The patch titled
Subject: mm: improve the comment in isolate_migratepages_block()
has been added to the -mm mm-unstable branch. Its filename is
mm-improve-the-comment-in-isolate_migratepages_block.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-improve-the-comment-in-isolate_migratepages_block.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: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Subject: mm: improve the comment in isolate_migratepages_block()
Date: Thu, 27 Jul 2023 21:39:44 +0100
A recent patch shows that not everybody understands that "stabilise the
mapping" really means "prevent the mapping from being freed", so change
the wording to hopefully make that more clear.
Link: https://lkml.kernel.org/r/ZMLWEB4m3zvX6SBN@xxxxxxxxxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
--- a/mm/compaction.c~mm-improve-the-comment-in-isolate_migratepages_block
+++ a/mm/compaction.c
@@ -1095,13 +1095,13 @@ isolate_migratepages_block(struct compac
bool migrate_dirty;
/*
- * Only pages without mappings or that have a
- * ->migrate_folio callback are possible to migrate
- * without blocking. However, we can be racing with
- * truncation so it's necessary to lock the page
- * to stabilise the mapping as truncation holds
- * the page lock until after the page is removed
- * from the page cache.
+ * Only folios without mappings or that have
+ * a ->migrate_folio callback are possible to
+ * migrate without blocking. However, we may
+ * be racing with truncation, which can free
+ * the mapping. Truncation holds the folio lock
+ * until after the folio is removed from the page
+ * cache so holding it ourselves is sufficient.
*/
if (!folio_trylock(folio))
goto isolate_fail_put;
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed-fix.patch
rmap-pass-the-folio-to-__page_check_anon_rmap.patch
highmem-add-memcpy_to_folio-and-memcpy_from_folio.patch
affs-convert-affs_symlink_read_folio-to-use-the-folio.patch
affs-convert-data-read-and-write-to-use-folios.patch
migrate-use-folio_set_bh-instead-of-set_bh_page.patch
ntfs3-convert-ntfs_get_block_vbo-to-use-a-folio.patch
jbd2-use-a-folio-in-jbd2_journal_write_metadata_buffer.patch
buffer-remove-set_bh_page.patch
zswap-make-zswap_store-take-a-folio.patch
memcg-convert-get_obj_cgroup_from_page-to-get_obj_cgroup_from_folio.patch
swap-remove-some-calls-to-compound_head-in-swap_readpage.patch
zswap-make-zswap_load-take-a-folio.patch
mm-remove-config_per_vma_lock-ifdefs.patch
mm-allow-per-vma-locks-on-file-backed-vmas.patch
mm-move-fault_flag_vma_lock-check-from-handle_mm_fault.patch
mm-handle-pud-faults-under-the-vma-lock.patch
mm-handle-some-pmd-faults-under-the-vma-lock.patch
mm-move-fault_flag_vma_lock-check-down-in-handle_pte_fault.patch
mm-move-fault_flag_vma_lock-check-down-from-do_fault.patch
mm-run-the-fault-around-code-under-the-vma-lock.patch
mm-handle-swap-and-numa-pte-faults-under-the-vma-lock.patch
mm-handle-faults-that-merely-update-the-accessed-bit-under-the-vma-lock.patch
mm-handle-faults-that-merely-update-the-accessed-bit-under-the-vma-lock-fix.patch
mm-improve-the-comment-in-isolate_migratepages_block.patch
