[merged mm-stable] mm-optimise-vmf_anon_prepare-for-vmas-without-an-anon_vma.patch removed from -mm tree

[merged mm-stable] mm-optimise-vmf_anon_prepare-for-vmas-without-an-anon_vma.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm: optimise vmf_anon_prepare() for VMAs without an anon_vma
has been removed from the -mm tree.  Its filename was
     mm-optimise-vmf_anon_prepare-for-vmas-without-an-anon_vma.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: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: mm: optimise vmf_anon_prepare() for VMAs without an anon_vma
Date: Fri, 26 Apr 2024 15:45:03 +0100

If the mmap_lock can be taken for read, we can call __anon_vma_prepare()
while holding it, saving ourselves a trip back through the fault handler.

Link: https://lkml.kernel.org/r/20240426144506.1290619-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jann Horn <jannh@google.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

--- a/mm/memory.c~mm-optimise-vmf_anon_prepare-for-vmas-without-an-anon_vma
+++ a/mm/memory.c
@@ -3232,16 +3232,21 @@ static inline vm_fault_t vmf_can_call_fa
 vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
+	vm_fault_t ret = 0;
 
 	if (likely(vma->anon_vma))
 		return 0;
 	if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
-		vma_end_read(vma);
-		return VM_FAULT_RETRY;
+		if (!mmap_read_trylock(vma->vm_mm)) {
+			vma_end_read(vma);
+			return VM_FAULT_RETRY;
+		}
 	}
 	if (__anon_vma_prepare(vma))
-		return VM_FAULT_OOM;
-	return 0;
+		ret = VM_FAULT_OOM;
+	if (vmf->flags & FAULT_FLAG_VMA_LOCK)
+		mmap_read_unlock(vma->vm_mm);
+	return ret;
 }
 
 /*
_

Patches currently in -mm which might be from willy@infradead.org are

squashfs-convert-squashfs_symlink_read_folio-to-use-folio-apis.patch
squashfs-remove-calls-to-set-the-folio-error-flag.patch
nilfs2-remove-calls-to-folio_set_error-and-folio_clear_error.patch