| Message ID | 1590294434-19125-1-git-send-email-jrdr.linux@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [linux-next,RFC,v2] mm/gup.c: Convert to use get_user_{page|pages}_fast_only() | expand |
On 2020-05-23 21:27, Souptick Joarder wrote: > API __get_user_pages_fast() renamed to get_user_pages_fast_only() > to align with pin_user_pages_fast_only(). > > As part of this we will get rid of write parameter. Instead caller > will pass FOLL_WRITE to get_user_pages_fast_only(). This will not > change any existing functionality of the API. > > All the callers are changed to pass FOLL_WRITE. This looks good. A few nits below, but with those fixed, feel free to add: Reviewed-by: John Hubbard <jhubbard@nvidia.com> > > There are few places where 1 is passed to 2nd parameter of > __get_user_pages_fast() and return value is checked for 1 > like [1]. Those are replaced with new inline > get_user_page_fast_only(). > > [1] if (__get_user_pages_fast(hva, 1, 1, &page) == 1) > We try to avoid talking *too* much about the previous version of the code. Just enough. So, instead of the above two paragraphs, I'd compress it down to: Also: introduce get_user_page_fast_only(), and use it in a few places that hard-code nr_pages to 1. ... > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 93d93bd..8d4597f 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1817,10 +1817,16 @@ extern int mprotect_fixup(struct vm_area_struct *vma, > /* > * doesn't attempt to fault and will return short. > */ > -int __get_user_pages_fast(unsigned long start, int nr_pages, int write, > - struct page **pages); > +int get_user_pages_fast_only(unsigned long start, int nr_pages, > + unsigned int gup_flags, struct page **pages); Silly nit: Can you please leave the original indentation in place? I don't normally comment about this, but I like the original indentation better, and it matches the pin_user_pages_fast() below, too. ... > @@ -2786,8 +2792,8 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages, > * If the architecture does not support this function, simply return with no > * pages pinned. > */ > -int __get_user_pages_fast(unsigned long start, int nr_pages, int write, > - struct page **pages) > +int get_user_pages_fast_only(unsigned long start, int nr_pages, > + unsigned int gup_flags, struct page **pages) Same thing here: you've changed the original indentation, which was (arguably, but to my mind anyway) more readable, and for no reason. It still would have fit within 80 cols. I'm sure it's a perfect 50/50 mix of people who prefer either indentation style, and so for brand new code, I'll remain silent, as long as it is consistent with either itself and/or the surrounding code. But changing it back and forth is a bit aggravating, and best avoided. :) thanks,
On Mon, May 25, 2020 at 6:36 AM John Hubbard <jhubbard@nvidia.com> wrote: > > On 2020-05-23 21:27, Souptick Joarder wrote: > > API __get_user_pages_fast() renamed to get_user_pages_fast_only() > > to align with pin_user_pages_fast_only(). > > > > As part of this we will get rid of write parameter. Instead caller > > will pass FOLL_WRITE to get_user_pages_fast_only(). This will not > > change any existing functionality of the API. > > > > All the callers are changed to pass FOLL_WRITE. > > This looks good. A few nits below, but with those fixed, feel free to > add: > > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > > > > > There are few places where 1 is passed to 2nd parameter of > > __get_user_pages_fast() and return value is checked for 1 > > like [1]. Those are replaced with new inline > > get_user_page_fast_only(). > > > > [1] if (__get_user_pages_fast(hva, 1, 1, &page) == 1) > > > > We try to avoid talking *too* much about the previous version of > the code. Just enough. So, instead of the above two paragraphs, > I'd compress it down to: > > Also: introduce get_user_page_fast_only(), and use it in a few > places that hard-code nr_pages to 1. > > ... > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 93d93bd..8d4597f 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -1817,10 +1817,16 @@ extern int mprotect_fixup(struct vm_area_struct *vma, > > /* > > * doesn't attempt to fault and will return short. > > */ > > -int __get_user_pages_fast(unsigned long start, int nr_pages, int write, > > - struct page **pages); > > +int get_user_pages_fast_only(unsigned long start, int nr_pages, > > + unsigned int gup_flags, struct page **pages); > > Silly nit: > > Can you please leave the original indentation in place? I don't normally > comment about this, but I like the original indentation better, and it matches > the pin_user_pages_fast() below, too. > > ... > > @@ -2786,8 +2792,8 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages, > > * If the architecture does not support this function, simply return with no > > * pages pinned. > > */ > > -int __get_user_pages_fast(unsigned long start, int nr_pages, int write, > > - struct page **pages) > > +int get_user_pages_fast_only(unsigned long start, int nr_pages, > > + unsigned int gup_flags, struct page **pages) > > > Same thing here: you've changed the original indentation, which was (arguably, but > to my mind anyway) more readable, and for no reason. It still would have fit within > 80 cols. > > I'm sure it's a perfect 50/50 mix of people who prefer either indentation style, and > so for brand new code, I'll remain silent, as long as it is consistent with either > itself and/or the surrounding code. But changing it back and forth is a bit > aggravating, and best avoided. :) Ok, along with these changes I will remove the *RFC* tag and repost it.
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index 18aed97..ddfc4c9 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -581,7 +581,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu, * We always ask for write permission since the common case * is that the page is writable. */ - if (__get_user_pages_fast(hva, 1, 1, &page) == 1) { + if (get_user_page_fast_only(hva, FOLL_WRITE, &page)) { write_ok = true; } else { /* Call KVM generic code to do the slow-path check */ diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c index 3248f78..5d4c087 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c @@ -795,7 +795,7 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu, * is that the page is writable. */ hva = gfn_to_hva_memslot(memslot, gfn); - if (!kvm_ro && __get_user_pages_fast(hva, 1, 1, &page) == 1) { + if (!kvm_ro && get_user_page_fast_only(hva, FOLL_WRITE, &page)) { upgrade_write = true; } else { unsigned long pfn; diff --git a/arch/powerpc/perf/callchain_64.c b/arch/powerpc/perf/callchain_64.c index 1bff896d..814d1c2 100644 --- a/arch/powerpc/perf/callchain_64.c +++ b/arch/powerpc/perf/callchain_64.c @@ -29,11 +29,9 @@ int read_user_stack_slow(void __user *ptr, void *buf, int nb) unsigned long addr = (unsigned long) ptr; unsigned long offset; struct page *page; - int nrpages; void *kaddr; - nrpages = __get_user_pages_fast(addr, 1, 1, &page); - if (nrpages == 1) { + if (get_user_page_fast_only(addr, FOLL_WRITE, &page)) { kaddr = page_address(page); /* align address to page boundary */ diff --git a/include/linux/mm.h b/include/linux/mm.h index 93d93bd..8d4597f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1817,10 +1817,16 @@ extern int mprotect_fixup(struct vm_area_struct *vma, /* * doesn't attempt to fault and will return short. */ -int __get_user_pages_fast(unsigned long start, int nr_pages, int write, - struct page **pages); +int get_user_pages_fast_only(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages); int pin_user_pages_fast_only(unsigned long start, int nr_pages, unsigned int gup_flags, struct page **pages); + +static inline bool get_user_page_fast_only(unsigned long addr, + unsigned int gup_flags, struct page **pagep) +{ + return get_user_pages_fast_only(addr, 1, gup_flags, pagep) == 1; +} /* * per-process(per-mm_struct) statistics. */ diff --git a/kernel/events/core.c b/kernel/events/core.c index c94eb27..856d98c 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6934,12 +6934,12 @@ static u64 perf_virt_to_phys(u64 virt) * Walking the pages tables for user address. * Interrupts are disabled, so it prevents any tear down * of the page tables. - * Try IRQ-safe __get_user_pages_fast first. + * Try IRQ-safe get_user_page_fast_only first. * If failed, leave phys_addr as 0. */ if (current->mm != NULL) { pagefault_disable(); - if (__get_user_pages_fast(virt, 1, 0, &p) == 1) + if (get_user_page_fast_only(virt, 0, &p)) phys_addr = page_to_phys(p) + virt % PAGE_SIZE; pagefault_enable(); } diff --git a/mm/gup.c b/mm/gup.c index 80f51a36..bb59f5c 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2278,7 +2278,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, * to be special. * * For a futex to be placed on a THP tail page, get_futex_key requires a - * __get_user_pages_fast implementation that can pin pages. Thus it's still + * get_user_pages_fast_only implementation that can pin pages. Thus it's still * useful to have gup_huge_pmd even if we can't operate on ptes. */ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, @@ -2683,7 +2683,7 @@ static inline void gup_pgd_range(unsigned long addr, unsigned long end, #ifndef gup_fast_permitted /* - * Check if it's allowed to use __get_user_pages_fast() for the range, or + * Check if it's allowed to use get_user_pages_fast_only() for the range, or * we need to fall back to the slow version: */ static bool gup_fast_permitted(unsigned long start, unsigned long end) @@ -2776,8 +2776,14 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages, return ret; } - -/* +/** + * get_user_pages_fast_only() - pin user pages in memory + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to * the regular GUP. * Note a difference with get_user_pages_fast: this always returns the @@ -2786,8 +2792,8 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages, * If the architecture does not support this function, simply return with no * pages pinned. */ -int __get_user_pages_fast(unsigned long start, int nr_pages, int write, - struct page **pages) +int get_user_pages_fast_only(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) { int nr_pinned; /* @@ -2797,10 +2803,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, * FOLL_FAST_ONLY is required in order to match the API description of * this routine: no fall back to regular ("slow") GUP. */ - unsigned int gup_flags = FOLL_GET | FOLL_FAST_ONLY; - - if (write) - gup_flags |= FOLL_WRITE; + gup_flags |= FOLL_GET | FOLL_FAST_ONLY; nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); @@ -2815,7 +2818,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, return nr_pinned; } -EXPORT_SYMBOL_GPL(__get_user_pages_fast); +EXPORT_SYMBOL_GPL(get_user_pages_fast_only); /** * get_user_pages_fast() - pin user pages in memory @@ -2886,8 +2889,8 @@ int pin_user_pages_fast(unsigned long start, int nr_pages, EXPORT_SYMBOL_GPL(pin_user_pages_fast); /* - * This is the FOLL_PIN equivalent of __get_user_pages_fast(). Behavior is the - * same, except that this one sets FOLL_PIN instead of FOLL_GET. + * This is the FOLL_PIN equivalent of get_user_pages_fast_only(). Behavior + * is the same, except that this one sets FOLL_PIN instead of FOLL_GET. * * The API rules are the same, too: no negative values may be returned. */ diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fc38d63..b62ea62 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1740,7 +1740,6 @@ static bool hva_to_pfn_fast(unsigned long addr, bool write_fault, bool *writable, kvm_pfn_t *pfn) { struct page *page[1]; - int npages; /* * Fast pin a writable pfn only if it is a write fault request @@ -1750,8 +1749,7 @@ static bool hva_to_pfn_fast(unsigned long addr, bool write_fault, if (!(write_fault || writable)) return false; - npages = __get_user_pages_fast(addr, 1, 1, page); - if (npages == 1) { + if (get_user_page_fast_only(addr, FOLL_WRITE, page)) { *pfn = page_to_pfn(page[0]); if (writable) @@ -1791,7 +1789,7 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault, if (unlikely(!write_fault) && writable) { struct page *wpage; - if (__get_user_pages_fast(addr, 1, 1, &wpage) == 1) { + if (get_user_page_fast_only(addr, FOLL_WRITE, &wpage)) { *writable = true; put_page(page); page = wpage; @@ -1998,7 +1996,7 @@ int gfn_to_page_many_atomic(struct kvm_memory_slot *slot, gfn_t gfn, if (entry < nr_pages) return 0; - return __get_user_pages_fast(addr, nr_pages, 1, pages); + return get_user_pages_fast_only(addr, nr_pages, FOLL_WRITE, pages); } EXPORT_SYMBOL_GPL(gfn_to_page_many_atomic);
API __get_user_pages_fast() renamed to get_user_pages_fast_only() to align with pin_user_pages_fast_only(). As part of this we will get rid of write parameter. Instead caller will pass FOLL_WRITE to get_user_pages_fast_only(). This will not change any existing functionality of the API. All the callers are changed to pass FOLL_WRITE. There are few places where 1 is passed to 2nd parameter of __get_user_pages_fast() and return value is checked for 1 like [1]. Those are replaced with new inline get_user_page_fast_only(). [1] if (__get_user_pages_fast(hva, 1, 1, &page) == 1) Updated the documentation of the API. Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Matthew Wilcox <willy@infradead.org> --- v2: Updated the subject line and change log. Address Matthew's comment to fix a bug and added new inline get_user_page_fast_only(). arch/powerpc/kvm/book3s_64_mmu_hv.c | 2 +- arch/powerpc/kvm/book3s_64_mmu_radix.c | 2 +- arch/powerpc/perf/callchain_64.c | 4 +--- include/linux/mm.h | 10 ++++++++-- kernel/events/core.c | 4 ++-- mm/gup.c | 29 ++++++++++++++++------------- virt/kvm/kvm_main.c | 8 +++----- 7 files changed, 32 insertions(+), 27 deletions(-)