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charset="us-ascii" Content-ID: <0643978759D03543AAFF76D809971BC1@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 088d4e8b-f3f5-492f-ed51-08d6ef83ae62 X-MS-Exchange-CrossTenant-originalarrivaltime: 12 Jun 2019 22:16:56.3836 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: songliubraving@fb.com X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR15MB1614 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-12_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906120155 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jun 12, 2019, at 3:03 PM, Song Liu wrote: >=20 > This patches introduces 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. >=20 > 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. >=20 > Signed-off-by: Song Liu Please ignore this one. It is a duplicated copy of 3/5, sent by accident.=20 Sorry for the noise.=20 Song > --- > include/linux/mm.h | 1 + > mm/gup.c | 38 +++++++++++++++++++++++++++++++++++--- > 2 files changed, 36 insertions(+), 3 deletions(-) >=20 > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 0ab8c7d84cd0..e605acc4fc81 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2642,6 +2642,7 @@ struct page *follow_page(struct vm_area_struct *vma= , unsigned long address, > #define FOLL_COW 0x4000 /* internal GUP flag */ > #define FOLL_ANON 0x8000 /* don't do file mappings */ > #define FOLL_LONGTERM 0x10000 /* mapping lifetime is indefinite: see belo= w */ > +#define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */ >=20 > /* > * NOTE on FOLL_LONGTERM: > diff --git a/mm/gup.c b/mm/gup.c > index ddde097cf9e4..3d05bddb56c9 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -398,7 +398,7 @@ static struct page *follow_pmd_mask(struct vm_area_st= ruct *vma, > 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 =3D pmd_page(*pmd); > if (is_huge_zero_page(page)) { > @@ -407,7 +407,7 @@ static struct page *follow_pmd_mask(struct vm_area_st= ruct *vma, > split_huge_pmd(vma, pmd, address); > if (pmd_trans_unstable(pmd)) > ret =3D -EBUSY; > - } else { > + } else if (flags & FOLL_SPLIT) { > if (unlikely(!try_get_page(page))) { > spin_unlock(ptl); > return ERR_PTR(-ENOMEM); > @@ -419,8 +419,40 @@ static struct page *follow_pmd_mask(struct vm_area_s= truct *vma, > put_page(page); > if (pmd_none(*pmd)) > return no_page_table(vma, flags); > - } > + } else { /* flags & FOLL_SPLIT_PMD */ > + unsigned long addr; > + pgprot_t prot; > + pte_t *pte; > + int i; > + > + spin_unlock(ptl); > + split_huge_pmd(vma, pmd, address); > + lock_page(page); > + pte =3D get_locked_pte(mm, address, &ptl); > + if (!pte) { > + unlock_page(page); > + return no_page_table(vma, flags); > + } >=20 > + /* get refcount for every small page */ > + page_ref_add(page, HPAGE_PMD_NR); > + > + prot =3D READ_ONCE(vma->vm_page_prot); > + for (i =3D 0, addr =3D address & PMD_MASK; > + i < HPAGE_PMD_NR; i++, addr +=3D PAGE_SIZE) { > + struct page *p =3D page + i; > + > + pte =3D pte_offset_map(pmd, addr); > + VM_BUG_ON(!pte_none(*pte)); > + set_pte_at(mm, addr, pte, mk_pte(p, prot)); > + page_add_file_rmap(p, false); > + } > + > + spin_unlock(ptl); > + unlock_page(page); > + add_mm_counter(mm, mm_counter_file(page), HPAGE_PMD_NR); > + ret =3D 0; > + } > return ret ? ERR_PTR(ret) : > follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); > } > --=20 > 2.17.1 >=20