629 DEFINE_MTHP_STAT_ATTR(split, MTHP_STAT_SPLIT);
1765 	 * under splitting since we don't split the page itself, only pmd to  in copy_huge_pmd()
1784 		/* Page maybe pinned: split and retry the fault on PTEs. */  in copy_huge_pmd()
1845 	 * folio_try_dup_anon_rmap_*() and split if duplicating fails.  in copy_huge_pud()
2163 	 * If user want to discard part-pages of THP, split it so MADV_FREE  in madvise_free_huge_pmd()
2278 	 * With split pmd lock we also need to move preallocated  in pmd_move_must_withdraw()
2936 		 * the whole access to the hugepage during the split (which  in __split_huge_pmd_locked()
2952 		 * remain set at all times on the pmd until the split is  in __split_huge_pmd_locked()
2973 		 * Without "freeze", we'll simply split the PMD, propagating the  in __split_huge_pmd_locked()
2982 		 * In case we cannot clear PageAnonExclusive(), split the PMD  in __split_huge_pmd_locked()
3132 	 * contain an hugepage: check if we need to split an huge pmd.  in split_huge_pmd_if_needed()
3145 	/* Check if we need to split start first. */  in vma_adjust_trans_huge()
3148 	/* Check if we need to split end next. */  in vma_adjust_trans_huge()
3151 	/* If we're incrementing next->vm_start, we might need to split it. */  in vma_adjust_trans_huge()
3292 /* Racy check whether the huge page can be split */
3417  * @folio: the to-be-split folio
3418  * @new_order: the smallest order of the after split folios (since buddy
3419  *             allocator like split generates folios with orders from @folio's
3421  * @split_at: in buddy allocator like split, the folio containing @split_at
3422  *            will be split until its order becomes @new_order.
3424  * @list: the after split folios will be added to @list if it is not NULL,
3429  * @uniform_split: if the split is uniform or not (buddy allocator like split)
3432  * 1. uniform split: the given @folio into multiple @new_order small folios,
3435  * 2. buddy allocator like (non-uniform) split: the given @folio is split into
3436  *    half and one of the half (containing the given page) is split into half
3441  * 1. uniform split: a single __split_folio_to_order() is called to split the
3445  * 2. non-uniform split: in general, folio_order - @new_order calls to
3446  *    __split_folio_to_order() are made in a for loop to split the @folio
3449  *    @page, which is split in next for loop.
3455  * 1. uniform split leaves @page (or the folio contains it) locked;
3456  * 2. buddy allocator like (non-uniform) split leaves @folio locked.
3460  * split. The caller needs to check the input folio.
3484 		/* a swapcache folio can only be uniformly split to order-0 */  in __split_unmapped_folio()
3501 	 * split to new_order one order at a time. For uniform split,  in __split_unmapped_folio()
3502 	 * folio is split to new_order directly.  in __split_unmapped_folio()
3519 			 * uniform split has xas_split_alloc() called before  in __split_unmapped_folio()
3521 			 * non-uniform split can handle ENOMEM.  in __split_unmapped_folio()
3544 		 * Iterate through after-split folios and perform related  in __split_unmapped_folio()
3545 		 * operations. But in buddy allocator like split, the folio  in __split_unmapped_folio()
3553 			 * for buddy allocator like split, the folio containing  in __split_unmapped_folio()
3554 			 * page will be split next and should not be released,  in __split_unmapped_folio()
3570 			 * entries are updated with all the other after-split  in __split_unmapped_folio()
3632 	 * For uniform split, it is left for caller to unlock.  in __split_unmapped_folio()
3633 	 * For buddy allocator like split, the first after-split folio is left  in __split_unmapped_folio()
3647 		 * of the tail pages after the split is complete.  in __split_unmapped_folio()
3660 				"Cannot split to order-1 folio");  in non_uniform_split_supported()
3665 		 * No split if the file system does not support large folio.  in non_uniform_split_supported()
3671 			"Cannot split file folio to non-0 order");  in non_uniform_split_supported()
3678 			"Cannot split swapcache folio to non-0 order");  in non_uniform_split_supported()
3691 				"Cannot split to order-1 folio");  in uniform_split_supported()
3697 				"Cannot split file folio to non-0 order");  in uniform_split_supported()
3704 			"Cannot split swapcache folio to non-0 order");  in uniform_split_supported()
3712  * __folio_split: split a folio at @split_at to a @new_order folio
3713  * @folio: folio to split
3717  * @list: after-split folios will be put on it if non NULL
3718  * @uniform_split: perform uniform split or not (non-uniform split)
3720  * It calls __split_unmapped_folio() to perform uniform and non-uniform split.
3721  * It is in charge of checking whether the split is supported or not and
3725  * split but not to @new_order, the caller needs to check)
3772 		 * is taken to serialise against parallel split or collapse  in __folio_split()
3802 			VM_WARN_ONCE(1, "Cannot split mapped folio below min-order: %u",  in __folio_split()
3841 	 * Racy check if we can split the page, before unmap_folio() will  in __folio_split()
3842 	 * split PMDs  in __folio_split()
3878 			 * split will see list corruption when checking the  in __folio_split()
3930  * @page can point to any page of the large folio to split. The split operation
3941  *    GUP pins, will result in the folio not getting split; instead, the caller
3959  * Returns 0 if the huge page was split successfully.
3964  * Returns -EBUSY when trying to split the huge zeropage, if the folio is
3972  * Returns -EINVAL when trying to split to an order that is incompatible
3984  * folio_split: split a folio at @split_at to a @new_order folio
3985  * @folio: folio to split
3990  * split but not to @new_order, the caller needs to check)
3995  * Split a folio at @split_at to a new_order folio, leave the
3999  * After the split, there will be a group of folios with different orders and
4003  * After split, folio is left locked for caller.
4047  * therefore important to unqueue deferred split before changing folio memcg.
4095 	 * Exclude swapcache: originally to avoid a corrupt deferred split  in deferred_split_folio()
4184 	int split = 0, removed = 0;  in deferred_split_scan()  local
4227 			split++;  in deferred_split_scan()
4265 	 * Stop shrinker if we didn't split any page, but the queue is empty.  in deferred_split_scan()
4268 	if (!split && list_empty(&ds_queue->split_queue))  in deferred_split_scan()
4270 	return split;  in deferred_split_scan()
4280 	unsigned long total = 0, split = 0;  in split_huge_pages_all()  local
4282 	pr_debug("Split all THPs\n");  in split_huge_pages_all()
4312 				split++;  in split_huge_pages_all()
4321 	pr_debug("%lu of %lu THP split\n", split, total);  in split_huge_pages_all()
4337 	unsigned long total = 0, split = 0;  in split_huge_pages_pid()  local
4358 	pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",  in split_huge_pages_pid()
4401 		 * will try to drop it before split and then check if the folio  in split_huge_pages_pid()
4402 		 * can be split or not. So skip the check here.  in split_huge_pages_pid()
4419 				split++;  in split_huge_pages_pid()
4424 				split++;  in split_huge_pages_pid()
4441 	pr_debug("%lu of %lu THP split\n", split, total);  in split_huge_pages_pid()
4457 	unsigned long total = 0, split = 0;  in split_huge_pages_in_file()  local
4469 	pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",  in split_huge_pages_in_file()
4500 				split++;  in split_huge_pages_in_file()
4505 				split++;  in split_huge_pages_in_file()
4518 	pr_debug("%lu of %lu file-backed THP split\n", split, total);  in split_huge_pages_in_file()