Re: [PATCH v3 0/2] Allow deferred execution of iomem_get_mapping()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Aug 05, 2021 at 02:43:46PM +0200, Greg Kroah-Hartman wrote:
> On Fri, Jul 30, 2021 at 02:50:13PM -0500, Bjorn Helgaas wrote:
> > On Fri, Jul 30, 2021 at 07:06:26AM +0200, Greg Kroah-Hartman wrote:
> > > On Thu, Jul 29, 2021 at 11:32:33PM +0000, Krzysztof Wilczyński wrote:
> > > > Hello,
> > > > 
> > > > At the moment, the dependency on iomem_get_mapping() that is currently
> > > > used in the pci_create_resource_files() and pci_create_legacy_files()
> > > > stops us from completely retiring the late_initcall() that is used to
> > > > invoke pci_sysfs_init() when creating sysfs object for PCI devices.
> > > > 
> > > > This dependency on iomem_get_mapping() stops us from retiring the
> > > > late_initcall at the moment as when we convert dynamically added sysfs
> > > > objects, that are primarily added in the pci_create_resource_files() and
> > > > pci_create_legacy_files(), as these attributes are added before the VFS
> > > > completes its initialisation, and since most of the PCI devices are
> > > > typically enumerated in subsys_initcall this leads to a failure and an
> > > > Oops related to iomem_get_mapping() access.
> > > > 
> > > > See relevant conversations:
> > > >   https://lore.kernel.org/linux-pci/20210204165831.2703772-1-daniel.vetter@ffwll.ch/
> > > >   https://lore.kernel.org/linux-pci/20210313215747.GA2394467@bjorn-Precision-5520/
> > > > 
> > > > After some deliberation about the problem at hand, Dan Williams
> > > > suggested a solution to the problem, as per:
> > > >   https://lore.kernel.org/linux-pci/CAPcyv4i0y_4cMGEpNVShLUyUk3nyWH203Ry3S87BqnDJE0Rmxg@mail.gmail.com/
> > > > 
> > > > The idea is to defer execution of the iomem_get_mapping() to only when
> > > > the sysfs open callback is run, and thus removing the reliance of
> > > > fs_initcalls to complete before any other sub-system that uses the
> > > > iomem_get_mapping().
> > > > 
> > > > Currently, the PCI sub-system will benefit the most from this change
> > > > allowing for it to complete the transition from dynamically created to
> > > > static sysfs objects.
> > > > 
> > > > This series aims to take Dan Williams' idea through the finish line.
> > > > 
> > > > Related to:
> > > >   https://lore.kernel.org/linux-pci/20210527205845.GA1421476@bjorn-Precision-5520/
> > > >   https://lore.kernel.org/linux-pci/20210507102706.7658-1-danijel.slivka@amd.com/
> > > >   https://lore.kernel.org/linux-pci/20200716110423.xtfyb3n6tn5ixedh@pali/
> > > > 
> > > > 	Krzysztof
> > > > 
> > > 
> > > No objection from me on these, Bjorn, mind if I take them through my
> > > driver core tree?
> > 
> > That'd be great!
> > 
> > Is your tree immutable?  I'm hoping we can take advantage of this to
> > get rid of pci_sysfs_init(), which will fix a race that people seem to
> > be hitting frequently now [1].  I think Krzysztof is getting pretty
> > close.
> > 
> > [1] https://lore.kernel.org/r/m3eebg9puj.fsf@t19.piap.pl
> 
> Yes, my tree is immutable.  Let me create a branch just for this that
> you can pull from after it passes 0-day...

Ok, here you go, a signed tag for you to pull from:


The following changes since commit ff1176468d368232b684f75e82563369208bc371:

  Linux 5.14-rc3 (2021-07-25 15:35:14 -0700)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git tags/sysfs_defferred_iomem_get_mapping-5.15

for you to fetch changes up to f06aff924f975881a6abf91d2af0078fc8cd37bf:

  sysfs: Rename struct bin_attribute member to f_mapping (2021-08-05 14:47:31 +0200)

----------------------------------------------------------------
sysfs: Allow deferred execution of iomem_get_mapping()

Tag for toerh trees/branches to pull from in order to have a stable base
to build off of for the "Allow deferred execution of
iomem_get_mapping()" set of sysfs changes

Link: https://lore.kernel.org/r/20210729233235.1508920-1-kw@linux.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

----------------------------------------------------------------
Krzysztof Wilczyński (2):
      sysfs: Invoke iomem_get_mapping() from the sysfs open callback
      sysfs: Rename struct bin_attribute member to f_mapping

 drivers/pci/pci-sysfs.c | 6 +++---
 fs/sysfs/file.c         | 4 ++--
 include/linux/sysfs.h   | 2 +-
 3 files changed, 6 insertions(+), 6 deletions(-)