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mm: Add f_ops->populate()

RFC PATCH Superseded Jarkko Sakkinen 3 participants 9 messages Mar 6, 2022 – Mar 7, 2022

Subsystems (10)
DRM drivers Memory management VFS Intel i915 +6 more subsystems

v1 of 2 Superseded Latest is v2 →

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Jarkko Sakkinen

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#0 lore raw

RFC PATCH 1/1 mm: Add f_ops->populate()

Sometimes you might want to use MAP_POPULATE to ask a device driver to initialize the device memory in some specific manner. SGX driver can use this to request more memory by issuing ENCLS[EAUG] x86 opcode for each page in the address range.

Add f_ops->populate() with the same parameters as f_ops->mmap() and make it conditionally called inside call_mmap(). Update call sites accodingly.

Signed-off-by Jarkko Sakkinen <[email protected]>
---
 arch/mips/kernel/vdso.c                    |  2 +-
 drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c |  2 +-
 fs/coda/file.c                             |  2 +-
 fs/overlayfs/file.c                        |  2 +-
 include/linux/fs.h                         | 10 ++++++++--
 include/linux/mm.h                         |  2 +-
 ipc/shm.c                                  |  2 +-
 mm/mmap.c                                  | 10 +++++-----
 mm/nommu.c                                 |  4 ++--
 9 files changed, 21 insertions(+), 15 deletions(-)
arch/mips/kernel/vdso.c +1 -1
index 3d0cf471f2fe..89f3f3da9abd 100644
@@ -102,7 +102,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 		base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
 				VM_READ | VM_EXEC |
 				VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
-				0, NULL);
+				0, NULL, false);
 		if (IS_ERR_VALUE(base)) {
 			ret = base;
 			goto out;
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c +1 -1
index 1b526039a60d..4c71f64d6a79 100644
@@ -107,7 +107,7 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *
 	if (!obj->base.filp)
 		return -ENODEV;
 
-	ret = call_mmap(obj->base.filp, vma);
+	ret = call_mmap(obj->base.filp, vma, false);
 	if (ret)
 		return ret;
fs/coda/file.c +1 -1
index 29dd87be2fb8..e14f312fdbf8 100644
@@ -173,7 +173,7 @@ coda_file_mmap(struct file *coda_file, struct vm_area_struct *vma)
 	spin_unlock(&cii->c_lock);
 
 	vma->vm_file = get_file(host_file);
-	ret = call_mmap(vma->vm_file, vma);
+	ret = call_mmap(vma->vm_file, vma, false);
 
 	if (ret) {
 		/* if call_mmap fails, our caller will put host_file so we
fs/overlayfs/file.c +1 -1
index fa125feed0ff..b963a9397e80 100644
@@ -503,7 +503,7 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 	vma_set_file(vma, realfile);
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
-	ret = call_mmap(vma->vm_file, vma);
+	ret = call_mmap(vma->vm_file, vma, false);
 	revert_creds(old_cred);
 	ovl_file_accessed(file);
include/linux/fs.h +8 -2
index e2d892b201b0..fb90284e1c82 100644
@@ -1993,6 +1993,7 @@ struct file_operations {
 	long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
 	long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
 	int (*mmap) (struct file *, struct vm_area_struct *);
+	int (*populate)(struct file *, struct vm_area_struct *);
 	unsigned long mmap_supported_flags;
 	int (*open) (struct inode *, struct file *);
 	int (*flush) (struct file *, fl_owner_t id);

@@ -2074,9 +2075,14 @@ static inline ssize_t call_write_iter(struct file *file, struct kiocb *kio,
 	return file->f_op->write_iter(kio, iter);
 }
 
-static inline int call_mmap(struct file *file, struct vm_area_struct *vma)
+static inline int call_mmap(struct file *file, struct vm_area_struct *vma, bool do_populate)
 {
-	return file->f_op->mmap(file, vma);
+	int ret = file->f_op->mmap(file, vma);
+
+	if (!ret && do_populate)
+		ret = file->f_op->populate(file, vma);
+
+	return ret;
 }
 
 extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
include/linux/mm.h +1 -1
index 213cc569b192..6c8c036f423b 100644
@@ -2683,7 +2683,7 @@ extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned lo
 
 extern unsigned long mmap_region(struct file *file, unsigned long addr,
 	unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
-	struct list_head *uf);
+	struct list_head *uf, bool do_populate);
 extern unsigned long do_mmap(struct file *file, unsigned long addr,
 	unsigned long len, unsigned long prot, unsigned long flags,
 	unsigned long pgoff, unsigned long *populate, struct list_head *uf);
ipc/shm.c +1 -1
index b3048ebd5c31..89b28f32acf0 100644
@@ -587,7 +587,7 @@ static int shm_mmap(struct file *file, struct vm_area_struct *vma)
 	if (ret)
 		return ret;
 
-	ret = call_mmap(sfd->file, vma);
+	ret = call_mmap(sfd->file, vma, do_populate);
 	if (ret) {
 		shm_close(vma);
 		return ret;
mm/mmap.c +5 -5
index 1e8fdb0b51ed..5eca79957d4c 100644
@@ -1413,6 +1413,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
 			unsigned long flags, unsigned long pgoff,
 			unsigned long *populate, struct list_head *uf)
 {
+	bool do_populate = (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE;
 	struct mm_struct *mm = current->mm;
 	vm_flags_t vm_flags;
 	int pkey = 0;

@@ -1579,10 +1580,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
 			vm_flags |= VM_NORESERVE;
 	}
 
-	addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
+	addr = mmap_region(file, addr, len, vm_flags, pgoff, uf, do_populate);
 	if (!IS_ERR_VALUE(addr) &&
-	    ((vm_flags & VM_LOCKED) ||
-	     (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
+	    ((vm_flags & VM_LOCKED) || do_populate))
 		*populate = len;
 	return addr;
 }

@@ -1721,7 +1721,7 @@ static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
 
 unsigned long mmap_region(struct file *file, unsigned long addr,
 		unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
-		struct list_head *uf)
+		struct list_head *uf, bool do_populate)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma, *prev, *merge;

@@ -1790,7 +1790,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		}
 
 		vma->vm_file = get_file(file);
-		error = call_mmap(file, vma);
+		error = call_mmap(file, vma, do_populate);
 		if (error)
 			goto unmap_and_free_vma;
mm/nommu.c +2 -2
index 55a9e48a7a02..a3c20b803c27 100644
@@ -941,7 +941,7 @@ static int do_mmap_shared_file(struct vm_area_struct *vma)
 {
 	int ret;
 
-	ret = call_mmap(vma->vm_file, vma);
+	ret = call_mmap(vma->vm_file, vma, false);
 	if (ret == 0) {
 		vma->vm_region->vm_top = vma->vm_region->vm_end;
 		return 0;

@@ -972,7 +972,7 @@ static int do_mmap_private(struct vm_area_struct *vma,
 	 * - VM_MAYSHARE will be set if it may attempt to share
 	 */
 	if (capabilities & NOMMU_MAP_DIRECT) {
-		ret = call_mmap(vma->vm_file, vma);
+		ret = call_mmap(vma->vm_file, vma, false);
 		if (ret == 0) {
 			/* shouldn't return success if we're not sharing */
 			BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
Signature · 1 line
2.35.1
#1 lore raw
Quoted 8 lines · Jarkko Sakkinen

Sometimes you might want to use MAP_POPULATE to ask a device driver to initialize the device memory in some specific manner. SGX driver can use this to request more memory by issuing ENCLS[EAUG] x86 opcode for each page in the address range.

Add f_ops->populate() with the same parameters as f_ops->mmap() and make it conditionally called inside call_mmap(). Update call sites accodingly.

Your device driver has a ->mmap operation. Why does it need another one? More explanation required here.

author maintainer
#2 lore raw
Quoted 6 lines · Matthew Wilcox
Quoted 5 lines · Jarkko Sakkinen

Sometimes you might want to use MAP_POPULATE to ask a device driver to initialize the device memory in some specific manner. SGX driver can use this to request more memory by issuing ENCLS[EAUG] x86 opcode for each page in the address range.

Quoted 6 lines
Quoted 3 lines

Add f_ops->populate() with the same parameters as f_ops->mmap() and make it conditionally called inside call_mmap(). Update call sites accodingly.

Your device driver has a ->mmap operation. Why does it need another one? More explanation required here.

f_ops->mmap() would require an additional parameter, which results heavy refactoring.

struct file_operations has 1125 references in the kernel tree, so I decided to check this way around first.

BR, Jarkko

#3 lore raw
Quoted 11 lines · Jarkko Sakkinen
Quoted 10 lines · Matthew Wilcox
Quoted 8 lines · Jarkko Sakkinen

Sometimes you might want to use MAP_POPULATE to ask a device driver to initialize the device memory in some specific manner. SGX driver can use this to request more memory by issuing ENCLS[EAUG] x86 opcode for each page in the address range.

Add f_ops->populate() with the same parameters as f_ops->mmap() and make it conditionally called inside call_mmap(). Update call sites accodingly.

Quoted 8 lines
Quoted 2 lines

Your device driver has a ->mmap operation. Why does it need another one? More explanation required here.

f_ops->mmap() would require an additional parameter, which results heavy refactoring.

struct file_operations has 1125 references in the kernel tree, so I decided to check this way around first.

Are you saying that your device driver behaves differently if MAP_POPULATE is set versus if it isn't? That seems hideously broken.

author maintainer
#4 lore raw
Quoted 15 lines · Matthew Wilcox
Quoted 14 lines · Jarkko Sakkinen
Quoted 12 lines · Matthew Wilcox
Quoted 8 lines · Jarkko Sakkinen

Sometimes you might want to use MAP_POPULATE to ask a device driver to initialize the device memory in some specific manner. SGX driver can use this to request more memory by issuing ENCLS[EAUG] x86 opcode for each page in the address range.

Add f_ops->populate() with the same parameters as f_ops->mmap() and make it conditionally called inside call_mmap(). Update call sites accodingly.

Your device driver has a ->mmap operation. Why does it need another one? More explanation required here.

Quoted 8 lines
Quoted 5 lines

f_ops->mmap() would require an additional parameter, which results heavy refactoring.

struct file_operations has 1125 references in the kernel tree, so I decided to check this way around first.

Are you saying that your device driver behaves differently if MAP_POPULATE is set versus if it isn't? That seems hideously broken.

MAP_POPULATE does not do anything (according to __mm_populate in mm/gup.c) with VMA's that have some sort of device/IO memory, i.e. vm_flags intersecting with VM_PFNMAP | VM_IO.

I can extend the guard obviously to:

if (!ret && do_populate && file->f_op->populate &&

    !!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
        file->f_op->populate(file, vma);

BR, Jarkko

#5 lore raw
Quoted 29 lines · Jarkko Sakkinen
Quoted 15 lines · Matthew Wilcox
Quoted 14 lines · Jarkko Sakkinen
Quoted 12 lines · Matthew Wilcox
Quoted 8 lines · Jarkko Sakkinen

Sometimes you might want to use MAP_POPULATE to ask a device driver to initialize the device memory in some specific manner. SGX driver can use this to request more memory by issuing ENCLS[EAUG] x86 opcode for each page in the address range.

Add f_ops->populate() with the same parameters as f_ops->mmap() and make it conditionally called inside call_mmap(). Update call sites accodingly.

Your device driver has a ->mmap operation. Why does it need another one? More explanation required here.

Quoted 8 lines
Quoted 5 lines

f_ops->mmap() would require an additional parameter, which results heavy refactoring.

struct file_operations has 1125 references in the kernel tree, so I decided to check this way around first.

Are you saying that your device driver behaves differently if MAP_POPULATE is set versus if it isn't? That seems hideously broken.

MAP_POPULATE does not do anything (according to __mm_populate in mm/gup.c) with VMA's that have some sort of device/IO memory, i.e. vm_flags intersecting with VM_PFNMAP | VM_IO.

Quoted 5 lines

I can extend the guard obviously to:

if (!ret && do_populate && file->f_op->populate &&

    !!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
        file->f_op->populate(file, vma);

Are you deliberately avoiding the question? I'm not asking about implementation. I'm asking about the semantics of MAP_POPULATE with your driver.

author maintainer
#6 lore raw
Quoted 32 lines · Matthew Wilcox
Quoted 31 lines · Jarkko Sakkinen
Quoted 15 lines · Matthew Wilcox
Quoted 14 lines · Jarkko Sakkinen
Quoted 12 lines · Matthew Wilcox
Quoted 8 lines · Jarkko Sakkinen

Sometimes you might want to use MAP_POPULATE to ask a device driver to initialize the device memory in some specific manner. SGX driver can use this to request more memory by issuing ENCLS[EAUG] x86 opcode for each page in the address range.

Add f_ops->populate() with the same parameters as f_ops->mmap() and make it conditionally called inside call_mmap(). Update call sites accodingly.

Your device driver has a ->mmap operation. Why does it need another one? More explanation required here.

Quoted 8 lines
Quoted 5 lines

f_ops->mmap() would require an additional parameter, which results heavy refactoring.

struct file_operations has 1125 references in the kernel tree, so I decided to check this way around first.

Are you saying that your device driver behaves differently if MAP_POPULATE is set versus if it isn't? That seems hideously broken.

MAP_POPULATE does not do anything (according to __mm_populate in mm/gup.c) with VMA's that have some sort of device/IO memory, i.e. vm_flags intersecting with VM_PFNMAP | VM_IO.

I can extend the guard obviously to:

Quoted 7 lines
Quoted 3 lines

if (!ret && do_populate && file->f_op->populate &&

    !!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
        file->f_op->populate(file, vma);

Are you deliberately avoiding the question? I'm not asking about implementation. I'm asking about the semantics of MAP_POPULATE with your driver.

No. I just noticed a bug in the guard from your comment that I wanted point out.

With the next version I post the corresponding change to the driver, in order to see this in context.

BR, Jarkko

#7 lore raw
Quoted 9 lines · Jarkko Sakkinen
Quoted 3 lines

Are you deliberately avoiding the question? I'm not asking about implementation. I'm asking about the semantics of MAP_POPULATE with your driver.

No. I just noticed a bug in the guard from your comment that I wanted point out.

With the next version I post the corresponding change to the driver, in order to see this in context.

Oh, good grief. Don't bother. NAK.

CI
#8 lore raw

[Intel-gfx] ✗ Fi.CI.BUILD: failure for mm: Add f_ops->populate() (rev3)

In reply to Jarkko Sakkinen
== Series Details ==

== Series Details ==

Series: mm: Add f_ops->populate() (rev3)
URL : https://patchwork.freedesktop.org/series/101097/
State : failure

== Summary ==

CALL scripts/checksyscalls.sh
CALL scripts/atomic/check-atomics.sh
DESCEND objtool
CHK include/generated/compile.h
CC ipc/shm.o
ipc/shm.c: In function ‘shm_mmap’:
ipc/shm.c:590:34: error: ‘do_populate’ undeclared (first use in this function); did you mean ‘mm_populate’?

  ret = call_mmap(sfd->file, vma, do_populate);
                                  ^~~~~~~~~~~
                                  mm_populate

ipc/shm.c:590:34: note: each undeclared identifier is reported only once for each function it appears in scripts/Makefile.build:288: recipe for target 'ipc/shm.o' failed
make[1]: *** [ipc/shm.o] Error 1
Makefile:1831: recipe for target 'ipc' failed
make: *** [ipc] Error 2