From dacb5de62b654f1f5df1147e263b5b4e5fe2af44 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 8 Jan 2021 13:13:41 -0800 Subject: [PATCH 1/2] mm: fix clear_refs_write locking Turning page table entries read-only requires the mmap_sem held for writing. So stop doing the odd games with turning things from read locks to write locks and back. Just get the write lock. Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 32 +++++++++----------------------- 1 file changed, 9 insertions(+), 23 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index ee5a235b3056..ab7d700b2caa 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1215,41 +1215,26 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, .type = type, }; + if (mmap_write_lock_killable(mm)) { + count = -EINTR; + goto out_mm; + } if (type == CLEAR_REFS_MM_HIWATER_RSS) { - if (mmap_write_lock_killable(mm)) { - count = -EINTR; - goto out_mm; - } - /* * Writing 5 to /proc/pid/clear_refs resets the peak * resident set size to this mm's current rss value. */ reset_mm_hiwater_rss(mm); - mmap_write_unlock(mm); - goto out_mm; + goto out_unlock; } - if (mmap_read_lock_killable(mm)) { - count = -EINTR; - goto out_mm; - } tlb_gather_mmu(&tlb, mm, 0, -1); if (type == CLEAR_REFS_SOFT_DIRTY) { for (vma = mm->mmap; vma; vma = vma->vm_next) { if (!(vma->vm_flags & VM_SOFTDIRTY)) continue; - mmap_read_unlock(mm); - if (mmap_write_lock_killable(mm)) { - count = -EINTR; - goto out_mm; - } - for (vma = mm->mmap; vma; vma = vma->vm_next) { - vma->vm_flags &= ~VM_SOFTDIRTY; - vma_set_page_prot(vma); - } - mmap_write_downgrade(mm); - break; + vma->vm_flags &= ~VM_SOFTDIRTY; + vma_set_page_prot(vma); } mmu_notifier_range_init(&range, MMU_NOTIFY_SOFT_DIRTY, @@ -1261,7 +1246,8 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, if (type == CLEAR_REFS_SOFT_DIRTY) mmu_notifier_invalidate_range_end(&range); tlb_finish_mmu(&tlb, 0, -1); - mmap_read_unlock(mm); +out_unlock: + mmap_write_unlock(mm); out_mm: mmput(mm); } -- 2.29.2.157.g1d47791a39