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mm/shmem, swap: tidy up THP swapin checks

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Move all THP swapin related checks under CONFIG_TRANSPARENT_HUGEPAGE, so
they will be trimmed off by the compiler if not needed.

And add a WARN if shmem sees a order > 0 entry when
CONFIG_TRANSPARENT_HUGEPAGE is disabled, that should never happen unless
things went very wrong.

There should be no observable feature change except the new added WARN.

Link: https://lkml.kernel.org/r/20250728075306.12704-4-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kairui Song 2025-07-28 15:53:01 +08:00 committed by Andrew Morton
parent 0cfc0e7e3d
commit c262ffd72c
1 changed files with 18 additions and 21 deletions
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39
mm/shmem.c
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@ -2017,26 +2017,38 @@ static struct folio *shmem_swap_alloc_folio(struct inode *inode,
swp_entry_t entry, int order, gfp_t gfp)
{
struct shmem_inode_info *info = SHMEM_I(inode);
int nr_pages = 1 << order;
struct folio *new;
void *shadow;
int nr_pages;
/*
* We have arrived here because our zones are constrained, so don't
* limit chance of success with further cpuset and node constraints.
*/
gfp &= ~GFP_CONSTRAINT_MASK;
if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && order > 0) {
gfp_t huge_gfp = vma_thp_gfp_mask(vma);
if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
if (WARN_ON_ONCE(order))
return ERR_PTR(-EINVAL);
} else if (order) {
/*
* If uffd is active for the vma, we need per-page fault
* fidelity to maintain the uffd semantics, then fallback
* to swapin order-0 folio, as well as for zswap case.
* Any existing sub folio in the swap cache also blocks
* mTHP swapin.
*/
if ((vma && unlikely(userfaultfd_armed(vma))) ||
!zswap_never_enabled() ||
non_swapcache_batch(entry, nr_pages) != nr_pages)
return ERR_PTR(-EINVAL);
gfp = limit_gfp_mask(huge_gfp, gfp);
gfp = limit_gfp_mask(vma_thp_gfp_mask(vma), gfp);
}
new = shmem_alloc_folio(gfp, order, info, index);
if (!new)
return ERR_PTR(-ENOMEM);
nr_pages = folio_nr_pages(new);
if (mem_cgroup_swapin_charge_folio(new, vma ? vma->vm_mm : NULL,
gfp, entry)) {
folio_put(new);
@ -2320,9 +2332,6 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
/* Look it up and read it in.. */
folio = swap_cache_get_folio(swap, NULL, 0);
if (!folio) {
int nr_pages = 1 << order;
bool fallback_order0 = false;
/* Or update major stats only when swapin succeeds?? */
if (fault_type) {
*fault_type |= VM_FAULT_MAJOR;
@ -2330,20 +2339,8 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
count_memcg_event_mm(fault_mm, PGMAJFAULT);
}
/*
* If uffd is active for the vma, we need per-page fault
* fidelity to maintain the uffd semantics, then fallback
* to swapin order-0 folio, as well as for zswap case.
* Any existing sub folio in the swap cache also blocks
* mTHP swapin.
*/
if (order > 0 && ((vma && unlikely(userfaultfd_armed(vma))) ||
!zswap_never_enabled() ||
non_swapcache_batch(swap, nr_pages) != nr_pages))
fallback_order0 = true;
/* Skip swapcache for synchronous device. */
if (!fallback_order0 && data_race(si->flags & SWP_SYNCHRONOUS_IO)) {
if (data_race(si->flags & SWP_SYNCHRONOUS_IO)) {
folio = shmem_swap_alloc_folio(inode, vma, index, swap, order, gfp);
if (!IS_ERR(folio)) {
skip_swapcache = true;