Commit f7355e99 authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/gup: remove FOLL_MIGRATION 

Fortunately, the last user (KSM) is gone, so let's just remove this rather
special code from generic GUP handling -- especially because KSM never
required the PMD handling as KSM only deals with individual base pages.

[akpm@linux-foundation.org: fix merge snafu]Link: https://lkml.kernel.org/r/20221021101141.84170-10-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent d7c0e68d

include/linux/mm.h

+0 −1
Original line number Diff line number Diff line
@@ -3057,7 +3057,6 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, 
				 * and return without waiting upon it */

#define FOLL_NOFAULT	0x80	/* do not fault in pages */

#define FOLL_HWPOISON	0x100	/* check page is hwpoisoned */

#define FOLL_MIGRATION	0x400	/* wait for page to replace migration entry */

#define FOLL_TRIED	0x800	/* a retry, previous pass started an IO */

#define FOLL_REMOTE	0x2000	/* we are working on non-current tsk/mm */

#define FOLL_ANON	0x8000	/* don't do file mappings */

mm/gup.c

+5 −50
Original line number Diff line number Diff line
@@ -537,30 +537,13 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, 
	if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==

			 (FOLL_PIN | FOLL_GET)))

		return ERR_PTR(-EINVAL);

retry:

	if (unlikely(pmd_bad(*pmd)))

		return no_page_table(vma, flags);



	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);

	pte = *ptep;

	if (!pte_present(pte)) {

		swp_entry_t entry;

		/*

		 * KSM's break_ksm() relies upon recognizing a ksm page

		 * even while it is being migrated, so for that case we

		 * need migration_entry_wait().

		 */

		if (likely(!(flags & FOLL_MIGRATION)))

	if (!pte_present(pte))

		goto no_page;

		if (pte_none(pte))

			goto no_page;

		entry = pte_to_swp_entry(pte);

		if (!is_migration_entry(entry))

			goto no_page;

		pte_unmap_unlock(ptep, ptl);

		migration_entry_wait(mm, pmd, address);

		goto retry;

	}

	if (pte_protnone(pte) && !gup_can_follow_protnone(flags))

		goto no_page;
@@ -668,28 +651,8 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, 
	pmdval = READ_ONCE(*pmd);

	if (pmd_none(pmdval))

		return no_page_table(vma, flags);

retry:

	if (!pmd_present(pmdval)) {

		/*

		 * Should never reach here, if thp migration is not supported;

		 * Otherwise, it must be a thp migration entry.

		 */

		VM_BUG_ON(!thp_migration_supported() ||

				  !is_pmd_migration_entry(pmdval));



		if (likely(!(flags & FOLL_MIGRATION)))

	if (!pmd_present(pmdval))

		return no_page_table(vma, flags);



		pmd_migration_entry_wait(mm, pmd);

		pmdval = READ_ONCE(*pmd);

		/*

		 * MADV_DONTNEED may convert the pmd to null because

		 * mmap_lock is held in read mode

		 */

		if (pmd_none(pmdval))

			return no_page_table(vma, flags);

		goto retry;

	}

	if (pmd_devmap(pmdval)) {

		ptl = pmd_lock(mm, pmd);

		page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
@@ -703,18 +666,10 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, 
	if (pmd_protnone(pmdval) && !gup_can_follow_protnone(flags))

		return no_page_table(vma, flags);



retry_locked:

	ptl = pmd_lock(mm, pmd);

	if (unlikely(pmd_none(*pmd))) {

		spin_unlock(ptl);

		return no_page_table(vma, flags);

	}

	if (unlikely(!pmd_present(*pmd))) {

		spin_unlock(ptl);

		if (likely(!(flags & FOLL_MIGRATION)))

		return no_page_table(vma, flags);

		pmd_migration_entry_wait(mm, pmd);

		goto retry_locked;

	}

	if (unlikely(!pmd_trans_huge(*pmd))) {

		spin_unlock(ptl);