[PATCH 2/2] mm: Use vma_start_write_killable() in dup_mmap()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Allow waiting for the VMA write lock to be interrupted by fatal signals.
We can remove the explicit check for fatal_signal_pending() as we will
check it during vma_start_write_killable().  This is an improvement as
we will not wait for the reader to finish before checking for signals.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/mmap.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 5fd3b80fda1d..03773fe777b7 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1750,7 +1750,9 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 	for_each_vma(vmi, mpnt) {
 		struct file *file;
 
-		vma_start_write(mpnt);
+		retval = vma_start_write_killable(mpnt);
+		if (retval < 0)
+			goto loop_out;
 		if (mpnt->vm_flags & VM_DONTCOPY) {
 			retval = vma_iter_clear_gfp(&vmi, mpnt->vm_start,
 						    mpnt->vm_end, GFP_KERNEL);
@@ -1761,14 +1763,6 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 			continue;
 		}
 		charge = 0;
-		/*
-		 * Don't duplicate many vmas if we've been oom-killed (for
-		 * example)
-		 */
-		if (fatal_signal_pending(current)) {
-			retval = -EINTR;
-			goto loop_out;
-		}
 		if (mpnt->vm_flags & VM_ACCOUNT) {
 			unsigned long len = vma_pages(mpnt);
 
-- 
2.47.2