linux-kernel - [PATCH V3 1/2] mm: export folio_expected

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Message-ID: <20250417060630.197278-2-shivankg@amd.com>
Date: Thu, 17 Apr 2025 06:06:32 +0000
From: Shivank Garg <shivankg@....com>
To: <shaggy@...nel.org>, <akpm@...ux-foundation.org>
CC: <willy@...radead.org>, <shivankg@....com>, <david@...hat.com>,
	<wangkefeng.wang@...wei.com>, <jane.chu@...cle.com>, <ziy@...dia.com>,
	<donettom@...ux.ibm.com>, <apopple@...dia.com>,
	<jfs-discussion@...ts.sourceforge.net>, <linux-kernel@...r.kernel.org>,
	<linux-mm@...ck.org>, <syzbot+8bb6fd945af4e0ad9299@...kaller.appspotmail.com>
Subject: [PATCH V3 1/2] mm: export folio_expected_refs for JFS migration handler

Export folio_expected_refs() to allow filesystem-specific migration
handlers like JFS metapage_migrate_folio to properly verify reference
counts before migration.

Signed-off-by: Shivank Garg <shivankg@....com>
---
 include/linux/migrate.h | 1 +
 mm/migrate.c            | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index aaa2114498d6..cb31c5b1eb6a 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -60,6 +60,7 @@ struct movable_operations {
 /* Defined in mm/debug.c: */
 extern const char *migrate_reason_names[MR_TYPES];
 
+int folio_expected_refs(struct address_space *mapping, struct folio *folio);
 #ifdef CONFIG_MIGRATION
 
 void putback_movable_pages(struct list_head *l);
diff --git a/mm/migrate.c b/mm/migrate.c
index 6e2488e5dbe4..0f01b8a87dec 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -445,7 +445,7 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
 }
 #endif
 
-static int folio_expected_refs(struct address_space *mapping,
+int folio_expected_refs(struct address_space *mapping,
 		struct folio *folio)
 {
 	int refs = 1;
@@ -458,6 +458,7 @@ static int folio_expected_refs(struct address_space *mapping,
 
 	return refs;
 }
+EXPORT_SYMBOL_GPL(folio_expected_refs);
 
 /*
  * Replace the folio in the mapping.
-- 
2.34.1