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received-spf: None (protection.outlook.com: mellanox.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: Vs9ITQhDo95Y04P7vJSqSGZG48VlfvfPENlCo1dwgbyOptbvw1pd2E1mK3POI+WEgDsqmUBS4RMZInyDX3g62MvJ16dEjM+owZnp17xkqnaVeKjELYMDp0KjC7FTz+1/xPuOF5qdDQiRHBBkcTBvl3bPKQGJHWkOGSICXO3U41R+fsyeueZt4AF/iVe9KGEh0B1WnyYvp3NNJGE1Jc4rFHAUK0uexqgFjSt/RtrBRXiaTfDoNZ2i3mR2GxGhND+T7rH/3P+RptLFNJtizlvJ+NzM+nRyKAaL5ii04o9jSIu+QNPEKqd6F+Qe6O1wSgaWM6Sz/eAeeLMvhLnh+gfKuTU8jVQ775LxRCSTRTxrWXGDXvu0o5tzQI2BKBW7YP6DtNfNJrMs8A2j+PCaBvHcUN7bDO1EAdnJAKQaypE2Zps= x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="iso-8859-1" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4cc061f5-56ad-4773-7c58-08d720bb3481 X-MS-Exchange-CrossTenant-originalarrivaltime: 14 Aug 2019 13:27:50.9468 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: a652971c-7d2e-4d9b-a6a4-d149256f461b X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: IMnZjJw4rXdPNRe7707GHxiF1SFEJxFKOQBVTYGk2VFuwM9F8tUpkMTyYxiO1iPafyZWUOCAlqhQrz4SzCWVzg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR05MB4543 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Aug 14, 2019 at 09:38:54AM +0200, Christoph Hellwig wrote: > On Tue, Aug 13, 2019 at 06:36:33PM -0700, Dan Williams wrote: > > Section alignment constraints somewhat save us here. The only example > > I can think of a PMD not containing a uniform pgmap association for > > each pte is the case when the pgmap overlaps normal dram, i.e. shares > > the same 'struct memory_section' for a given span. Otherwise, distinct > > pgmaps arrange to manage their own exclusive sections (and now > > subsections as of v5.3). Otherwise the implementation could not > > guarantee different mapping lifetimes. > >=20 > > That said, this seems to want a better mechanism to determine "pfn is > > ZONE_DEVICE". >=20 > So I guess this patch is fine for now, and once you provide a better > mechanism we can switch over to it? What about the version I sent to just get rid of all the strange put_dev_pagemaps while scanning? Odds are good we will work with only a single pagemap, so it makes some sense to cache it once we find it? diff --git a/mm/hmm.c b/mm/hmm.c index 9a908902e4cc38..4e30128c23a505 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -497,10 +497,6 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, } pfns[i] =3D hmm_device_entry_from_pfn(range, pfn) | cpu_flags; } - if (hmm_vma_walk->pgmap) { - put_dev_pagemap(hmm_vma_walk->pgmap); - hmm_vma_walk->pgmap =3D NULL; - } hmm_vma_walk->last =3D end; return 0; #else @@ -604,10 +600,6 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, un= signed long addr, return 0; =20 fault: - if (hmm_vma_walk->pgmap) { - put_dev_pagemap(hmm_vma_walk->pgmap); - hmm_vma_walk->pgmap =3D NULL; - } pte_unmap(ptep); /* Fault any virtual address we were asked to fault */ return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk); @@ -690,16 +682,6 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, return r; } } - if (hmm_vma_walk->pgmap) { - /* - * We do put_dev_pagemap() here and not in hmm_vma_handle_pte() - * so that we can leverage get_dev_pagemap() optimization which - * will not re-take a reference on a pgmap if we already have - * one. - */ - put_dev_pagemap(hmm_vma_walk->pgmap); - hmm_vma_walk->pgmap =3D NULL; - } pte_unmap(ptep - 1); =20 hmm_vma_walk->last =3D addr; @@ -751,10 +733,6 @@ static int hmm_vma_walk_pud(pud_t *pudp, pfns[i] =3D hmm_device_entry_from_pfn(range, pfn) | cpu_flags; } - if (hmm_vma_walk->pgmap) { - put_dev_pagemap(hmm_vma_walk->pgmap); - hmm_vma_walk->pgmap =3D NULL; - } hmm_vma_walk->last =3D end; return 0; } @@ -1026,6 +1004,14 @@ long hmm_range_fault(struct hmm_range *range, unsign= ed int flags) /* Keep trying while the range is valid. */ } while (ret =3D=3D -EBUSY && range->valid); =20 + /* + * We do put_dev_pagemap() here so that we can leverage + * get_dev_pagemap() optimization which will not re-take a + * reference on a pgmap if we already have one. + */ + if (hmm_vma_walk->pgmap) + put_dev_pagemap(hmm_vma_walk->pgmap); + if (ret) { unsigned long i; =20