The patch titled
Subject: mm: drop per-VMA lock when returning VM_FAULT_RETRY or VM_FAULT_COMPLETED
has been added to the -mm mm-unstable branch. Its filename is
mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed.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: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Subject: mm: drop per-VMA lock when returning VM_FAULT_RETRY or VM_FAULT_COMPLETED
Date: Fri, 30 Jun 2023 14:19:54 -0700
handle_mm_fault returning VM_FAULT_RETRY or VM_FAULT_COMPLETED means
mmap_lock has been released. However with per-VMA locks behavior is
different and the caller should still release it. To make the rules
consistent for the caller, drop the per-VMA lock when returning
VM_FAULT_RETRY or VM_FAULT_COMPLETED. Currently the only path returning
VM_FAULT_RETRY under per-VMA locks is do_swap_page and no path returns
VM_FAULT_COMPLETED for now.
Link: https://lkml.kernel.org/r/20230630211957.1341547-4-surenb@xxxxxxxxxx
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Acked-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
Cc: Laurent Dufour <ldufour@xxxxxxxxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Michel Lespinasse <michel@xxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Punit Agrawal <punit.agrawal@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm64/mm/fault.c | 3 ++-
arch/powerpc/mm/fault.c | 3 ++-
arch/s390/mm/fault.c | 3 ++-
arch/x86/mm/fault.c | 3 ++-
mm/memory.c | 12 ++++++++++++
5 files changed, 20 insertions(+), 4 deletions(-)
--- a/arch/arm64/mm/fault.c~mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed
+++ a/arch/arm64/mm/fault.c
@@ -602,7 +602,8 @@ static int __kprobes do_page_fault(unsig
goto lock_mmap;
}
fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs);
- vma_end_read(vma);
+ if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+ vma_end_read(vma);
if (!(fault & VM_FAULT_RETRY)) {
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
--- a/arch/powerpc/mm/fault.c~mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed
+++ a/arch/powerpc/mm/fault.c
@@ -489,7 +489,8 @@ static int ___do_page_fault(struct pt_re
}
fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
- vma_end_read(vma);
+ if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+ vma_end_read(vma);
if (!(fault & VM_FAULT_RETRY)) {
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
--- a/arch/s390/mm/fault.c~mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed
+++ a/arch/s390/mm/fault.c
@@ -418,7 +418,8 @@ static inline vm_fault_t do_exception(st
goto lock_mmap;
}
fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
- vma_end_read(vma);
+ if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+ vma_end_read(vma);
if (!(fault & VM_FAULT_RETRY)) {
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
goto out;
--- a/arch/x86/mm/fault.c~mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed
+++ a/arch/x86/mm/fault.c
@@ -1341,7 +1341,8 @@ void do_user_addr_fault(struct pt_regs *
goto lock_mmap;
}
fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
- vma_end_read(vma);
+ if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+ vma_end_read(vma);
if (!(fault & VM_FAULT_RETRY)) {
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
--- a/mm/memory.c~mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed
+++ a/mm/memory.c
@@ -3733,6 +3733,7 @@ vm_fault_t do_swap_page(struct vm_fault
if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
ret = VM_FAULT_RETRY;
+ vma_end_read(vma);
goto out;
}
@@ -5185,6 +5186,17 @@ static vm_fault_t sanitize_fault_flags(s
!is_cow_mapping(vma->vm_flags)))
return VM_FAULT_SIGSEGV;
}
+#ifdef CONFIG_PER_VMA_LOCK
+ /*
+ * Per-VMA locks can't be used with FAULT_FLAG_RETRY_NOWAIT because of
+ * the assumption that lock is dropped on VM_FAULT_RETRY.
+ */
+ if (WARN_ON_ONCE((*flags &
+ (FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT)) ==
+ (FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT)))
+ return VM_FAULT_SIGSEGV;
+#endif
+
return 0;
}
_
Patches currently in -mm which might be from surenb@xxxxxxxxxx are
swap-remove-remnants-of-polling-from-read_swap_cache_async.patch
mm-add-missing-vm_fault_result_trace-name-for-vm_fault_completed.patch
mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed.patch
mm-change-folio_lock_or_retry-to-use-vm_fault-directly.patch
mm-handle-swap-page-faults-under-per-vma-lock.patch
mm-handle-userfaults-under-vma-lock.patch
