From: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Date: Wed, 17 Sep 2025 19:11:14 +0000 (+0100)
Subject: mm: add shmem_zero_setup_desc()
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=895cf51d60e80241952594d569e0a28d500885f7;p=users%2Fjedix%2Flinux-maple.git

mm: add shmem_zero_setup_desc()

Add the ability to set up a shared anonymous mapping based on a VMA
descriptor rather than a VMA.

This is a prerequisite for converting to the char mm driver to use the
mmap_prepare hook.

Link: https://lkml.kernel.org/r/fe4367c705612574477374ffac8497add2655e43.1758135681.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Chatre, Reinette <reinette.chatre@intel.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Dave Martin <dave.martin@arm.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Morse <james.morse@arm.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nicolas Pitre <nico@fluxnic.net>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Robin Murohy <robin.murphy@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 0e47465ef0fd..5b368f9549d6 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -94,7 +94,8 @@ extern struct file *shmem_kernel_file_setup(const char *name, loff_t size,
 					    unsigned long flags);
 extern struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt,
 		const char *name, loff_t size, unsigned long flags);
-extern int shmem_zero_setup(struct vm_area_struct *);
+int shmem_zero_setup(struct vm_area_struct *vma);
+int shmem_zero_setup_desc(struct vm_area_desc *desc);
 extern unsigned long shmem_get_unmapped_area(struct file *, unsigned long addr,
 		unsigned long len, unsigned long pgoff, unsigned long flags);
 extern int shmem_lock(struct file *file, int lock, struct ucounts *ucounts);
diff --git a/mm/shmem.c b/mm/shmem.c
index 4f0d0e8386c5..45f51745ad88 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -5879,14 +5879,9 @@ struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
 }
 EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt);
 
-/**
- * shmem_zero_setup - setup a shared anonymous mapping
- * @vma: the vma to be mmapped is prepared by do_mmap
- */
-int shmem_zero_setup(struct vm_area_struct *vma)
+static struct file *__shmem_zero_setup(unsigned long start, unsigned long end, vm_flags_t vm_flags)
 {
-	struct file *file;
-	loff_t size = vma->vm_end - vma->vm_start;
+	loff_t size = end - start;
 
 	/*
 	 * Cloning a new file under mmap_lock leads to a lock ordering conflict
@@ -5894,7 +5889,18 @@ int shmem_zero_setup(struct vm_area_struct *vma)
 	 * accessible to the user through its mapping, use S_PRIVATE flag to
 	 * bypass file security, in the same way as shmem_kernel_file_setup().
 	 */
-	file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags);
+	return shmem_kernel_file_setup("dev/zero", size, vm_flags);
+}
+
+/**
+ * shmem_zero_setup - setup a shared anonymous mapping
+ * @vma: the vma to be mmapped is prepared by do_mmap
+ * Returns: 0 on success, or error
+ */
+int shmem_zero_setup(struct vm_area_struct *vma)
+{
+	struct file *file = __shmem_zero_setup(vma->vm_start, vma->vm_end, vma->vm_flags);
+
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 
@@ -5906,6 +5912,25 @@ int shmem_zero_setup(struct vm_area_struct *vma)
 	return 0;
 }
 
+/**
+ * shmem_zero_setup_desc - same as shmem_zero_setup, but determined by VMA
+ * descriptor for convenience.
+ * @desc: Describes VMA
+ * Returns: 0 on success, or error
+ */
+int shmem_zero_setup_desc(struct vm_area_desc *desc)
+{
+	struct file *file = __shmem_zero_setup(desc->start, desc->end, desc->vm_flags);
+
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	desc->vm_file = file;
+	desc->vm_ops = &shmem_anon_vm_ops;
+
+	return 0;
+}
+
 /**
  * shmem_read_folio_gfp - read into page cache, using specified page allocation flags.
  * @mapping:	the folio's address_space