| Message ID | 20240704182718.2653918-7-Liam.Howlett@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Avoid MAP_FIXED gap exposure | expand |
On Thu, Jul 04, 2024 at 02:27:08PM GMT, Liam R. Howlett wrote: > Clean up the code by changing the munmap operation to use a structure > for the accounting and munmap variables. > > Since remove_mt() is only called in one location and the contents will > be reduce to almost nothing. The remains of the function can be added > to vms_complete_munmap_vmas(). > > Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> > --- > mm/internal.h | 6 ++++ > mm/mmap.c | 81 ++++++++++++++++++++++++++------------------------- > 2 files changed, 47 insertions(+), 40 deletions(-) > > diff --git a/mm/internal.h b/mm/internal.h > index f1e6dea2efcf..8cbbbe7d40f3 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1488,12 +1488,18 @@ struct vma_munmap_struct { > struct vma_iterator *vmi; > struct mm_struct *mm; > struct vm_area_struct *vma; /* The first vma to munmap */ > + struct vm_area_struct *next; /* vma after the munmap area */ > + struct vm_area_struct *prev; /* vma before the munmap area */ I mean this is about as pedantic as it gets, and, admittedly an annoying comment to make, but the ordering... can't we at least put prev before next? ;) This is actually a comment you can fully disregard, by the way! > struct list_head *uf; /* Userfaultfd list_head */ > unsigned long start; /* Aligned start addr */ > unsigned long end; /* Aligned end addr */ > int vma_count; /* Number of vmas that will be removed */ > unsigned long nr_pages; /* Number of pages being removed */ > unsigned long locked_vm; /* Number of locked pages */ > + unsigned long nr_accounted; /* Number of VM_ACCOUNT pages */ > + unsigned long exec_vm; > + unsigned long stack_vm; > + unsigned long data_vm; > bool unlock; /* Unlock after the munmap */ > }; > > diff --git a/mm/mmap.c b/mm/mmap.c > index 76e93146ee9d..2a1a49f98fa3 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -523,7 +523,8 @@ static inline void init_vma_munmap(struct vma_munmap_struct *vms, > vms->unlock = unlock; > vms->uf = uf; > vms->vma_count = 0; > - vms->nr_pages = vms->locked_vm = 0; > + vms->nr_pages = vms->locked_vm = vms->nr_accounted = 0; > + vms->exec_vm = vms->stack_vm = vms->data_vm = 0; > } > > /* > @@ -2388,30 +2389,6 @@ struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr) > return vma; > } > > -/* > - * Ok - we have the memory areas we should free on a maple tree so release them, > - * and do the vma updates. > - * > - * Called with the mm semaphore held. > - */ > -static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas) > -{ > - unsigned long nr_accounted = 0; > - struct vm_area_struct *vma; > - > - /* Update high watermark before we lower total_vm */ > - update_hiwater_vm(mm); > - mas_for_each(mas, vma, ULONG_MAX) { > - long nrpages = vma_pages(vma); > - > - if (vma->vm_flags & VM_ACCOUNT) > - nr_accounted += nrpages; > - vm_stat_account(mm, vma->vm_flags, -nrpages); > - remove_vma(vma, false); > - } > - vm_unacct_memory(nr_accounted); > -} > - > /* > * Get rid of page table information in the indicated region. > * > @@ -2634,12 +2611,15 @@ static inline void abort_munmap_vmas(struct ma_state *mas_detach) > * vms_complete_munmap_vmas() - Finish the munmap() operation > * @vms: The vma munmap struct > * @mas_detach: The maple state of the detached vmas > + * > + * This function updates the mm_struct, unmaps the region, frees the resources > + * used for the munmap() and may downgrade the lock - if requested. Everything > + * needed to be done once the vma maple tree is updated. > */ > - > static void vms_complete_munmap_vmas(struct vma_munmap_struct *vms, > struct ma_state *mas_detach) > { > - struct vm_area_struct *prev, *next; > + struct vm_area_struct *vma; > struct mm_struct *mm; > > mm = vms->mm; > @@ -2648,21 +2628,26 @@ static void vms_complete_munmap_vmas(struct vma_munmap_struct *vms, > if (vms->unlock) > mmap_write_downgrade(mm); > > - prev = vma_iter_prev_range(vms->vmi); > - next = vma_next(vms->vmi); > - if (next) > - vma_iter_prev_range(vms->vmi); > - > /* > * We can free page tables without write-locking mmap_lock because VMAs > * were isolated before we downgraded mmap_lock. > */ > mas_set(mas_detach, 1); > - unmap_region(mm, mas_detach, vms->vma, prev, next, vms->start, vms->end, > - vms->vma_count, !vms->unlock); > - /* Statistics and freeing VMAs */ > + unmap_region(mm, mas_detach, vms->vma, vms->prev, vms->next, > + vms->start, vms->end, vms->vma_count, !vms->unlock); > + /* Update high watermark before we lower total_vm */ > + update_hiwater_vm(mm); > + /* Stat accounting */ > + WRITE_ONCE(mm->total_vm, READ_ONCE(mm->total_vm) - vms->nr_pages); > + mm->exec_vm -= vms->exec_vm; > + mm->stack_vm -= vms->stack_vm; > + mm->data_vm -= vms->data_vm; OK I was going to ask you're READ_ONCE()'ing and WRITE_ONCE()'ing mm->total_vm but not the other statistics, but the original vm_stat_account() does this so. Yeah :) > + /* Remove and clean up vmas */ > mas_set(mas_detach, 0); > - remove_mt(mm, mas_detach); > + mas_for_each(mas_detach, vma, ULONG_MAX) > + remove_vma(vma, false); > + > + vm_unacct_memory(vms->nr_accounted); > validate_mm(mm); > if (vms->unlock) > mmap_read_unlock(mm); > @@ -2710,13 +2695,14 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms, > if (error) > goto start_split_failed; > } > + vms->prev = vma_prev(vms->vmi); > > /* > * Detach a range of VMAs from the mm. Using next as a temp variable as > * it is always overwritten. > */ > - next = vms->vma; > - do { > + for_each_vma_range(*(vms->vmi), next, vms->end) { > + long nrpages; > /* Does it split the end? */ > if (next->vm_end > vms->end) { > error = __split_vma(vms->vmi, next, vms->end, 0); > @@ -2725,8 +2711,21 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms, > } > vma_start_write(next); > mas_set(mas_detach, vms->vma_count++); > + nrpages = vma_pages(next); > + > + vms->nr_pages += nrpages; > if (next->vm_flags & VM_LOCKED) > - vms->locked_vm += vma_pages(next); > + vms->locked_vm += nrpages; > + > + if (next->vm_flags & VM_ACCOUNT) > + vms->nr_accounted += nrpages; > + > + if (is_exec_mapping(next->vm_flags)) > + vms->exec_vm += nrpages; > + else if (is_stack_mapping(next->vm_flags)) > + vms->stack_vm += nrpages; > + else if (is_data_mapping(next->vm_flags)) > + vms->data_vm += nrpages; > > error = mas_store_gfp(mas_detach, next, GFP_KERNEL); > if (error) > @@ -2752,7 +2751,9 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms, > BUG_ON(next->vm_start < vms->start); > BUG_ON(next->vm_start > vms->end); > #endif > - } for_each_vma_range(*(vms->vmi), next, vms->end); > + } > + > + vms->next = vma_next(vms->vmi); > > #if defined(CONFIG_DEBUG_VM_MAPLE_TREE) > /* Make sure no VMAs are about to be lost. */ > -- > 2.43.0 > This is a big improvement overall, very fiddly code. Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
* Lorenzo Stoakes <lorenzo.stoakes@oracle.com> [240705 15:27]: > On Thu, Jul 04, 2024 at 02:27:08PM GMT, Liam R. Howlett wrote: > > Clean up the code by changing the munmap operation to use a structure > > for the accounting and munmap variables. > > > > Since remove_mt() is only called in one location and the contents will > > be reduce to almost nothing. The remains of the function can be added > > to vms_complete_munmap_vmas(). > > > > Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> > > --- > > mm/internal.h | 6 ++++ > > mm/mmap.c | 81 ++++++++++++++++++++++++++------------------------- > > 2 files changed, 47 insertions(+), 40 deletions(-) > > > > diff --git a/mm/internal.h b/mm/internal.h > > index f1e6dea2efcf..8cbbbe7d40f3 100644 > > --- a/mm/internal.h > > +++ b/mm/internal.h > > @@ -1488,12 +1488,18 @@ struct vma_munmap_struct { > > struct vma_iterator *vmi; > > struct mm_struct *mm; > > struct vm_area_struct *vma; /* The first vma to munmap */ > > + struct vm_area_struct *next; /* vma after the munmap area */ > > + struct vm_area_struct *prev; /* vma before the munmap area */ > > I mean this is about as pedantic as it gets, and, admittedly an annoying > comment to make, but the ordering... can't we at least put prev before > next? ;) I can do that, no problem. ... > > This is a big improvement overall, very fiddly code. > > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Thanks!
diff --git a/mm/internal.h b/mm/internal.h index f1e6dea2efcf..8cbbbe7d40f3 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1488,12 +1488,18 @@ struct vma_munmap_struct { struct vma_iterator *vmi; struct mm_struct *mm; struct vm_area_struct *vma; /* The first vma to munmap */ + struct vm_area_struct *next; /* vma after the munmap area */ + struct vm_area_struct *prev; /* vma before the munmap area */ struct list_head *uf; /* Userfaultfd list_head */ unsigned long start; /* Aligned start addr */ unsigned long end; /* Aligned end addr */ int vma_count; /* Number of vmas that will be removed */ unsigned long nr_pages; /* Number of pages being removed */ unsigned long locked_vm; /* Number of locked pages */ + unsigned long nr_accounted; /* Number of VM_ACCOUNT pages */ + unsigned long exec_vm; + unsigned long stack_vm; + unsigned long data_vm; bool unlock; /* Unlock after the munmap */ }; diff --git a/mm/mmap.c b/mm/mmap.c index 76e93146ee9d..2a1a49f98fa3 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -523,7 +523,8 @@ static inline void init_vma_munmap(struct vma_munmap_struct *vms, vms->unlock = unlock; vms->uf = uf; vms->vma_count = 0; - vms->nr_pages = vms->locked_vm = 0; + vms->nr_pages = vms->locked_vm = vms->nr_accounted = 0; + vms->exec_vm = vms->stack_vm = vms->data_vm = 0; } /* @@ -2388,30 +2389,6 @@ struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr) return vma; } -/* - * Ok - we have the memory areas we should free on a maple tree so release them, - * and do the vma updates. - * - * Called with the mm semaphore held. - */ -static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas) -{ - unsigned long nr_accounted = 0; - struct vm_area_struct *vma; - - /* Update high watermark before we lower total_vm */ - update_hiwater_vm(mm); - mas_for_each(mas, vma, ULONG_MAX) { - long nrpages = vma_pages(vma); - - if (vma->vm_flags & VM_ACCOUNT) - nr_accounted += nrpages; - vm_stat_account(mm, vma->vm_flags, -nrpages); - remove_vma(vma, false); - } - vm_unacct_memory(nr_accounted); -} - /* * Get rid of page table information in the indicated region. * @@ -2634,12 +2611,15 @@ static inline void abort_munmap_vmas(struct ma_state *mas_detach) * vms_complete_munmap_vmas() - Finish the munmap() operation * @vms: The vma munmap struct * @mas_detach: The maple state of the detached vmas + * + * This function updates the mm_struct, unmaps the region, frees the resources + * used for the munmap() and may downgrade the lock - if requested. Everything + * needed to be done once the vma maple tree is updated. */ - static void vms_complete_munmap_vmas(struct vma_munmap_struct *vms, struct ma_state *mas_detach) { - struct vm_area_struct *prev, *next; + struct vm_area_struct *vma; struct mm_struct *mm; mm = vms->mm; @@ -2648,21 +2628,26 @@ static void vms_complete_munmap_vmas(struct vma_munmap_struct *vms, if (vms->unlock) mmap_write_downgrade(mm); - prev = vma_iter_prev_range(vms->vmi); - next = vma_next(vms->vmi); - if (next) - vma_iter_prev_range(vms->vmi); - /* * We can free page tables without write-locking mmap_lock because VMAs * were isolated before we downgraded mmap_lock. */ mas_set(mas_detach, 1); - unmap_region(mm, mas_detach, vms->vma, prev, next, vms->start, vms->end, - vms->vma_count, !vms->unlock); - /* Statistics and freeing VMAs */ + unmap_region(mm, mas_detach, vms->vma, vms->prev, vms->next, + vms->start, vms->end, vms->vma_count, !vms->unlock); + /* Update high watermark before we lower total_vm */ + update_hiwater_vm(mm); + /* Stat accounting */ + WRITE_ONCE(mm->total_vm, READ_ONCE(mm->total_vm) - vms->nr_pages); + mm->exec_vm -= vms->exec_vm; + mm->stack_vm -= vms->stack_vm; + mm->data_vm -= vms->data_vm; + /* Remove and clean up vmas */ mas_set(mas_detach, 0); - remove_mt(mm, mas_detach); + mas_for_each(mas_detach, vma, ULONG_MAX) + remove_vma(vma, false); + + vm_unacct_memory(vms->nr_accounted); validate_mm(mm); if (vms->unlock) mmap_read_unlock(mm); @@ -2710,13 +2695,14 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms, if (error) goto start_split_failed; } + vms->prev = vma_prev(vms->vmi); /* * Detach a range of VMAs from the mm. Using next as a temp variable as * it is always overwritten. */ - next = vms->vma; - do { + for_each_vma_range(*(vms->vmi), next, vms->end) { + long nrpages; /* Does it split the end? */ if (next->vm_end > vms->end) { error = __split_vma(vms->vmi, next, vms->end, 0); @@ -2725,8 +2711,21 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms, } vma_start_write(next); mas_set(mas_detach, vms->vma_count++); + nrpages = vma_pages(next); + + vms->nr_pages += nrpages; if (next->vm_flags & VM_LOCKED) - vms->locked_vm += vma_pages(next); + vms->locked_vm += nrpages; + + if (next->vm_flags & VM_ACCOUNT) + vms->nr_accounted += nrpages; + + if (is_exec_mapping(next->vm_flags)) + vms->exec_vm += nrpages; + else if (is_stack_mapping(next->vm_flags)) + vms->stack_vm += nrpages; + else if (is_data_mapping(next->vm_flags)) + vms->data_vm += nrpages; error = mas_store_gfp(mas_detach, next, GFP_KERNEL); if (error) @@ -2752,7 +2751,9 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms, BUG_ON(next->vm_start < vms->start); BUG_ON(next->vm_start > vms->end); #endif - } for_each_vma_range(*(vms->vmi), next, vms->end); + } + + vms->next = vma_next(vms->vmi); #if defined(CONFIG_DEBUG_VM_MAPLE_TREE) /* Make sure no VMAs are about to be lost. */
Clean up the code by changing the munmap operation to use a structure for the accounting and munmap variables. Since remove_mt() is only called in one location and the contents will be reduce to almost nothing. The remains of the function can be added to vms_complete_munmap_vmas(). Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> --- mm/internal.h | 6 ++++ mm/mmap.c | 81 ++++++++++++++++++++++++++------------------------- 2 files changed, 47 insertions(+), 40 deletions(-)