mm: userfaultfd: remove stale comment about core dump locking

Commit Message

Jann Horn Aug. 15, 2023, 9:22 p.m. UTC

Since commit 7f3bfab52cab ("mm/gup: take mmap_lock in get_dump_page()"),
which landed in v5.10, core dumping doesn't enter fault handling without
holding the mmap_lock anymore. Remove the stale parts of the comments, but
leave the behavior as-is - letting core dumping block on userfault handling
would be a bad idea and could lead to deadlocks if the dumping process was
handling its own userfaults.

Signed-off-by: Jann Horn <[e-mail]>
---
 fs/userfaultfd.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)


base-commit: f8a7ed854c1a66b1984a64baf0ece09e44552fab

Patch

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 1091cb461747..56eaae9dac1a 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -428,15 +428,11 @@  vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
 	 * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with
 	 * the no_page_table() helper in follow_page_mask(), but the
 	 * shmem_vm_ops->fault method is invoked even during
-	 * coredumping without mmap_lock and it ends up here.
+	 * coredumping and it ends up here.
 	 */
 	if (current->flags & (PF_EXITING|PF_DUMPCORE))
 		goto out;
 
-	/*
-	 * Coredumping runs without mmap_lock so we can only check that
-	 * the mmap_lock is held, if PF_DUMPCORE was not set.
-	 */
 	assert_fault_locked(vmf);
 
 	ctx = vma->vm_userfaultfd_ctx.ctx;