lkml.org 
[lkml]   [2022]   [Jan]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 18/35] mm: implement speculative handling in do_anonymous_page()
Date
Change do_anonymous_page() to handle the speculative case.
This involves aborting speculative faults if they have to allocate a new
anon_vma, and using pte_map_lock() instead of pte_offset_map_lock()
to complete the page fault.

Signed-off-by: Michel Lespinasse <michel@lespinasse.org>
---
mm/memory.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 1ce837e47395..8d036140634d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3846,8 +3846,12 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
vma->vm_page_prot));
} else {
/* Allocate our own private page. */
- if (unlikely(anon_vma_prepare(vma)))
- goto oom;
+ if (unlikely(!vma->anon_vma)) {
+ if (vmf->flags & FAULT_FLAG_SPECULATIVE)
+ return VM_FAULT_RETRY;
+ if (__anon_vma_prepare(vma))
+ goto oom;
+ }
page = alloc_zeroed_user_highpage_movable(vma, vmf->address);
if (!page)
goto oom;
@@ -3869,8 +3873,10 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
entry = pte_mkwrite(pte_mkdirty(entry));
}

- vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
- &vmf->ptl);
+ if (!pte_map_lock(vmf)) {
+ ret = VM_FAULT_RETRY;
+ goto release;
+ }
if (!pte_none(*vmf->pte)) {
update_mmu_tlb(vma, vmf->address, vmf->pte);
goto unlock;
@@ -3885,6 +3891,8 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
pte_unmap_unlock(vmf->pte, vmf->ptl);
if (page)
put_page(page);
+ if (vmf->flags & FAULT_FLAG_SPECULATIVE)
+ return VM_FAULT_RETRY;
return handle_userfault(vmf, VM_UFFD_MISSING);
}

@@ -3902,6 +3910,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
return 0;
unlock:
pte_unmap_unlock(vmf->pte, vmf->ptl);
+release:
if (page)
put_page(page);
return ret;
--
2.20.1
\
 
 \ /
  Last update: 2022-01-28 14:20    [W:0.286 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site