From 93bb8e352a9136a56dd26762bf54cf6554cfa96c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Krzysztof=20Wilczy=C5=84ski?= <kw@linux.com>
Date: Thu, 29 Jul 2021 23:32:34 +0000
Subject: [PATCH] sysfs: Invoke iomem_get_mapping() from the sysfs open
 callback
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Git-commit: 93bb8e352a9136a56dd26762bf54cf6554cfa96c
References: jsc#SLE-19359
Patch-mainline: v5.15-rc1

Defer invocation of the iomem_get_mapping() to the sysfs open callback
so that it can be executed as needed when the binary sysfs object has
been accessed.

To do that, convert the "mapping" member of the struct bin_attribute
from a pointer to the struct address_space into a function pointer with
a signature that requires the same return type, and then updates the
sysfs_kf_bin_open() to invoke provided function should the function
pointer be valid.

Also, convert every invocation of iomem_get_mapping() into a function
pointer assignment, therefore allowing for the iomem_get_mapping()
invocation to be deferred to when the sysfs open callback runs.

Thus, this change removes the need for the fs_initcalls to complete
before any other sub-system that uses the iomem_get_mapping() would be
able to invoke it safely without leading to a failure and an Oops
related to an invalid iomem_get_mapping() access.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Link: https://lore.kernel.org/r/20210729233235.1508920-2-kw@linux.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/pci/pci-sysfs.c |    6 +++---
 fs/sysfs/file.c         |    2 +-
 include/linux/sysfs.h   |    2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -965,7 +965,7 @@ void pci_create_legacy_files(struct pci_
 	b->legacy_io->read = pci_read_legacy_io;
 	b->legacy_io->write = pci_write_legacy_io;
 	b->legacy_io->mmap = pci_mmap_legacy_io;
-	b->legacy_io->mapping = iomem_get_mapping();
+	b->legacy_io->mapping = iomem_get_mapping;
 	pci_adjust_legacy_attr(b, pci_mmap_io);
 	error = device_create_bin_file(&b->dev, b->legacy_io);
 	if (error)
@@ -978,7 +978,7 @@ void pci_create_legacy_files(struct pci_
 	b->legacy_mem->size = 1024*1024;
 	b->legacy_mem->attr.mode = 0600;
 	b->legacy_mem->mmap = pci_mmap_legacy_mem;
-	b->legacy_mem->mapping = iomem_get_mapping();
+	b->legacy_mem->mapping = iomem_get_mapping;
 	pci_adjust_legacy_attr(b, pci_mmap_mem);
 	error = device_create_bin_file(&b->dev, b->legacy_mem);
 	if (error)
@@ -1195,7 +1195,7 @@ static int pci_create_attr(struct pci_de
 		}
 	}
 	if (res_attr->mmap)
-		res_attr->mapping = iomem_get_mapping();
+		res_attr->mapping = iomem_get_mapping;
 	res_attr->attr.name = res_attr_name;
 	res_attr->attr.mode = 0600;
 	res_attr->size = pci_resource_len(pdev, num);
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -175,7 +175,7 @@ static int sysfs_kf_bin_open(struct kern
 	struct bin_attribute *battr = of->kn->priv;
 
 	if (battr->mapping)
-		of->file->f_mapping = battr->mapping;
+		of->file->f_mapping = battr->mapping();
 
 	return 0;
 }
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -176,7 +176,7 @@ struct bin_attribute {
 	struct attribute	attr;
 	size_t			size;
 	void			*private;
-	struct address_space	*mapping;
+	struct address_space *(*mapping)(void);
 	ssize_t (*read)(struct file *, struct kobject *, struct bin_attribute *,
 			char *, loff_t, size_t);
 	ssize_t (*write)(struct file *, struct kobject *, struct bin_attribute *,