mm: remove unused vmf_insert_mixed_prot()

Patch series "Remove drm/ttm-specific mm changes".

Functionality was added specifically for the DRM TTM driver to support
mapping memory for VM_MIXEDMAP VMAs with customised protection flags,
however this has now been rolled back as issues were found with this
approach.

This series removes the mm changes too, retaining some of the useful
comments.

This patch (of 3):

The sole user of vmf_insert_mixed_prot(), the drm ttm module, stopped
using this in commit f91142c62161 ("drm/ttm: nuke VM_MIXEDMAP on BO
mappings v3") citing use of VM_MIXEDMAP in this case being terribly
broken.

Remove this now-dead code and references to it, but retain the useful
description of the prot != vma->vm_page_prot case, moving it to
vmf_insert_pfn_prot() instead.

Link: https://lkml.kernel.org/r/cover.1678661628.git.lstoakes@gmail.com
Link: https://lkml.kernel.org/r/a069644388e6f1593a7020d15840e6fc9f39bcaf.1678661628.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Aaron Tomlin <atomlin@atomlin.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index c3abad7e6ccbdedaef0009e827a038f41884706c..55d02356146c355de346d120d512964073a1171a 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3179,8 +3179,6 @@ vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
                        unsigned long pfn, pgprot_t pgprot);
 vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
                        pfn_t pfn);
-vm_fault_t vmf_insert_mixed_prot(struct vm_area_struct *vma, unsigned long addr,
-                       pfn_t pfn, pgprot_t pgprot);
 vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
                unsigned long addr, pfn_t pfn);
 int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len);

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0722859c36478d92f06455c6841144a7bfe5d207..651a5c256732fb46e51176ef6fa48f162c3c9f0b 100644 (file)
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -485,12 +485,7 @@ struct vm_area_struct {
                                           within vm_mm. */
 
        struct mm_struct *vm_mm;        /* The address space we belong to. */
-
-       /*
-        * Access permissions of this VMA.
-        * See vmf_insert_mixed_prot() for discussion.
-        */
-       pgprot_t vm_page_prot;
+       pgprot_t vm_page_prot;          /* Access permissions of this VMA. */
 
        /*
         * Flags, see mm.h.

diff --git a/mm/memory.c b/mm/memory.c
index 0ee13d3de88cd1bab6979b5860e99bb1de9a801f..7716f2cc4b6877527120454aae4a6d8f99b532ad 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2165,8 +2165,20 @@ out_unlock:
  * vmf_insert_pfn_prot should only be used if using multiple VMAs is
  * impractical.
  *
- * See vmf_insert_mixed_prot() for a discussion of the implication of using
- * a value of @pgprot different from that of @vma->vm_page_prot.
+ * pgprot typically only differs from @vma->vm_page_prot when drivers set
+ * caching- and encryption bits different than those of @vma->vm_page_prot,
+ * because the caching- or encryption mode may not be known at mmap() time.
+ *
+ * This is ok as long as @vma->vm_page_prot is not used by the core vm
+ * to set caching and encryption bits for those vmas (except for COW pages).
+ * This is ensured by core vm only modifying these page table entries using
+ * functions that don't touch caching- or encryption bits, using pte_modify()
+ * if needed. (See for example mprotect()).
+ *
+ * Also when new page-table entries are created, this is only done using the
+ * fault() callback, and never using the value of vma->vm_page_prot,
+ * except for page-table entries that point to anonymous pages as the result
+ * of COW.
  *
  * Context: Process context.  May allocate using %GFP_KERNEL.
  * Return: vm_fault_t value.
@@ -2241,9 +2253,9 @@ static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)
 }
 
 static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma,
-               unsigned long addr, pfn_t pfn, pgprot_t pgprot,
-               bool mkwrite)
+               unsigned long addr, pfn_t pfn, bool mkwrite)
 {
+       pgprot_t pgprot = vma->vm_page_prot;
        int err;
 
        BUG_ON(!vm_mixed_ok(vma, pfn));
@@ -2286,43 +2298,10 @@ static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma,
        return VM_FAULT_NOPAGE;
 }
 
-/**
- * vmf_insert_mixed_prot - insert single pfn into user vma with specified pgprot
- * @vma: user vma to map to
- * @addr: target user address of this page
- * @pfn: source kernel pfn
- * @pgprot: pgprot flags for the inserted page
- *
- * This is exactly like vmf_insert_mixed(), except that it allows drivers
- * to override pgprot on a per-page basis.
- *
- * Typically this function should be used by drivers to set caching- and
- * encryption bits different than those of @vma->vm_page_prot, because
- * the caching- or encryption mode may not be known at mmap() time.
- * This is ok as long as @vma->vm_page_prot is not used by the core vm
- * to set caching and encryption bits for those vmas (except for COW pages).
- * This is ensured by core vm only modifying these page table entries using
- * functions that don't touch caching- or encryption bits, using pte_modify()
- * if needed. (See for example mprotect()).
- * Also when new page-table entries are created, this is only done using the
- * fault() callback, and never using the value of vma->vm_page_prot,
- * except for page-table entries that point to anonymous pages as the result
- * of COW.
- *
- * Context: Process context.  May allocate using %GFP_KERNEL.
- * Return: vm_fault_t value.
- */
-vm_fault_t vmf_insert_mixed_prot(struct vm_area_struct *vma, unsigned long addr,
-                                pfn_t pfn, pgprot_t pgprot)
-{
-       return __vm_insert_mixed(vma, addr, pfn, pgprot, false);
-}
-EXPORT_SYMBOL(vmf_insert_mixed_prot);
-
 vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
                pfn_t pfn)
 {
-       return __vm_insert_mixed(vma, addr, pfn, vma->vm_page_prot, false);
+       return __vm_insert_mixed(vma, addr, pfn, false);
 }
 EXPORT_SYMBOL(vmf_insert_mixed);
 
@@ -2334,7 +2313,7 @@ EXPORT_SYMBOL(vmf_insert_mixed);
 vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
                unsigned long addr, pfn_t pfn)
 {
-       return __vm_insert_mixed(vma, addr, pfn, vma->vm_page_prot, true);
+       return __vm_insert_mixed(vma, addr, pfn, true);
 }
 EXPORT_SYMBOL(vmf_insert_mixed_mkwrite);