The patch titled
Subject: mm/shmem: fix shmem_split_large_entry()
has been added to the -mm mm-unstable branch. Its filename is
mm-shmem-use-xas_try_split-in-shmem_split_large_entry-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shmem-use-xas_try_split-in-shmem_split_large_entry-fix.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: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm/shmem: fix shmem_split_large_entry()
Date: Tue, 25 Feb 2025 12:03:34 -0500
The swap entry offset was updated incorrectly. fix it.
Link: https://lkml.kernel.org/r/AF487A7A-F685-485D-8D74-756C843D6F0A@xxxxxxxxxx
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Kairui Song <kasong@xxxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Kirill A. Shuemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Mattew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Yang Shi <yang@xxxxxxxxxxxxxxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 41 ++++++++++++++++++++++++++---------------
1 file changed, 26 insertions(+), 15 deletions(-)
--- a/mm/shmem.c~mm-shmem-use-xas_try_split-in-shmem_split_large_entry-fix
+++ a/mm/shmem.c
@@ -2162,7 +2162,7 @@ static int shmem_split_large_entry(struc
{
struct address_space *mapping = inode->i_mapping;
XA_STATE_ORDER(xas, &mapping->i_pages, index, 0);
- int split_order = 0;
+ int split_order = 0, entry_order = 0;
int i;
/* Convert user data gfp flags to xarray node gfp flags */
@@ -2180,35 +2180,46 @@ static int shmem_split_large_entry(struc
}
order = xas_get_order(&xas);
+ entry_order = order;
/* Try to split large swap entry in pagecache */
if (order > 0) {
int cur_order = order;
+ pgoff_t swap_index = round_down(index, 1 << order);
split_order = xas_try_split_min_order(cur_order);
while (cur_order > 0) {
+ pgoff_t aligned_index =
+ round_down(index, 1 << cur_order);
+ pgoff_t swap_offset = aligned_index - swap_index;
+
xas_set_order(&xas, index, split_order);
xas_try_split(&xas, old, cur_order, GFP_NOWAIT);
if (xas_error(&xas))
goto unlock;
+
+ /*
+ * Re-set the swap entry after splitting, and
+ * the swap offset of the original large entry
+ * must be continuous.
+ */
+ for (i = 0; i < 1 << cur_order;
+ i += (1 << split_order)) {
+ swp_entry_t tmp;
+
+ tmp = swp_entry(swp_type(swap),
+ swp_offset(swap) +
+ swap_offset +
+ i);
+ __xa_store(&mapping->i_pages,
+ aligned_index + i,
+ swp_to_radix_entry(tmp), 0);
+ }
cur_order = split_order;
split_order =
xas_try_split_min_order(split_order);
}
-
- /*
- * Re-set the swap entry after splitting, and the swap
- * offset of the original large entry must be continuous.
- */
- for (i = 0; i < 1 << order; i++) {
- pgoff_t aligned_index = round_down(index, 1 << order);
- swp_entry_t tmp;
-
- tmp = swp_entry(swp_type(swap), swp_offset(swap) + i);
- __xa_store(&mapping->i_pages, aligned_index + i,
- swp_to_radix_entry(tmp), 0);
- }
}
unlock:
@@ -2221,7 +2232,7 @@ unlock:
if (xas_error(&xas))
return xas_error(&xas);
- return split_order;
+ return entry_order;
}
/*
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
selftests-mm-make-file-backed-thp-split-work-by-writing-pmd-size-data.patch
mm-huge_memory-allow-split-shmem-large-folio-to-any-lower-order.patch
selftests-mm-test-splitting-file-backed-thp-to-any-lower-order.patch
xarray-add-xas_try_split-to-split-a-multi-index-entry.patch
mm-huge_memory-add-two-new-not-yet-used-functions-for-folio_split.patch
mm-huge_memory-move-folio-split-common-code-to-__folio_split.patch
mm-huge_memory-add-buddy-allocator-like-non-uniform-folio_split.patch
mm-huge_memory-remove-the-old-unused-__split_huge_page.patch
mm-huge_memory-add-folio_split-to-debugfs-testing-interface.patch
mm-truncate-use-buddy-allocator-like-folio-split-for-truncate-operation.patch
selftests-mm-add-tests-for-folio_split-buddy-allocator-like-split.patch
mm-filemap-use-xas_try_split-in-__filemap_add_folio.patch
mm-shmem-use-xas_try_split-in-shmem_split_large_entry.patch
mm-shmem-use-xas_try_split-in-shmem_split_large_entry-fix.patch
