+ userfaultfd-mfill_atomic-remove-retry-logic.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: userfaultfd: mfill_atomic(): remove retry logic
has been added to the -mm mm-unstable branch.  Its filename is
     userfaultfd-mfill_atomic-remove-retry-logic.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-mfill_atomic-remove-retry-logic.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Subject: userfaultfd: mfill_atomic(): remove retry logic
Date: Thu, 2 Apr 2026 07:11:52 +0300

Since __mfill_atomic_pte() handles the retry for both anonymous and shmem,
there is no need to retry copying the date from the userspace in the loop
in mfill_atomic().

Drop the retry logic from mfill_atomic().

Link: https://lkml.kernel.org/r/20260402041156.1377214-12-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrei Vagin <avagin@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Harry Yoo <harry.yoo@oracle.com>
Cc: Harry Yoo (Oracle) <harry@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nikita Kalyazin <kalyazin@amazon.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/userfaultfd.c |   24 ------------------------
 1 file changed, 24 deletions(-)

--- a/mm/userfaultfd.c~userfaultfd-mfill_atomic-remove-retry-logic
+++ a/mm/userfaultfd.c
@@ -29,7 +29,6 @@ struct mfill_state {
 	struct vm_area_struct *vma;
 	unsigned long src_addr;
 	unsigned long dst_addr;
-	struct folio *folio;
 	pmd_t *pmd;
 };
 
@@ -899,7 +898,6 @@ static __always_inline ssize_t mfill_ato
 	VM_WARN_ON_ONCE(src_start + len <= src_start);
 	VM_WARN_ON_ONCE(dst_start + len <= dst_start);
 
-retry:
 	err = mfill_get_vma(&state);
 	if (err)
 		goto out;
@@ -926,26 +924,6 @@ retry:
 		err = mfill_atomic_pte(&state);
 		cond_resched();
 
-		if (unlikely(err == -ENOENT)) {
-			void *kaddr;
-
-			mfill_put_vma(&state);
-			VM_WARN_ON_ONCE(!state.folio);
-
-			kaddr = kmap_local_folio(state.folio, 0);
-			err = copy_from_user(kaddr,
-					     (const void __user *)state.src_addr,
-					     PAGE_SIZE);
-			kunmap_local(kaddr);
-			if (unlikely(err)) {
-				err = -EFAULT;
-				goto out;
-			}
-			flush_dcache_folio(state.folio);
-			goto retry;
-		} else
-			VM_WARN_ON_ONCE(state.folio);
-
 		if (!err) {
 			state.dst_addr += PAGE_SIZE;
 			state.src_addr += PAGE_SIZE;
@@ -960,8 +938,6 @@ retry:
 
 	mfill_put_vma(&state);
 out:
-	if (state.folio)
-		folio_put(state.folio);
 	VM_WARN_ON_ONCE(copied < 0);
 	VM_WARN_ON_ONCE(err > 0);
 	VM_WARN_ON_ONCE(!copied && !err);
_

Patches currently in -mm which might be from rppt@kernel.org are

userfaultfd-introduce-mfill_copy_folio_locked-helper.patch
userfaultfd-introduce-struct-mfill_state.patch
userfaultfd-introduce-mfill_establish_pmd-helper.patch
userfaultfd-introduce-mfill_get_vma-and-mfill_put_vma.patch
userfaultfd-retry-copying-with-locks-dropped-in-mfill_atomic_pte_copy.patch
userfaultfd-move-vma_can_userfault-out-of-line.patch
userfaultfd-introduce-vm_uffd_ops.patch
shmem-userfaultfd-use-a-vma-callback-to-handle-uffdio_continue.patch
userfaultfd-introduce-vm_uffd_ops-alloc_folio.patch
shmem-userfaultfd-implement-shmem-uffd-operations-using-vm_uffd_ops.patch
userfaultfd-mfill_atomic-remove-retry-logic.patch