+ mm-abstract-merge-for-new-vmas-into-vma_merge_new_vma.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: abstract merge for new VMAs into vma_merge_new_vma()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-abstract-merge-for-new-vmas-into-vma_merge_new_vma.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-abstract-merge-for-new-vmas-into-vma_merge_new_vma.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Lorenzo Stoakes <lstoakes@gmail.com>
Subject: mm: abstract merge for new VMAs into vma_merge_new_vma()
Date: Mon, 9 Oct 2023 21:53:19 +0100

Only in mmap_region() and copy_vma() do we attempt to merge VMAs which
occupy entirely new regions of virtual memory.

We can abstract this logic and make the intent of this invocations of it
completely explicit, rather than invoking vma_merge() with an inscrutable
wall of parameters.

This also paves the way for a simplification of the core vma_merge()
implementation, as we seek to make it entirely an implementation detail.

Note that on mmap_region(), VMA fields are initialised to zero, so we can
simply reference these rather than explicitly specifying NULL.

Link: https://lkml.kernel.org/r/8525290591267805ffabf8a31b53f0290a6a4276.1696884493.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mmap.c |   27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

--- a/mm/mmap.c~mm-abstract-merge-for-new-vmas-into-vma_merge_new_vma
+++ a/mm/mmap.c
@@ -2483,6 +2483,22 @@ struct vm_area_struct *vma_modify(struct
 }
 
 /*
+ * Attempt to merge a newly mapped VMA with those adjacent to it. The caller
+ * must ensure that [start, end) does not overlap any existing VMA.
+ */
+static struct vm_area_struct *vma_merge_new_vma(struct vma_iterator *vmi,
+						struct vm_area_struct *prev,
+						struct vm_area_struct *vma,
+						unsigned long start,
+						unsigned long end,
+						pgoff_t pgoff)
+{
+	return vma_merge(vmi, vma->vm_mm, prev, start, end, vma->vm_flags,
+			 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
+			 vma->vm_userfaultfd_ctx, anon_vma_name(vma));
+}
+
+/*
  * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
  * @vmi: The vma iterator
  * @vma: The starting vm_area_struct
@@ -2837,10 +2853,9 @@ cannot_expand:
 		 * vma again as we may succeed this time.
 		 */
 		if (unlikely(vm_flags != vma->vm_flags && prev)) {
-			merge = vma_merge(&vmi, mm, prev, vma->vm_start,
-				    vma->vm_end, vma->vm_flags, NULL,
-				    vma->vm_file, vma->vm_pgoff, NULL,
-				    NULL_VM_UFFD_CTX, NULL);
+			merge = vma_merge_new_vma(&vmi, prev, vma,
+						  vma->vm_start, vma->vm_end,
+						  pgoff);
 			if (merge) {
 				/*
 				 * ->mmap() can change vma->vm_file and fput
@@ -3382,9 +3397,7 @@ struct vm_area_struct *copy_vma(struct v
 	if (new_vma && new_vma->vm_start < addr + len)
 		return NULL;	/* should never get here */
 
-	new_vma = vma_merge(&vmi, mm, prev, addr, addr + len, vma->vm_flags,
-			    vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
-			    vma->vm_userfaultfd_ctx, anon_vma_name(vma));
+	new_vma = vma_merge_new_vma(&vmi, prev, vma, addr, addr + len, pgoff);
 	if (new_vma) {
 		/*
 		 * Source vma may have been merged into new_vma
_

Patches currently in -mm which might be from lstoakes@gmail.com are

mm-filemap-clarify-filemap_fault-comments-for-not-uptodate-case.patch
mm-filemap-clarify-filemap_fault-comments-for-not-uptodate-case-fix.patch
mm-make-__access_remote_vm-static.patch
mm-gup-explicitly-define-and-check-internal-gup-flags-disallow-foll_touch.patch
mm-gup-make-failure-to-pin-an-error-if-foll_nowait-not-specified.patch
mm-gup-adapt-get_user_page_vma_remote-to-never-return-null.patch
mm-move-vma_policy-and-anon_vma_name-decls-to-mm_typesh.patch
mm-abstract-the-vma_merge-split_vma-pattern-for-mprotect-et-al.patch
mm-make-vma_merge-and-split_vma-internal.patch
mm-abstract-merge-for-new-vmas-into-vma_merge_new_vma.patch
mm-abstract-vma-merge-and-extend-into-vma_merge_extend-helper.patch