysfs: Define device attributes with DEVICE_ATTR*()")
Fixes: 4e2b79436e4f ("PCI: sysfs: Change DEVICE_ATTR() to DEVICE_ATTR_WO()")
Link: https://lore.kernel.org/r/20200325151708.32612-1-skunberg.kelsey@xxxxxxxxx
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@xxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v5.4+

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 13f766db0684..335dd6fbf039 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -464,7 +464,8 @@ static ssize_t dev_rescan_store(struct device *dev,
}
return count;
}
-static DEVICE_ATTR_WO(dev_rescan);
+static struct device_attribute dev_attr_dev_rescan = __ATTR(rescan, 0200, NULL,
+ dev_rescan_store);

static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
@@ -501,7 +502,8 @@ static ssize_t bus_rescan_store(struct device *dev,
}
return count;
}
-static DEVICE_ATTR_WO(bus_rescan);
+static struct device_attribute dev_attr_bus_rescan = __ATTR(rescan, 0200, NULL,
+ bus_rescan_store);

#if defined(CONFIG_PM) && defined(CONFIG_ACPI)
static ssize_t d3cold_allowed_store(struct device *dev,