[RFC PATCH v2 37/51] filemap: Pass address_space mapping to ->free_folio()

[Ackerley Tng <ackerleytng@google.com>]

From: Elliot Berman <quic_eberman@quicinc.com>

The plan is to be able to support multiple allocators for guest_memfd
folios. To allow each allocator to handle release of a folio from a
guest_memfd filemap, ->free_folio() needs to retrieve allocator
information that is stored on the guest_memfd inode.

->free_folio() shouldn't assume that folio->mapping is set/valid, and
the mapping is well-known to callers of .free_folio(). Hence, pass
address_space mapping to ->free_folio() for the callback to retrieve
any necessary information.

Link: https://lore.kernel.org/all/15f665b4-2d33-41ca-ac50-fafe24ade32f@redhat.com/
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Change-Id: I8bac907832a0b2491fa403a6ab72fcef1b4713ee
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
Tested-by: Mike Day <michael.day@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 Documentation/filesystems/locking.rst |  2 +-
 Documentation/filesystems/vfs.rst     | 15 +++++++++------
 fs/nfs/dir.c                          |  9 +++++++--
 fs/orangefs/inode.c                   |  3 ++-
 include/linux/fs.h                    |  2 +-
 mm/filemap.c                          |  9 +++++----
 mm/secretmem.c                        |  3 ++-
 mm/vmscan.c                           |  4 ++--
 virt/kvm/guest_memfd.c                |  3 ++-
 9 files changed, 31 insertions(+), 19 deletions(-)

diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
index 0ec0bb6eb0fb..c3d7430481ae 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -263,7 +263,7 @@ prototypes::
 	sector_t (*bmap)(struct address_space *, sector_t);
 	void (*invalidate_folio) (struct folio *, size_t start, size_t len);
 	bool (*release_folio)(struct folio *, gfp_t);
-	void (*free_folio)(struct folio *);
+	void (*free_folio)(struct address_space *, struct folio *);
 	int (*direct_IO)(struct kiocb *, struct iov_iter *iter);
 	int (*migrate_folio)(struct address_space *, struct folio *dst,
 			struct folio *src, enum migrate_mode);
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index ae79c30b6c0c..bba1ac848f96 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -833,7 +833,7 @@ cache in your filesystem.  The following members are defined:
 		sector_t (*bmap)(struct address_space *, sector_t);
 		void (*invalidate_folio) (struct folio *, size_t start, size_t len);
 		bool (*release_folio)(struct folio *, gfp_t);
-		void (*free_folio)(struct folio *);
+		void (*free_folio)(struct address_space *, struct folio *);
 		ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
 		int (*migrate_folio)(struct mapping *, struct folio *dst,
 				struct folio *src, enum migrate_mode);
@@ -1011,11 +1011,14 @@ cache in your filesystem.  The following members are defined:
 	clear the uptodate flag if it cannot free private data yet.
 
 ``free_folio``
-	free_folio is called once the folio is no longer visible in the
-	page cache in order to allow the cleanup of any private data.
-	Since it may be called by the memory reclaimer, it should not
-	assume that the original address_space mapping still exists, and
-	it should not block.
+	free_folio is called once the folio is no longer visible in
+	the page cache in order to allow the cleanup of any private
+	data.  Since it may be called by the memory reclaimer, it
+	should not assume that the original address_space mapping
+	still exists at folio->mapping. The mapping the folio used to
+	belong to is instead passed for free_folio to read any
+	information it might need from the mapping. free_folio should
+	not block.
 
 ``direct_IO``
 	called by the generic read/write routines to perform direct_IO -
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index bd23fc736b39..148433f6d9d4 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -55,7 +55,7 @@ static int nfs_closedir(struct inode *, struct file *);
 static int nfs_readdir(struct file *, struct dir_context *);
 static int nfs_fsync_dir(struct file *, loff_t, loff_t, int);
 static loff_t nfs_llseek_dir(struct file *, loff_t, int);
-static void nfs_readdir_clear_array(struct folio *);
+static void nfs_free_folio(struct address_space *, struct folio *);
 static int nfs_do_create(struct inode *dir, struct dentry *dentry,
 			 umode_t mode, int open_flags);
 
@@ -69,7 +69,7 @@ const struct file_operations nfs_dir_operations = {
 };
 
 const struct address_space_operations nfs_dir_aops = {
-	.free_folio = nfs_readdir_clear_array,
+	.free_folio = nfs_free_folio,
 };
 
 #define NFS_INIT_DTSIZE PAGE_SIZE
@@ -230,6 +230,11 @@ static void nfs_readdir_clear_array(struct folio *folio)
 	kunmap_local(array);
 }
 
+static void nfs_free_folio(struct address_space *mapping, struct folio *folio)
+{
+	nfs_readdir_clear_array(folio);
+}
+
 static void nfs_readdir_folio_reinit_array(struct folio *folio, u64 last_cookie,
 					   u64 change_attr)
 {
diff --git a/fs/orangefs/inode.c b/fs/orangefs/inode.c
index 5ac743c6bc2e..884cc5295f3e 100644
--- a/fs/orangefs/inode.c
+++ b/fs/orangefs/inode.c
@@ -449,7 +449,8 @@ static bool orangefs_release_folio(struct folio *folio, gfp_t foo)
 	return !folio_test_private(folio);
 }
 
-static void orangefs_free_folio(struct folio *folio)
+static void orangefs_free_folio(struct address_space *mapping,
+				struct folio *folio)
 {
 	kfree(folio_detach_private(folio));
 }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0fded2e3c661..9862ea92a2af 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -455,7 +455,7 @@ struct address_space_operations {
 	sector_t (*bmap)(struct address_space *, sector_t);
 	void (*invalidate_folio) (struct folio *, size_t offset, size_t len);
 	bool (*release_folio)(struct folio *, gfp_t);
-	void (*free_folio)(struct folio *folio);
+	void (*free_folio)(struct address_space *mapping, struct folio *folio);
 	ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
 	/*
 	 * migrate the contents of a folio to the specified target. If
diff --git a/mm/filemap.c b/mm/filemap.c
index bed7160db214..a02c3d8e00e8 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -226,11 +226,11 @@ void __filemap_remove_folio(struct folio *folio, void *shadow)
 
 void filemap_free_folio(struct address_space *mapping, struct folio *folio)
 {
-	void (*free_folio)(struct folio *);
+	void (*free_folio)(struct address_space*, struct folio *);
 
 	free_folio = mapping->a_ops->free_folio;
 	if (free_folio)
-		free_folio(folio);
+		free_folio(mapping, folio);
 
 	folio_put_refs(folio, folio_nr_pages(folio));
 }
@@ -820,7 +820,8 @@ EXPORT_SYMBOL(file_write_and_wait_range);
 void replace_page_cache_folio(struct folio *old, struct folio *new)
 {
 	struct address_space *mapping = old->mapping;
-	void (*free_folio)(struct folio *) = mapping->a_ops->free_folio;
+	void (*free_folio)(struct address_space *, struct folio *) =
+		mapping->a_ops->free_folio;
 	pgoff_t offset = old->index;
 	XA_STATE(xas, &mapping->i_pages, offset);
 
@@ -849,7 +850,7 @@ void replace_page_cache_folio(struct folio *old, struct folio *new)
 		__lruvec_stat_add_folio(new, NR_SHMEM);
 	xas_unlock_irq(&xas);
 	if (free_folio)
-		free_folio(old);
+		free_folio(mapping, old);
 	folio_put(old);
 }
 EXPORT_SYMBOL_GPL(replace_page_cache_folio);
diff --git a/mm/secretmem.c b/mm/secretmem.c
index c0e459e58cb6..178507c1b900 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -152,7 +152,8 @@ static int secretmem_migrate_folio(struct address_space *mapping,
 	return -EBUSY;
 }
 
-static void secretmem_free_folio(struct folio *folio)
+static void secretmem_free_folio(struct address_space *mapping,
+				 struct folio *folio)
 {
 	set_direct_map_default_noflush(&folio->page);
 	folio_zero_segment(folio, 0, folio_size(folio));
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3783e45bfc92..b8add4d0cf18 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -788,7 +788,7 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,
 		xa_unlock_irq(&mapping->i_pages);
 		put_swap_folio(folio, swap);
 	} else {
-		void (*free_folio)(struct folio *);
+		void (*free_folio)(struct address_space *, struct folio *);
 
 		free_folio = mapping->a_ops->free_folio;
 		/*
@@ -817,7 +817,7 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,
 		spin_unlock(&mapping->host->i_lock);
 
 		if (free_folio)
-			free_folio(folio);
+			free_folio(mapping, folio);
 	}
 
 	return 1;
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 24d270b9b725..c578d0ebe314 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -1319,7 +1319,8 @@ static void kvm_gmem_invalidate(struct folio *folio)
 static inline void kvm_gmem_invalidate(struct folio *folio) {}
 #endif
 
-static void kvm_gmem_free_folio(struct folio *folio)
+static void kvm_gmem_free_folio(struct address_space *mapping,
+				struct folio *folio)
 {
 	folio_clear_unevictable(folio);
 
-- 
2.49.0.1045.g170613ef41-goog