2023-06-28 09:27:59

by Suren Baghdasaryan

Subject: [PATCH v4 4/6] mm: change folio_lock_or_retry to use vm_fault directly

Change folio_lock_or_retry to accept vm_fault struct and return the
vm_fault_t directly.

Suggested-by: Matthew Wilcox <[email protected]>
Signed-off-by: Suren Baghdasaryan <[email protected]>
---
include/linux/pagemap.h | 9 ++++-----
mm/filemap.c | 22 ++++++++++++----------
mm/memory.c | 14 ++++++--------
3 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a56308a9d1a4..59d070c55c97 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -896,8 +896,7 @@ static inline bool wake_page_match(struct wait_page_queue *wait_page,

void __folio_lock(struct folio *folio);
int __folio_lock_killable(struct folio *folio);
-bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
- unsigned int flags);
+vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf);
void unlock_page(struct page *page);
void folio_unlock(struct folio *folio);

@@ -1001,11 +1000,11 @@ static inline int folio_lock_killable(struct folio *folio)
* Return value and mmap_lock implications depend on flags; see
* __folio_lock_or_retry().
*/
-static inline bool folio_lock_or_retry(struct folio *folio,
- struct mm_struct *mm, unsigned int flags)
+static inline vm_fault_t folio_lock_or_retry(struct folio *folio,
+ struct vm_fault *vmf)
{
might_sleep();
- return folio_trylock(folio) || __folio_lock_or_retry(folio, mm, flags);
+ return folio_trylock(folio) ? 0 : __folio_lock_or_retry(folio, vmf);
}

/*
diff --git a/mm/filemap.c b/mm/filemap.c
index 00f01d8ead47..52bcf12dcdbf 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1701,32 +1701,34 @@ static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)

/*
* Return values:
- * true - folio is locked; mmap_lock is still held.
- * false - folio is not locked.
+ * 0 - folio is locked.
+ * VM_FAULT_RETRY - folio is not locked.
* 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 neither ALLOW_RETRY nor KILLABLE are set, will always return true
+ * If neither ALLOW_RETRY nor KILLABLE are set, will always return 0
* with the folio locked and the mmap_lock unperturbed.
*/
-bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
- unsigned int flags)
+vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf)
{
+ struct mm_struct *mm = vmf->vma->vm_mm;
+ unsigned int flags = vmf->flags;
+
if (fault_flag_allow_retry_first(flags)) {
/*
* CAUTION! In this case, mmap_lock is not released
- * even though return 0.
+ * even though return VM_FAULT_RETRY.
*/
if (flags & FAULT_FLAG_RETRY_NOWAIT)
- return false;
+ return VM_FAULT_RETRY;

mmap_read_unlock(mm);
if (flags & FAULT_FLAG_KILLABLE)
folio_wait_locked_killable(folio);
else
folio_wait_locked(folio);
- return false;
+ return VM_FAULT_RETRY;
}
if (flags & FAULT_FLAG_KILLABLE) {
bool ret;
@@ -1734,13 +1736,13 @@ bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
ret = __folio_lock_killable(folio);
if (ret) {
mmap_read_unlock(mm);
- return false;
+ return VM_FAULT_RETRY;
}
} else {
__folio_lock(folio);
}

- return true;
+ return 0;
}

/**
diff --git a/mm/memory.c b/mm/memory.c
index f14d45957b83..345080052003 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3568,6 +3568,7 @@ static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf)
struct folio *folio = page_folio(vmf->page);
struct vm_area_struct *vma = vmf->vma;
struct mmu_notifier_range range;
+ vm_fault_t ret;

/*
* We need a reference to lock the folio because we don't hold
@@ -3580,9 +3581,10 @@ static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf)
if (!folio_try_get(folio))
return 0;

- if (!folio_lock_or_retry(folio, vma->vm_mm, vmf->flags)) {
+ ret = folio_lock_or_retry(folio, vmf);
+ if (ret) {
folio_put(folio);
- return VM_FAULT_RETRY;
+ return ret;
}
mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0,
vma->vm_mm, vmf->address & PAGE_MASK,
@@ -3704,7 +3706,6 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
bool exclusive = false;
swp_entry_t entry;
pte_t pte;
- int locked;
vm_fault_t ret = 0;
void *shadow = NULL;

@@ -3826,12 +3827,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
goto out_release;
}

- locked = folio_lock_or_retry(folio, vma->vm_mm, vmf->flags);
-
- if (!locked) {
- ret |= VM_FAULT_RETRY;
+ ret |= folio_lock_or_retry(folio, vmf);
+ if (ret & VM_FAULT_RETRY)
goto out_release;
- }

if (swapcache) {
/*
--
2.41.0.162.gfafddb0af9-goog

2023-06-28 14:14:56

by Peter Xu

Subject: Re: [PATCH v4 4/6] mm: change folio_lock_or_retry to use vm_fault directly

On Wed, Jun 28, 2023 at 12:17:58AM -0700, Suren Baghdasaryan wrote:
> Change folio_lock_or_retry to accept vm_fault struct and return the
> vm_fault_t directly.
>
> Suggested-by: Matthew Wilcox <[email protected]>
> Signed-off-by: Suren Baghdasaryan <[email protected]>

Acked-by: Peter Xu <[email protected]>

--
Peter Xu