linux-kernel - [RFC PATCH v11 10/29] mm: Add AS_UNMOVABLE to mark mapping as completely unmovable

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Message-ID: <20230718234512.1690985-11-seanjc@google.com>
Date:   Tue, 18 Jul 2023 16:44:53 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Sean Christopherson <seanjc@...gle.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>
Cc:     kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.linux.dev, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Fuad Tabba <tabba@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [RFC PATCH v11 10/29] mm: Add AS_UNMOVABLE to mark mapping as
 completely unmovable

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 include/linux/pagemap.h | 11 +++++++++++
 mm/compaction.c         |  4 ++++
 mm/migrate.c            |  2 ++
 3 files changed, 17 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 716953ee1ebd..931d2f1da7d5 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -203,6 +203,7 @@ enum mapping_flags {
 	/* writeback related tags are not used */
 	AS_NO_WRITEBACK_TAGS = 5,
 	AS_LARGE_FOLIO_SUPPORT = 6,
+	AS_UNMOVABLE	= 7,	/* The mapping cannot be moved, ever */
 };
 
 /**
@@ -273,6 +274,16 @@ static inline int mapping_use_writeback_tags(struct address_space *mapping)
 	return !test_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags);
 }
 
+static inline void mapping_set_unmovable(struct address_space *mapping)
+{
+	set_bit(AS_UNMOVABLE, &mapping->flags);
+}
+
+static inline bool mapping_unmovable(struct address_space *mapping)
+{
+	return test_bit(AS_UNMOVABLE, &mapping->flags);
+}
+
 static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
 {
 	return mapping->gfp_mask;
diff --git a/mm/compaction.c b/mm/compaction.c
index dbc9f86b1934..a3d2b132df52 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1047,6 +1047,10 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 		if (!mapping && (folio_ref_count(folio) - 1) > folio_mapcount(folio))
 			goto isolate_fail_put;
 
+		/* The mapping truly isn't movable. */
+		if (mapping && mapping_unmovable(mapping))
+			goto isolate_fail_put;
+
 		/*
 		 * Only allow to migrate anonymous pages in GFP_NOFS context
 		 * because those do not depend on fs locks.
diff --git a/mm/migrate.c b/mm/migrate.c
index 24baad2571e3..c00a4ca86698 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -954,6 +954,8 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 
 		if (!mapping)
 			rc = migrate_folio(mapping, dst, src, mode);
+		else if (mapping_unmovable(mapping))
+			rc = -EOPNOTSUPP;
 		else if (mapping->a_ops->migrate_folio)
 			/*
 			 * Most folios have a mapping and most filesystems
-- 
2.41.0.255.g8b1d071c50-goog