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.
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
---
Patch applies cleanly over linux-next and mm-unstable
mm/filemap.c | 6 ++++++
mm/memory.c | 5 -----
2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 6f3a7e53fccf..67b937b0f436 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1706,6 +1706,8 @@ static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
* 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 folio *folio, struct wait_page_queue *wait)
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
diff --git a/mm/memory.c b/mm/memory.c
index d88f370eacd1..3301a8d01820 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3715,11 +3715,6 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
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)) {
--
2.40.0.634.g4ca3ef3211-goog
