Commit 29a951df authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1d94330a

fs/proc/task_mmu.c

+9 −23
Original line number Diff line number Diff line
@@ -1215,42 +1215,27 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, 
			.type = type,

		};



		if (type == CLEAR_REFS_MM_HIWATER_RSS) {

		if (mmap_write_lock_killable(mm)) {

			count = -EINTR;

			goto out_mm;

		}



		if (type == CLEAR_REFS_MM_HIWATER_RSS) {

			/*

			 * 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;

			}



			mmu_notifier_range_init(&range, MMU_NOTIFY_SOFT_DIRTY,

						0, NULL, mm, 0, -1UL);
@@ -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);

	}