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SubjectRe: [Linux-kernel-mentees] [PATCH v2] PCI: sysfs: Change bus_rescan and dev_rescan to rescan
Hi Kelsey,

On Wed, Mar 25, 2020 at 09:17:08AM -0600, Kelsey Skunberg wrote:
> From: Kelsey Skunberg <kelsey.skunberg@gmail.com>
>
> rename device attribute name arguments 'bus_rescan' and 'dev_rescan' to 'rescan'
> to avoid breaking userspace applications.
>
> The attribute argument names were changed in the following commits:
> 8bdfa145f582 ("PCI: sysfs: Define device attributes with DEVICE_ATTR*()")
> 4e2b79436e4f ("PCI: sysfs: Change DEVICE_ATTR() to DEVICE_ATTR_WO()")
>
> Revert the names used for attributes back to the names used before the above
> patches were applied. This also requires to change DEVICE_ATTR_WO() to
> DEVICE_ATTR() and __ATTR().
>
> Note when using DEVICE_ATTR() the attribute is automatically named
> dev_attr_<name>.attr. To avoid duplicated names between attributes, use
> __ATTR() instead of DEVICE_ATTR() to a assign a custom attribute name for
> dev_rescan.
>
> change bus_rescan_store() to dev_bus_rescan_store() to complete matching the
> names used before the mentioned patches were applied.
>
> Fixes: 8bdfa145f582 ("PCI: sysfs: Define device attributes with DEVICE_ATTR*()")
> Fixes: 4e2b79436e4f ("PCI: sysfs: Change DEVICE_ATTR() to DEVICE_ATTR_WO()")
>
> Cc: stable <stable@vger.kernel.org>
> Signed-off-by: Kelsey Skunberg <kelsey.skunberg@gmail.com>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>
> v2 updates:
> commit log updated to include 'Fixes: *' and Cc: stable to aid commit
> being backported properly.
>
> drivers/pci/pci-sysfs.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 13f766db0684..667e13d597ff 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -464,7 +464,10 @@ static ssize_t dev_rescan_store(struct device *dev,
> }
> return count;
> }
> -static DEVICE_ATTR_WO(dev_rescan);
> +static struct device_attribute dev_rescan_attr = __ATTR(rescan,
> + 0220, NULL,
> + dev_rescan_store);
> +
>
> static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
> const char *buf, size_t count)
> @@ -481,9 +484,9 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
> static DEVICE_ATTR_IGNORE_LOCKDEP(remove, 0220, NULL,
> remove_store);
>
> -static ssize_t bus_rescan_store(struct device *dev,
> - struct device_attribute *attr,
> - const char *buf, size_t count)
> +static ssize_t dev_bus_rescan_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> {
> unsigned long val;
> struct pci_bus *bus = to_pci_bus(dev);
> @@ -501,7 +504,7 @@ static ssize_t bus_rescan_store(struct device *dev,
> }
> return count;
> }
> -static DEVICE_ATTR_WO(bus_rescan);
> +static DEVICE_ATTR(rescan, 0220, NULL, dev_bus_rescan_store);
>
> #if defined(CONFIG_PM) && defined(CONFIG_ACPI)
> static ssize_t d3cold_allowed_store(struct device *dev,
> @@ -641,7 +644,7 @@ static struct attribute *pcie_dev_attrs[] = {
> };
>
> static struct attribute *pcibus_attrs[] = {
> - &dev_attr_bus_rescan.attr,
> + &dev_attr_rescan.attr,
> &dev_attr_cpuaffinity.attr,
> &dev_attr_cpulistaffinity.attr,
> NULL,
> @@ -1487,7 +1490,7 @@ static umode_t pci_dev_attrs_are_visible(struct kobject *kobj,
>
> static struct attribute *pci_dev_hp_attrs[] = {
> &dev_attr_remove.attr,
> - &dev_attr_dev_rescan.attr,
> + &dev_rescan_attr.attr,
> NULL,
> };

Thanks for taking care of this! Two questions:

1) You supplied permissions of 0220, but DEVICE_ATTR_WO()
uses__ATTR_WO(), which uses 0200. Shouldn't we keep 0200?

2) I think the use of __ATTR() for the device side and DEVICE_ATTR()
for the bus side is confusing. Couldn't we accomplish the same thing
with a patch like the following (compiled but not tested)?

Bjorn


commit 06094b3fd9f1 ("PCI: sysfs: Revert "rescan" file renames")
Author: Kelsey Skunberg <kelsey.skunberg@gmail.com>
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.

The argument to DEVICE_ATTR_WO() determines both the struct
device_attribute name and the .store() function name. We have to
use __ATTR() so we can specify different .store() functions for
the two "rescan" files.

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

[bhelgaas: commit log]
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@gmail.com
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@gmail.com>
Cc: stable@vger.kernel.org # v5.4+

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 13f766db0684..bf025a2c296d 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,
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