The quilt patch titled
Subject: mm: handle swap page faults under vma lock if page is uncontended
has been removed from the -mm tree. Its filename was
mm-handle-swap-page-faults-if-the-faulting-page-can-be-locked.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: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Subject: mm: handle swap page faults under vma lock if page is uncontended
Date: Fri, 14 Apr 2023 11:00:43 -0700
When page fault is handled under VMA lock protection, all swap page faults
are retried with mmap_lock because folio_lock_or_retry implementation has
to drop and reacquire mmap_lock if folio could not be immediately locked.
Instead of retrying all swapped page faults, retry only when folio locking
fails.
Link: https://lkml.kernel.org/r/20230414180043.1839745-1-surenb@xxxxxxxxxx
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
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: Michal Hocko <mhocko@xxxxxxxx>
Cc: Michel Lespinasse <michel@xxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Punit Agrawal <punit.agrawal@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 6 ++++++
mm/memory.c | 5 -----
2 files changed, 6 insertions(+), 5 deletions(-)
--- a/mm/filemap.c~mm-handle-swap-page-faults-if-the-faulting-page-can-be-locked
+++ a/mm/filemap.c
@@ -1706,6 +1706,8 @@ static int __folio_lock_async(struct fol
* mmap_lock has been released (mmap_read_unlock(), unless flags had both
* FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
* which case mmap_lock is still held.
+ * If flags had FAULT_FLAG_VMA_LOCK set, meaning the operation is performed
+ * with VMA lock only, the VMA lock is still held.
*
* If neither ALLOW_RETRY nor KILLABLE are set, will always return true
* with the folio locked and the mmap_lock unperturbed.
@@ -1713,6 +1715,10 @@ static int __folio_lock_async(struct fol
bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
unsigned int flags)
{
+ /* Can't do this if not holding mmap_lock */
+ if (flags & FAULT_FLAG_VMA_LOCK)
+ return false;
+
if (fault_flag_allow_retry_first(flags)) {
/*
* CAUTION! In this case, mmap_lock is not released
--- a/mm/memory.c~mm-handle-swap-page-faults-if-the-faulting-page-can-be-locked
+++ a/mm/memory.c
@@ -3711,11 +3711,6 @@ vm_fault_t do_swap_page(struct vm_fault
if (!pte_unmap_same(vmf))
goto out;
- if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
- ret = VM_FAULT_RETRY;
- goto out;
- }
-
entry = pte_to_swp_entry(vmf->orig_pte);
if (unlikely(non_swap_entry(entry))) {
if (is_migration_entry(entry)) {
_
Patches currently in -mm which might be from surenb@xxxxxxxxxx are
