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| author |   Song Liu <songliubraving@fb.com> | 2019-09-23 15:38:25 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2019-09-24 15:54:11 -0700 |
| commit | bfe7b00de6d1e25fee08484c4fbf1c1ed175be78 (patch) | |
| tree | f24b90ed0dcca9ecfac4d5407b5d1fe88c8d9c23 /mm | |
| parent | uprobe: use original page when all uprobes are removed (diff) | |
| download | wireguard-linux-bfe7b00de6d1e25fee08484c4fbf1c1ed175be78.tar.xz wireguard-linux-bfe7b00de6d1e25fee08484c4fbf1c1ed175be78.zip | |
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>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/gup.c | 8 |
1 files changed, 6 insertions, 2 deletions
@@ -384,7 +384,7 @@ retry_locked: spin_unlock(ptl); return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); } - if (flags & FOLL_SPLIT) { + if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) { int ret; page = pmd_page(*pmd); if (is_huge_zero_page(page)) { @@ -393,7 +393,7 @@ retry_locked: split_huge_pmd(vma, pmd, address); if (pmd_trans_unstable(pmd)) ret = -EBUSY; - } else { + } else if (flags & FOLL_SPLIT) { if (unlikely(!try_get_page(page))) { spin_unlock(ptl); return ERR_PTR(-ENOMEM); @@ -405,6 +405,10 @@ retry_locked: put_page(page); if (pmd_none(*pmd)) 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) : |