[PATCH 00/10] Push the vm_fault_t conversion further

[PATCH 00/10] Push the vm_fault_t conversion further

[Matthew Wilcox]

This patch series reaps some of the benefits of the vm_fault_t work that
Souptick has been diligently plugging away at by converting insert_pfn()
to return a vm_fault_t.

Eventually, we'll be able to do the same thing to insert_page(),
but there's more work to be done converting all current callers of
vm_insert_page() to vmf_insert_page(), and this patch series provides
a nice clean-up.

Nicolas, I'd like your reviewed-by on patch 1 please.

Matthew Wilcox (10):
  cramfs: Convert to use vmf_insert_mixed
  mm: Remove vm_insert_mixed
  mm: Introduce vmf_insert_pfn_prot
  x86: Convert vdso to use vm_fault_t
  mm: Make vm_insert_pfn_prot static
  mm: Remove references to vm_insert_pfn
  mm: Remove vm_insert_pfn
  mm: Inline vm_insert_pfn_prot into caller
  mm: Convert __vm_insert_mixed to vm_fault_t
  mm: Convert insert_pfn to vm_fault_t

 Documentation/x86/pat.txt     |   4 +-
 arch/x86/entry/vdso/vma.c     |  24 +++----
 fs/cramfs/inode.c             |   9 ++-
 include/asm-generic/pgtable.h |   4 +-
 include/linux/hmm.h           |   2 +-
 include/linux/mm.h            |  32 +--------
 mm/memory.c                   | 122 +++++++++++++++++-----------------
 7 files changed, 84 insertions(+), 113 deletions(-)

-- 
2.18.0

[PATCH 01/10] cramfs: Convert to use vmf_insert_mixed

[Matthew Wilcox]

cramfs is the only remaining user of vm_insert_mixed; convert it.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 fs/cramfs/inode.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index f408994fc632..b72449c19cd1 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -417,10 +417,15 @@ static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 		 */
 		int i;
 		vma->vm_flags |= VM_MIXEDMAP;
-		for (i = 0; i < pages && !ret; i++) {
+		for (i = 0; i < pages; i++) {
+			vm_fault_t vmf;
 			unsigned long off = i * PAGE_SIZE;
 			pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
-			ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
+			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
+			if (vmf & VM_FAULT_ERROR) {
+				pages = i;
+				break;
+			}
 		}
 	}
 
-- 
2.18.0

[PATCH 02/10] mm: Remove vm_insert_mixed

[Matthew Wilcox]

All callers are now converted to vmf_insert_mixed() so convert
vmf_insert_mixed() from being a compatibility wrapper into the real
function.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 include/linux/mm.h | 15 +--------------
 mm/memory.c        | 14 ++++++++++----
 2 files changed, 11 insertions(+), 18 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a61ebe8ad4ca..ce1b24376d72 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2482,7 +2482,7 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn);
 int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn, pgprot_t pgprot);
-int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
+vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 			pfn_t pfn);
 vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
 		unsigned long addr, pfn_t pfn);
@@ -2501,19 +2501,6 @@ static inline vm_fault_t vmf_insert_page(struct vm_area_struct *vma,
 	return VM_FAULT_NOPAGE;
 }
 
-static inline vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma,
-				unsigned long addr, pfn_t pfn)
-{
-	int err = vm_insert_mixed(vma, addr, pfn);
-
-	if (err == -ENOMEM)
-		return VM_FAULT_OOM;
-	if (err < 0 && err != -EBUSY)
-		return VM_FAULT_SIGBUS;
-
-	return VM_FAULT_NOPAGE;
-}
-
 static inline vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma,
 			unsigned long addr, unsigned long pfn)
 {
diff --git a/mm/memory.c b/mm/memory.c
index c467102a5cbc..f0b123a94426 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1940,13 +1940,19 @@ static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 	return insert_pfn(vma, addr, pfn, pgprot, mkwrite);
 }
 
-int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
-			pfn_t pfn)
+vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
+		pfn_t pfn)
 {
-	return __vm_insert_mixed(vma, addr, pfn, false);
+	int err = __vm_insert_mixed(vma, addr, pfn, false);
 
+	if (err == -ENOMEM)
+		return VM_FAULT_OOM;
+	if (err < 0 && err != -EBUSY)
+		return VM_FAULT_SIGBUS;
+
+	return VM_FAULT_NOPAGE;
 }
-EXPORT_SYMBOL(vm_insert_mixed);
+EXPORT_SYMBOL(vmf_insert_mixed);
 
 /*
  *  If the insertion of PTE failed because someone else already added a
-- 
2.18.0

[PATCH 03/10] mm: Introduce vmf_insert_pfn_prot

[Matthew Wilcox]

Like vm_insert_pfn_prot(), but returns a vm_fault_t instead of an errno.
Also unexport vm_insert_pfn_prot as it has no modular users.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 include/linux/mm.h |  2 ++
 mm/memory.c        | 47 ++++++++++++++++++++++++++++++----------------
 2 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ce1b24376d72..e8bc1a16d44c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2482,6 +2482,8 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn);
 int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn, pgprot_t pgprot);
+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_mkwrite(struct vm_area_struct *vma,
diff --git a/mm/memory.c b/mm/memory.c
index f0b123a94426..8c116c0f64d8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1843,21 +1843,6 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 }
 EXPORT_SYMBOL(vm_insert_pfn);
 
-/**
- * vm_insert_pfn_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 vm_insert_pfn, except that it allows drivers to
- * to override pgprot on a per-page basis.
- *
- * This only makes sense for IO mappings, and it makes no sense for
- * cow mappings.  In general, using multiple vmas is preferable;
- * vm_insert_pfn_prot should only be used if using multiple VMAs is
- * impractical.
- */
 int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn, pgprot_t pgprot)
 {
@@ -1887,7 +1872,37 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 
 	return ret;
 }
-EXPORT_SYMBOL(vm_insert_pfn_prot);
+
+/**
+ * vmf_insert_pfn_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_pfn(), except that it allows drivers to
+ * to override pgprot on a per-page basis.
+ *
+ * This only makes sense for IO mappings, and it makes no sense for
+ * COW mappings.  In general, using multiple vmas is preferable;
+ * vm_insert_pfn_prot should only be used if using multiple VMAs is
+ * impractical.
+ *
+ * Return: vm_fault_t value.
+ */
+vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
+			unsigned long pfn, pgprot_t pgprot)
+{
+	int err = vm_insert_pfn_prot(vma, addr, pfn, pgprot);
+
+	if (err == -ENOMEM)
+		return VM_FAULT_OOM;
+	if (err < 0 && err != -EBUSY)
+		return VM_FAULT_SIGBUS;
+
+	return VM_FAULT_NOPAGE;
+}
+EXPORT_SYMBOL(vmf_insert_pfn_prot);
 
 static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)
 {
-- 
2.18.0

[PATCH 04/10] x86: Convert vdso to use vm_fault_t

[Matthew Wilcox]

Return vm_fault_t codes directly from the appropriate mm routines instead
of converting from errnos ourselves.  Fixes a minor bug where we'd return
SIGBUS instead of the correct OOM code if we ran out of memory allocating
page tables.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/entry/vdso/vma.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 5b8b556dbb12..d1daa53215a4 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -39,7 +39,7 @@ void __init init_vdso_image(const struct vdso_image *image)
 
 struct linux_binprm;
 
-static int vdso_fault(const struct vm_special_mapping *sm,
+static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
 		      struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	const struct vdso_image *image = vma->vm_mm->context.vdso_image;
@@ -84,12 +84,11 @@ static int vdso_mremap(const struct vm_special_mapping *sm,
 	return 0;
 }
 
-static int vvar_fault(const struct vm_special_mapping *sm,
+static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 		      struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	const struct vdso_image *image = vma->vm_mm->context.vdso_image;
 	long sym_offset;
-	int ret = -EFAULT;
 
 	if (!image)
 		return VM_FAULT_SIGBUS;
@@ -108,29 +107,24 @@ static int vvar_fault(const struct vm_special_mapping *sm,
 		return VM_FAULT_SIGBUS;
 
 	if (sym_offset == image->sym_vvar_page) {
-		ret = vm_insert_pfn(vma, vmf->address,
-				    __pa_symbol(&__vvar_page) >> PAGE_SHIFT);
+		return vmf_insert_pfn(vma, vmf->address,
+				__pa_symbol(&__vvar_page) >> PAGE_SHIFT);
 	} else if (sym_offset == image->sym_pvclock_page) {
 		struct pvclock_vsyscall_time_info *pvti =
 			pvclock_get_pvti_cpu0_va();
 		if (pvti && vclock_was_used(VCLOCK_PVCLOCK)) {
-			ret = vm_insert_pfn_prot(
-				vma,
-				vmf->address,
-				__pa(pvti) >> PAGE_SHIFT,
-				pgprot_decrypted(vma->vm_page_prot));
+			return vmf_insert_pfn_prot(vma, vmf->address,
+					__pa(pvti) >> PAGE_SHIFT,
+					pgprot_decrypted(vma->vm_page_prot));
 		}
 	} else if (sym_offset == image->sym_hvclock_page) {
 		struct ms_hyperv_tsc_page *tsc_pg = hv_get_tsc_page();
 
 		if (tsc_pg && vclock_was_used(VCLOCK_HVCLOCK))
-			ret = vm_insert_pfn(vma, vmf->address,
-					    vmalloc_to_pfn(tsc_pg));
+			return vmf_insert_pfn(vma, vmf->address,
+					vmalloc_to_pfn(tsc_pg));
 	}
 
-	if (ret == 0 || ret == -EBUSY)
-		return VM_FAULT_NOPAGE;
-
 	return VM_FAULT_SIGBUS;
 }
 
-- 
2.18.0

[PATCH 05/10] mm: Make vm_insert_pfn_prot static

[Matthew Wilcox]

Now this is no longer used outside mm/memory.c, make it static.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 include/linux/mm.h |  2 --
 mm/memory.c        | 50 +++++++++++++++++++++++-----------------------
 2 files changed, 25 insertions(+), 27 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e8bc1a16d44c..1552c67c835e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2480,8 +2480,6 @@ int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
 int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn);
-int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
-			unsigned long pfn, pgprot_t pgprot);
 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,
diff --git a/mm/memory.c b/mm/memory.c
index 8c116c0f64d8..8392a104a36d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1819,31 +1819,7 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 	return retval;
 }
 
-/**
- * vm_insert_pfn - insert single pfn into user vma
- * @vma: user vma to map to
- * @addr: target user address of this page
- * @pfn: source kernel pfn
- *
- * Similar to vm_insert_page, this allows drivers to insert individual pages
- * they've allocated into a user vma. Same comments apply.
- *
- * This function should only be called from a vm_ops->fault handler, and
- * in that case the handler should return NULL.
- *
- * vma cannot be a COW mapping.
- *
- * As this is called only for pages that do not currently exist, we
- * do not need to flush old virtual caches or the TLB.
- */
-int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
-			unsigned long pfn)
-{
-	return vm_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
-}
-EXPORT_SYMBOL(vm_insert_pfn);
-
-int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
+static int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn, pgprot_t pgprot)
 {
 	int ret;
@@ -1873,6 +1849,30 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 	return ret;
 }
 
+/**
+ * vm_insert_pfn - insert single pfn into user vma
+ * @vma: user vma to map to
+ * @addr: target user address of this page
+ * @pfn: source kernel pfn
+ *
+ * Similar to vm_insert_page, this allows drivers to insert individual pages
+ * they've allocated into a user vma. Same comments apply.
+ *
+ * This function should only be called from a vm_ops->fault handler, and
+ * in that case the handler should return NULL.
+ *
+ * vma cannot be a COW mapping.
+ *
+ * As this is called only for pages that do not currently exist, we
+ * do not need to flush old virtual caches or the TLB.
+ */
+int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+			unsigned long pfn)
+{
+	return vm_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
+}
+EXPORT_SYMBOL(vm_insert_pfn);
+
 /**
  * vmf_insert_pfn_prot - insert single pfn into user vma with specified pgprot
  * @vma: user vma to map to
-- 
2.18.0

[PATCH 06/10] mm: Remove references to vm_insert_pfn

[Matthew Wilcox]

Documentation and comments.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 Documentation/x86/pat.txt     | 4 ++--
 include/asm-generic/pgtable.h | 4 ++--
 include/linux/hmm.h           | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt
index 2a4ee6302122..481d8d8536ac 100644
--- a/Documentation/x86/pat.txt
+++ b/Documentation/x86/pat.txt
@@ -90,12 +90,12 @@ pci proc               |    --    |    --      |       WC         |
 Advanced APIs for drivers
 -------------------------
 A. Exporting pages to users with remap_pfn_range, io_remap_pfn_range,
-vm_insert_pfn
+vmf_insert_pfn
 
 Drivers wanting to export some pages to userspace do it by using mmap
 interface and a combination of
 1) pgprot_noncached()
-2) io_remap_pfn_range() or remap_pfn_range() or vm_insert_pfn()
+2) io_remap_pfn_range() or remap_pfn_range() or vmf_insert_pfn()
 
 With PAT support, a new API pgprot_writecombine is being added. So, drivers can
 continue to use the above sequence, with either pgprot_noncached() or
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 88ebc6102c7c..5657a20e0c59 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -757,7 +757,7 @@ static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
 /*
  * Interfaces that can be used by architecture code to keep track of
  * memory type of pfn mappings specified by the remap_pfn_range,
- * vm_insert_pfn.
+ * vmf_insert_pfn.
  */
 
 /*
@@ -773,7 +773,7 @@ static inline int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
 
 /*
  * track_pfn_insert is called when a _new_ single pfn is established
- * by vm_insert_pfn().
+ * by vmf_insert_pfn().
  */
 static inline void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
 				    pfn_t pfn)
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 4c92e3ba3e16..dde947083d4e 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -107,7 +107,7 @@ enum hmm_pfn_flag_e {
  * HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory
  * HMM_PFN_NONE: corresponding CPU page table entry is pte_none()
  * HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e., the
- *      result of vm_insert_pfn() or vm_insert_page(). Therefore, it should not
+ *      result of vmf_insert_pfn() or vm_insert_page(). Therefore, it should not
  *      be mirrored by a device, because the entry will never have HMM_PFN_VALID
  *      set and the pfn value is undefined.
  *
-- 
2.18.0

[PATCH 07/10] mm: Remove vm_insert_pfn

[Matthew Wilcox]

All callers are now converted to vmf_insert_pfn so convert
vmf_insert_pfn() from being a compatibility wrapper around vm_insert_pfn()
to being a compatibility wrapper around vmf_insert_pfn_prot().

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 include/linux/mm.h | 15 +------------
 mm/memory.c        | 54 +++++++++++++++++++++++++---------------------
 2 files changed, 30 insertions(+), 39 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1552c67c835e..bd5e2469b637 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2478,7 +2478,7 @@ struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
 int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
 			unsigned long pfn, unsigned long size, pgprot_t);
 int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
-int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn);
 vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn, pgprot_t pgprot);
@@ -2501,19 +2501,6 @@ static inline vm_fault_t vmf_insert_page(struct vm_area_struct *vma,
 	return VM_FAULT_NOPAGE;
 }
 
-static inline vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma,
-			unsigned long addr, unsigned long pfn)
-{
-	int err = vm_insert_pfn(vma, addr, pfn);
-
-	if (err == -ENOMEM)
-		return VM_FAULT_OOM;
-	if (err < 0 && err != -EBUSY)
-		return VM_FAULT_SIGBUS;
-
-	return VM_FAULT_NOPAGE;
-}
-
 static inline vm_fault_t vmf_error(int err)
 {
 	if (err == -ENOMEM)
diff --git a/mm/memory.c b/mm/memory.c
index 8392a104a36d..d5ccbadd81c1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1849,30 +1849,6 @@ static int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 	return ret;
 }
 
-/**
- * vm_insert_pfn - insert single pfn into user vma
- * @vma: user vma to map to
- * @addr: target user address of this page
- * @pfn: source kernel pfn
- *
- * Similar to vm_insert_page, this allows drivers to insert individual pages
- * they've allocated into a user vma. Same comments apply.
- *
- * This function should only be called from a vm_ops->fault handler, and
- * in that case the handler should return NULL.
- *
- * vma cannot be a COW mapping.
- *
- * As this is called only for pages that do not currently exist, we
- * do not need to flush old virtual caches or the TLB.
- */
-int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
-			unsigned long pfn)
-{
-	return vm_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
-}
-EXPORT_SYMBOL(vm_insert_pfn);
-
 /**
  * vmf_insert_pfn_prot - insert single pfn into user vma with specified pgprot
  * @vma: user vma to map to
@@ -1885,9 +1861,10 @@ EXPORT_SYMBOL(vm_insert_pfn);
  *
  * This only makes sense for IO mappings, and it makes no sense for
  * COW mappings.  In general, using multiple vmas is preferable;
- * vm_insert_pfn_prot should only be used if using multiple VMAs is
+ * vmf_insert_pfn_prot should only be used if using multiple VMAs is
  * impractical.
  *
+ * Context: Process context.  May allocate using %GFP_KERNEL.
  * Return: vm_fault_t value.
  */
 vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
@@ -1904,6 +1881,33 @@ vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 }
 EXPORT_SYMBOL(vmf_insert_pfn_prot);
 
+/**
+ * vmf_insert_pfn - insert single pfn into user vma
+ * @vma: user vma to map to
+ * @addr: target user address of this page
+ * @pfn: source kernel pfn
+ *
+ * Similar to vm_insert_page, this allows drivers to insert individual pages
+ * they've allocated into a user vma. Same comments apply.
+ *
+ * This function should only be called from a vm_ops->fault handler, and
+ * in that case the handler should return the result of this function.
+ *
+ * vma cannot be a COW mapping.
+ *
+ * As this is called only for pages that do not currently exist, we
+ * do not need to flush old virtual caches or the TLB.
+ *
+ * Context: Process context.  May allocate using %GFP_KERNEL.
+ * Return: vm_fault_t value.
+ */
+vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+			unsigned long pfn)
+{
+	return vmf_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
+}
+EXPORT_SYMBOL(vmf_insert_pfn);
+
 static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)
 {
 	/* these checks mirror the abort conditions in vm_normal_page */
-- 
2.18.0

[PATCH 08/10] mm: Inline vm_insert_pfn_prot into caller

[Matthew Wilcox]

vm_insert_pfn_prot() is only called from vmf_insert_pfn_prot(),
so inline it and convert some of the errnos into vm_fault codes earlier.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 mm/memory.c | 55 +++++++++++++++++++++++------------------------------
 1 file changed, 24 insertions(+), 31 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index d5ccbadd81c1..9e97926fee19 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1819,36 +1819,6 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 	return retval;
 }
 
-static int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
-			unsigned long pfn, pgprot_t pgprot)
-{
-	int ret;
-	/*
-	 * Technically, architectures with pte_special can avoid all these
-	 * restrictions (same for remap_pfn_range).  However we would like
-	 * consistency in testing and feature parity among all, so we should
-	 * try to keep these invariants in place for everybody.
-	 */
-	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
-	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
-						(VM_PFNMAP|VM_MIXEDMAP));
-	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
-	BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
-
-	if (addr < vma->vm_start || addr >= vma->vm_end)
-		return -EFAULT;
-
-	if (!pfn_modify_allowed(pfn, pgprot))
-		return -EACCES;
-
-	track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV));
-
-	ret = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot,
-			false);
-
-	return ret;
-}
-
 /**
  * vmf_insert_pfn_prot - insert single pfn into user vma with specified pgprot
  * @vma: user vma to map to
@@ -1870,7 +1840,30 @@ static int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn, pgprot_t pgprot)
 {
-	int err = vm_insert_pfn_prot(vma, addr, pfn, pgprot);
+	int err;
+
+	/*
+	 * Technically, architectures with pte_special can avoid all these
+	 * restrictions (same for remap_pfn_range).  However we would like
+	 * consistency in testing and feature parity among all, so we should
+	 * try to keep these invariants in place for everybody.
+	 */
+	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
+	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
+						(VM_PFNMAP|VM_MIXEDMAP));
+	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
+	BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
+
+	if (addr < vma->vm_start || addr >= vma->vm_end)
+		return VM_FAULT_SIGBUS;
+
+	if (!pfn_modify_allowed(pfn, pgprot))
+		return VM_FAULT_SIGBUS;
+
+	track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV));
+
+	err = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot,
+			false);
 
 	if (err == -ENOMEM)
 		return VM_FAULT_OOM;
-- 
2.18.0

[PATCH 09/10] mm: Convert __vm_insert_mixed to vm_fault_t

[Matthew Wilcox]

Both of its callers currently convert its errno return into a
vm_fault_t, so move the conversion into __vm_insert_mixed.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 mm/memory.c | 36 +++++++++++++++---------------------
 1 file changed, 15 insertions(+), 21 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 9e97926fee19..9fef202b4ea7 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1915,20 +1915,21 @@ static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)
 	return false;
 }
 
-static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
-			pfn_t pfn, bool mkwrite)
+static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma,
+		unsigned long addr, pfn_t pfn, bool mkwrite)
 {
 	pgprot_t pgprot = vma->vm_page_prot;
+	int err;
 
 	BUG_ON(!vm_mixed_ok(vma, pfn));
 
 	if (addr < vma->vm_start || addr >= vma->vm_end)
-		return -EFAULT;
+		return VM_FAULT_SIGBUS;
 
 	track_pfn_insert(vma, &pgprot, pfn);
 
 	if (!pfn_modify_allowed(pfn_t_to_pfn(pfn), pgprot))
-		return -EACCES;
+		return VM_FAULT_SIGBUS;
 
 	/*
 	 * If we don't have pte special, then we have to use the pfn_valid()
@@ -1947,15 +1948,10 @@ static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 		 * result in pfn_t_has_page() == false.
 		 */
 		page = pfn_to_page(pfn_t_to_pfn(pfn));
-		return insert_page(vma, addr, page, pgprot);
+		err = insert_page(vma, addr, page, pgprot);
+	} else {
+		err = insert_pfn(vma, addr, pfn, pgprot, mkwrite);
 	}
-	return insert_pfn(vma, addr, pfn, pgprot, mkwrite);
-}
-
-vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
-		pfn_t pfn)
-{
-	int err = __vm_insert_mixed(vma, addr, pfn, false);
 
 	if (err == -ENOMEM)
 		return VM_FAULT_OOM;
@@ -1964,6 +1960,12 @@ vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 
 	return VM_FAULT_NOPAGE;
 }
+
+vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
+		pfn_t pfn)
+{
+	return __vm_insert_mixed(vma, addr, pfn, false);
+}
 EXPORT_SYMBOL(vmf_insert_mixed);
 
 /*
@@ -1971,18 +1973,10 @@ EXPORT_SYMBOL(vmf_insert_mixed);
  *  different entry in the mean time, we treat that as success as we assume
  *  the same entry was actually inserted.
  */
-
 vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
 		unsigned long addr, pfn_t pfn)
 {
-	int err;
-
-	err =  __vm_insert_mixed(vma, addr, pfn, true);
-	if (err == -ENOMEM)
-		return VM_FAULT_OOM;
-	if (err < 0 && err != -EBUSY)
-		return VM_FAULT_SIGBUS;
-	return VM_FAULT_NOPAGE;
+	return __vm_insert_mixed(vma, addr, pfn, true);
 }
 EXPORT_SYMBOL(vmf_insert_mixed_mkwrite);
 
-- 
2.18.0

[PATCH 10/10] mm: Convert insert_pfn to vm_fault_t

[Matthew Wilcox]

All callers convert its errno into a vm_fault_t, so convert it to
return a vm_fault_t directly.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 mm/memory.c | 24 +++++-------------------
 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 9fef202b4ea7..368b65390762 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1767,19 +1767,16 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
 }
 EXPORT_SYMBOL(vm_insert_page);
 
-static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 			pfn_t pfn, pgprot_t prot, bool mkwrite)
 {
 	struct mm_struct *mm = vma->vm_mm;
-	int retval;
 	pte_t *pte, entry;
 	spinlock_t *ptl;
 
-	retval = -ENOMEM;
 	pte = get_locked_pte(mm, addr, &ptl);
 	if (!pte)
-		goto out;
-	retval = -EBUSY;
+		return VM_FAULT_OOM;
 	if (!pte_none(*pte)) {
 		if (mkwrite) {
 			/*
@@ -1812,11 +1809,9 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 	set_pte_at(mm, addr, pte, entry);
 	update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
 
-	retval = 0;
 out_unlock:
 	pte_unmap_unlock(pte, ptl);
-out:
-	return retval;
+	return VM_FAULT_NOPAGE;
 }
 
 /**
@@ -1840,8 +1835,6 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn, pgprot_t pgprot)
 {
-	int err;
-
 	/*
 	 * Technically, architectures with pte_special can avoid all these
 	 * restrictions (same for remap_pfn_range).  However we would like
@@ -1862,15 +1855,8 @@ vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 
 	track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV));
 
-	err = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot,
+	return insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot,
 			false);
-
-	if (err == -ENOMEM)
-		return VM_FAULT_OOM;
-	if (err < 0 && err != -EBUSY)
-		return VM_FAULT_SIGBUS;
-
-	return VM_FAULT_NOPAGE;
 }
 EXPORT_SYMBOL(vmf_insert_pfn_prot);
 
@@ -1950,7 +1936,7 @@ static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma,
 		page = pfn_to_page(pfn_t_to_pfn(pfn));
 		err = insert_page(vma, addr, page, pgprot);
 	} else {
-		err = insert_pfn(vma, addr, pfn, pgprot, mkwrite);
+		return insert_pfn(vma, addr, pfn, pgprot, mkwrite);
 	}
 
 	if (err == -ENOMEM)
-- 
2.18.0

Re: [PATCH 01/10] cramfs: Convert to use vmf_insert_mixed

[Nicolas Pitre]

On Tue, 28 Aug 2018, Matthew Wilcox wrote:

> cramfs is the only remaining user of vm_insert_mixed; convert it.
> 
> Signed-off-by: Matthew Wilcox <willy@infradead.org>
> ---
>  fs/cramfs/inode.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> index f408994fc632..b72449c19cd1 100644
> --- a/fs/cramfs/inode.c
> +++ b/fs/cramfs/inode.c
> @@ -417,10 +417,15 @@ static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
>  		 */
>  		int i;
>  		vma->vm_flags |= VM_MIXEDMAP;
> -		for (i = 0; i < pages && !ret; i++) {
> +		for (i = 0; i < pages; i++) {
> +			vm_fault_t vmf;
>  			unsigned long off = i * PAGE_SIZE;
>  			pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
> -			ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
> +			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
> +			if (vmf & VM_FAULT_ERROR) {
> +				pages = i;
> +				break;
> +			}

I'd suggest this to properly deal with errers instead:

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index f408994fc6..0c35e62f10 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -418,9 +418,12 @@ static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 		int i;
 		vma->vm_flags |= VM_MIXEDMAP;
 		for (i = 0; i < pages && !ret; i++) {
+			vm_fault_t vmf;
 			unsigned long off = i * PAGE_SIZE;
 			pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
-			ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
+			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
+			if (vmf & VM_FAULT_ERROR)
+				ret = vm_fault_to_errno(vmf, 0);
 		}
 	}
 

Nicolas

Re: [PATCH 01/10] cramfs: Convert to use vmf_insert_mixed

[Matthew Wilcox]

On Tue, Aug 28, 2018 at 01:49:25PM -0400, Nicolas Pitre wrote:
> On Tue, 28 Aug 2018, Matthew Wilcox wrote:
> > -			ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
> > +			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
> > +			if (vmf & VM_FAULT_ERROR) {
> > +				pages = i;
> > +				break;
> > +			}
> 
> I'd suggest this to properly deal with errers instead:
> 
> -			ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
> +			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
> +			if (vmf & VM_FAULT_ERROR)
> +				ret = vm_fault_to_errno(vmf, 0);

By my reading of this function, the intent is actually to return 0
here and allow demand paging to work.  Of course, I've spent all of
twenty minutes staring at this function, so I defer to the maintainer.
I think you'd need to be running a make-memory-allocations-fail fuzzer
to hit this, so it's likely never been tested.

Re: [PATCH 01/10] cramfs: Convert to use vmf_insert_mixed

[Nicolas Pitre]

On Tue, 28 Aug 2018, Matthew Wilcox wrote:

> On Tue, Aug 28, 2018 at 01:49:25PM -0400, Nicolas Pitre wrote:
> > On Tue, 28 Aug 2018, Matthew Wilcox wrote:
> > > -			ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
> > > +			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
> > > +			if (vmf & VM_FAULT_ERROR) {
> > > +				pages = i;
> > > +				break;
> > > +			}
> > 
> > I'd suggest this to properly deal with errers instead:
> > 
> > -			ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
> > +			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
> > +			if (vmf & VM_FAULT_ERROR)
> > +				ret = vm_fault_to_errno(vmf, 0);
> 
> By my reading of this function, the intent is actually to return 0
> here and allow demand paging to work.  Of course, I've spent all of
> twenty minutes staring at this function, so I defer to the maintainer.

Demand paging is used when the filesystem layout isn't amenable to a 
direct mapping.  It is not a fallback for when we're OOM or some other 
internal errors which ought to be reported immediately.

> I think you'd need to be running a make-memory-allocations-fail fuzzer
> to hit this, so it's likely never been tested.

Well, it has been tested sort of, e.g. when vm_insert_mixed() returned 
an error due to misaligned addresses during development.  Normally, 
vm_insert_mixed() and vmf_insert_mixed() should always succeed, and if 
they don't we certainly don't want to ignore it.


Nicolas