[merged mm-stable] mm-various-small-mmap_prepare-cleanups.patch removed from -mm tree

[merged mm-stable] mm-various-small-mmap_prepare-cleanups.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm: various small mmap_prepare cleanups
has been removed from the -mm tree.  Its filename was
     mm-various-small-mmap_prepare-cleanups.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: "Lorenzo Stoakes (Oracle)" <ljs@kernel.org>
Subject: mm: various small mmap_prepare cleanups
Date: Fri, 20 Mar 2026 22:39:27 +0000

Patch series "mm: expand mmap_prepare functionality and usage", v4.

This series expands the mmap_prepare functionality, which is intended to
replace the deprecated f_op->mmap hook which has been the source of bugs
and security issues for some time.

This series starts with some cleanup of existing mmap_prepare logic, then
adds documentation for the mmap_prepare call to make it easier for
filesystem and driver writers to understand how it works.

It then importantly adds a vm_ops->mapped hook, a key feature that was
missing from mmap_prepare previously - this is invoked when a driver which
specifies mmap_prepare has successfully been mapped but not merged with
another VMA.

mmap_prepare is invoked prior to a merge being attempted, so you cannot
manipulate state such as reference counts as if it were a new mapping.

The vm_ops->mapped hook allows a driver to perform tasks required at this
stage, and provides symmetry against subsequent vm_ops->open,close calls.

The series uses this to correct the afs implementation which wrongly
manipulated reference count at mmap_prepare time.

It then adds an mmap_prepare equivalent of vm_iomap_memory() -
mmap_action_simple_ioremap(), then uses this to update a number of drivers.

It then splits out the mmap_prepare compatibility layer (which allows for
invocation of mmap_prepare hooks in an mmap() hook) in such a way as to
allow for more incremental implementation of mmap_prepare hooks.

It then uses this to extend mmap_prepare usage in drivers.

Finally it adds an mmap_prepare equivalent of vm_map_pages(), which lays
the foundation for future work which will extend mmap_prepare to DMA
coherent mappings.


This patch (of 21):

Rather than passing arbitrary fields, pass a vm_area_desc pointer to mmap
prepare functions to mmap prepare, and an action and vma pointer to mmap
complete in order to put all the action-specific logic in the function
actually doing the work.

Additionally, allow mmap prepare functions to return an error so we can
error out as soon as possible if there is something logically incorrect in
the input.

Update remap_pfn_range_prepare() to properly check the input range for the
CoW case.

Also remove io_remap_pfn_range_complete(), as we can simply set up the
fields correctly in io_remap_pfn_range_prepare() and use
remap_pfn_range_complete() for this.

While we're here, make remap_pfn_range_prepare_vma() a little neater, and
pass mmap_action directly to call_action_complete().

Then, update compat_vma_mmap() to perform its logic directly, as
__compat_vma_map() is not used by anything so we don't need to export it.

Also update compat_vma_mmap() to use vfs_mmap_prepare() rather than
calling the mmap_prepare op directly.

Finally, update the VMA userland tests to reflect the changes.

Link: https://lkml.kernel.org/r/cover.1774045440.git.ljs@kernel.org
Link: https://lkml.kernel.org/r/99f408e4694f44ab12bdc55fe0bd9685d3bd1117.1774045440.git.ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bodo Stroesser <bostroesser@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: David Hildenbrand <david@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Long Li <longli@microsoft.com>
Cc: Marc Dionne <marc.dionne@auristor.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Richard Weinberger <richard@nod.at>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/fs.h                |    2 
 include/linux/mm.h                |    7 -
 mm/internal.h                     |   34 ++++---
 mm/memory.c                       |   45 ++++++----
 mm/util.c                         |  121 ++++++++++++----------------
 mm/vma.c                          |   24 +++--
 tools/testing/vma/include/dup.h   |    7 +
 tools/testing/vma/include/stubs.h |    8 -
 8 files changed, 127 insertions(+), 121 deletions(-)

--- a/include/linux/fs.h~mm-various-small-mmap_prepare-cleanups
+++ a/include/linux/fs.h
@@ -2058,8 +2058,6 @@ static inline bool can_mmap_file(struct
 	return true;
 }
 
-int __compat_vma_mmap(const struct file_operations *f_op,
-		struct file *file, struct vm_area_struct *vma);
 int compat_vma_mmap(struct file *file, struct vm_area_struct *vma);
 
 static inline int vfs_mmap(struct file *file, struct vm_area_struct *vma)
--- a/include/linux/mm.h~mm-various-small-mmap_prepare-cleanups
+++ a/include/linux/mm.h
@@ -4304,10 +4304,9 @@ static inline void mmap_action_ioremap_f
 	mmap_action_ioremap(desc, desc->start, start_pfn, vma_desc_size(desc));
 }
 
-void mmap_action_prepare(struct mmap_action *action,
-			 struct vm_area_desc *desc);
-int mmap_action_complete(struct mmap_action *action,
-			 struct vm_area_struct *vma);
+int mmap_action_prepare(struct vm_area_desc *desc);
+int mmap_action_complete(struct vm_area_struct *vma,
+			 struct mmap_action *action);
 
 /* Look up the first VMA which exactly match the interval vm_start ... vm_end */
 static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
--- a/mm/internal.h~mm-various-small-mmap_prepare-cleanups
+++ a/mm/internal.h
@@ -1839,26 +1839,28 @@ int walk_page_range_debug(struct mm_stru
 void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm);
 int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm);
 
-void remap_pfn_range_prepare(struct vm_area_desc *desc, unsigned long pfn);
-int remap_pfn_range_complete(struct vm_area_struct *vma, unsigned long addr,
-		unsigned long pfn, unsigned long size, pgprot_t pgprot);
+int remap_pfn_range_prepare(struct vm_area_desc *desc);
+int remap_pfn_range_complete(struct vm_area_struct *vma,
+			     struct mmap_action *action);
 
-static inline void io_remap_pfn_range_prepare(struct vm_area_desc *desc,
-		unsigned long orig_pfn, unsigned long size)
+static inline int io_remap_pfn_range_prepare(struct vm_area_desc *desc)
 {
+	struct mmap_action *action = &desc->action;
+	const unsigned long orig_pfn = action->remap.start_pfn;
+	const pgprot_t orig_pgprot = action->remap.pgprot;
+	const unsigned long size = action->remap.size;
 	const unsigned long pfn = io_remap_pfn_range_pfn(orig_pfn, size);
+	int err;
 
-	return remap_pfn_range_prepare(desc, pfn);
-}
-
-static inline int io_remap_pfn_range_complete(struct vm_area_struct *vma,
-		unsigned long addr, unsigned long orig_pfn, unsigned long size,
-		pgprot_t orig_prot)
-{
-	const unsigned long pfn = io_remap_pfn_range_pfn(orig_pfn, size);
-	const pgprot_t prot = pgprot_decrypted(orig_prot);
-
-	return remap_pfn_range_complete(vma, addr, pfn, size, prot);
+	action->remap.start_pfn = pfn;
+	action->remap.pgprot = pgprot_decrypted(orig_pgprot);
+	err = remap_pfn_range_prepare(desc);
+	if (err)
+		return err;
+
+	/* Remap does the actual work. */
+	action->type = MMAP_REMAP_PFN;
+	return 0;
 }
 
 #ifdef CONFIG_MMU_NOTIFIER
--- a/mm/memory.c~mm-various-small-mmap_prepare-cleanups
+++ a/mm/memory.c
@@ -3099,26 +3099,34 @@ static int do_remap_pfn_range(struct vm_
 }
 #endif
 
-void remap_pfn_range_prepare(struct vm_area_desc *desc, unsigned long pfn)
+int remap_pfn_range_prepare(struct vm_area_desc *desc)
 {
-	/*
-	 * We set addr=VMA start, end=VMA end here, so this won't fail, but we
-	 * check it again on complete and will fail there if specified addr is
-	 * invalid.
-	 */
-	get_remap_pgoff(vma_desc_is_cow_mapping(desc), desc->start, desc->end,
-			desc->start, desc->end, pfn, &desc->pgoff);
+	const struct mmap_action *action = &desc->action;
+	const unsigned long start = action->remap.start;
+	const unsigned long end = start + action->remap.size;
+	const unsigned long pfn = action->remap.start_pfn;
+	const bool is_cow = vma_desc_is_cow_mapping(desc);
+	int err;
+
+	err = get_remap_pgoff(is_cow, start, end, desc->start, desc->end, pfn,
+			      &desc->pgoff);
+	if (err)
+		return err;
+
 	vma_desc_set_flags_mask(desc, VMA_REMAP_FLAGS);
+	return 0;
 }
 
-static int remap_pfn_range_prepare_vma(struct vm_area_struct *vma, unsigned long addr,
-		unsigned long pfn, unsigned long size)
+static int remap_pfn_range_prepare_vma(struct vm_area_struct *vma,
+				       unsigned long addr, unsigned long pfn,
+				       unsigned long size)
 {
-	unsigned long end = addr + PAGE_ALIGN(size);
+	const unsigned long end = addr + PAGE_ALIGN(size);
+	const bool is_cow = is_cow_mapping(vma->vm_flags);
 	int err;
 
-	err = get_remap_pgoff(is_cow_mapping(vma->vm_flags), addr, end,
-			      vma->vm_start, vma->vm_end, pfn, &vma->vm_pgoff);
+	err = get_remap_pgoff(is_cow, addr, end, vma->vm_start, vma->vm_end,
+			      pfn, &vma->vm_pgoff);
 	if (err)
 		return err;
 
@@ -3151,10 +3159,15 @@ int remap_pfn_range(struct vm_area_struc
 }
 EXPORT_SYMBOL(remap_pfn_range);
 
-int remap_pfn_range_complete(struct vm_area_struct *vma, unsigned long addr,
-		unsigned long pfn, unsigned long size, pgprot_t prot)
+int remap_pfn_range_complete(struct vm_area_struct *vma,
+			     struct mmap_action *action)
 {
-	return do_remap_pfn_range(vma, addr, pfn, size, prot);
+	const unsigned long start = action->remap.start;
+	const unsigned long pfn = action->remap.start_pfn;
+	const unsigned long size = action->remap.size;
+	const pgprot_t prot = action->remap.pgprot;
+
+	return do_remap_pfn_range(vma, start, pfn, size, prot);
 }
 
 /**
--- a/mm/util.c~mm-various-small-mmap_prepare-cleanups
+++ a/mm/util.c
@@ -1164,43 +1164,6 @@ EXPORT_SYMBOL(flush_dcache_folio);
 #endif
 
 /**
- * __compat_vma_mmap() - See description for compat_vma_mmap()
- * for details. This is the same operation, only with a specific file operations
- * struct which may or may not be the same as vma->vm_file->f_op.
- * @f_op: The file operations whose .mmap_prepare() hook is specified.
- * @file: The file which backs or will back the mapping.
- * @vma: The VMA to apply the .mmap_prepare() hook to.
- * Returns: 0 on success or error.
- */
-int __compat_vma_mmap(const struct file_operations *f_op,
-		struct file *file, struct vm_area_struct *vma)
-{
-	struct vm_area_desc desc = {
-		.mm = vma->vm_mm,
-		.file = file,
-		.start = vma->vm_start,
-		.end = vma->vm_end,
-
-		.pgoff = vma->vm_pgoff,
-		.vm_file = vma->vm_file,
-		.vma_flags = vma->flags,
-		.page_prot = vma->vm_page_prot,
-
-		.action.type = MMAP_NOTHING, /* Default */
-	};
-	int err;
-
-	err = f_op->mmap_prepare(&desc);
-	if (err)
-		return err;
-
-	mmap_action_prepare(&desc.action, &desc);
-	set_vma_from_desc(vma, &desc);
-	return mmap_action_complete(&desc.action, vma);
-}
-EXPORT_SYMBOL(__compat_vma_mmap);
-
-/**
  * compat_vma_mmap() - Apply the file's .mmap_prepare() hook to an
  * existing VMA and execute any requested actions.
  * @file: The file which possesss an f_op->mmap_prepare() hook.
@@ -1228,7 +1191,31 @@ EXPORT_SYMBOL(__compat_vma_mmap);
  */
 int compat_vma_mmap(struct file *file, struct vm_area_struct *vma)
 {
-	return __compat_vma_mmap(file->f_op, file, vma);
+	struct vm_area_desc desc = {
+		.mm = vma->vm_mm,
+		.file = file,
+		.start = vma->vm_start,
+		.end = vma->vm_end,
+
+		.pgoff = vma->vm_pgoff,
+		.vm_file = vma->vm_file,
+		.vma_flags = vma->flags,
+		.page_prot = vma->vm_page_prot,
+
+		.action.type = MMAP_NOTHING, /* Default */
+	};
+	int err;
+
+	err = vfs_mmap_prepare(file, &desc);
+	if (err)
+		return err;
+
+	err = mmap_action_prepare(&desc);
+	if (err)
+		return err;
+
+	set_vma_from_desc(vma, &desc);
+	return mmap_action_complete(vma, &desc.action);
 }
 EXPORT_SYMBOL(compat_vma_mmap);
 
@@ -1320,8 +1307,8 @@ again:
 	}
 }
 
-static int mmap_action_finish(struct mmap_action *action,
-		const struct vm_area_struct *vma, int err)
+static int mmap_action_finish(struct vm_area_struct *vma,
+			      struct mmap_action *action, int err)
 {
 	/*
 	 * If an error occurs, unmap the VMA altogether and return an error. We
@@ -1353,37 +1340,38 @@ static int mmap_action_finish(struct mma
 /**
  * mmap_action_prepare - Perform preparatory setup for an VMA descriptor
  * action which need to be performed.
- * @desc: The VMA descriptor to prepare for @action.
- * @action: The action to perform.
+ * @desc: The VMA descriptor to prepare for its @desc->action.
+ *
+ * Returns: %0 on success, otherwise error.
  */
-void mmap_action_prepare(struct mmap_action *action,
-			 struct vm_area_desc *desc)
+int mmap_action_prepare(struct vm_area_desc *desc)
 {
-	switch (action->type) {
+	switch (desc->action.type) {
 	case MMAP_NOTHING:
-		break;
+		return 0;
 	case MMAP_REMAP_PFN:
-		remap_pfn_range_prepare(desc, action->remap.start_pfn);
-		break;
+		return remap_pfn_range_prepare(desc);
 	case MMAP_IO_REMAP_PFN:
-		io_remap_pfn_range_prepare(desc, action->remap.start_pfn,
-					   action->remap.size);
-		break;
+		return io_remap_pfn_range_prepare(desc);
 	}
+
+	WARN_ON_ONCE(1);
+	return -EINVAL;
 }
 EXPORT_SYMBOL(mmap_action_prepare);
 
 /**
  * mmap_action_complete - Execute VMA descriptor action.
- * @action: The action to perform.
  * @vma: The VMA to perform the action upon.
+ * @action: The action to perform.
  *
  * Similar to mmap_action_prepare().
  *
  * Return: 0 on success, or error, at which point the VMA will be unmapped.
  */
-int mmap_action_complete(struct mmap_action *action,
-			 struct vm_area_struct *vma)
+int mmap_action_complete(struct vm_area_struct *vma,
+			 struct mmap_action *action)
+
 {
 	int err = 0;
 
@@ -1391,25 +1379,22 @@ int mmap_action_complete(struct mmap_act
 	case MMAP_NOTHING:
 		break;
 	case MMAP_REMAP_PFN:
-		err = remap_pfn_range_complete(vma, action->remap.start,
-				action->remap.start_pfn, action->remap.size,
-				action->remap.pgprot);
+		err = remap_pfn_range_complete(vma, action);
 		break;
 	case MMAP_IO_REMAP_PFN:
-		err = io_remap_pfn_range_complete(vma, action->remap.start,
-				action->remap.start_pfn, action->remap.size,
-				action->remap.pgprot);
+		/* Should have been delegated. */
+		WARN_ON_ONCE(1);
+		err = -EINVAL;
 		break;
 	}
 
-	return mmap_action_finish(action, vma, err);
+	return mmap_action_finish(vma, action, err);
 }
 EXPORT_SYMBOL(mmap_action_complete);
 #else
-void mmap_action_prepare(struct mmap_action *action,
-			struct vm_area_desc *desc)
+int mmap_action_prepare(struct vm_area_desc *desc)
 {
-	switch (action->type) {
+	switch (desc->action.type) {
 	case MMAP_NOTHING:
 		break;
 	case MMAP_REMAP_PFN:
@@ -1417,11 +1402,13 @@ void mmap_action_prepare(struct mmap_act
 		WARN_ON_ONCE(1); /* nommu cannot handle these. */
 		break;
 	}
+
+	return 0;
 }
 EXPORT_SYMBOL(mmap_action_prepare);
 
-int mmap_action_complete(struct mmap_action *action,
-			struct vm_area_struct *vma)
+int mmap_action_complete(struct vm_area_struct *vma,
+			 struct mmap_action *action)
 {
 	int err = 0;
 
@@ -1436,7 +1423,7 @@ int mmap_action_complete(struct mmap_act
 		break;
 	}
 
-	return mmap_action_finish(action, vma, err);
+	return mmap_action_finish(vma, action, err);
 }
 EXPORT_SYMBOL(mmap_action_complete);
 #endif
--- a/mm/vma.c~mm-various-small-mmap_prepare-cleanups
+++ a/mm/vma.c
@@ -2640,15 +2640,18 @@ static void __mmap_complete(struct mmap_
 	vma_set_page_prot(vma);
 }
 
-static void call_action_prepare(struct mmap_state *map,
-				struct vm_area_desc *desc)
+static int call_action_prepare(struct mmap_state *map,
+			       struct vm_area_desc *desc)
 {
-	struct mmap_action *action = &desc->action;
+	int err;
 
-	mmap_action_prepare(action, desc);
+	err = mmap_action_prepare(desc);
+	if (err)
+		return err;
 
-	if (action->hide_from_rmap_until_complete)
+	if (desc->action.hide_from_rmap_until_complete)
 		map->hold_file_rmap_lock = true;
+	return 0;
 }
 
 /*
@@ -2672,7 +2675,9 @@ static int call_mmap_prepare(struct mmap
 	if (err)
 		return err;
 
-	call_action_prepare(map, desc);
+	err = call_action_prepare(map, desc);
+	if (err)
+		return err;
 
 	/* Update fields permitted to be changed. */
 	map->pgoff = desc->pgoff;
@@ -2727,13 +2732,12 @@ static bool can_set_ksm_flags_early(stru
 }
 
 static int call_action_complete(struct mmap_state *map,
-				struct vm_area_desc *desc,
+				struct mmap_action *action,
 				struct vm_area_struct *vma)
 {
-	struct mmap_action *action = &desc->action;
 	int ret;
 
-	ret = mmap_action_complete(action, vma);
+	ret = mmap_action_complete(vma, action);
 
 	/* If we held the file rmap we need to release it. */
 	if (map->hold_file_rmap_lock) {
@@ -2795,7 +2799,7 @@ static unsigned long __mmap_region(struc
 	__mmap_complete(&map, vma);
 
 	if (have_mmap_prepare && allocated_new) {
-		error = call_action_complete(&map, &desc, vma);
+		error = call_action_complete(&map, &desc.action, vma);
 
 		if (error)
 			return error;
--- a/tools/testing/vma/include/dup.h~mm-various-small-mmap_prepare-cleanups
+++ a/tools/testing/vma/include/dup.h
@@ -1277,9 +1277,12 @@ static inline int __compat_vma_mmap(cons
 	if (err)
 		return err;
 
-	mmap_action_prepare(&desc.action, &desc);
+	err = mmap_action_prepare(&desc);
+	if (err)
+		return err;
+
 	set_vma_from_desc(vma, &desc);
-	return mmap_action_complete(&desc.action, vma);
+	return mmap_action_complete(vma, &desc.action);
 }
 
 static inline int compat_vma_mmap(struct file *file,
--- a/tools/testing/vma/include/stubs.h~mm-various-small-mmap_prepare-cleanups
+++ a/tools/testing/vma/include/stubs.h
@@ -81,13 +81,13 @@ static inline void free_anon_vma_name(st
 {
 }
 
-static inline void mmap_action_prepare(struct mmap_action *action,
-					   struct vm_area_desc *desc)
+static inline int mmap_action_prepare(struct vm_area_desc *desc)
 {
+	return 0;
 }
 
-static inline int mmap_action_complete(struct mmap_action *action,
-					   struct vm_area_struct *vma)
+static inline int mmap_action_complete(struct vm_area_struct *vma,
+				       struct mmap_action *action)
 {
 	return 0;
 }
_

Patches currently in -mm which might be from ljs@kernel.org are

maintainers-update-mglru-entry-to-reflect-current-status.patch
selftests-mm-add-merge-test-for-partial-msealed-range.patch