The patch titled
Subject: mm/memory: change vmf_anon_prepare() to be non-static
has been added to the -mm mm-unstable branch. Its filename is
mm-memory-change-vmf_anon_prepare-to-be-non-static.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory-change-vmf_anon_prepare-to-be-non-static.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Vishal Moola (Oracle)" <vishal.moola@xxxxxxxxx>
Subject: mm/memory: change vmf_anon_prepare() to be non-static
Date: Wed, 21 Feb 2024 15:47:28 -0800
Patch series "Handle hugetlb faults under the VMA lock", v2.
It is generally safe to handle hugetlb faults under the VMA lock. The
only time this is unsafe is when no anon_vma has been allocated to this
vma yet, so we can use vmf_anon_prepare() instead of anon_vma_prepare() to
bailout if necessary. This should only happen for the first hugetlb page
in the vma.
Additionally, this patchset begins to use struct vm_fault within
hugetlb_fault(). This works towards cleaning up hugetlb code, and should
significantly reduce the number of arguments passed to functions.
The last patch in this series may cause ltp hugemmap10 to "fail". This is
because vmf_anon_prepare() may bailout with no anon_vma under the VMA lock
after allocating a folio for the hugepage. In free_huge_folio(), this
folio is completely freed on bailout iff there is a surplus of hugetlb
pages. This will remove a folio off the freelist and decrement the number
of hugepages while ltp expects these counters to remain unchanged on
failure. The rest of the ltp testcases pass.
This patch (of 2):
In order to handle hugetlb faults under the VMA lock, hugetlb can use
vmf_anon_prepare() to ensure we can safely prepare an anon_vma. Change it
to be a non-static function so it can be used within hugetlb as well.
Link: https://lkml.kernel.org/r/20240221234732.187629-6-vishal.moola@xxxxxxxxx
Link: https://lkml.kernel.org/r/20240221234732.187629-2-vishal.moola@xxxxxxxxx
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/internal.h | 1 +
mm/memory.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)
--- a/mm/internal.h~mm-memory-change-vmf_anon_prepare-to-be-non-static
+++ a/mm/internal.h
@@ -103,6 +103,7 @@ static inline void wake_throttle_isolate
wake_up(wqh);
}
+vm_fault_t vmf_anon_prepare(struct vm_fault *vmf);
vm_fault_t do_swap_page(struct vm_fault *vmf);
void folio_rotate_reclaimable(struct folio *folio);
bool __folio_end_writeback(struct folio *folio);
--- a/mm/memory.c~mm-memory-change-vmf_anon_prepare-to-be-non-static
+++ a/mm/memory.c
@@ -3280,7 +3280,7 @@ static inline vm_fault_t vmf_can_call_fa
return VM_FAULT_RETRY;
}
-static vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)
+vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
_
Patches currently in -mm which might be from vishal.moola@xxxxxxxxx are
mm-memory-change-vmf_anon_prepare-to-be-non-static.patch
hugetlb-move-vm_struct-declaration-to-the-top-of-hugetlb_fault.patch
hugetlb-pass-struct-vm_fault-through-to-hugetlb_handle_userfault.patch
hugetlb-use-vmf_anon_prepare-instead-of-anon_vma_prepare.patch
hugetlb-allow-faults-to-be-handled-under-the-vma-lock.patch
