forked from Minki/linux
mm, thp: introduce FOLL_SPLIT_PMD
Introduce a new foll_flag: FOLL_SPLIT_PMD. As the name says FOLL_SPLIT_PMD splits huge pmd for given mm_struct, the underlining huge page stays as-is. FOLL_SPLIT_PMD is useful for cases where we need to use regular pages, but would switch back to huge page and huge pmd on. One of such example is uprobe. The following patches use FOLL_SPLIT_PMD in uprobe. Link: http://lkml.kernel.org/r/20190815164525.1848545-4-songliubraving@fb.com Signed-off-by: Song Liu <songliubraving@fb.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
fb4fb04ff4
commit
bfe7b00de6
@ -2591,6 +2591,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
|
|||||||
#define FOLL_COW 0x4000 /* internal GUP flag */
|
#define FOLL_COW 0x4000 /* internal GUP flag */
|
||||||
#define FOLL_ANON 0x8000 /* don't do file mappings */
|
#define FOLL_ANON 0x8000 /* don't do file mappings */
|
||||||
#define FOLL_LONGTERM 0x10000 /* mapping lifetime is indefinite: see below */
|
#define FOLL_LONGTERM 0x10000 /* mapping lifetime is indefinite: see below */
|
||||||
|
#define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */
|
||||||
|
|
||||||
/*
|
/*
|
||||||
* NOTE on FOLL_LONGTERM:
|
* NOTE on FOLL_LONGTERM:
|
||||||
|
8
mm/gup.c
8
mm/gup.c
@ -384,7 +384,7 @@ retry_locked:
|
|||||||
spin_unlock(ptl);
|
spin_unlock(ptl);
|
||||||
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
|
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
|
||||||
}
|
}
|
||||||
if (flags & FOLL_SPLIT) {
|
if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) {
|
||||||
int ret;
|
int ret;
|
||||||
page = pmd_page(*pmd);
|
page = pmd_page(*pmd);
|
||||||
if (is_huge_zero_page(page)) {
|
if (is_huge_zero_page(page)) {
|
||||||
@ -393,7 +393,7 @@ retry_locked:
|
|||||||
split_huge_pmd(vma, pmd, address);
|
split_huge_pmd(vma, pmd, address);
|
||||||
if (pmd_trans_unstable(pmd))
|
if (pmd_trans_unstable(pmd))
|
||||||
ret = -EBUSY;
|
ret = -EBUSY;
|
||||||
} else {
|
} else if (flags & FOLL_SPLIT) {
|
||||||
if (unlikely(!try_get_page(page))) {
|
if (unlikely(!try_get_page(page))) {
|
||||||
spin_unlock(ptl);
|
spin_unlock(ptl);
|
||||||
return ERR_PTR(-ENOMEM);
|
return ERR_PTR(-ENOMEM);
|
||||||
@ -405,6 +405,10 @@ retry_locked:
|
|||||||
put_page(page);
|
put_page(page);
|
||||||
if (pmd_none(*pmd))
|
if (pmd_none(*pmd))
|
||||||
return no_page_table(vma, flags);
|
return no_page_table(vma, flags);
|
||||||
|
} else { /* flags & FOLL_SPLIT_PMD */
|
||||||
|
spin_unlock(ptl);
|
||||||
|
split_huge_pmd(vma, pmd, address);
|
||||||
|
ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
|
||||||
}
|
}
|
||||||
|
|
||||||
return ret ? ERR_PTR(ret) :
|
return ret ? ERR_PTR(ret) :
|
||||||
|
Loading…
Reference in New Issue
Block a user