From: Yang Shi <shy828301@xxxxxxxxx>
Subject: mm: gup: remove FOLL_SPLIT
Since commit 5a52c9df62b4 ("uprobe: use FOLL_SPLIT_PMD instead of
FOLL_SPLIT") and commit ba925fa35057 ("s390/gmap: improve THP splitting")
FOLL_SPLIT has not been used anymore. Remove the dead code.
Link: https://lkml.kernel.org/r/20210330203900.9222-1-shy828301@xxxxxxxxx
Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/transhuge.rst | 5 -----
include/linux/mm.h | 1 -
mm/gup.c | 28 ++--------------------------
3 files changed, 2 insertions(+), 32 deletions(-)
--- a/Documentation/vm/transhuge.rst~mm-gup-remove-foll_split
+++ a/Documentation/vm/transhuge.rst
@@ -53,11 +53,6 @@ prevent the page from being split by any
of handling GUP on hugetlbfs will also work fine on transparent
hugepage backed mappings.
-In case you can't handle compound pages if they're returned by
-follow_page, the FOLL_SPLIT bit can be specified as a parameter to
-follow_page, so that it will split the hugepages before returning
-them.
-
Graceful fallback
=================
--- a/include/linux/mm.h~mm-gup-remove-foll_split
+++ a/include/linux/mm.h
@@ -2791,7 +2791,6 @@ struct page *follow_page(struct vm_area_
#define FOLL_NOWAIT 0x20 /* if a disk transfer is needed, start the IO
* and return without waiting upon it */
#define FOLL_POPULATE 0x40 /* fault in page */
-#define FOLL_SPLIT 0x80 /* don't return transhuge pages, split them */
#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
#define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
--- a/mm/gup.c~mm-gup-remove-foll_split
+++ a/mm/gup.c
@@ -516,18 +516,6 @@ retry:
}
}
- if (flags & FOLL_SPLIT && PageTransCompound(page)) {
- get_page(page);
- pte_unmap_unlock(ptep, ptl);
- lock_page(page);
- ret = split_huge_page(page);
- unlock_page(page);
- put_page(page);
- if (ret)
- return ERR_PTR(ret);
- goto retry;
- }
-
/* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
if (unlikely(!try_grab_page(page, flags))) {
page = ERR_PTR(-ENOMEM);
@@ -672,7 +660,7 @@ retry_locked:
spin_unlock(ptl);
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
}
- if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) {
+ if (flags & FOLL_SPLIT_PMD) {
int ret;
page = pmd_page(*pmd);
if (is_huge_zero_page(page)) {
@@ -681,19 +669,7 @@ retry_locked:
split_huge_pmd(vma, pmd, address);
if (pmd_trans_unstable(pmd))
ret = -EBUSY;
- } else if (flags & FOLL_SPLIT) {
- if (unlikely(!try_get_page(page))) {
- spin_unlock(ptl);
- return ERR_PTR(-ENOMEM);
- }
- spin_unlock(ptl);
- lock_page(page);
- ret = split_huge_page(page);
- unlock_page(page);
- put_page(page);
- if (pmd_none(*pmd))
- return no_page_table(vma, flags);
- } else { /* flags & FOLL_SPLIT_PMD */
+ } else {
spin_unlock(ptl);
split_huge_pmd(vma, pmd, address);
ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
_
