From: Matthew Wilcox (Oracle) <willy@infradead.org>
Date: Mon, 10 Nov 2025 20:32:02 +0000 (+0000)
Subject: mm: use vma_start_write_killable() in dup_mmap()
X-Git-Tag: v6.19-rc1~112^2~125
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7370f8e1b3a8b908b2a4a9d5d02970697e9aba62;p=thirdparty%2Fkernel%2Flinux.git

mm: use vma_start_write_killable() in dup_mmap()

Allow waiting for the VMA write lock to be interrupted by fatal signals.
The explicit check for fatal_signal_pending() can be removed as it is
checked during vma_start_write_killable().  Improves the latency of
killing the task as we do not wait for the reader to finish before
checking for signals.

Link: https://lkml.kernel.org/r/20251110203204.1454057-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Chris Li <chriscli@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/mmap.c b/mm/mmap.c
index 4f51ca6449034..dc51680824ecd 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1747,7 +1747,9 @@ __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);
@@ -1758,14 +1760,6 @@ __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);