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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: David 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2022-10-21 12:11:41 +02:00 committed by Andrew Morton
parent d7c0e68dab
commit f7355e99d9
2 changed files with 5 additions and 51 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/mm.h
View File

@ -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 */

55
mm/gup.c
View File

@ -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)))
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_present(pte))
goto no_page;
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)))
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_present(pmdval))
return no_page_table(vma, flags);
if (pmd_devmap(pmdval)) {
ptl = pmd_lock(mm, pmd);
page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
@ -703,18 +666,10 @@ retry:
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;
return no_page_table(vma, flags);
}
if (unlikely(!pmd_trans_huge(*pmd))) {
spin_unlock(ptl);