Replace vma_start_write() with vma_start_write_killable() in syscalls, improving reaction time to the kill signal.
In a number of places we now lock VMA earlier than before to avoid doing work and undoing it later if a fatal signal is pending. This is safe because the moves are happening within sections where we already hold the mmap_write_lock, so the moves do not change the locking order relative to other kernel locks. Suggested-by: Matthew Wilcox <[email protected]> Signed-off-by: Suren Baghdasaryan <[email protected]> --- mm/madvise.c | 13 ++++++++++--- mm/memory.c | 2 ++ mm/mempolicy.c | 11 +++++++++-- mm/mlock.c | 30 ++++++++++++++++++++++++------ mm/mprotect.c | 25 +++++++++++++++++-------- mm/mremap.c | 8 +++++--- mm/mseal.c | 24 +++++++++++++++++++----- 7 files changed, 86 insertions(+), 27 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 69708e953cf5..f2c7b0512cdf 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -172,10 +172,17 @@ static int madvise_update_vma(vm_flags_t new_flags, if (IS_ERR(vma)) return PTR_ERR(vma); - madv_behavior->vma = vma; + /* + * If a new vma was created during vma_modify_XXX, the resulting + * vma is already locked. Skip re-locking new vma in this case. + */ + if (vma == madv_behavior->vma) { + if (vma_start_write_killable(vma)) + return -EINTR; + } else { + madv_behavior->vma = vma; + } - /* vm_flags is protected by the mmap_lock held in write mode. */ - vma_start_write(vma); vma->flags = new_vma_flags; if (set_new_anon_name) return replace_anon_vma_name(vma, anon_name); diff --git a/mm/memory.c b/mm/memory.c index e44469f9cf65..9f99ec634831 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -366,6 +366,8 @@ void free_pgd_range(struct mmu_gather *tlb, * page tables that should be removed. This can differ from the vma mappings on * some archs that may have mappings that need to be removed outside the vmas. * Note that the prev->vm_end and next->vm_start are often used. + * We don't use vma_start_write_killable() because page tables should be freed + * even if the task is being killed. * * The vma_end differs from the pg_end when a dup_mmap() failed and the tree has * unrelated data to the mm_struct being torn down. diff --git a/mm/mempolicy.c b/mm/mempolicy.c index fd08771e2057..c38a90487531 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1784,7 +1784,8 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le return -EINVAL; if (end == start) return 0; - mmap_write_lock(mm); + if (mmap_write_lock_killable(mm)) + return -EINTR; prev = vma_prev(&vmi); for_each_vma_range(vmi, vma, end) { /* @@ -1801,13 +1802,19 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le err = -EOPNOTSUPP; break; } + /* + * Lock the VMA early to avoid extra work if fatal signal + * is pending. + */ + err = vma_start_write_killable(vma); + if (err) + break; new = mpol_dup(old); if (IS_ERR(new)) { err = PTR_ERR(new); break; } - vma_start_write(vma); new->home_node = home_node; err = mbind_range(&vmi, vma, &prev, start, end, new); mpol_put(new); diff --git a/mm/mlock.c b/mm/mlock.c index 8c227fefa2df..2ed454db7cf7 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -419,8 +419,10 @@ static int mlock_pte_range(pmd_t *pmd, unsigned long addr, * * Called for mlock(), mlock2() and mlockall(), to set @vma VM_LOCKED; * called for munlock() and munlockall(), to clear VM_LOCKED from @vma. + * + * Return: 0 on success, -EINTR if fatal signal is pending. */ -static void mlock_vma_pages_range(struct vm_area_struct *vma, +static int mlock_vma_pages_range(struct vm_area_struct *vma, unsigned long start, unsigned long end, vma_flags_t *new_vma_flags) { @@ -442,7 +444,9 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma, */ if (vma_flags_test(new_vma_flags, VMA_LOCKED_BIT)) vma_flags_set(new_vma_flags, VMA_IO_BIT); - vma_start_write(vma); + if (vma_start_write_killable(vma)) + return -EINTR; + vma_flags_reset_once(vma, new_vma_flags); lru_add_drain(); @@ -453,6 +457,7 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma, vma_flags_clear(new_vma_flags, VMA_IO_BIT); vma_flags_reset_once(vma, new_vma_flags); } + return 0; } /* @@ -506,11 +511,15 @@ static int mlock_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma, */ if (vma_flags_test(&new_vma_flags, VMA_LOCKED_BIT) && vma_flags_test(&old_vma_flags, VMA_LOCKED_BIT)) { + ret = vma_start_write_killable(vma); + if (ret) + goto out; /* mm->locked_vm is fine as nr_pages == 0 */ /* No work to do, and mlocking twice would be wrong */ - vma_start_write(vma); vma->flags = new_vma_flags; } else { - mlock_vma_pages_range(vma, start, end, &new_vma_flags); + ret = mlock_vma_pages_range(vma, start, end, &new_vma_flags); + if (ret) + mm->locked_vm -= nr_pages; } out: *prev = vma; @@ -739,9 +748,18 @@ static int apply_mlockall_flags(int flags) error = mlock_fixup(&vmi, vma, &prev, vma->vm_start, vma->vm_end, newflags); - /* Ignore errors, but prev needs fixing up. */ - if (error) + if (error) { + /* + * If we failed due to a pending fatal signal, return + * now. If we locked the vma before signal arrived, it + * will be unlocked when we drop mmap_write_lock. + */ + if (fatal_signal_pending(current)) + return -EINTR; + + /* Ignore errors, but prev needs fixing up. */ prev = vma; + } cond_resched(); } out: diff --git a/mm/mprotect.c b/mm/mprotect.c index 110d47a36d4b..d6227877465f 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -700,6 +700,7 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, const vma_flags_t old_vma_flags = READ_ONCE(vma->flags); vma_flags_t new_vma_flags = legacy_to_vma_flags(newflags); long nrpages = (end - start) >> PAGE_SHIFT; + struct vm_area_struct *new_vma; unsigned int mm_cp_flags = 0; unsigned long charged = 0; int error; @@ -756,19 +757,27 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, vma_flags_clear(&new_vma_flags, VMA_ACCOUNT_BIT); } - vma = vma_modify_flags(vmi, *pprev, vma, start, end, &new_vma_flags); - if (IS_ERR(vma)) { - error = PTR_ERR(vma); + new_vma = vma_modify_flags(vmi, *pprev, vma, start, end, + &new_vma_flags); + if (IS_ERR(new_vma)) { + error = PTR_ERR(new_vma); goto fail; } - *pprev = vma; - /* - * vm_flags and vm_page_prot are protected by the mmap_lock - * held in write mode. + * If a new vma was created during vma_modify_flags, the resulting + * vma is already locked. Skip re-locking new vma in this case. */ - vma_start_write(vma); + if (new_vma == vma) { + error = vma_start_write_killable(vma); + if (error) + goto fail; + } else { + vma = new_vma; + } + + *pprev = vma; + vma_flags_reset_once(vma, &new_vma_flags); if (vma_wants_manual_pte_write_upgrade(vma)) mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; diff --git a/mm/mremap.c b/mm/mremap.c index e9c8b1d05832..0860102bddab 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -1348,6 +1348,11 @@ static unsigned long move_vma(struct vma_remap_struct *vrm) if (err) return err; + /* We don't want racing faults. */ + err = vma_start_write_killable(vrm->vma); + if (err) + return err; + /* * If accounted, determine the number of bytes the operation will * charge. @@ -1355,9 +1360,6 @@ static unsigned long move_vma(struct vma_remap_struct *vrm) if (!vrm_calc_charge(vrm)) return -ENOMEM; - /* We don't want racing faults. */ - vma_start_write(vrm->vma); - /* Perform copy step. */ err = copy_vma_and_data(vrm, &new_vma); /* diff --git a/mm/mseal.c b/mm/mseal.c index 603df53ad267..1ea19fd3d384 100644 --- a/mm/mseal.c +++ b/mm/mseal.c @@ -70,14 +70,28 @@ static int mseal_apply(struct mm_struct *mm, if (!vma_test(vma, VMA_SEALED_BIT)) { vma_flags_t vma_flags = vma->flags; + struct vm_area_struct *new_vma; vma_flags_set(&vma_flags, VMA_SEALED_BIT); - vma = vma_modify_flags(&vmi, prev, vma, curr_start, - curr_end, &vma_flags); - if (IS_ERR(vma)) - return PTR_ERR(vma); - vma_start_write(vma); + new_vma = vma_modify_flags(&vmi, prev, vma, curr_start, + curr_end, &vma_flags); + if (IS_ERR(new_vma)) + return PTR_ERR(new_vma); + + /* + * If a new vma was created during vma_modify_flags, + * the resulting vma is already locked. + * Skip re-locking new vma in this case. + */ + if (new_vma == vma) { + int err = vma_start_write_killable(vma); + if (err) + return err; + } else { + vma = new_vma; + } + vma_set_flags(vma, VMA_SEALED_BIT); } -- 2.53.0.1018.g2bb0e51243-goog
