From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zi Yan Subject: Re: [PATCH 01/21] mm/page_isolation: protect cma from isolate_single_pageblock Date: Tue, 13 Sep 2022 21:09:36 -0400 Message-ID: <71D040CB-0E26-4CD3-9121-54D740F24594@nvidia.com> References: <20220913195508.3511038-1-opendmb@gmail.com> <20220913195508.3511038-2-opendmb@gmail.com> <36E322BF-F052-4A8B-9FA5-4E0AA84E4AAF@nvidia.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="=_MailMate_616185E2-29EC-4B0E-8755-A12BD9249736_="; micalg=pgp-sha512; protocol="application/pgp-signature" Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=2v/TCRcZ/UTFjnI4Zbvw/IAbK4sfnHYDS7H9Kum4LEk=; b=AldNPiGotb9KR0Fj/6sXxGG8JjkolBYvub3KBHYFtCyDusseiwPmAC4zdSiEh27xZlOJsJQaoDmgd4YttXS/WajMq6N7SzGBdTlccDAU443A9Qk8neTs6PO0PGHuvxLBBTz6zrbwXT1fTpfR5L7pAW9xCEe3+GGto02YX34EdcEkHk3HxgQU2770tYLeR70eR0OjFY4LqulH8mWusjR+h1HHrr8AbyR8uAbghw4okObfapb4Vrn6iMon126z2iyUBdzdcOxfWtHLZ+xGrGHEE2B9H34VIspYBxWd34dmsCGteUaAHizF1I4hChjIqDYuLjYXmAUWUx9F6v0WPhVxYA== In-Reply-To: List-ID: To: Doug Berger Cc: Andrew Morton , Jonathan Corbet , Rob Herring , Krzysztof Kozlowski , Frank Rowand , Mike Kravetz , Muchun Song , Mike Rapoport , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Borislav Petkov , "Paul E. McKenney" , Neeraj Upadhyay , Randy Dunlap , Damien Le Moal , Florian Fainelli , David Hildenbrand , Oscar Salvador --=_MailMate_616185E2-29EC-4B0E-8755-A12BD9249736_= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On 13 Sep 2022, at 20:59, Doug Berger wrote: > On 9/13/2022 5:02 PM, Zi Yan wrote: >> On 13 Sep 2022, at 15:54, Doug Berger wrote: >> >>> The function set_migratetype_isolate() has special handling for >>> pageblocks of MIGRATE_CMA type that protects them from being >>> isolated for MIGRATE_MOVABLE requests. >>> >>> Since isolate_single_pageblock() doesn't receive the migratetype >>> argument of start_isolate_page_range() it used the migratetype >>> of the pageblock instead of the requested migratetype which >>> defeats this MIGRATE_CMA check. >>> >>> This allows an attempt to create a gigantic page within a CMA >>> region to change the migratetype of the first and last pageblocks >>> from MIGRATE_CMA to MIGRATE_MOVABLE when they are restored after >>> failure, which corrupts the CMA region. >>> >>> The calls to (un)set_migratetype_isolate() for the first and last >>> pageblocks of the start_isolate_page_range() are moved back into >>> that function to allow access to its migratetype argument and make >>> it easier to see how all of the pageblocks in the range are >>> isolated. >>> >>> Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock g= ranularity") >>> Signed-off-by: Doug Berger >>> --- >>> mm/page_isolation.c | 75 +++++++++++++++++++++---------------------= --- >>> 1 file changed, 35 insertions(+), 40 deletions(-) >> >> Thanks for the fix. > Thanks for the review. > >> >> Why not just pass migratetype into isolate_single_pageblock() and use >> it when set_migratetype_isolate() is used? That would have much >> fewer changes. What is the reason of pulling skip isolation logic out?= > I found the skip_isolation logic confusing and thought that setting and= restoring the migratetype within the same function and consolidating the= error recovery paths also within that function was easier to understand = and less prone to accidental breakage. > > In particular, setting MIGRATE_ISOLATE in isolate_single_pageblock() an= d having to remember to unset it in start_isolate_page_range() differentl= y on different error paths was troublesome for me. Wouldn't this work as well? diff --git a/mm/page_isolation.c b/mm/page_isolation.c index c1307d1bea81..a312cabd0d95 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -288,6 +288,7 @@ __first_valid_page(unsigned long pfn, unsigned long n= r_pages) * @isolate_before: isolate the pageblock before the boundary_pfn * @skip_isolation: the flag to skip the pageblock isolation in secon= d * isolate_single_pageblock() + * @migratetype: Migrate type to set in error recovery. * * Free and in-use pages can be as big as MAX_ORDER and contain more tha= n one * pageblock. When not all pageblocks within a page are isolated at the = same @@ -302,9 +303,9 @@ __first_valid_page(unsigned long pfn, unsigned long n= r_pages) * the in-use page then splitting the free page. */ static int isolate_single_pageblock(unsigned long boundary_pfn, int flag= s, - gfp_t gfp_flags, bool isolate_before, bool skip_i= solation) + gfp_t gfp_flags, bool isolate_before, bool skip_i= solation, + int migratetype) { - unsigned char saved_mt; unsigned long start_pfn; unsigned long isolate_pageblock; unsigned long pfn; @@ -328,12 +329,10 @@ static int isolate_single_pageblock(unsigned long b= oundary_pfn, int flags, start_pfn =3D max(ALIGN_DOWN(isolate_pageblock, MAX_ORDER_NR_PAG= ES), zone->zone_start_pfn); - saved_mt =3D get_pageblock_migratetype(pfn_to_page(isolate_pagebl= ock)); - if (skip_isolation) - VM_BUG_ON(!is_migrate_isolate(saved_mt)); + VM_BUG_ON(!is_migrate_isolate(get_pageblock_migratetype(p= fn_to_page(isolate_pageblock)))); else { - ret =3D set_migratetype_isolate(pfn_to_page(isolate_pageb= lock), saved_mt, flags, + ret =3D set_migratetype_isolate(pfn_to_page(isolate_pageb= lock), migratetype, flags, isolate_pageblock, isolate_pageblock + pa= geblock_nr_pages); if (ret) @@ -475,7 +474,7 @@ static int isolate_single_pageblock(unsigned long bou= ndary_pfn, int flags, failed: /* restore the original migratetype */ if (!skip_isolation) - unset_migratetype_isolate(pfn_to_page(isolate_pageblock),= saved_mt); + unset_migratetype_isolate(pfn_to_page(isolate_pageblock),= migratetype); return -EBUSY; } @@ -537,7 +536,8 @@ int start_isolate_page_range(unsigned long start_pfn,= unsigned long end_pfn, bool skip_isolation =3D false; /* isolate [isolate_start, isolate_start + pageblock_nr_pages) pa= geblock */ - ret =3D isolate_single_pageblock(isolate_start, flags, gfp_flags,= false, skip_isolation); + ret =3D isolate_single_pageblock(isolate_start, flags, gfp_flags,= false, + skip_isolation, migratetype); if (ret) return ret; @@ -545,7 +545,8 @@ int start_isolate_page_range(unsigned long start_pfn,= unsigned long end_pfn, skip_isolation =3D true; /* isolate [isolate_end - pageblock_nr_pages, isolate_end) pagebl= ock */ - ret =3D isolate_single_pageblock(isolate_end, flags, gfp_flags, t= rue, skip_isolation); + ret =3D isolate_single_pageblock(isolate_end, flags, gfp_flags, t= rue, + skip_isolation, migratetype); if (ret) { unset_migratetype_isolate(pfn_to_page(isolate_start), mig= ratetype); return ret; > > It could certainly be done differently, but this was my preference. A smaller patch can make review easier, right? >> >> Ultimately, I would like to make MIGRATE_ISOLATE a separate bit, >> so that migratetype will not be overwritten during page isolation. >> Then, set_migratetype_isolate() and start_isolate_page_range() >> will not have migratetype to set in error recovery any more. >> That is on my TODO. >> >>> >>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >>> index 9d73dc38e3d7..8e16aa22cb61 100644 >>> --- a/mm/page_isolation.c >>> +++ b/mm/page_isolation.c >>> @@ -286,8 +286,6 @@ __first_valid_page(unsigned long pfn, unsigned lo= ng nr_pages) >>> * @flags: isolation flags >>> * @gfp_flags: GFP flags used for migrating pages >>> * @isolate_before: isolate the pageblock before the boundary_pfn >>> - * @skip_isolation: the flag to skip the pageblock isolation in seco= nd >>> - * isolate_single_pageblock() >>> * >>> * Free and in-use pages can be as big as MAX_ORDER-1 and contain m= ore than one >>> * pageblock. When not all pageblocks within a page are isolated at= the same >>> @@ -302,9 +300,8 @@ __first_valid_page(unsigned long pfn, unsigned lo= ng nr_pages) >>> * the in-use page then splitting the free page. >>> */ >>> static int isolate_single_pageblock(unsigned long boundary_pfn, int= flags, >>> - gfp_t gfp_flags, bool isolate_before, bool skip_isolation) >>> + gfp_t gfp_flags, bool isolate_before) >>> { >>> - unsigned char saved_mt; >>> unsigned long start_pfn; >>> unsigned long isolate_pageblock; >>> unsigned long pfn; >>> @@ -328,18 +325,6 @@ static int isolate_single_pageblock(unsigned lon= g boundary_pfn, int flags, >>> start_pfn =3D max(ALIGN_DOWN(isolate_pageblock, MAX_ORDER_NR_PAGE= S), >>> zone->zone_start_pfn); >>> >>> - saved_mt =3D get_pageblock_migratetype(pfn_to_page(isolate_pagebloc= k)); >>> - >>> - if (skip_isolation) >>> - VM_BUG_ON(!is_migrate_isolate(saved_mt)); >>> - else { >>> - ret =3D set_migratetype_isolate(pfn_to_page(isolate_pageblock), sa= ved_mt, flags, >>> - isolate_pageblock, isolate_pageblock + pageblock_nr_pages); >>> - >>> - if (ret) >>> - return ret; >>> - } >>> - >>> /* >>> * Bail out early when the to-be-isolated pageblock does not form >>> * a free or in-use page across boundary_pfn: >>> @@ -428,7 +413,7 @@ static int isolate_single_pageblock(unsigned long= boundary_pfn, int flags, >>> ret =3D set_migratetype_isolate(page, page_mt, >>> flags, head_pfn, head_pfn + nr_pages); >>> if (ret) >>> - goto failed; >>> + return ret; >>> } >>> >>> ret =3D __alloc_contig_migrate_range(&cc, head_pfn, >>> @@ -443,7 +428,7 @@ static int isolate_single_pageblock(unsigned long= boundary_pfn, int flags, >>> unset_migratetype_isolate(page, page_mt); >>> >>> if (ret) >>> - goto failed; >>> + return -EBUSY; >>> /* >>> * reset pfn to the head of the free page, so >>> * that the free page handling code above can split >>> @@ -459,24 +444,19 @@ static int isolate_single_pageblock(unsigned lo= ng boundary_pfn, int flags, >>> while (!PageBuddy(pfn_to_page(outer_pfn))) { >>> /* stop if we cannot find the free page */ >>> if (++order >=3D MAX_ORDER) >>> - goto failed; >>> + return -EBUSY; >>> outer_pfn &=3D ~0UL << order; >>> } >>> pfn =3D outer_pfn; >>> continue; >>> } else >>> #endif >>> - goto failed; >>> + return -EBUSY; >>> } >>> >>> pfn++; >>> } >>> return 0; >>> -failed: >>> - /* restore the original migratetype */ >>> - if (!skip_isolation) >>> - unset_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt= ); >>> - return -EBUSY; >>> } >>> >>> /** >>> @@ -534,21 +514,30 @@ int start_isolate_page_range(unsigned long star= t_pfn, unsigned long end_pfn, >>> unsigned long isolate_start =3D ALIGN_DOWN(start_pfn, pageblock_nr= _pages); >>> unsigned long isolate_end =3D ALIGN(end_pfn, pageblock_nr_pages); >>> int ret; >>> - bool skip_isolation =3D false; >>> >>> /* isolate [isolate_start, isolate_start + pageblock_nr_pages) pag= eblock */ >>> - ret =3D isolate_single_pageblock(isolate_start, flags, gfp_flags, f= alse, skip_isolation); >>> + ret =3D set_migratetype_isolate(pfn_to_page(isolate_start), migrate= type, >>> + flags, isolate_start, isolate_start + pageblock_nr_pages); >>> if (ret) >>> return ret; >>> - >>> - if (isolate_start =3D=3D isolate_end - pageblock_nr_pages) >>> - skip_isolation =3D true; >>> + ret =3D isolate_single_pageblock(isolate_start, flags, gfp_flags, f= alse); >>> + if (ret) >>> + goto unset_start_block; >>> >>> /* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblo= ck */ >>> - ret =3D isolate_single_pageblock(isolate_end, flags, gfp_flags, tru= e, skip_isolation); >>> + pfn =3D isolate_end - pageblock_nr_pages; >>> + if (isolate_start !=3D pfn) { >>> + ret =3D set_migratetype_isolate(pfn_to_page(pfn), migratetype, >>> + flags, pfn, pfn + pageblock_nr_pages); >>> + if (ret) >>> + goto unset_start_block; >>> + } >>> + ret =3D isolate_single_pageblock(isolate_end, flags, gfp_flags, tru= e); >>> if (ret) { >>> - unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype)= ; >>> - return ret; >>> + if (isolate_start !=3D pfn) >>> + goto unset_end_block; >>> + else >>> + goto unset_start_block; >>> } >>> >>> /* skip isolated pageblocks at the beginning and end */ >>> @@ -557,15 +546,21 @@ int start_isolate_page_range(unsigned long star= t_pfn, unsigned long end_pfn, >>> pfn +=3D pageblock_nr_pages) { >>> page =3D __first_valid_page(pfn, pageblock_nr_pages); >>> if (page && set_migratetype_isolate(page, migratetype, flags, >>> - start_pfn, end_pfn)) { >>> - undo_isolate_page_range(isolate_start, pfn, migratetype); >>> - unset_migratetype_isolate( >>> - pfn_to_page(isolate_end - pageblock_nr_pages), >>> - migratetype); >>> - return -EBUSY; >>> - } >>> + start_pfn, end_pfn)) >>> + goto unset_isolated_blocks; >>> } >>> return 0; >>> + >>> +unset_isolated_blocks: >>> + ret =3D -EBUSY; >>> + undo_isolate_page_range(isolate_start + pageblock_nr_pages, pfn, >>> + migratetype); >>> +unset_end_block: >>> + unset_migratetype_isolate(pfn_to_page(isolate_end - pageblock_nr_pa= ges), >>> + migratetype); >>> +unset_start_block: >>> + unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);= >>> + return ret; >>> } >>> >>> /* >>> -- = >>> 2.25.1 >> >> >> -- >> Best Regards, >> Yan, Zi -- Best Regards, Yan, Zi --=_MailMate_616185E2-29EC-4B0E-8755-A12BD9249736_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; 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