| Message ID | 20240129124649.189745-13-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/memory: optimize fork() with PTE-mapped THP | expand |
On Mon, Jan 29, 2024 at 01:46:46PM +0100, David Hildenbrand wrote: > We already read it, let's just forward it. > > This patch is based on work by Ryan Roberts. > > Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> > Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org> > --- > mm/memory.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index a3bdb25f4c8d..41b24da5be38 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -959,10 +959,9 @@ static inline void __copy_present_pte(struct vm_area_struct *dst_vma, > */ > static inline int > copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, > - pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss, > - struct folio **prealloc) > + pte_t *dst_pte, pte_t *src_pte, pte_t pte, unsigned long addr, > + int *rss, struct folio **prealloc) > { > - pte_t pte = ptep_get(src_pte); > struct page *page; > struct folio *folio; > > @@ -1103,7 +1102,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, > } > /* copy_present_pte() will clear `*prealloc' if consumed */ > ret = copy_present_pte(dst_vma, src_vma, dst_pte, src_pte, > - addr, rss, &prealloc); > + ptent, addr, rss, &prealloc); > /* > * If we need a pre-allocated page for this pte, drop the > * locks, allocate, and try again. > -- > 2.43.0 > >
On 29.01.24 13:46, David Hildenbrand wrote: > We already read it, let's just forward it. > > This patch is based on work by Ryan Roberts. > > Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > mm/memory.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index a3bdb25f4c8d..41b24da5be38 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -959,10 +959,9 @@ static inline void __copy_present_pte(struct vm_area_struct *dst_vma, > */ > static inline int > copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, > - pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss, > - struct folio **prealloc) > + pte_t *dst_pte, pte_t *src_pte, pte_t pte, unsigned long addr, > + int *rss, struct folio **prealloc) > { > - pte_t pte = ptep_get(src_pte); > struct page *page; > struct folio *folio; > > @@ -1103,7 +1102,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, > } > /* copy_present_pte() will clear `*prealloc' if consumed */ > ret = copy_present_pte(dst_vma, src_vma, dst_pte, src_pte, > - addr, rss, &prealloc); > + ptent, addr, rss, &prealloc); > /* > * If we need a pre-allocated page for this pte, drop the > * locks, allocate, and try again. The following fixup for that device-exclusive thingy on top (fixing a hmm selftest I just discovered to be broken). From 8f9e44f25087dc71890b8d9bd680375691232e85 Mon Sep 17 00:00:00 2001 From: David Hildenbrand <david@redhat.com> Date: Wed, 14 Feb 2024 23:09:29 +0100 Subject: [PATCH] fixup: mm/memory: pass PTE to copy_present_pte() For device-exclusive nonswp entries (is_device_exclusive_entry()), copy_nonpresent_pte() can turn the PTEs into actual present PTEs while holding the page table lock. We hae to re-read the PTE after that operation, such that we won't be working on the stale non-present PTE, assuming it would be present. This fixes the hmm "exclusive_cow" selftest. ./run_vmtests.sh -t hmm # # RUN hmm.hmm_device_private.exclusive_cow ... # # OK hmm.hmm_device_private.exclusive_cow # ok 23 hmm.hmm_device_private.exclusive_cow Signed-off-by: David Hildenbrand <david@redhat.com> --- mm/memory.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/memory.c b/mm/memory.c index 3b8e56eb08a3..29a75f38df7c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1208,6 +1208,8 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, progress += 8; continue; } + ptent = ptep_get(src_pte); + VM_WARN_ON_ONCE(!pte_present(ptent)); /* * Device exclusive entry restored, continue by copying
diff --git a/mm/memory.c b/mm/memory.c index a3bdb25f4c8d..41b24da5be38 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -959,10 +959,9 @@ static inline void __copy_present_pte(struct vm_area_struct *dst_vma, */ static inline int copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, - pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss, - struct folio **prealloc) + pte_t *dst_pte, pte_t *src_pte, pte_t pte, unsigned long addr, + int *rss, struct folio **prealloc) { - pte_t pte = ptep_get(src_pte); struct page *page; struct folio *folio; @@ -1103,7 +1102,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, } /* copy_present_pte() will clear `*prealloc' if consumed */ ret = copy_present_pte(dst_vma, src_vma, dst_pte, src_pte, - addr, rss, &prealloc); + ptent, addr, rss, &prealloc); /* * If we need a pre-allocated page for this pte, drop the * locks, allocate, and try again.