Instead of using i_private_data and i_private_lock, just create aio
inodes with appropriate necessary fields.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/aio.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 66 insertions(+), 12 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index a07bdd1aaaa6..ba9b9fa2446b 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -218,6 +218,17 @@ struct aio_kiocb {
 	struct eventfd_ctx	*ki_eventfd;
 };
 
+struct aio_inode_info {
+	struct inode vfs_inode;
+	spinlock_t migrate_lock;
+	struct kioctx *ctx;
+};
+
+static inline struct aio_inode_info *AIO_I(struct inode *inode)
+{
+	return container_of(inode, struct aio_inode_info, vfs_inode);
+}
+
 /*------ sysctl variables----*/
 static DEFINE_SPINLOCK(aio_nr_lock);
 static unsigned long aio_nr;		/* current system wide number of aio requests */
@@ -251,6 +262,7 @@ static void __init aio_sysctl_init(void)
 
 static struct kmem_cache	*kiocb_cachep;
 static struct kmem_cache	*kioctx_cachep;
+static struct kmem_cache	*aio_inode_cachep;
 
 static struct vfsmount *aio_mnt;
 
@@ -261,11 +273,12 @@ static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
 {
 	struct file *file;
 	struct inode *inode = alloc_anon_inode(aio_mnt->mnt_sb);
+
 	if (IS_ERR(inode))
 		return ERR_CAST(inode);
 
 	inode->i_mapping->a_ops = &aio_ctx_aops;
-	inode->i_mapping->i_private_data = ctx;
+	AIO_I(inode)->ctx = ctx;
 	inode->i_size = PAGE_SIZE * nr_pages;
 
 	file = alloc_file_pseudo(inode, aio_mnt, "[aio]",
@@ -275,14 +288,49 @@ static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
 	return file;
 }
 
+static struct inode *aio_alloc_inode(struct super_block *sb)
+{
+	struct aio_inode_info *ai;
+
+	ai = alloc_inode_sb(sb, aio_inode_cachep, GFP_KERNEL);
+	if (!ai)
+		return NULL;
+	ai->ctx = NULL;
+
+	return &ai->vfs_inode;
+}
+
+static void aio_free_inode(struct inode *inode)
+{
+	kmem_cache_free(aio_inode_cachep, AIO_I(inode));
+}
+
+static const struct super_operations aio_super_operations = {
+	.alloc_inode	= aio_alloc_inode,
+	.free_inode	= aio_free_inode,
+	.statfs		= simple_statfs,
+};
+
 static int aio_init_fs_context(struct fs_context *fc)
 {
-	if (!init_pseudo(fc, AIO_RING_MAGIC))
+	struct pseudo_fs_context *pfc;
+
+	pfc = init_pseudo(fc, AIO_RING_MAGIC);
+	if (!pfc)
 		return -ENOMEM;
 	fc->s_iflags |= SB_I_NOEXEC;
+	pfc->ops = &aio_super_operations;
 	return 0;
 }
 
+static void init_once(void *obj)
+{
+	struct aio_inode_info *ai = obj;
+
+	inode_init_once(&ai->vfs_inode);
+	spin_lock_init(&ai->migrate_lock);
+}
+
 /* aio_setup
  *	Creates the slab caches used by the aio routines, panic on
  *	failure as this is done early during the boot sequence.
@@ -294,6 +342,11 @@ static int __init aio_setup(void)
 		.init_fs_context = aio_init_fs_context,
 		.kill_sb	= kill_anon_super,
 	};
+
+	aio_inode_cachep = kmem_cache_create("aio_inode_cache",
+				sizeof(struct aio_inode_info), 0,
+				(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_ACCOUNT),
+				init_once);
 	aio_mnt = kern_mount(&aio_fs);
 	if (IS_ERR(aio_mnt))
 		panic("Failed to create aio fs mount.");
@@ -308,17 +361,17 @@ __initcall(aio_setup);
 static void put_aio_ring_file(struct kioctx *ctx)
 {
 	struct file *aio_ring_file = ctx->aio_ring_file;
-	struct address_space *i_mapping;
 
 	if (aio_ring_file) {
-		truncate_setsize(file_inode(aio_ring_file), 0);
+		struct inode *inode = file_inode(aio_ring_file);
+
+		truncate_setsize(inode, 0);
 
 		/* Prevent further access to the kioctx from migratepages */
-		i_mapping = aio_ring_file->f_mapping;
-		spin_lock(&i_mapping->i_private_lock);
-		i_mapping->i_private_data = NULL;
+		spin_lock(&AIO_I(inode)->migrate_lock);
+		AIO_I(inode)->ctx = NULL;
 		ctx->aio_ring_file = NULL;
-		spin_unlock(&i_mapping->i_private_lock);
+		spin_unlock(&AIO_I(inode)->migrate_lock);
 
 		fput(aio_ring_file);
 	}
@@ -408,13 +461,14 @@ static int aio_migrate_folio(struct address_space *mapping, struct folio *dst,
 			struct folio *src, enum migrate_mode mode)
 {
 	struct kioctx *ctx;
+	struct aio_inode_info *ai = AIO_I(mapping->host);
 	unsigned long flags;
 	pgoff_t idx;
 	int rc = 0;
 
-	/* mapping->i_private_lock here protects against the kioctx teardown.  */
-	spin_lock(&mapping->i_private_lock);
-	ctx = mapping->i_private_data;
+	/* ai->migrate_lock here protects against the kioctx teardown.  */
+	spin_lock(&ai->migrate_lock);
+	ctx = ai->ctx;
 	if (!ctx) {
 		rc = -EINVAL;
 		goto out;
@@ -467,7 +521,7 @@ static int aio_migrate_folio(struct address_space *mapping, struct folio *dst,
 out_unlock:
 	mutex_unlock(&ctx->ring_lock);
 out:
-	spin_unlock(&mapping->i_private_lock);
+	spin_unlock(&ai->migrate_lock);
 	return rc;
 }
 #else
-- 
2.51.0