remove the vmas parameter from GUP APIs
Subsystems (36)
v3 cover remove the vmas parameter from GUP APIs
(pin_/get)_user_pages[_remote]() each provide an optional output parameter for an array of VMA objects associated with each page in the input range.
These provide the means for VMAs to be returned, as long as mm->mmap_lock is never released during the GUP operation (i.e. the internal flag FOLL_UNLOCKABLE is not specified).
In addition, these VMAs have also to only be accessed under the mmap_lock, and become invalidated the moment it is released.
The vast majority of invocations do not use this functionality and of those that do, all but one retrieve a single VMA to perform checks upon.
It is not egregious in the single VMA cases to simply replace the operation with a vma_lookup(). In these cases we duplicate the (fast) lookup on a slow path already under the mmap_lock.
The special case is io_uring, where io_pin_pages() specifically needs to assert that all the VMAs possess the same vm->vm_file (possibly NULL) and they are either anonymous or hugetlb pages.
To continue to provide this functionality, we introduce the FOLL_SAME_PAGE flag which asserts that the vma->vm_file remains the same throughout, erroring out if this is not the case.
We can then replace the io_uring case by passing FOLL_SAME_FILE and looking up the first VMA manually and performing the required checks on this alone. The combination of the two amount to the same checks being performed (and avoids an allocation).
Eliminating this parameter eliminates an entire class of errors - the vmas array used to become a set of dangling pointers if access after release of mmap_lock was attempted, this is simply no longer possible.
In addition the API is simplified and now clearly expresses what it is for
- applying the specified GUP flags and (if pinning) returning pinned pages.
This change additionally opens the door to further potential improvements in GUP and the possible marrying of disparate code paths.
I have run the gup_test and a simple io_uring program which exercises the use of FOLL_SAME_PAGE with no issues.
Thanks to Matthew Wilcox for suggesting this refactoring!
v3:
- Always explicitly handle !vma cases, feeding back an error to the user if appropriate, indicating the operation did not completely succeed if not and always with a warning since these conditions should be impossible.
v2:
- Only lookup the VMA if the pin succeeded (other than __access_remote_vm() which has different semantics)
- Be pedantically careful about ensuring that under no circumstances can we fail to unpin a page
https://lore.kernel.org/linux-mm/[email protected]/
v1:
https://lore.kernel.org/linux-mm/[email protected]/
Lorenzo Stoakes (7):
mm/gup: remove unused vmas parameter from get_user_pages() mm/gup: remove unused vmas parameter from pin_user_pages_remote() mm/gup: remove vmas parameter from get_user_pages_remote() mm/gup: introduce the FOLL_SAME_FILE GUP flag
io_uring: rsrc: use FOLL_SAME_FILE on pin_user_pages() mm/gup: remove vmas parameter from pin_user_pages() mm/gup: remove vmas array from internal GUP functions
arch/arm64/kernel/mte.c | 7 +- arch/powerpc/mm/book3s64/iommu_api.c | 2 +- arch/s390/kvm/interrupt.c | 2 +- arch/x86/kernel/cpu/sgx/ioctl.c | 2 +- drivers/gpu/drm/radeon/radeon_ttm.c | 2 +- drivers/infiniband/hw/qib/qib_user_pages.c | 2 +- drivers/infiniband/hw/usnic/usnic_uiom.c | 2 +- drivers/infiniband/sw/siw/siw_mem.c | 2 +- drivers/iommu/iommufd/pages.c | 4 +- drivers/media/v4l2-core/videobuf-dma-sg.c | 2 +- drivers/misc/sgi-gru/grufault.c | 2 +- drivers/vdpa/vdpa_user/vduse_dev.c | 2 +- drivers/vfio/vfio_iommu_type1.c | 2 +- drivers/vhost/vdpa.c | 2 +- fs/exec.c | 2 +- include/linux/hugetlb.h | 10 +- include/linux/mm.h | 10 +- include/linux/mm_types.h | 2 + io_uring/rsrc.c | 40 +++---- kernel/events/uprobes.c | 14 ++- mm/gup.c | 121 ++++++++------------- mm/gup_test.c | 14 +-- mm/hugetlb.c | 24 ++-- mm/memory.c | 8 +- mm/process_vm_access.c | 2 +- mm/rmap.c | 2 +- net/xdp/xdp_umem.c | 2 +- security/tomoyo/domain.c | 2 +- virt/kvm/async_pf.c | 3 +- virt/kvm/kvm_main.c | 2 +- 30 files changed, 132 insertions(+), 161 deletions(-)
Signature · 1 line
2.40.0
PATCH v3 1/7 mm/gup: remove unused vmas parameter from get_user_pages()
No invocation of get_user_pages() uses the vmas parameter, so remove it.
The GUP API is confusing and caveated. Recent changes have done much to improve that, however there is more we can do. Exporting vmas is a prime target as the caller has to be extremely careful to preclude their use after the mmap_lock has expired or otherwise be left with dangling pointers.
Removing the vmas parameter focuses the GUP functions upon their primary purpose - pinning (and outputting) pages as well as performing the actions implied by the input flags.
This is part of a patch series aiming to remove the vmas parameter altogether.
--- arch/x86/kernel/cpu/sgx/ioctl.c | 2 +- drivers/gpu/drm/radeon/radeon_ttm.c | 2 +- drivers/misc/sgi-gru/grufault.c | 2 +- include/linux/mm.h | 3 +-- mm/gup.c | 9 +++------ mm/gup_test.c | 5 ++--- virt/kvm/kvm_main.c | 2 +- 7 files changed, 10 insertions(+), 15 deletions(-)
arch/x86/kernel/cpu/sgx/ioctl.c +1 -1
@@ -214,7 +214,7 @@ static int __sgx_encl_add_page(struct sgx_encl *encl,if (!(vma->vm_flags &VM_MAYEXEC ))return -EACCES ; - ret =get_user_pages (src,1 ,0 , &src_page,NULL ); + ret =get_user_pages (src,1 ,0 , &src_page);if (ret <1 )return -EFAULT ;
drivers/gpu/drm/radeon/radeon_ttm.c +1 -1
@@ -362,7 +362,7 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_device *bdev, struct ttm_tt *ttmstruct page **pages = ttm->pages + pinned; r =get_user_pages (userptr, num_pages, write ?FOLL_WRITE :0 , - pages,NULL ); + pages);if (r <0 ) goto release_pages;
drivers/misc/sgi-gru/grufault.c +1 -1
@@ -185,7 +185,7 @@ static int non_atomic_pte_lookup(struct vm_area_struct *vma,#else *pageshift =PAGE_SHIFT ;#endif -if (get_user_pages (vaddr,1 , write ?FOLL_WRITE :0 , &page,NULL ) <=0 ) +if (get_user_pages (vaddr,1 , write ?FOLL_WRITE :0 , &page) <=0 )return -EFAULT ; *paddr =page_to_phys (page);put_page (page);
include/linux/mm.h +1 -2
@@ -2380,8 +2380,7 @@ long pin_user_pages_remote(struct mm_struct *mm, unsigned int gup_flags, struct page **pages, struct vm_area_struct **vmas, int *locked);long get_user_pages (unsigned long start,unsigned long nr_pages, -unsigned int gup_flags,struct page **pages, -struct vm_area_struct **vmas); +unsigned int gup_flags,struct page **pages);long pin_user_pages (unsigned long start,unsigned long nr_pages,unsigned int gup_flags,struct page **pages,struct vm_area_struct **vmas);
mm/gup.c +3 -6
@@ -2251,8 +2251,6 @@ long get_user_pages_remote(struct mm_struct *mm,* @pages: array that receives pointers to the pages pinned. * Should be at least nr_pages long. Or NULL, if caller * only intends to ensure the pages are faulted in. -* @vmas: array of pointers to vmas corresponding to each page. -* Or NULL if the caller does not require them. * * This is the same as get_user_pages_remote(), just with a less-flexible * calling convention where we assume that the mm being operated on belongs to
@@ -2260,16 +2258,15 @@ long get_user_pages_remote(struct mm_struct *mm,* obviously don't pass FOLL_REMOTE in here. */ long get_user_pages (unsigned long start,unsigned long nr_pages, -unsigned int gup_flags,struct page **pages, -struct vm_area_struct **vmas) +unsigned int gup_flags,struct page **pages) {int locked =1 ; -if (!is_valid_gup_args (pages, vmas,NULL , &gup_flags,FOLL_TOUCH )) +if (!is_valid_gup_args (pages,NULL ,NULL , &gup_flags,FOLL_TOUCH ))return -EINVAL ;return __get_user_pages_locked (current->mm, start, nr_pages, pages, - vmas, &locked, gup_flags); +NULL , &locked, gup_flags); }EXPORT_SYMBOL (get_user_pages);
mm/gup_test.c +2 -3
@@ -139,8 +139,7 @@ static int __gup_test_ioctl(unsigned int cmd, pages + i);break ;case GUP_BASIC_TEST : - nr =get_user_pages (addr, nr, gup->gup_flags, pages + i, -NULL ); + nr =get_user_pages (addr, nr, gup->gup_flags, pages + i);break ;case PIN_FAST_BENCHMARK : nr = pin_user_pages_fast(addr, nr, gup->gup_flags,
@@ -161,7 +160,7 @@ static int __gup_test_ioctl(unsigned int cmd, pages + i, NULL); else nr =get_user_pages (addr, nr, gup->gup_flags, - pages + i,NULL ); + pages + i);break ;default : ret = -EINVAL ;
virt/kvm/kvm_main.c +1 -1
@@ -2474,7 +2474,7 @@ static inline int check_user_page_hwpoison(unsigned long addr) {int rc, flags =FOLL_HWPOISON |FOLL_WRITE ; - rc =get_user_pages (addr,1 , flags,NULL ,NULL ); + rc =get_user_pages (addr,1 , flags,NULL );return rc == -EHWPOISON ; }
Signature · 1 line
2.40.0
Re: [PATCH v3 1/7] mm/gup: remove unused vmas parameter from get_user_pages()
Quoted 13 lines · Lorenzo Stoakes
No invocation of
get_user_pages()uses the vmas parameter, so remove it.The GUP API is confusing and caveated. Recent changes have done much to improve that, however there is more we can do. Exporting vmas is a prime target as the caller has to be extremely careful to preclude their use after the
mmap_lockhas expired or otherwise be left with dangling pointers.Removing the vmas parameter focuses the GUP functions upon their primary purpose - pinning (and outputting) pages as well as performing the actions implied by the input flags.
Quoted 7 lines
This is part of a patch series aiming to remove the vmas parameter altogether.
Signed-off-by Lorenzo Stoakes <[email protected]>Suggested-by Matthew Wilcox (Oracle) <[email protected]>---
Signature · 3 lines
Thanks, David / dhildenb
PATCH v3 2/7 mm/gup: remove unused vmas parameter from pin_user_pages_remote()
In reply to Lorenzo StoakesNo invocation of pin_user_pages_remote() uses the vmas parameter, so remove it. This forms part of a larger patch set eliminating the use of the vmas parameters altogether.
--- drivers/iommu/iommufd/pages.c | 4 ++-- drivers/vfio/vfio_iommu_type1.c | 2 +- include/linux/mm.h | 2 +- mm/gup.c | 8 +++----- mm/process_vm_access.c | 2 +- 5 files changed, 8 insertions(+), 10 deletions(-)
drivers/iommu/iommufd/pages.c +2 -2
@@ -786,7 +786,7 @@ static int pfn_reader_user_pin(struct pfn_reader_user *user, user->locked =1 ; } rc =pin_user_pages_remote (pages->source_mm, uptr, npages, - user->gup_flags, user->upages,NULL , + user->gup_flags, user->upages, &user->locked); }if (rc <=0 ) {
@@ -1787,7 +1787,7 @@ static int iopt_pages_rw_page(struct iopt_pages *pages, unsigned long index, rc =pin_user_pages_remote ( pages->source_mm, (uintptr_t )(pages->uptr + index *PAGE_SIZE ),1 , (flags &IOMMUFD_ACCESS_RW_WRITE ) ?FOLL_WRITE :0 , &page, -NULL ,NULL ); +NULL );mmap_read_unlock (pages->source_mm);if (rc !=1 ) {if (WARN_ON (rc >=0 ))
drivers/vfio/vfio_iommu_type1.c +1 -1
@@ -562,7 +562,7 @@ static int vaddr_get_pfns(struct mm_struct *mm, unsigned long vaddr,mmap_read_lock (mm); ret =pin_user_pages_remote (mm, vaddr, npages, flags |FOLL_LONGTERM , - pages,NULL ,NULL ); + pages,NULL );if (ret >0 ) {int i;
include/linux/mm.h +1 -1
@@ -2378,7 +2378,7 @@ long get_user_pages_remote(struct mm_struct *mm,long pin_user_pages_remote (struct mm_struct *mm,unsigned long start,unsigned long nr_pages,unsigned int gup_flags,struct page **pages, -struct vm_area_struct **vmas,int *locked); +int *locked);long get_user_pages (unsigned long start,unsigned long nr_pages,unsigned int gup_flags,struct page **pages); long pin_user_pages(unsigned long start, unsigned long nr_pages,
mm/gup.c +3 -5
@@ -3093,8 +3093,6 @@ EXPORT_SYMBOL_GPL(pin_user_pages_fast);* @gup_flags: flags modifying lookup behaviour * @pages: array that receives pointers to the pages pinned. * Should be at least nr_pages long. -* @vmas: array of pointers to vmas corresponding to each page. -* Or NULL if the caller does not require them. * @locked: pointer to lock flag indicating whether lock is held and * subsequently whether VM_FAULT_RETRY functionality can be * utilised. Lock must initially be held.
@@ -3109,14 +3107,14 @@ EXPORT_SYMBOL_GPL(pin_user_pages_fast);long pin_user_pages_remote (struct mm_struct *mm,unsigned long start,unsigned long nr_pages,unsigned int gup_flags,struct page **pages, -struct vm_area_struct **vmas,int *locked) +int *locked) {int local_locked =1 ; -if (!is_valid_gup_args (pages, vmas, locked, &gup_flags, +if (!is_valid_gup_args (pages,NULL , locked, &gup_flags,FOLL_PIN |FOLL_TOUCH |FOLL_REMOTE ))return 0 ; -return __gup_longterm_locked (mm, start, nr_pages, pages, vmas, +return __gup_longterm_locked (mm, start, nr_pages, pages,NULL , locked ? locked : &local_locked, gup_flags); }
mm/process_vm_access.c +1 -1
@@ -104,7 +104,7 @@ static int process_vm_rw_single_vec(unsigned long addr,mmap_read_lock (mm); pinned_pages =pin_user_pages_remote (mm, pa, pinned_pages, flags, process_pages, -NULL , &locked); + &locked);if (locked)mmap_read_unlock (mm);if (pinned_pages <=0 )
Signature · 1 line
2.40.0
Re: [PATCH v3 2/7] mm/gup: remove unused vmas parameter from pin_user_pages_remote()
Quoted 6 lines · Lorenzo Stoakes
No invocation of
pin_user_pages_remote()uses the vmas parameter, so remove it. This forms part of a larger patch set eliminating the use of the vmas parameters altogether.Signed-off-by Lorenzo Stoakes <[email protected]>---
Signature · 3 lines
Thanks, David / dhildenb
PATCH v3 3/7 mm/gup: remove vmas parameter from get_user_pages_remote()
In reply to Lorenzo StoakesThe 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.
This forms part of a broader set of patches intended to eliminate the vmas parameter altogether.
--- arch/arm64/kernel/mte.c | 7 ++++--- arch/s390/kvm/interrupt.c | 2 +- fs/exec.c | 2 +- include/linux/mm.h | 2 +- kernel/events/uprobes.c | 14 +++++++++----- mm/gup.c | 12 ++++-------- mm/memory.c | 8 ++++++-- mm/rmap.c | 2 +- security/tomoyo/domain.c | 2 +- virt/kvm/async_pf.c | 3 +-- 10 files changed, 29 insertions(+), 25 deletions(-)
arch/arm64/kernel/mte.c +4 -3
@@ -419,7 +419,6 @@ long get_mte_ctrl(struct task_struct *task)static int __access_remote_tags (struct mm_struct *mm,unsigned long addr,struct iovec *kiov,unsigned int gup_flags) { -struct vm_area_struct *vma;void __user *buf = kiov->iov_base;size_t len = kiov->iov_len;int ret;
@@ -432,12 +431,13 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,return -EIO ;while (len) { +struct vm_area_struct *vma;unsigned long tags, offset;void *maddr;struct page *page =NULL ; ret =get_user_pages_remote (mm, addr,1 , gup_flags, &page, - &vma,NULL ); +NULL );if (ret <=0 )break ;
@@ -448,7 +448,8 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,* would cause the existing tags to be cleared if the page * was never mapped with PROT_MTE. */ -if (!(vma->vm_flags &VM_MTE )) { + vma =vma_lookup (mm, addr); +if (WARN_ON_ONCE (!vma) || !(vma->vm_flags &VM_MTE )) { ret = -EOPNOTSUPP ;put_page (page);break ;
arch/s390/kvm/interrupt.c +1 -1
@@ -2777,7 +2777,7 @@ static struct page *get_map_page(struct kvm *kvm, u64 uaddr)mmap_read_lock (kvm->mm);get_user_pages_remote (kvm->mm, uaddr,1 ,FOLL_WRITE , - &page,NULL ,NULL ); + &page,NULL );mmap_read_unlock (kvm->mm);return page; }
fs/exec.c +1 -1
@@ -219,7 +219,7 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,*/ mmap_read_lock (bprm->mm); ret =get_user_pages_remote (bprm->mm, pos,1 , gup_flags, - &page,NULL ,NULL ); + &page,NULL );mmap_read_unlock (bprm->mm);if (ret <=0 )return NULL ;
include/linux/mm.h +1 -1
@@ -2374,7 +2374,7 @@ extern int __access_remote_vm(struct mm_struct *mm, unsigned long addr,long get_user_pages_remote (struct mm_struct *mm,unsigned long start,unsigned long nr_pages,unsigned int gup_flags,struct page **pages, -struct vm_area_struct **vmas,int *locked); +int *locked); long pin_user_pages_remote(struct mm_struct *mm, unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages,
kernel/events/uprobes.c +9 -5
@@ -365,7 +365,6 @@ __update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d) {void *kaddr;struct page *page; -struct vm_area_struct *vma;int ret;short *ptr;
@@ -373,7 +372,7 @@ __update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d)return -EINVAL ; ret =get_user_pages_remote (mm, vaddr,1 , -FOLL_WRITE , &page, &vma,NULL ); +FOLL_WRITE , &page,NULL );if (unlikely (ret <=0 )) {/* * We are asking for 1 page. If get_user_pages_remote() fails,
@@ -475,10 +474,16 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, gup_flags |=FOLL_SPLIT_PMD ;/* Read the page with vaddr into memory */ ret =get_user_pages_remote (mm, vaddr,1 , gup_flags, - &old_page, &vma,NULL ); + &old_page,NULL );if (ret <=0 )return ret; + vma =vma_lookup (mm, vaddr); +if (WARN_ON_ONCE (!vma)) { + ret = -EINVAL ; + goto put_old; + } + ret =verify_opcode (old_page, vaddr, &opcode);if (ret <=0 ) goto put_old;
@@ -2027,8 +2032,7 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)* but we treat this as a 'remote' access since it is * essentially a kernel access to the memory. */ - result =get_user_pages_remote (mm, vaddr,1 ,FOLL_FORCE , &page, -NULL ,NULL ); + result =get_user_pages_remote (mm, vaddr,1 ,FOLL_FORCE , &page,NULL );if (result <0 )return result;
mm/gup.c +4 -8
@@ -2165,8 +2165,6 @@ static bool is_valid_gup_args(struct page **pages, struct vm_area_struct **vmas,* @pages: array that receives pointers to the pages pinned. * Should be at least nr_pages long. Or NULL, if caller * only intends to ensure the pages are faulted in. -* @vmas: array of pointers to vmas corresponding to each page. -* Or NULL if the caller does not require them. * @locked: pointer to lock flag indicating whether lock is held and * subsequently whether VM_FAULT_RETRY functionality can be * utilised. Lock must initially be held.
@@ -2181,8 +2179,6 @@ static bool is_valid_gup_args(struct page **pages, struct vm_area_struct **vmas,* * The caller is responsible for releasing returned @pages, via put_page(). * -* @vmas are valid only as long as mmap_lock is held. -* * Must be called with mmap_lock held for read or write. * * get_user_pages_remote walks a process's page tables and takes a reference
@@ -2219,15 +2215,15 @@ static bool is_valid_gup_args(struct page **pages, struct vm_area_struct **vmas,long get_user_pages_remote (struct mm_struct *mm,unsigned long start,unsigned long nr_pages,unsigned int gup_flags,struct page **pages, -struct vm_area_struct **vmas,int *locked) +int *locked) {int local_locked =1 ; -if (!is_valid_gup_args (pages, vmas, locked, &gup_flags, +if (!is_valid_gup_args (pages,NULL , locked, &gup_flags,FOLL_TOUCH |FOLL_REMOTE ))return -EINVAL ; -return __get_user_pages_locked (mm, start, nr_pages, pages, vmas, +return __get_user_pages_locked (mm, start, nr_pages, pages,NULL , locked ? locked : &local_locked, gup_flags); }
@@ -2237,7 +2233,7 @@ EXPORT_SYMBOL(get_user_pages_remote);long get_user_pages_remote (struct mm_struct *mm,unsigned long start,unsigned long nr_pages,unsigned int gup_flags,struct page **pages, -struct vm_area_struct **vmas,int *locked) +int *locked) {return 0 ; }
mm/memory.c +6 -2
@@ -5591,7 +5591,9 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,struct page *page =NULL ; ret =get_user_pages_remote (mm, addr,1 , - gup_flags, &page, &vma,NULL ); + gup_flags, &page,NULL ); + vma =vma_lookup (mm, addr); +if (ret <=0 ) {#ifndef CONFIG_HAVE_IOREMAP_PROT break ;
@@ -5600,7 +5602,6 @@ 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)
@@ -5610,6 +5611,9 @@ int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,break ; bytes = ret;#endif + }else if (unlikely (!vma)) { +VM_WARN_ON_ONCE (1 ); +break ; }else { bytes = len; offset = addr & (PAGE_SIZE -1 );
mm/rmap.c +1 -1
@@ -2324,7 +2324,7 @@ int make_device_exclusive_range(struct mm_struct *mm, unsigned long start, npages =get_user_pages_remote (mm, start, npages,FOLL_GET |FOLL_WRITE |FOLL_SPLIT_PMD , - pages,NULL ,NULL ); + pages,NULL );if (npages <0 )return npages;
security/tomoyo/domain.c +1 -1
@@ -916,7 +916,7 @@ bool tomoyo_dump_page(struct linux_binprm *bprm, unsigned long pos,*/ mmap_read_lock (bprm->mm); ret =get_user_pages_remote (bprm->mm, pos,1 , -FOLL_FORCE , &page,NULL ,NULL ); +FOLL_FORCE , &page,NULL );mmap_read_unlock (bprm->mm);if (ret <=0 )return false;
virt/kvm/async_pf.c +1 -2
@@ -61,8 +61,7 @@ static void async_pf_execute(struct work_struct *work)* access remotely. */ mmap_read_lock (mm); -get_user_pages_remote (mm, addr,1 ,FOLL_WRITE ,NULL ,NULL , - &locked); +get_user_pages_remote (mm, addr,1 ,FOLL_WRITE ,NULL , &locked);if (locked)mmap_read_unlock (mm);
Signature · 1 line
2.40.0
Re: [PATCH v3 3/7] mm/gup: remove vmas parameter from get_user_pages_remote()
Quoted 11 lines · Lorenzo Stoakes
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 usingvma_lookup()when the original lookup failed so by doing the lookup directly this also de-duplicates the code.
Quoted 6 lines
This forms part of a broader set of patches intended to eliminate the vmas parameter altogether.
Signed-off-by Lorenzo Stoakes <[email protected]>--- arch/arm64/kernel/mte.c | 7 ++++---
For arm64:
Re: [PATCH v3 3/7] mm/gup: remove vmas parameter from get_user_pages_remote()
In reply to Lorenzo StoakesQuoted 11 lines · Lorenzo Stoakes
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 usingvma_lookup()when the original lookup failed so by doing the lookup directly this also de-duplicates the code.
Quoted 5 lines
This forms part of a broader set of patches intended to eliminate the vmas parameter altogether.
Signed-off-by Lorenzo Stoakes <[email protected]>---
I guess we should never drop the mmap lock temporarily in these cases, so it's fine.
Signature · 3 lines
Thanks, David / dhildenb
PATCH v3 4/7 mm/gup: introduce the FOLL_SAME_FILE GUP flag
In reply to Lorenzo StoakesThis flag causes GUP to assert that all VMAs within the input range possess the same vma->vm_file. If not, the operation fails.
This is part of a patch series which eliminates the vmas parameter from the GUP API, implementing the one remaining assertion within the entire kernel that requires access to the VMAs associated with a GUP range.
--- include/linux/mm_types.h | 2 ++ mm/gup.c | 16 ++++++++++++---- 2 files changed, 14 insertions(+), 4 deletions(-)
include/linux/mm_types.h +2 -0
@@ -1185,6 +1185,8 @@ enum {FOLL_PCI_P2PDMA =1 <<10 ,/* allow interrupts from generic signals */ FOLL_INTERRUPTIBLE =1 <<11 , +/* assert that the range spans VMAs with the same vma->vm_file */ + FOLL_SAME_FILE = 1 << 12, /* See also internal only FOLL flags in mm/internal.h */ };
mm/gup.c +12 -4
@@ -959,7 +959,8 @@ static int faultin_page(struct vm_area_struct *vma,return 0 ; } -static int check_vma_flags (struct vm_area_struct *vma,unsigned long gup_flags) +static int check_vma_flags (struct vm_area_struct *vma,struct file *file, +unsigned long gup_flags) {vm_flags_t vm_flags = vma->vm_flags;int write = (gup_flags &FOLL_WRITE );
@@ -968,7 +969,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)if (vm_flags & (VM_IO |VM_PFNMAP ))return -EFAULT ; -if (gup_flags &FOLL_ANON && !vma_is_anonymous (vma)) +if ((gup_flags &FOLL_ANON ) && !vma_is_anonymous (vma))return -EFAULT ;if ((gup_flags &FOLL_LONGTERM ) &&vma_is_fsdax (vma))
@@ -977,6 +978,9 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)if (vma_is_secretmem (vma))return -EFAULT ; +if ((gup_flags &FOLL_SAME_FILE ) && vma->vm_file != file) +return -EFAULT ; +if (write) {if (!(vm_flags &VM_WRITE )) {if (!(gup_flags &FOLL_FORCE ))
@@ -1081,6 +1085,7 @@ static long __get_user_pages(struct mm_struct *mm,long ret =0 , i =0 ;struct vm_area_struct *vma =NULL ;struct follow_page_context ctx = {NULL }; +struct file *file =NULL ;if (!nr_pages)return 0 ;
@@ -1111,10 +1116,13 @@ static long __get_user_pages(struct mm_struct *mm, ret = -EFAULT ; goto out; } - ret =check_vma_flags (vma, gup_flags); + ret =check_vma_flags (vma, i ==0 ? vma->vm_file : file, + gup_flags);if (ret) goto out; + file = vma->vm_file; +if (is_vm_hugetlb_page (vma)) { i = follow_hugetlb_page(mm, vma, pages, vmas, &start, &nr_pages, i,
@@ -1595,7 +1603,7 @@ long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,* We want to report -EINVAL instead of -EFAULT for any permission * problems or incompatible mappings. */ -if (check_vma_flags (vma, gup_flags)) +if (check_vma_flags (vma, vma->vm_file, gup_flags))return -EINVAL ; ret = __get_user_pages(mm, start, nr_pages, gup_flags,
Signature · 1 line
2.40.0
Re: [PATCH v3 4/7] mm/gup: introduce the FOLL_SAME_FILE GUP flag
Quoted 8 lines · Lorenzo Stoakes
This flag causes GUP to assert that all VMAs within the input range possess the same
vma->vm_file. If not, the operation fails.This is part of a patch series which eliminates the vmas parameter from the GUP API, implementing the one remaining assertion within the entire kernel that requires access to the VMAs associated with a GUP range.
Signed-off-by Lorenzo Stoakes <[email protected]>
[...]
mm/gup.c long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start, · line 1607
Quoted 9 lines
---
&start,&nr_pages, i,mm/gup.c +1
-1@@ -1595,7 +1603,7 @@ long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,* We want to report -EINVAL instead of -EFAULT for any permission * problems or incompatible mappings. */ -if (check_vma_flags (vma, gup_flags)) +if (check_vma_flags (vma, vma->vm_file, gup_flags))return -EINVAL ;
FOLL_SAME_FILE is never set here, just pass NULL instead of vma->vm_file.
As we're not allowing to drop the mmap lock, why can't io_uring simply go over all VMAs once, after pinning succeeded, and make sure that the files match (or even before pinning)?
In most cases, we're dealing with a single VMA only, it's not like the common case is that io_uring pins accross 100s of VMAs.
So I really wonder if the GUP complexity is justified by something. (removing the VMAs is certainly a welcome surprise -- as it doesn't make any sense when used with FOLL_UNLOCKABLE).
Signature · 3 lines
Thanks, David / dhildenb
Re: [PATCH v3 4/7] mm/gup: introduce the FOLL_SAME_FILE GUP flag
Quoted 25 lines · David Hildenbrand
Quoted 8 lines · Lorenzo Stoakes
This flag causes GUP to assert that all VMAs within the input range possess the same
vma->vm_file. If not, the operation fails.This is part of a patch series which eliminates the vmas parameter from the GUP API, implementing the one remaining assertion within the entire kernel that requires access to the VMAs associated with a GUP range.
Signed-off-by Lorenzo Stoakes <[email protected]>[...]
mm/gup.c long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start, · line 1607
Quoted 9 lines
---
&start,&nr_pages, i,mm/gup.c +1
-1@@ -1595,7 +1603,7 @@ long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,* We want to report -EINVAL instead of -EFAULT for any permission * problems or incompatible mappings. */ -if (check_vma_flags (vma, gup_flags)) +if (check_vma_flags (vma, vma->vm_file, gup_flags))return -EINVAL ;
FOLL_SAME_FILEis never set here, just pass NULL instead ofvma->vm_file.
Quoted 8 lines
As we're not allowing to drop the mmap lock, why can't
io_uringsimply go over all VMAs once, after pinning succeeded, and make sure that the files match (or even before pinning)?In most cases, we're dealing with a single VMA only, it's not like the common case is that
io_uringpins accross 100s of VMAs.So I really wonder if the GUP complexity is justified by something.
This is one that needs some input from Jens I think (added to cc, for some reason I didn't include him on this one but I did on the one updating uring to use it).
I agree it'd be better not to introduce this flag if we can avoid it, intent was to avoid having to add complexity to the uring code when we're already iterating through VMAs in the GUP code, but as you say it's highly likely most cases will consist of a single VMA anyway.
If Jens is OK with us iterating here I'm more than happy to respin without adding the flag!
Quoted 2 lines
(removing the VMAs is certainly a welcome surprise -- as it doesn't make any sense when used with
FOLL_UNLOCKABLE).
This is a product of reading the GUP code when writing the GUP bit for the book and wishing it were more sane :) I suspect I'll have some more patches in this area aimed at marrying the disparate APIs where sensible to do so.
Quoted 7 lines
--
Thanks,David / dhildenb
PATCH v3 5/7 io_uring: rsrc: use FOLL_SAME_FILE on pin_user_pages()
In reply to Lorenzo StoakesCommit edd478269640 ("io_uring/rsrc: disallow multi-source reg buffers") prevents io_pin_pages() from pinning pages spanning multiple VMAs with permitted characteristics (anon/huge), requiring that all VMAs share the same vm_file.
The newly introduced FOLL_SAME_FILE flag permits this to be expressed as a GUP flag rather than having to retrieve VMAs to perform the check.
We then only need to perform a VMA lookup for the first VMA to assert the anon/hugepage requirement as we know the rest of the VMAs will possess the same characteristics.
Doing this eliminates the one instance of vmas being used by pin_user_pages().
--- io_uring/rsrc.c | 40 ++++++++++++++++++---------------------- 1 file changed, 18 insertions(+), 22 deletions(-)
io_uring/rsrc.c +18 -22
@@ -1141,9 +1141,8 @@ static int io_buffer_account_pin(struct io_ring_ctx *ctx, struct page **pages,struct page **io_pin_pages (unsigned long ubuf,unsigned long len,int *npages) {unsigned long start, end, nr_pages; -struct vm_area_struct **vmas =NULL ;struct page **pages =NULL ; -int i, pret, ret = -ENOMEM ; +int pret, ret = -ENOMEM ; end = (ubuf + len +PAGE_SIZE -1 ) >>PAGE_SHIFT ; start = ubuf >>PAGE_SHIFT ;
@@ -1153,31 +1152,29 @@ struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages)if (!pages) goto done; - vmas =kvmalloc_array (nr_pages,sizeof (struct vm_area_struct *), -GFP_KERNEL ); -if (!vmas) - goto done; - ret =0 ;mmap_read_lock (current->mm); - pret =pin_user_pages (ubuf, nr_pages,FOLL_WRITE |FOLL_LONGTERM , - pages, vmas); + pret =pin_user_pages (ubuf, nr_pages, +FOLL_WRITE |FOLL_LONGTERM |FOLL_SAME_FILE , + pages,NULL );if (pret == nr_pages) { -struct file *file = vmas[0 ]->vm_file; +/* +* lookup the first VMA, we require that all VMAs in range +* maintain the same file characteristics, as enforced by +* FOLL_SAME_FILE +*/ +struct vm_area_struct *vma =vma_lookup (current->mm, ubuf); +struct file *file; -/* don't support file backed memory */ -for (i =0 ; i < nr_pages; i++) { -if (vmas[i]->vm_file != file) { - ret = -EINVAL ; -break ; - } -if (!file) -continue ; -if (!vma_is_shmem (vmas[i]) && !is_file_hugepages (file)) { +if (WARN_ON_ONCE (!vma)) { + ret = -EINVAL ; + }else { +/* don't support file backed memory */ + file = vma->vm_file; +if (file && !vma_is_shmem (vma) && !is_file_hugepages (file)) ret = -EOPNOTSUPP ; -break ; - } } + *npages = nr_pages; }else { ret = pret <0 ? pret : -EFAULT ;
@@ -1194,7 +1191,6 @@ struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages) } ret =0 ; done: -kvfree (vmas);if (ret <0 ) {kvfree (pages); pages =ERR_PTR (ret);
Signature · 1 line
2.40.0
PATCH v3 6/7 mm/gup: remove vmas parameter from pin_user_pages()
In reply to Lorenzo StoakesAfter the introduction of FOLL_SAME_FILE we no longer require vmas for any invocation of pin_user_pages(), so eliminate this parameter from the function and all callers.
This clears the way to removing the vmas parameter from GUP altogether.
--- arch/powerpc/mm/book3s64/iommu_api.c | 2 +- drivers/infiniband/hw/qib/qib_user_pages.c | 2 +- drivers/infiniband/hw/usnic/usnic_uiom.c | 2 +- drivers/infiniband/sw/siw/siw_mem.c | 2 +- drivers/media/v4l2-core/videobuf-dma-sg.c | 2 +- drivers/vdpa/vdpa_user/vduse_dev.c | 2 +- drivers/vhost/vdpa.c | 2 +- include/linux/mm.h | 3 +-- io_uring/rsrc.c | 2 +- mm/gup.c | 9 +++------ mm/gup_test.c | 9 ++++----- net/xdp/xdp_umem.c | 2 +- 12 files changed, 17 insertions(+), 22 deletions(-)
arch/powerpc/mm/book3s64/iommu_api.c +1 -1
@@ -105,7 +105,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua, ret =pin_user_pages (ua + (entry <<PAGE_SHIFT ), n,FOLL_WRITE |FOLL_LONGTERM , - mem->hpages + entry,NULL ); + mem->hpages + entry);if (ret == n) { pinned += n;continue ;
drivers/infiniband/hw/qib/qib_user_pages.c +1 -1
@@ -111,7 +111,7 @@ int qib_get_user_pages(unsigned long start_page, size_t num_pages, ret =pin_user_pages (start_page + got *PAGE_SIZE , num_pages - got,FOLL_LONGTERM |FOLL_WRITE , - p + got,NULL ); + p + got);if (ret <0 ) {mmap_read_unlock (current->mm); goto bail_release;
drivers/infiniband/hw/usnic/usnic_uiom.c +1 -1
@@ -140,7 +140,7 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable, ret =pin_user_pages (cur_base, min_t(unsigned long, npages,PAGE_SIZE /sizeof (struct page *)), - gup_flags, page_list,NULL ); + gup_flags, page_list);if (ret <0 ) goto out;
drivers/infiniband/sw/siw/siw_mem.c +1 -1
@@ -422,7 +422,7 @@ struct siw_umem *siw_umem_get(u64 start, u64 len, bool writable) umem->page_chunk[i].plist = plist;while (nents) { rv =pin_user_pages (first_page_va, nents, foll_flags, - plist,NULL ); + plist);if (rv <0 ) goto out_sem_up;
drivers/media/v4l2-core/videobuf-dma-sg.c +1 -1
@@ -180,7 +180,7 @@ static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma, data, size, dma->nr_pages); err =pin_user_pages (data &PAGE_MASK , dma->nr_pages, gup_flags, - dma->pages,NULL ); + dma->pages);if (err != dma->nr_pages) { dma->nr_pages = (err >=0 ) ? err :0 ;
drivers/vdpa/vdpa_user/vduse_dev.c +1 -1
@@ -995,7 +995,7 @@ static int vduse_dev_reg_umem(struct vduse_dev *dev, goto out; pinned =pin_user_pages (uaddr, npages,FOLL_LONGTERM |FOLL_WRITE , - page_list,NULL ); + page_list);if (pinned != npages) { ret = pinned <0 ? pinned : -ENOMEM ; goto out;
drivers/vhost/vdpa.c +1 -1
@@ -952,7 +952,7 @@ static int vhost_vdpa_pa_map(struct vhost_vdpa *v,while (npages) { sz2pin = min_t(unsigned long, npages, list_size); pinned =pin_user_pages (cur_base, sz2pin, - gup_flags, page_list,NULL ); + gup_flags, page_list);if (sz2pin != pinned) {if (pinned <0 ) { ret = pinned;
include/linux/mm.h +1 -2
@@ -2382,8 +2382,7 @@ long pin_user_pages_remote(struct mm_struct *mm,long get_user_pages (unsigned long start,unsigned long nr_pages,unsigned int gup_flags,struct page **pages);long pin_user_pages (unsigned long start,unsigned long nr_pages, -unsigned int gup_flags,struct page **pages, -struct vm_area_struct **vmas); +unsigned int gup_flags,struct page **pages);long get_user_pages_unlocked (unsigned long start,unsigned long nr_pages,struct page **pages,unsigned int gup_flags); long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
io_uring/rsrc.c +1 -1
@@ -1156,7 +1156,7 @@ struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages)mmap_read_lock (current->mm); pret =pin_user_pages (ubuf, nr_pages,FOLL_WRITE |FOLL_LONGTERM |FOLL_SAME_FILE , - pages,NULL ); + pages);if (pret == nr_pages) {/* * lookup the first VMA, we require that all VMAs in range
mm/gup.c +3 -6
@@ -3132,8 +3132,6 @@ EXPORT_SYMBOL(pin_user_pages_remote);* @gup_flags: flags modifying lookup behaviour * @pages: array that receives pointers to the pages pinned. * Should be at least nr_pages long. -* @vmas: array of pointers to vmas corresponding to each page. -* Or NULL if the caller does not require them. * * Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and * FOLL_PIN is set.
@@ -3142,15 +3140,14 @@ EXPORT_SYMBOL(pin_user_pages_remote);* see Documentation/core-api/pin_user_pages.rst for details. */ long pin_user_pages (unsigned long start,unsigned long nr_pages, -unsigned int gup_flags,struct page **pages, -struct vm_area_struct **vmas) +unsigned int gup_flags,struct page **pages) {int locked =1 ; -if (!is_valid_gup_args (pages, vmas,NULL , &gup_flags,FOLL_PIN )) +if (!is_valid_gup_args (pages,NULL ,NULL , &gup_flags,FOLL_PIN ))return 0 ;return __gup_longterm_locked (current->mm, start, nr_pages, - pages, vmas, &locked, gup_flags); + pages,NULL , &locked, gup_flags); }EXPORT_SYMBOL (pin_user_pages);
mm/gup_test.c +4 -5
@@ -146,18 +146,17 @@ static int __gup_test_ioctl(unsigned int cmd, pages + i);break ;case PIN_BASIC_TEST : - nr =pin_user_pages (addr, nr, gup->gup_flags, pages + i, -NULL ); + nr =pin_user_pages (addr, nr, gup->gup_flags, pages + i);break ;case PIN_LONGTERM_BENCHMARK : nr =pin_user_pages (addr, nr, gup->gup_flags |FOLL_LONGTERM , - pages + i,NULL ); + pages + i);break ;case DUMP_USER_PAGES_TEST :if (gup->test_flags &GUP_TEST_FLAG_DUMP_PAGES_USE_PIN ) nr =pin_user_pages (addr, nr, gup->gup_flags, - pages + i,NULL ); + pages + i);else nr =get_user_pages (addr, nr, gup->gup_flags, pages + i);
@@ -270,7 +269,7 @@ static inline int pin_longterm_test_start(unsigned long arg) gup_flags, pages); else cur_pages =pin_user_pages (addr, remaining_pages, - gup_flags, pages,NULL ); + gup_flags, pages);if (cur_pages <0 ) {pin_longterm_test_stop (); ret = cur_pages;
net/xdp/xdp_umem.c +1 -1
@@ -103,7 +103,7 @@ static int xdp_umem_pin_pages(struct xdp_umem *umem, unsigned long address)mmap_read_lock (current->mm); npgs =pin_user_pages (address, umem->npgs, - gup_flags |FOLL_LONGTERM , &umem->pgs[0 ],NULL ); + gup_flags |FOLL_LONGTERM , &umem->pgs[0 ]);mmap_read_unlock (current->mm);if (npgs != umem->npgs) {
Signature · 1 line
2.40.0
Re: [PATCH v3 6/7] mm/gup: remove vmas parameter from pin_user_pages()
Quoted 8 lines · Lorenzo Stoakes
After the introduction of
FOLL_SAME_FILEwe no longer require vmas for any invocation ofpin_user_pages(), so eliminate this parameter from the function and all callers.This clears the way to removing the vmas parameter from GUP altogether.
Signed-off-by Lorenzo Stoakes <[email protected]>---
Ideally, we'd avoid FOLL_SAME_FILE as well
Signature · 3 lines
Thanks, David / dhildenb
Re: [PATCH v3 6/7] mm/gup: remove vmas parameter from pin_user_pages()
In reply to Lorenzo StoakesQuoted 27 lines · Lorenzo Stoakes
After the introduction of
FOLL_SAME_FILEwe no longer require vmas for any invocation ofpin_user_pages(), so eliminate this parameter from the function and all callers.This clears the way to removing the vmas parameter from GUP altogether.
Signed-off-by Lorenzo Stoakes <[email protected]>--- arch/powerpc/mm/book3s64/iommu_api.c | 2 +- drivers/infiniband/hw/qib/qib_user_pages.c | 2 +- drivers/infiniband/hw/usnic/usnic_uiom.c | 2 +- drivers/infiniband/sw/siw/siw_mem.c | 2 +- drivers/media/v4l2-core/videobuf-dma-sg.c | 2 +- drivers/vdpa/vdpa_user/vduse_dev.c | 2 +- drivers/vhost/vdpa.c | 2 +- include/linux/mm.h | 3 +-- io_uring/rsrc.c | 2 +- mm/gup.c | 9 +++------ mm/gup_test.c | 9 ++++----- net/xdp/xdp_umem.c | 2 +- 12 files changed, 17 insertions(+), 22 deletions(-)drivers/infiniband/hw/qib/qib_user_pages.c +0
-0
drivers/infiniband/hw/qib/qib_user_pages.c int qib_get_user_pages(unsigned long start_page, size_t num_pages, · line 117
Quoted 8 lines
drivers/infiniband/hw/qib/qib_user_pages.c +1
-1@@ -111,7 +111,7 @@ int qib_get_user_pages(unsigned long start_page, size_t num_pages, ret =pin_user_pages (start_page + got *PAGE_SIZE , num_pages - got,FOLL_LONGTERM |FOLL_WRITE , - p + got,NULL ); + p + got);if (ret <0 ) {mmap_read_unlock (current->mm); goto bail_release;
For Qib...
PATCH v3 7/7 mm/gup: remove vmas array from internal GUP functions
In reply to Lorenzo StoakesNow we have eliminated all callers to GUP APIs which use the vmas parameter, eliminate it altogether.
This eliminates a class of bugs where vmas might have been kept around longer than the mmap_lock and thus we need not be concerned about locks being dropped during this operation leaving behind dangling pointers.
This simplifies the GUP API and makes it considerably clearer as to its purpose - follow flags are applied and if pinning, an array of pages is returned.
--- include/linux/hugetlb.h | 10 ++--- mm/gup.c | 83 +++++++++++++++-------------------------- mm/hugetlb.c | 24 +++++------- 3 files changed, 45 insertions(+), 72 deletions(-)
include/linux/hugetlb.h +4 -6
@@ -141,9 +141,8 @@ 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);long follow_hugetlb_page (struct mm_struct *,struct vm_area_struct *, -struct page **,struct vm_area_struct **, -unsigned long *,unsigned long *,long ,unsigned int , -int *); +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 );
@@ -297,9 +296,8 @@ static inline struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,static inline long follow_hugetlb_page (struct mm_struct *mm,struct vm_area_struct *vma,struct page **pages, -struct vm_area_struct **vmas,unsigned long *position, -unsigned long *nr_pages,long i,unsigned int flags, -int *nonblocking) +unsigned long *position,unsigned long *nr_pages, +long i,unsigned int flags,int *nonblocking) {BUG ();return 0 ;
mm/gup.c +31 -52
267 lines not on this page · raw message
mm/hugetlb.c +10 -14
@@ -6371,17 +6371,14 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, }#endif /* CONFIG_USERFAULTFD */ -static void record_subpages_vmas (struct page *page,struct vm_area_struct *vma, -int refs,struct page **pages, -struct vm_area_struct **vmas) +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); -if (vmas) - vmas[nr] = vma; } }
@@ -6454,9 +6451,9 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, }long follow_hugetlb_page (struct mm_struct *mm,struct vm_area_struct *vma, -struct page **pages,struct vm_area_struct **vmas, -unsigned long *position,unsigned long *nr_pages, -long i,unsigned int flags,int *locked) +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;
@@ -6584,7 +6581,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,* If subpage information not requested, update counters * and skip the same_page loop below. */ -if (!pages && !vmas && !pfn_offset && +if (!pages && !pfn_offset && (vaddr +huge_page_size (h) < vma->vm_end) && (remainder >=pages_per_huge_page (h))) { vaddr +=huge_page_size (h);
@@ -6599,11 +6596,10 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, refs =min3 (pages_per_huge_page (h) - pfn_offset, remainder, (vma->vm_end -ALIGN_DOWN (vaddr,PAGE_SIZE )) >>PAGE_SHIFT ); -if (pages || vmas) -record_subpages_vmas (nth_page (page, pfn_offset), - vma, refs, -likely (pages) ? pages + i :NULL , - vmas ? vmas + i :NULL ); +if (pages) +record_subpages (nth_page (page, pfn_offset), + vma, refs, +likely (pages) ? pages + i :NULL );if (pages) {/*
Signature · 1 line
2.40.0
Re: [PATCH v3 7/7] mm/gup: remove vmas array from internal GUP functions
Quoted 7 lines · Lorenzo Stoakes
Now we have eliminated all callers to GUP APIs which use the vmas parameter, eliminate it altogether.
This eliminates a class of bugs where vmas might have been kept around longer than the
mmap_lockand thus we need not be concerned about locks being dropped during this operation leaving behind dangling pointers.
Quoted 6 lines
This simplifies the GUP API and makes it considerably clearer as to its purpose - follow flags are applied and if pinning, an array of pages is returned.
Signed-off-by Lorenzo Stoakes <[email protected]>---
Signature · 3 lines
Thanks, David / dhildenb