On 2023-05-14 22:26, Lorenzo Stoakes wrote:
> The only instances of get_user_pages_remote() invocations which used the
> vmas parameter were for a single page which can instead simply look up the
> VMA directly. In particular:-
>
> - __update_ref_ctr() looked up the VMA but did nothing with it so we simply
> remove it.
>
> - __access_remote_vm() was already using vma_lookup() when the original
> lookup failed so by doing the lookup directly this also de-duplicates the
> code.
>
> We are able to perform these VMA operations as we already hold the
> mmap_lock in order to be able to call get_user_pages_remote().
>
> As part of this work we add get_user_page_vma_remote() which abstracts the
> VMA lookup, error handling and decrementing the page reference count should
> the VMA lookup fail.
>
> This forms part of a broader set of patches intended to eliminate the vmas
> parameter altogether.
>
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> (for arm64)
> Acked-by: David Hildenbrand <david@xxxxxxxxxx>
> Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx> (for s390)
> Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
> ---
> arch/arm64/kernel/mte.c | 17 +++++++++--------
> arch/s390/kvm/interrupt.c | 2 +-
> fs/exec.c | 2 +-
> include/linux/mm.h | 34 +++++++++++++++++++++++++++++++---
> kernel/events/uprobes.c | 13 +++++--------
> mm/gup.c | 12 ++++--------
> mm/memory.c | 14 +++++++-------
> mm/rmap.c | 2 +-
> security/tomoyo/domain.c | 2 +-
> virt/kvm/async_pf.c | 3 +--
> 10 files changed, 61 insertions(+), 40 deletions(-)
>
[...]
> diff --git a/mm/memory.c b/mm/memory.c
> index 146bb94764f8..63632a5eafc1 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -5590,7 +5590,6 @@ EXPORT_SYMBOL_GPL(generic_access_phys);
> int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
> int len, unsigned int gup_flags)
> {
> - struct vm_area_struct *vma;
> void *old_buf = buf;
> int write = gup_flags & FOLL_WRITE;
>
> @@ -5599,13 +5598,15 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
>
> /* ignore errors, just check how much was successfully transferred */
> while (len) {
> - int bytes, ret, offset;
> + int bytes, offset;
> void *maddr;
> - struct page *page = NULL;
> + struct vm_area_struct *vma;
> + struct page *page = get_user_page_vma_remote(mm, addr,
> + gup_flags, &vma);
> +
> + if (IS_ERR_OR_NULL(page)) {
> + int ret = 0;
I see the warning below when building without CONFIG_HAVE_IOREMAP_PROT set.
make --silent --keep-going --jobs=32 \
O=/home/anders/.cache/tuxmake/builds/1244/build ARCH=arm \
CROSS_COMPILE=arm-linux-gnueabihf- /home/anders/src/kernel/next/mm/memory.c: In function '__access_remote_vm':
/home/anders/src/kernel/next/mm/memory.c:5608:29: warning: unused variable 'ret' [-Wunused-variable]
5608 | int ret = 0;
| ^~~
>
> - ret = get_user_pages_remote(mm, addr, 1,
> - gup_flags, &page, &vma, NULL);
> - if (ret <= 0) {
> #ifndef CONFIG_HAVE_IOREMAP_PROT
> break;
> #else
> @@ -5613,7 +5614,6 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
> * Check if this is a VM_IO | VM_PFNMAP VMA, which
> * we can access using slightly different code.
> */
> - vma = vma_lookup(mm, addr);
> if (!vma)
> break;
> if (vma->vm_ops && vma->vm_ops->access)
Cheers,
Anders
