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mm: gup: remove FOLL_SPLIT 

Since commit 5a52c9df62 ("uprobe: use FOLL_SPLIT_PMD instead of
FOLL_SPLIT") and commit ba925fa350 ("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@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yang Shi 2021-04-29 22:55:56 -07:00 committed by Linus Torvalds
parent 1d4b0166e3
commit 4066c11948
3 changed files with 2 additions and 32 deletions
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5
Documentation/vm/transhuge.rst
View File

@ -53,11 +53,6 @@ prevent the page from being split by anyone.
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
=================

1
include/linux/mm.h
View File

@ -2791,7 +2791,6 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
#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 */

28
mm/gup.c
View File

@ -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;