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mm: shmem: allow fallback to smaller large orders for tmpfs mmap() access

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After commit 69e0a3b490 ("mm: shmem: fix the strategy for the tmpfs
'huge=' options"), we have fixed the large order allocation strategy for
tmpfs, which always tries PMD-sized large folios first, and if that fails,
falls back to smaller large folios.  For tmpfs large folio allocation via
mmap(), we should maintain the same strategy as well.  Let's unify the
large order allocation strategy for tmpfs.

There is no functional change for large folio allocation of anonymous shmem.

Link: https://lkml.kernel.org/r/283a0bdfd6ac7aa334a491422bcae70919c572bd.1763008453.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Baolin Wang
2025-11-14 08:46:32 +08:00
committed by Andrew Morton
parent 1b1a4e4d67
commit 8826f09616
1 changed files with 3 additions and 14 deletions
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17
mm/shmem.c
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@@ -645,34 +645,23 @@ static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index
* the mTHP interface, so we still use PMD-sized huge order to
* check whether global control is enabled.
*
* For tmpfs mmap()'s huge order, we still use PMD-sized order to
* allocate huge pages due to lack of a write size hint.
*
* For tmpfs with 'huge=always' or 'huge=within_size' mount option,
* we will always try PMD-sized order first. If that failed, it will
* fall back to small large folios.
*/
switch (SHMEM_SB(inode->i_sb)->huge) {
case SHMEM_HUGE_ALWAYS:
if (vma)
return maybe_pmd_order;
return THP_ORDERS_ALL_FILE_DEFAULT;
case SHMEM_HUGE_WITHIN_SIZE:
if (vma)
within_size_orders = maybe_pmd_order;
else
within_size_orders = THP_ORDERS_ALL_FILE_DEFAULT;
within_size_orders = shmem_get_orders_within_size(inode, within_size_orders,
index, write_end);
within_size_orders = shmem_get_orders_within_size(inode,
THP_ORDERS_ALL_FILE_DEFAULT, index, write_end);
if (within_size_orders > 0)
return within_size_orders;
fallthrough;
case SHMEM_HUGE_ADVISE:
if (vm_flags & VM_HUGEPAGE)
return maybe_pmd_order;
return THP_ORDERS_ALL_FILE_DEFAULT;
fallthrough;
default:
return 0;