| Message ID | 20220824175757.20590-7-mike.kravetz@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | hugetlb: Use new vma mutex for huge pmd sharing synchronization | expand |
On 2022/8/25 1:57, Mike Kravetz wrote: > Allocate a rw semaphore and hang off vm_private_data for > synchronization use by vmas that could be involved in pmd sharing. Only > add infrastructure for the new lock here. Actual use will be added in > subsequent patch. > > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> <snip> > +static void hugetlb_vma_lock_free(struct vm_area_struct *vma) > +{ > + /* > + * Only present in sharable vmas. See comment in > + * __unmap_hugepage_range_final about the neeed to check both s/neeed/need/ > + * VM_SHARED and VM_MAYSHARE in free path I think there might be some wrong checks around this patch. As above comment said, we need to check both flags, so we should do something like below instead? if (!(vma->vm_flags & (VM_MAYSHARE | VM_SHARED) == (VM_MAYSHARE | VM_SHARED))) > + */ > + if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) > + return; > + > + if (vma->vm_private_data) { > + kfree(vma->vm_private_data); > + vma->vm_private_data = NULL; > + } > +} > + > +static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma) > +{ > + struct rw_semaphore *vma_sema; > + > + /* Only establish in (flags) sharable vmas */ > + if (!vma || !(vma->vm_flags & VM_MAYSHARE)) > + return; > + > + /* Should never get here with non-NULL vm_private_data */ We can get here with non-NULL vm_private_data when called from hugetlb_vm_op_open during fork? Also there's one missing change on comment: diff --git a/mm/hugetlb.c b/mm/hugetlb.c index d0617d64d718..4bc844a1d312 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -863,7 +863,7 @@ __weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma) * faults in a MAP_PRIVATE mapping. Only the process that called mmap() * is guaranteed to have their future faults succeed. * - * With the exception of reset_vma_resv_huge_pages() which is called at fork(), + * With the exception of hugetlb_dup_vma_private() which is called at fork(), * the reserve counters are updated with the hugetlb_lock held. It is safe * to reset the VMA at fork() time as it is not in use yet and there is no * chance of the global counters getting corrupted as a result of the values. Otherwise this patch looks good to me. Thanks. Thanks, Miaohe Lin
On 08/27/22 17:30, Miaohe Lin wrote: > On 2022/8/25 1:57, Mike Kravetz wrote: > > Allocate a rw semaphore and hang off vm_private_data for > > synchronization use by vmas that could be involved in pmd sharing. Only > > add infrastructure for the new lock here. Actual use will be added in > > subsequent patch. > > > > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> > > <snip> > > > +static void hugetlb_vma_lock_free(struct vm_area_struct *vma) > > +{ > > + /* > > + * Only present in sharable vmas. See comment in > > + * __unmap_hugepage_range_final about the neeed to check both > > s/neeed/need/ > > > + * VM_SHARED and VM_MAYSHARE in free path > > I think there might be some wrong checks around this patch. As above comment said, we > need to check both flags, so we should do something like below instead? > > if (!(vma->vm_flags & (VM_MAYSHARE | VM_SHARED) == (VM_MAYSHARE | VM_SHARED))) > > > + */ Thanks. I will update. > > + if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) > > + return; > > + > > + if (vma->vm_private_data) { > > + kfree(vma->vm_private_data); > > + vma->vm_private_data = NULL; > > + } > > +} > > + > > +static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma) > > +{ > > + struct rw_semaphore *vma_sema; > > + > > + /* Only establish in (flags) sharable vmas */ > > + if (!vma || !(vma->vm_flags & VM_MAYSHARE)) > > + return; > > + > > + /* Should never get here with non-NULL vm_private_data */ > > We can get here with non-NULL vm_private_data when called from hugetlb_vm_op_open during fork? Right! In fork, We allocate a new semaphore in hugetlb_dup_vma_private, and then shortly after call hugetlb_vm_op_open. It works as is, and I can update the comment. However, I wonder if we should just clear vm_private_data in hugetlb_dup_vma_private and let hugetlb_vm_op_open do the allocation. > > Also there's one missing change on comment: > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index d0617d64d718..4bc844a1d312 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -863,7 +863,7 @@ __weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma) > * faults in a MAP_PRIVATE mapping. Only the process that called mmap() > * is guaranteed to have their future faults succeed. > * > - * With the exception of reset_vma_resv_huge_pages() which is called at fork(), > + * With the exception of hugetlb_dup_vma_private() which is called at fork(), > * the reserve counters are updated with the hugetlb_lock held. It is safe > * to reset the VMA at fork() time as it is not in use yet and there is no > * chance of the global counters getting corrupted as a result of the values. > > > Otherwise this patch looks good to me. Thanks. Will update, Thank you!
On 2022/8/30 6:24, Mike Kravetz wrote: > On 08/27/22 17:30, Miaohe Lin wrote: >> On 2022/8/25 1:57, Mike Kravetz wrote: >>> Allocate a rw semaphore and hang off vm_private_data for >>> synchronization use by vmas that could be involved in pmd sharing. Only >>> add infrastructure for the new lock here. Actual use will be added in >>> subsequent patch. >>> >>> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> >> >> <snip> >> >>> +static void hugetlb_vma_lock_free(struct vm_area_struct *vma) >>> +{ >>> + /* >>> + * Only present in sharable vmas. See comment in >>> + * __unmap_hugepage_range_final about the neeed to check both >> >> s/neeed/need/ >> >>> + * VM_SHARED and VM_MAYSHARE in free path >> >> I think there might be some wrong checks around this patch. As above comment said, we >> need to check both flags, so we should do something like below instead? >> >> if (!(vma->vm_flags & (VM_MAYSHARE | VM_SHARED) == (VM_MAYSHARE | VM_SHARED))) >> >>> + */ > > Thanks. I will update. > >>> + if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) >>> + return; >>> + >>> + if (vma->vm_private_data) { >>> + kfree(vma->vm_private_data); >>> + vma->vm_private_data = NULL; >>> + } >>> +} >>> + >>> +static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma) >>> +{ >>> + struct rw_semaphore *vma_sema; >>> + >>> + /* Only establish in (flags) sharable vmas */ >>> + if (!vma || !(vma->vm_flags & VM_MAYSHARE)) >>> + return; >>> + >>> + /* Should never get here with non-NULL vm_private_data */ >> >> We can get here with non-NULL vm_private_data when called from hugetlb_vm_op_open during fork? > > Right! > > In fork, We allocate a new semaphore in hugetlb_dup_vma_private, and then > shortly after call hugetlb_vm_op_open. > > It works as is, and I can update the comment. However, I wonder if we should > just clear vm_private_data in hugetlb_dup_vma_private and let hugetlb_vm_op_open > do the allocation. I think it's a good idea. We can also avoid allocating memory for vma_lock (via clear_vma_resv_huge_pages()) and then free the corresponding vma right away (via do_munmap())in move_vma(). But maybe I'm miss something. Thanks, Miaohe Lin > >> >> Also there's one missing change on comment: >> >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index d0617d64d718..4bc844a1d312 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -863,7 +863,7 @@ __weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma) >> * faults in a MAP_PRIVATE mapping. Only the process that called mmap() >> * is guaranteed to have their future faults succeed. >> * >> - * With the exception of reset_vma_resv_huge_pages() which is called at fork(), >> + * With the exception of hugetlb_dup_vma_private() which is called at fork(), >> * the reserve counters are updated with the hugetlb_lock held. It is safe >> * to reset the VMA at fork() time as it is not in use yet and there is no >> * chance of the global counters getting corrupted as a result of the values. >> >> >> Otherwise this patch looks good to me. Thanks. > > Will update, Thank you! >
On 08/29/22 15:24, Mike Kravetz wrote: > On 08/27/22 17:30, Miaohe Lin wrote: > > On 2022/8/25 1:57, Mike Kravetz wrote: > > > Allocate a rw semaphore and hang off vm_private_data for > > > synchronization use by vmas that could be involved in pmd sharing. Only > > > add infrastructure for the new lock here. Actual use will be added in > > > subsequent patch. > > > > > > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> > > > > <snip> > > > > > +static void hugetlb_vma_lock_free(struct vm_area_struct *vma) > > > +{ > > > + /* > > > + * Only present in sharable vmas. See comment in > > > + * __unmap_hugepage_range_final about the neeed to check both > > > > s/neeed/need/ > > > > > + * VM_SHARED and VM_MAYSHARE in free path > > > > I think there might be some wrong checks around this patch. As above comment said, we > > need to check both flags, so we should do something like below instead? > > > > if (!(vma->vm_flags & (VM_MAYSHARE | VM_SHARED) == (VM_MAYSHARE | VM_SHARED))) > > > > > + */ > > Thanks. I will update. > > > > + if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) > > > + return; I think you misunderstood the comment which I admit was not very clear. And, I misunderstood your suggestion. I believe the code is correct as it. Here is the proposed update comment/code: /* * Only present in sharable vmas. See comment in * __unmap_hugepage_range_final about how VM_SHARED could * be set without VM_MAYSHARE. As a result, we need to * check if either is set in the free path. */ if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) return; Hopefully, that makes more sense.
On 2022/9/8 4:50, Mike Kravetz wrote: > On 08/29/22 15:24, Mike Kravetz wrote: >> On 08/27/22 17:30, Miaohe Lin wrote: >>> On 2022/8/25 1:57, Mike Kravetz wrote: >>>> Allocate a rw semaphore and hang off vm_private_data for >>>> synchronization use by vmas that could be involved in pmd sharing. Only >>>> add infrastructure for the new lock here. Actual use will be added in >>>> subsequent patch. >>>> >>>> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> >>> >>> <snip> >>> >>>> +static void hugetlb_vma_lock_free(struct vm_area_struct *vma) >>>> +{ >>>> + /* >>>> + * Only present in sharable vmas. See comment in >>>> + * __unmap_hugepage_range_final about the neeed to check both >>> >>> s/neeed/need/ >>> >>>> + * VM_SHARED and VM_MAYSHARE in free path >>> >>> I think there might be some wrong checks around this patch. As above comment said, we >>> need to check both flags, so we should do something like below instead? >>> >>> if (!(vma->vm_flags & (VM_MAYSHARE | VM_SHARED) == (VM_MAYSHARE | VM_SHARED))) >>> >>>> + */ >> >> Thanks. I will update. >> >>>> + if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) >>>> + return; > > I think you misunderstood the comment which I admit was not very clear. And, > I misunderstood your suggestion. I believe the code is correct as it. Here > is the proposed update comment/code: > > /* > * Only present in sharable vmas. See comment in > * __unmap_hugepage_range_final about how VM_SHARED could > * be set without VM_MAYSHARE. As a result, we need to > * check if either is set in the free path. > */ > if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) > return; > > Hopefully, that makes more sense. Somewhat confusing. Thanks for clarifying, Mike. Thanks, Miaohe Lin
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index acace1a25226..852f911d676e 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -126,7 +126,7 @@ struct hugepage_subpool *hugepage_new_subpool(struct hstate *h, long max_hpages, long min_hpages); void hugepage_put_subpool(struct hugepage_subpool *spool); -void reset_vma_resv_huge_pages(struct vm_area_struct *vma); +void hugetlb_dup_vma_private(struct vm_area_struct *vma); void clear_vma_resv_huge_pages(struct vm_area_struct *vma); int hugetlb_sysctl_handler(struct ctl_table *, int, void *, size_t *, loff_t *); int hugetlb_overcommit_handler(struct ctl_table *, int, void *, size_t *, @@ -214,6 +214,13 @@ struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address, struct page *follow_huge_pgd(struct mm_struct *mm, unsigned long address, pgd_t *pgd, int flags); +void hugetlb_vma_lock_read(struct vm_area_struct *vma); +void hugetlb_vma_unlock_read(struct vm_area_struct *vma); +void hugetlb_vma_lock_write(struct vm_area_struct *vma); +void hugetlb_vma_unlock_write(struct vm_area_struct *vma); +int hugetlb_vma_trylock_write(struct vm_area_struct *vma); +void hugetlb_vma_assert_locked(struct vm_area_struct *vma); + int pmd_huge(pmd_t pmd); int pud_huge(pud_t pud); unsigned long hugetlb_change_protection(struct vm_area_struct *vma, @@ -225,7 +232,7 @@ void hugetlb_unshare_all_pmds(struct vm_area_struct *vma); #else /* !CONFIG_HUGETLB_PAGE */ -static inline void reset_vma_resv_huge_pages(struct vm_area_struct *vma) +static inline void hugetlb_dup_vma_private(struct vm_area_struct *vma) { } @@ -336,6 +343,31 @@ static inline int prepare_hugepage_range(struct file *file, return -EINVAL; } +static inline void hugetlb_vma_lock_read(struct vm_area_struct *vma) +{ +} + +static inline void hugetlb_vma_unlock_read(struct vm_area_struct *vma) +{ +} + +static inline void hugetlb_vma_lock_write(struct vm_area_struct *vma) +{ +} + +static inline void hugetlb_vma_unlock_write(struct vm_area_struct *vma) +{ +} + +static inline int hugetlb_vma_trylock_write(struct vm_area_struct *vma) +{ + return 1; +} + +static inline void hugetlb_vma_assert_locked(struct vm_area_struct *vma) +{ +} + static inline int pmd_huge(pmd_t pmd) { return 0; diff --git a/kernel/fork.c b/kernel/fork.c index 9470220e8f43..421c143286d2 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -675,12 +675,10 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, } /* - * Clear hugetlb-related page reserves for children. This only - * affects MAP_PRIVATE mappings. Faults generated by the child - * are not guaranteed to succeed, even if read-only + * Copy/update hugetlb private vma information. */ if (is_vm_hugetlb_page(tmp)) - reset_vma_resv_huge_pages(tmp); + hugetlb_dup_vma_private(tmp); /* * Link in the new vma and copy the page table entries. diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 758b6844d566..6fb0bff2c7ee 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -91,6 +91,8 @@ struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp; /* Forward declaration */ static int hugetlb_acct_memory(struct hstate *h, long delta); +static void hugetlb_vma_lock_free(struct vm_area_struct *vma); +static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma); static inline bool subpool_is_free(struct hugepage_subpool *spool) { @@ -1008,12 +1010,25 @@ static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag) return (get_vma_private_data(vma) & flag) != 0; } -/* Reset counters to 0 and clear all HPAGE_RESV_* flags */ -void reset_vma_resv_huge_pages(struct vm_area_struct *vma) +void hugetlb_dup_vma_private(struct vm_area_struct *vma) { VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma); + /* + * Clear vm_private_data + * - For MAP_PRIVATE mappings, this is the reserve map which does + * not apply to children. Faults generated by the children are + * not guaranteed to succeed, even if read-only. + * - For shared mappings this is a per-vma semaphore that may be + * allocated below. + */ + vma->vm_private_data = (void *)0; if (!(vma->vm_flags & VM_MAYSHARE)) - vma->vm_private_data = (void *)0; + return; + + /* + * Allocate semaphore if pmd sharing is possible. + */ + hugetlb_vma_lock_alloc(vma); } /* @@ -1044,7 +1059,7 @@ void clear_vma_resv_huge_pages(struct vm_area_struct *vma) kref_put(&reservations->refs, resv_map_release); } - reset_vma_resv_huge_pages(vma); + hugetlb_dup_vma_private(vma); } /* Returns true if the VMA has associated reserve pages */ @@ -4623,16 +4638,21 @@ static void hugetlb_vm_op_open(struct vm_area_struct *vma) resv_map_dup_hugetlb_cgroup_uncharge_info(resv); kref_get(&resv->refs); } + + hugetlb_vma_lock_alloc(vma); } static void hugetlb_vm_op_close(struct vm_area_struct *vma) { struct hstate *h = hstate_vma(vma); - struct resv_map *resv = vma_resv_map(vma); + struct resv_map *resv; struct hugepage_subpool *spool = subpool_vma(vma); unsigned long reserve, start, end; long gbl_reserve; + hugetlb_vma_lock_free(vma); + + resv = vma_resv_map(vma); if (!resv || !is_vma_resv_set(vma, HPAGE_RESV_OWNER)) return; @@ -6447,6 +6467,11 @@ bool hugetlb_reserve_pages(struct inode *inode, return false; } + /* + * vma specific semaphore used for pmd sharing synchronization + */ + hugetlb_vma_lock_alloc(vma); + /* * Only apply hugepage reservation if asked. At fault time, an * attempt will be made for VM_NORESERVE to allocate a page @@ -6470,12 +6495,11 @@ bool hugetlb_reserve_pages(struct inode *inode, resv_map = inode_resv_map(inode); chg = region_chg(resv_map, from, to, ®ions_needed); - } else { /* Private mapping. */ resv_map = resv_map_alloc(); if (!resv_map) - return false; + goto out_err; chg = to - from; @@ -6570,6 +6594,7 @@ bool hugetlb_reserve_pages(struct inode *inode, hugetlb_cgroup_uncharge_cgroup_rsvd(hstate_index(h), chg * pages_per_huge_page(h), h_cg); out_err: + hugetlb_vma_lock_free(vma); if (!vma || vma->vm_flags & VM_MAYSHARE) /* Only call region_abort if the region_chg succeeded but the * region_add failed or didn't run. @@ -6649,14 +6674,34 @@ static unsigned long page_table_shareable(struct vm_area_struct *svma, } static bool __vma_aligned_range_pmd_shareable(struct vm_area_struct *vma, - unsigned long start, unsigned long end) + unsigned long start, unsigned long end, + bool check_vma_lock) { +#ifdef CONFIG_USERFAULTFD + if (uffd_disable_huge_pmd_share(vma)) + return false; +#endif /* * check on proper vm_flags and page table alignment */ - if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, start, end)) - return true; - return false; + if (!(vma->vm_flags & VM_MAYSHARE)) + return false; + if (check_vma_lock && !vma->vm_private_data) + return false; + if (!range_in_vma(vma, start, end)) + return false; + return true; +} + +static bool vma_pmd_shareable(struct vm_area_struct *vma) +{ + unsigned long start = ALIGN(vma->vm_start, PUD_SIZE), + end = ALIGN_DOWN(vma->vm_end, PUD_SIZE); + + if (start >= end) + return false; + + return __vma_aligned_range_pmd_shareable(vma, start, end, false); } static bool vma_addr_pmd_shareable(struct vm_area_struct *vma, @@ -6665,15 +6710,11 @@ static bool vma_addr_pmd_shareable(struct vm_area_struct *vma, unsigned long start = addr & PUD_MASK; unsigned long end = start + PUD_SIZE; - return __vma_aligned_range_pmd_shareable(vma, start, end); + return __vma_aligned_range_pmd_shareable(vma, start, end, true); } bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) { -#ifdef CONFIG_USERFAULTFD - if (uffd_disable_huge_pmd_share(vma)) - return false; -#endif return vma_addr_pmd_shareable(vma, addr); } @@ -6704,6 +6745,95 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, *end = ALIGN(*end, PUD_SIZE); } +static bool __vma_shareable_flags_pmd(struct vm_area_struct *vma) +{ + return vma->vm_flags & (VM_MAYSHARE | VM_SHARED) && + vma->vm_private_data; +} + +void hugetlb_vma_lock_read(struct vm_area_struct *vma) +{ + if (__vma_shareable_flags_pmd(vma)) + down_read((struct rw_semaphore *)vma->vm_private_data); +} + +void hugetlb_vma_unlock_read(struct vm_area_struct *vma) +{ + if (__vma_shareable_flags_pmd(vma)) + up_read((struct rw_semaphore *)vma->vm_private_data); +} + +void hugetlb_vma_lock_write(struct vm_area_struct *vma) +{ + if (__vma_shareable_flags_pmd(vma)) + down_write((struct rw_semaphore *)vma->vm_private_data); +} + +void hugetlb_vma_unlock_write(struct vm_area_struct *vma) +{ + if (__vma_shareable_flags_pmd(vma)) + up_write((struct rw_semaphore *)vma->vm_private_data); +} + +int hugetlb_vma_trylock_write(struct vm_area_struct *vma) +{ + if (!__vma_shareable_flags_pmd(vma)) + return 1; + + return down_write_trylock((struct rw_semaphore *)vma->vm_private_data); +} + +void hugetlb_vma_assert_locked(struct vm_area_struct *vma) +{ + if (__vma_shareable_flags_pmd(vma)) + lockdep_assert_held((struct rw_semaphore *) + vma->vm_private_data); +} + +static void hugetlb_vma_lock_free(struct vm_area_struct *vma) +{ + /* + * Only present in sharable vmas. See comment in + * __unmap_hugepage_range_final about the neeed to check both + * VM_SHARED and VM_MAYSHARE in free path + */ + if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) + return; + + if (vma->vm_private_data) { + kfree(vma->vm_private_data); + vma->vm_private_data = NULL; + } +} + +static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma) +{ + struct rw_semaphore *vma_sema; + + /* Only establish in (flags) sharable vmas */ + if (!vma || !(vma->vm_flags & VM_MAYSHARE)) + return; + + /* Should never get here with non-NULL vm_private_data */ + if (vma->vm_private_data) + return; + + /* Check size/alignment for pmd sharing possible */ + if (!vma_pmd_shareable(vma)) + return; + + vma_sema = kmalloc(sizeof(*vma_sema), GFP_KERNEL); + if (!vma_sema) + /* + * If we can not allocate semaphore, then vma can not + * participate in pmd sharing. + */ + return; + + init_rwsem(vma_sema); + vma->vm_private_data = vma_sema; +} + /* * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc() * and returns the corresponding pte. While this is not necessary for the @@ -6790,6 +6920,14 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma, } #else /* !CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ +static void hugetlb_vma_lock_free(struct vm_area_struct *vma) +{ +} + +static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma) +{ +} + pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, pud_t *pud) { diff --git a/mm/rmap.c b/mm/rmap.c index ad9c97c6445c..55209e029847 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -24,7 +24,7 @@ * mm->mmap_lock * mapping->invalidate_lock (in filemap_fault) * page->flags PG_locked (lock_page) - * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share) + * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below) * mapping->i_mmap_rwsem * anon_vma->rwsem * mm->page_table_lock or pte_lock @@ -44,6 +44,12 @@ * anon_vma->rwsem,mapping->i_mmap_rwsem (memory_failure, collect_procs_anon) * ->tasklist_lock * pte map lock + * + * hugetlbfs PageHuge() take locks in this order: + * hugetlb_fault_mutex (hugetlbfs specific page fault mutex) + * vma_lock (hugetlb specific lock for pmd_sharing) + * mapping->i_mmap_rwsem (also used for hugetlb pmd sharing) + * page->flags PG_locked (lock_page) */ #include <linux/mm.h>
Allocate a rw semaphore and hang off vm_private_data for synchronization use by vmas that could be involved in pmd sharing. Only add infrastructure for the new lock here. Actual use will be added in subsequent patch. Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> --- include/linux/hugetlb.h | 36 ++++++++- kernel/fork.c | 6 +- mm/hugetlb.c | 170 ++++++++++++++++++++++++++++++++++++---- mm/rmap.c | 8 +- 4 files changed, 197 insertions(+), 23 deletions(-)