| Message ID | 20230613215346.1022773-8-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/gup: Unify hugetlb, speed up thp | expand |
On Tue, Jun 13, 2023 at 05:53:46PM -0400, Peter Xu wrote: > Now __get_user_pages() should be well prepared to handle thp completely, > as long as hugetlb gup requests even without the hugetlb's special path. > > Time to retire follow_hugetlb_page(). > > Tweak the comments in follow_page_mask() to reflect reality, by dropping > the "follow_page()" description. > > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > include/linux/hugetlb.h | 12 --- > mm/gup.c | 19 ---- > mm/hugetlb.c | 223 ---------------------------------------- > 3 files changed, 254 deletions(-) It is a like a dream come true :) I don't know enough about hugetlb details but this series broadly made sense to me Thanks, Jason
On Tue, Jun 13, 2023 at 05:53:46PM -0400, Peter Xu wrote: > Now __get_user_pages() should be well prepared to handle thp completely, > as long as hugetlb gup requests even without the hugetlb's special path. > > Time to retire follow_hugetlb_page(). Nit, but there's a couple left over references to this function in comments in fs/userfaultfd.c and mm/hugetlb.c. > > Tweak the comments in follow_page_mask() to reflect reality, by dropping > the "follow_page()" description. > > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > include/linux/hugetlb.h | 12 --- > mm/gup.c | 19 ---- > mm/hugetlb.c | 223 ---------------------------------------- > 3 files changed, 254 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 0d6f389d98de..44e5836eed15 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -133,9 +133,6 @@ int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, > struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, > unsigned long address, unsigned int flags, > unsigned int *page_mask); > -long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, > - struct page **, unsigned long *, unsigned long *, > - long, unsigned int, int *); > void unmap_hugepage_range(struct vm_area_struct *, > unsigned long, unsigned long, struct page *, > zap_flags_t); > @@ -305,15 +302,6 @@ static inline struct page *hugetlb_follow_page_mask( > BUILD_BUG(); /* should never be compiled in if !CONFIG_HUGETLB_PAGE*/ > } > > -static inline long follow_hugetlb_page(struct mm_struct *mm, > - struct vm_area_struct *vma, struct page **pages, > - unsigned long *position, unsigned long *nr_pages, > - long i, unsigned int flags, int *nonblocking) > -{ > - BUG(); > - return 0; > -} > - > static inline int copy_hugetlb_page_range(struct mm_struct *dst, > struct mm_struct *src, > struct vm_area_struct *dst_vma, > diff --git a/mm/gup.c b/mm/gup.c > index cdabc8ea783b..a65b80953b7a 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -789,9 +789,6 @@ static struct page *follow_page_mask(struct vm_area_struct *vma, > * Call hugetlb_follow_page_mask for hugetlb vmas as it will use > * special hugetlb page table walking code. This eliminates the > * need to check for hugetlb entries in the general walking code. > - * > - * hugetlb_follow_page_mask is only for follow_page() handling here. > - * Ordinary GUP uses follow_hugetlb_page for hugetlb processing. > */ > if (is_vm_hugetlb_page(vma)) > return hugetlb_follow_page_mask(vma, address, flags, > @@ -1149,22 +1146,6 @@ static long __get_user_pages(struct mm_struct *mm, > ret = check_vma_flags(vma, gup_flags); > if (ret) > goto out; > - > - if (is_vm_hugetlb_page(vma)) { > - i = follow_hugetlb_page(mm, vma, pages, > - &start, &nr_pages, i, > - gup_flags, locked); > - if (!*locked) { > - /* > - * We've got a VM_FAULT_RETRY > - * and we've lost mmap_lock. > - * We must stop here. > - */ > - BUG_ON(gup_flags & FOLL_NOWAIT); > - goto out; > - } > - continue; > - } > } > retry: > /* > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 31d8f18bc2e4..b7ff413ff68b 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6425,37 +6425,6 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, > } > #endif /* CONFIG_USERFAULTFD */ > > -static void record_subpages(struct page *page, struct vm_area_struct *vma, > - int refs, struct page **pages) > -{ > - int nr; > - > - for (nr = 0; nr < refs; nr++) { > - if (likely(pages)) > - pages[nr] = nth_page(page, nr); > - } > -} > - > -static inline bool __follow_hugetlb_must_fault(struct vm_area_struct *vma, > - unsigned int flags, pte_t *pte, > - bool *unshare) > -{ > - pte_t pteval = huge_ptep_get(pte); > - > - *unshare = false; > - if (is_swap_pte(pteval)) > - return true; > - if (huge_pte_write(pteval)) > - return false; > - if (flags & FOLL_WRITE) > - return true; > - if (gup_must_unshare(vma, flags, pte_page(pteval))) { > - *unshare = true; > - return true; > - } > - return false; > -} > - > struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, > unsigned long address, unsigned int flags, > unsigned int *page_mask) > @@ -6518,198 +6487,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, > return page; > } > > -long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, > - struct page **pages, unsigned long *position, > - unsigned long *nr_pages, long i, unsigned int flags, > - int *locked) > -{ > - unsigned long pfn_offset; > - unsigned long vaddr = *position; > - unsigned long remainder = *nr_pages; > - struct hstate *h = hstate_vma(vma); > - int err = -EFAULT, refs; > - > - while (vaddr < vma->vm_end && remainder) { > - pte_t *pte; > - spinlock_t *ptl = NULL; > - bool unshare = false; > - int absent; > - struct page *page; > - > - /* > - * If we have a pending SIGKILL, don't keep faulting pages and > - * potentially allocating memory. > - */ > - if (fatal_signal_pending(current)) { > - remainder = 0; > - break; > - } > - > - hugetlb_vma_lock_read(vma); > - /* > - * Some archs (sparc64, sh*) have multiple pte_ts to > - * each hugepage. We have to make sure we get the > - * first, for the page indexing below to work. > - * > - * Note that page table lock is not held when pte is null. > - */ > - pte = hugetlb_walk(vma, vaddr & huge_page_mask(h), > - huge_page_size(h)); > - if (pte) > - ptl = huge_pte_lock(h, mm, pte); > - absent = !pte || huge_pte_none(huge_ptep_get(pte)); > - > - /* > - * When coredumping, it suits get_dump_page if we just return > - * an error where there's an empty slot with no huge pagecache > - * to back it. This way, we avoid allocating a hugepage, and > - * the sparse dumpfile avoids allocating disk blocks, but its > - * huge holes still show up with zeroes where they need to be. > - */ > - if (absent && (flags & FOLL_DUMP) && > - !hugetlbfs_pagecache_present(h, vma, vaddr)) { > - if (pte) > - spin_unlock(ptl); > - hugetlb_vma_unlock_read(vma); > - remainder = 0; > - break; > - } > - > - /* > - * We need call hugetlb_fault for both hugepages under migration > - * (in which case hugetlb_fault waits for the migration,) and > - * hwpoisoned hugepages (in which case we need to prevent the > - * caller from accessing to them.) In order to do this, we use > - * here is_swap_pte instead of is_hugetlb_entry_migration and > - * is_hugetlb_entry_hwpoisoned. This is because it simply covers > - * both cases, and because we can't follow correct pages > - * directly from any kind of swap entries. > - */ > - if (absent || > - __follow_hugetlb_must_fault(vma, flags, pte, &unshare)) { > - vm_fault_t ret; > - unsigned int fault_flags = 0; > - > - if (pte) > - spin_unlock(ptl); > - hugetlb_vma_unlock_read(vma); > - > - if (flags & FOLL_WRITE) > - fault_flags |= FAULT_FLAG_WRITE; > - else if (unshare) > - fault_flags |= FAULT_FLAG_UNSHARE; > - if (locked) { > - fault_flags |= FAULT_FLAG_ALLOW_RETRY | > - FAULT_FLAG_KILLABLE; > - if (flags & FOLL_INTERRUPTIBLE) > - fault_flags |= FAULT_FLAG_INTERRUPTIBLE; > - } > - if (flags & FOLL_NOWAIT) > - fault_flags |= FAULT_FLAG_ALLOW_RETRY | > - FAULT_FLAG_RETRY_NOWAIT; > - if (flags & FOLL_TRIED) { > - /* > - * Note: FAULT_FLAG_ALLOW_RETRY and > - * FAULT_FLAG_TRIED can co-exist > - */ > - fault_flags |= FAULT_FLAG_TRIED; > - } > - ret = hugetlb_fault(mm, vma, vaddr, fault_flags); > - if (ret & VM_FAULT_ERROR) { > - err = vm_fault_to_errno(ret, flags); > - remainder = 0; > - break; > - } > - if (ret & VM_FAULT_RETRY) { > - if (locked && > - !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) > - *locked = 0; > - *nr_pages = 0; > - /* > - * VM_FAULT_RETRY must not return an > - * error, it will return zero > - * instead. > - * > - * No need to update "position" as the > - * caller will not check it after > - * *nr_pages is set to 0. > - */ > - return i; > - } > - continue; > - } > - > - pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT; > - page = pte_page(huge_ptep_get(pte)); > - > - VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) && > - !PageAnonExclusive(page), page); > - > - /* > - * If subpage information not requested, update counters > - * and skip the same_page loop below. > - */ > - if (!pages && !pfn_offset && > - (vaddr + huge_page_size(h) < vma->vm_end) && > - (remainder >= pages_per_huge_page(h))) { > - vaddr += huge_page_size(h); > - remainder -= pages_per_huge_page(h); > - i += pages_per_huge_page(h); > - spin_unlock(ptl); > - hugetlb_vma_unlock_read(vma); > - continue; > - } > - > - /* vaddr may not be aligned to PAGE_SIZE */ > - refs = min3(pages_per_huge_page(h) - pfn_offset, remainder, > - (vma->vm_end - ALIGN_DOWN(vaddr, PAGE_SIZE)) >> PAGE_SHIFT); > - > - if (pages) > - record_subpages(nth_page(page, pfn_offset), > - vma, refs, > - likely(pages) ? pages + i : NULL); > - > - if (pages) { > - /* > - * try_grab_folio() should always succeed here, > - * because: a) we hold the ptl lock, and b) we've just > - * checked that the huge page is present in the page > - * tables. If the huge page is present, then the tail > - * pages must also be present. The ptl prevents the > - * head page and tail pages from being rearranged in > - * any way. As this is hugetlb, the pages will never > - * be p2pdma or not longterm pinable. So this page > - * must be available at this point, unless the page > - * refcount overflowed: > - */ > - if (WARN_ON_ONCE(!try_grab_folio(pages[i], refs, > - flags))) { > - spin_unlock(ptl); > - hugetlb_vma_unlock_read(vma); > - remainder = 0; > - err = -ENOMEM; > - break; > - } > - } > - > - vaddr += (refs << PAGE_SHIFT); > - remainder -= refs; > - i += refs; > - > - spin_unlock(ptl); > - hugetlb_vma_unlock_read(vma); > - } > - *nr_pages = remainder; > - /* > - * setting position is actually required only if remainder is > - * not zero but it's faster not to add a "if (remainder)" > - * branch. > - */ > - *position = vaddr; > - > - return i ? i : err; > -} > - > long hugetlb_change_protection(struct vm_area_struct *vma, > unsigned long address, unsigned long end, > pgprot_t newprot, unsigned long cp_flags) > -- > 2.40.1 > Absolutely wonderful to see such delightful code deletion :) I haven't really dug into the huge page side of this in great detail, so I can't give a meaningful tag, but I can certainly appreciate the code you're removing here!
On Sat, Jun 17, 2023 at 09:40:41PM +0100, Lorenzo Stoakes wrote: > On Tue, Jun 13, 2023 at 05:53:46PM -0400, Peter Xu wrote: > > Now __get_user_pages() should be well prepared to handle thp completely, > > as long as hugetlb gup requests even without the hugetlb's special path. > > > > Time to retire follow_hugetlb_page(). > > Nit, but there's a couple left over references to this function in comments > in fs/userfaultfd.c and mm/hugetlb.c. Indeed, let me touch those too when respin. > Absolutely wonderful to see such delightful code deletion :) > > I haven't really dug into the huge page side of this in great detail, so I > can't give a meaningful tag, but I can certainly appreciate the code you're > removing here! Yeah, hopefully it'll make the code also cleaner. Thanks a lot,
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 0d6f389d98de..44e5836eed15 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -133,9 +133,6 @@ int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, unsigned long address, unsigned int flags, unsigned int *page_mask); -long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, - struct page **, unsigned long *, unsigned long *, - long, unsigned int, int *); void unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long, struct page *, zap_flags_t); @@ -305,15 +302,6 @@ static inline struct page *hugetlb_follow_page_mask( BUILD_BUG(); /* should never be compiled in if !CONFIG_HUGETLB_PAGE*/ } -static inline long follow_hugetlb_page(struct mm_struct *mm, - struct vm_area_struct *vma, struct page **pages, - unsigned long *position, unsigned long *nr_pages, - long i, unsigned int flags, int *nonblocking) -{ - BUG(); - return 0; -} - static inline int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, struct vm_area_struct *dst_vma, diff --git a/mm/gup.c b/mm/gup.c index cdabc8ea783b..a65b80953b7a 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -789,9 +789,6 @@ static struct page *follow_page_mask(struct vm_area_struct *vma, * Call hugetlb_follow_page_mask for hugetlb vmas as it will use * special hugetlb page table walking code. This eliminates the * need to check for hugetlb entries in the general walking code. - * - * hugetlb_follow_page_mask is only for follow_page() handling here. - * Ordinary GUP uses follow_hugetlb_page for hugetlb processing. */ if (is_vm_hugetlb_page(vma)) return hugetlb_follow_page_mask(vma, address, flags, @@ -1149,22 +1146,6 @@ static long __get_user_pages(struct mm_struct *mm, ret = check_vma_flags(vma, gup_flags); if (ret) goto out; - - if (is_vm_hugetlb_page(vma)) { - i = follow_hugetlb_page(mm, vma, pages, - &start, &nr_pages, i, - gup_flags, locked); - if (!*locked) { - /* - * We've got a VM_FAULT_RETRY - * and we've lost mmap_lock. - * We must stop here. - */ - BUG_ON(gup_flags & FOLL_NOWAIT); - goto out; - } - continue; - } } retry: /* diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 31d8f18bc2e4..b7ff413ff68b 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6425,37 +6425,6 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, } #endif /* CONFIG_USERFAULTFD */ -static void record_subpages(struct page *page, struct vm_area_struct *vma, - int refs, struct page **pages) -{ - int nr; - - for (nr = 0; nr < refs; nr++) { - if (likely(pages)) - pages[nr] = nth_page(page, nr); - } -} - -static inline bool __follow_hugetlb_must_fault(struct vm_area_struct *vma, - unsigned int flags, pte_t *pte, - bool *unshare) -{ - pte_t pteval = huge_ptep_get(pte); - - *unshare = false; - if (is_swap_pte(pteval)) - return true; - if (huge_pte_write(pteval)) - return false; - if (flags & FOLL_WRITE) - return true; - if (gup_must_unshare(vma, flags, pte_page(pteval))) { - *unshare = true; - return true; - } - return false; -} - struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, unsigned long address, unsigned int flags, unsigned int *page_mask) @@ -6518,198 +6487,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, return page; } -long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, - struct page **pages, unsigned long *position, - unsigned long *nr_pages, long i, unsigned int flags, - int *locked) -{ - unsigned long pfn_offset; - unsigned long vaddr = *position; - unsigned long remainder = *nr_pages; - struct hstate *h = hstate_vma(vma); - int err = -EFAULT, refs; - - while (vaddr < vma->vm_end && remainder) { - pte_t *pte; - spinlock_t *ptl = NULL; - bool unshare = false; - int absent; - struct page *page; - - /* - * If we have a pending SIGKILL, don't keep faulting pages and - * potentially allocating memory. - */ - if (fatal_signal_pending(current)) { - remainder = 0; - break; - } - - hugetlb_vma_lock_read(vma); - /* - * Some archs (sparc64, sh*) have multiple pte_ts to - * each hugepage. We have to make sure we get the - * first, for the page indexing below to work. - * - * Note that page table lock is not held when pte is null. - */ - pte = hugetlb_walk(vma, vaddr & huge_page_mask(h), - huge_page_size(h)); - if (pte) - ptl = huge_pte_lock(h, mm, pte); - absent = !pte || huge_pte_none(huge_ptep_get(pte)); - - /* - * When coredumping, it suits get_dump_page if we just return - * an error where there's an empty slot with no huge pagecache - * to back it. This way, we avoid allocating a hugepage, and - * the sparse dumpfile avoids allocating disk blocks, but its - * huge holes still show up with zeroes where they need to be. - */ - if (absent && (flags & FOLL_DUMP) && - !hugetlbfs_pagecache_present(h, vma, vaddr)) { - if (pte) - spin_unlock(ptl); - hugetlb_vma_unlock_read(vma); - remainder = 0; - break; - } - - /* - * We need call hugetlb_fault for both hugepages under migration - * (in which case hugetlb_fault waits for the migration,) and - * hwpoisoned hugepages (in which case we need to prevent the - * caller from accessing to them.) In order to do this, we use - * here is_swap_pte instead of is_hugetlb_entry_migration and - * is_hugetlb_entry_hwpoisoned. This is because it simply covers - * both cases, and because we can't follow correct pages - * directly from any kind of swap entries. - */ - if (absent || - __follow_hugetlb_must_fault(vma, flags, pte, &unshare)) { - vm_fault_t ret; - unsigned int fault_flags = 0; - - if (pte) - spin_unlock(ptl); - hugetlb_vma_unlock_read(vma); - - if (flags & FOLL_WRITE) - fault_flags |= FAULT_FLAG_WRITE; - else if (unshare) - fault_flags |= FAULT_FLAG_UNSHARE; - if (locked) { - fault_flags |= FAULT_FLAG_ALLOW_RETRY | - FAULT_FLAG_KILLABLE; - if (flags & FOLL_INTERRUPTIBLE) - fault_flags |= FAULT_FLAG_INTERRUPTIBLE; - } - if (flags & FOLL_NOWAIT) - fault_flags |= FAULT_FLAG_ALLOW_RETRY | - FAULT_FLAG_RETRY_NOWAIT; - if (flags & FOLL_TRIED) { - /* - * Note: FAULT_FLAG_ALLOW_RETRY and - * FAULT_FLAG_TRIED can co-exist - */ - fault_flags |= FAULT_FLAG_TRIED; - } - ret = hugetlb_fault(mm, vma, vaddr, fault_flags); - if (ret & VM_FAULT_ERROR) { - err = vm_fault_to_errno(ret, flags); - remainder = 0; - break; - } - if (ret & VM_FAULT_RETRY) { - if (locked && - !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) - *locked = 0; - *nr_pages = 0; - /* - * VM_FAULT_RETRY must not return an - * error, it will return zero - * instead. - * - * No need to update "position" as the - * caller will not check it after - * *nr_pages is set to 0. - */ - return i; - } - continue; - } - - pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT; - page = pte_page(huge_ptep_get(pte)); - - VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) && - !PageAnonExclusive(page), page); - - /* - * If subpage information not requested, update counters - * and skip the same_page loop below. - */ - if (!pages && !pfn_offset && - (vaddr + huge_page_size(h) < vma->vm_end) && - (remainder >= pages_per_huge_page(h))) { - vaddr += huge_page_size(h); - remainder -= pages_per_huge_page(h); - i += pages_per_huge_page(h); - spin_unlock(ptl); - hugetlb_vma_unlock_read(vma); - continue; - } - - /* vaddr may not be aligned to PAGE_SIZE */ - refs = min3(pages_per_huge_page(h) - pfn_offset, remainder, - (vma->vm_end - ALIGN_DOWN(vaddr, PAGE_SIZE)) >> PAGE_SHIFT); - - if (pages) - record_subpages(nth_page(page, pfn_offset), - vma, refs, - likely(pages) ? pages + i : NULL); - - if (pages) { - /* - * try_grab_folio() should always succeed here, - * because: a) we hold the ptl lock, and b) we've just - * checked that the huge page is present in the page - * tables. If the huge page is present, then the tail - * pages must also be present. The ptl prevents the - * head page and tail pages from being rearranged in - * any way. As this is hugetlb, the pages will never - * be p2pdma or not longterm pinable. So this page - * must be available at this point, unless the page - * refcount overflowed: - */ - if (WARN_ON_ONCE(!try_grab_folio(pages[i], refs, - flags))) { - spin_unlock(ptl); - hugetlb_vma_unlock_read(vma); - remainder = 0; - err = -ENOMEM; - break; - } - } - - vaddr += (refs << PAGE_SHIFT); - remainder -= refs; - i += refs; - - spin_unlock(ptl); - hugetlb_vma_unlock_read(vma); - } - *nr_pages = remainder; - /* - * setting position is actually required only if remainder is - * not zero but it's faster not to add a "if (remainder)" - * branch. - */ - *position = vaddr; - - return i ? i : err; -} - long hugetlb_change_protection(struct vm_area_struct *vma, unsigned long address, unsigned long end, pgprot_t newprot, unsigned long cp_flags)
Now __get_user_pages() should be well prepared to handle thp completely, as long as hugetlb gup requests even without the hugetlb's special path. Time to retire follow_hugetlb_page(). Tweak the comments in follow_page_mask() to reflect reality, by dropping the "follow_page()" description. Signed-off-by: Peter Xu <peterx@redhat.com> --- include/linux/hugetlb.h | 12 --- mm/gup.c | 19 ---- mm/hugetlb.c | 223 ---------------------------------------- 3 files changed, 254 deletions(-)