+ vmcore-convert-mmap_vmcore_fault-to-use-folios.patch added to mm-new branch

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

The patch titled
     Subject: vmcore: convert mmap_vmcore_fault() to use folios
has been added to the -mm mm-new branch.  Its filename is
     vmcore-convert-mmap_vmcore_fault-to-use-folios.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/vmcore-convert-mmap_vmcore_fault-to-use-folios.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Tal Zussman <tz2294@columbia.edu>
Subject: vmcore: convert mmap_vmcore_fault() to use folios
Date: Tue, 15 Sep 2026 19:42:15 -0400

Use a folio for the page cache page the s390 fault handler reads the old
kernel's memory into.  This removes four compound_head() calls and one of
the last callers of find_or_create_page().

The vmcore mapping only has order-0 folios, so the logic is unchanged.

Compile tested for s390.

Link: https://lore.kernel.org/20260915-vmcore-fault-folio-v1-1-a0cb6278670f@columbia.edu
Signed-off-by: Tal Zussman <tz2294@columbia.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Dave Young <ruirui.yang@linux.dev>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
---

 fs/proc/vmcore.c |   27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

--- a/fs/proc/vmcore.c~vmcore-convert-mmap_vmcore_fault-to-use-folios
+++ a/fs/proc/vmcore.c
@@ -474,29 +474,30 @@ static vm_fault_t mmap_vmcore_fault(stru
 	pgoff_t index = vmf->pgoff;
 	struct iov_iter iter;
 	struct kvec kvec;
-	struct page *page;
+	struct folio *folio;
 	loff_t offset;
 	int rc;
 
-	page = find_or_create_page(mapping, index, GFP_KERNEL);
-	if (!page)
+	folio = __filemap_get_folio(mapping, index,
+			FGP_LOCK | FGP_ACCESSED | FGP_CREAT, GFP_KERNEL);
+	if (IS_ERR(folio))
 		return VM_FAULT_OOM;
-	if (!PageUptodate(page)) {
-		offset = (loff_t) index << PAGE_SHIFT;
-		kvec.iov_base = page_address(page);
-		kvec.iov_len = PAGE_SIZE;
-		iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, PAGE_SIZE);
+	if (!folio_test_uptodate(folio)) {
+		offset = folio_pos(folio);
+		kvec.iov_base = folio_address(folio);
+		kvec.iov_len = folio_size(folio);
+		iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, folio_size(folio));
 
 		rc = __read_vmcore(&iter, &offset);
 		if (rc < 0) {
-			unlock_page(page);
-			put_page(page);
+			folio_unlock(folio);
+			folio_put(folio);
 			return vmf_error(rc);
 		}
-		SetPageUptodate(page);
+		folio_mark_uptodate(folio);
 	}
-	unlock_page(page);
-	vmf->page = page;
+	folio_unlock(folio);
+	vmf->page = folio_file_page(folio, index);
 	return 0;
 #else
 	return VM_FAULT_SIGBUS;
_

Patches currently in -mm which might be from tz2294@columbia.edu are

mm-page_io-convert-write-completion-handlers-to-folios.patch
mm-remove-pagereclaim.patch
mm-page_io-use-swap-entries-directly-in-zeromap-helpers.patch
mm-page_io-rename-bio_associate_blkg_from_page.patch
mm-page_io-refer-to-folios-in-swap_writeout-comments.patch
mm-swap-rename-__swap_writepage-to-__swap_writeout.patch
mm-remove-unused-mark_page_reserved.patch
mm-remove-unused-totalram_pages_inc-and-totalram_pages_dec.patch
mm-remove-pagewriteback.patch
mm-swap-add-folio_swap_entry-and-folio_page_swap_entry.patch
mm-swap-add-folio_swap_entry-and-folio_page_swap_entry-fix.patch
mm-huge_memory-add-a-comment-to-the-open-coded-swap-entry.patch
mm-rmap-use-folio_page_swap_entry-in-ttu_anon_swapbacked_folio.patch
mm-zswap-use-folio_swap_entry-in-zswap_store_page.patch
mm-swapfile-use-folio_page_swap_entry.patch
arm64-mte-make-mte_save_tags-and-mte_restore_tags-static.patch
arm64-mte-pass-the-swap-entry-to-mte_save_tags.patch
mm-swap-remove-page_swap_entry.patch
mm-memcontrol-take-a-const-folio-in-folio_memcg-and-friends.patch
mm-memcontrol-constify-obj_cgroup_memcg-and-friends.patch
mm-memcontrol-constify-the-lruvec-helpers.patch
mm-page_io-take-a-const-folio-in-bio_associate_blkg_from_folio.patch
mm-memcontrol-constify-the-mem_cgroup-accessors.patch
mm-page_counter-constify-page_counter_read-and-page_counter_margin.patch
mm-memcontrol-constify-the-reclaim-protection-helpers.patch
mm-memcontrol-constify-the-memcg-and-lruvec-stat-readers.patch
mm-memcontrol-constify-the-swap-accounting-helpers.patch
mm-memcontrol-constify-mem_cgroup_swappiness-and-mem_cgroup_get_max.patch
mm-memcontrol-constify-the-zswap-and-socket-pressure-helpers.patch
vmcore-convert-mmap_vmcore_fault-to-use-folios.patch