netfs: Fix gcc-12 warning by embedding vfs inode in netfs_i_context

While randstruct was satisfied with using an open-coded "void *" offset
cast for the netfs_i_context <-> inode casting, __builtin_object_size() as
used by FORTIFY_SOURCE was not as easily fooled.  This was causing the
following complaint[1] from gcc v12:

  In file included from include/linux/string.h:253,
                   from include/linux/ceph/ceph_debug.h:7,
                   from fs/ceph/inode.c:2:
  In function 'fortify_memset_chk',
      inlined from 'netfs_i_context_init' at include/linux/netfs.h:326:2,
      inlined from 'ceph_alloc_inode' at fs/ceph/inode.c:463:2:
  include/linux/fortify-string.h:242:25: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
    242 |                         __write_overflow_field(p_size_field, size);
        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by embedding a struct inode into struct netfs_i_context (which
should perhaps be renamed to struct netfs_inode).  The struct inode
vfs_inode fields are then removed from the 9p, afs, ceph and cifs inode
structs and vfs_inode is then simply changed to "netfs.inode" in those
filesystems.

Further, rename netfs_i_context to netfs_inode, get rid of the
netfs_inode() function that converted a netfs_i_context pointer to an
inode pointer (that can now be done with &ctx->inode) and rename the
netfs_i_context() function to netfs_inode() (which is now a wrapper
around container_of()).

Most of the changes were done with:

  perl -p -i -e 's/vfs_inode/netfs.inode/'g \
        `git grep -l 'vfs_inode' -- fs/{9p,afs,ceph,cifs}/*.[ch]`

Kees suggested doing it with a pair structure[2] and a special
declarator to insert that into the network filesystem's inode
wrapper[3], but I think it's cleaner to embed it - and then it doesn't
matter if struct randomisation reorders things.

Dave Chinner suggested using a filesystem-specific VFS_I() function in
each filesystem to convert that filesystem's own inode wrapper struct
into the VFS inode struct[4].

Version #2:
 - Fix a couple of missed name changes due to a disabled cifs option.
 - Rename nfs_i_context to nfs_inode
 - Use "netfs" instead of "nic" as the member name in per-fs inode wrapper
   structs.

[ This also undoes commit 507160f ("netfs: gcc-12: temporarily
  disable '-Wattribute-warning' for now") that is no longer needed ]

Fixes: bc899ee ("netfs: Add a netfs inode context")
Reported-by: Jeff Layton <[email protected]>
Signed-off-by: David Howells <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Xiubo Li <[email protected]>
cc: Jonathan Corbet <[email protected]>
cc: Eric Van Hensbergen <[email protected]>
cc: Latchesar Ionkov <[email protected]>
cc: Dominique Martinet <[email protected]>
cc: Christian Schoenebeck <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Ilya Dryomov <[email protected]>
cc: Steve French <[email protected]>
cc: William Kucharski <[email protected]>
cc: "Matthew Wilcox (Oracle)" <[email protected]>
cc: Dave Chinner <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]/ [1]
Link: https://lore.kernel.org/r/[email protected]/ [2]
Link: https://lore.kernel.org/r/[email protected]/ [3]
Link: https://lore.kernel.org/r/[email protected]/ [4]
Link: https://lore.kernel.org/r/165296786831.3591209.12111293034669289733.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/165305805651.4094995.7763502506786714216.stgit@warthog.procyon.org.uk # v2
Signed-off-by: Linus Torvalds <[email protected]>

Documentation/filesystems/netfs_library.rst

@@ -37,30 +37,31 @@ The network filesystem helper library needs a place to store a bit of state for
 its use on each netfs inode it is helping to manage.  To this end, a context
 structure is defined::
 
-	struct netfs_i_context {
+	struct netfs_inode {
+		struct inode inode;
 		const struct netfs_request_ops *ops;
-		struct fscache_cookie	*cache;
+		struct fscache_cookie *cache;
 	};
 
-A network filesystem that wants to use netfs lib must place one of these
-directly after the VFS ``struct inode`` it allocates, usually as part of its
-own struct.  This can be done in a way similar to the following::
+A network filesystem that wants to use netfs lib must place one of these in its
+inode wrapper struct instead of the VFS ``struct inode``.  This can be done in
+a way similar to the following::
 
 	struct my_inode {
-		struct {
-			/* These must be contiguous */
-			struct inode		vfs_inode;
-			struct netfs_i_context  netfs_ctx;
-		};
+		struct netfs_inode netfs; /* Netfslib context and vfs inode */
 		...
 	};
 
-This allows netfslib to find its state by simple offset from the inode pointer,
-thereby allowing the netfslib helper functions to be pointed to directly by the
-VFS/VM operation tables.
+This allows netfslib to find its state by using ``container_of()`` from the
+inode pointer, thereby allowing the netfslib helper functions to be pointed to
+directly by the VFS/VM operation tables.
 
 The structure contains the following fields:
 
+ * ``inode``
+
+   The VFS inode structure.
+
  * ``ops``
 
    The set of operations provided by the network filesystem to netfslib.
@@ -78,14 +79,12 @@ To help deal with the per-inode context, a number helper functions are
 provided.  Firstly, a function to perform basic initialisation on a context and
 set the operations table pointer::
 
-	void netfs_i_context_init(struct inode *inode,
-				  const struct netfs_request_ops *ops);
+	void netfs_inode_init(struct inode *inode,
+			      const struct netfs_request_ops *ops);
 
-then two functions to cast between the VFS inode structure and the netfs
-context::
+then a function to cast from the VFS inode structure to the netfs context::
 
-	struct netfs_i_context *netfs_i_context(struct inode *inode);
-	struct inode *netfs_inode(struct netfs_i_context *ctx);
+	struct netfs_inode *netfs_node(struct inode *inode);
 
 and finally, a function to get the cache cookie pointer from the context
 attached to an inode (or NULL if fscache is disabled)::

fs/9p/cache.c

@@ -62,12 +62,12 @@ void v9fs_cache_inode_get_cookie(struct inode *inode)
 	version = cpu_to_le32(v9inode->qid.version);
 	path = cpu_to_le64(v9inode->qid.path);
 	v9ses = v9fs_inode2v9ses(inode);
-	v9inode->netfs_ctx.cache =
+	v9inode->netfs.cache =
 		fscache_acquire_cookie(v9fs_session_cache(v9ses),
 				       0,
 				       &path, sizeof(path),
 				       &version, sizeof(version),
-				       i_size_read(&v9inode->vfs_inode));
+				       i_size_read(&v9inode->netfs.inode));
 
 	p9_debug(P9_DEBUG_FSC, "inode %p get cookie %p\n",
 		 inode, v9fs_inode_cookie(v9inode));

fs/9p/v9fs.c

@@ -625,7 +625,7 @@ static void v9fs_inode_init_once(void *foo)
 	struct v9fs_inode *v9inode = (struct v9fs_inode *)foo;
 
 	memset(&v9inode->qid, 0, sizeof(v9inode->qid));
-	inode_init_once(&v9inode->vfs_inode);
+	inode_init_once(&v9inode->netfs.inode);
 }
 
 /**

fs/9p/v9fs.h

@@ -109,11 +109,7 @@ struct v9fs_session_info {
 #define V9FS_INO_INVALID_ATTR 0x01
 
 struct v9fs_inode {
-	struct {
-		/* These must be contiguous */
-		struct inode	vfs_inode;	/* the VFS's inode record */
-		struct netfs_i_context netfs_ctx; /* Netfslib context */
-	};
+	struct netfs_inode netfs; /* Netfslib context and vfs inode */
 	struct p9_qid qid;
 	unsigned int cache_validity;
 	struct p9_fid *writeback_fid;
@@ -122,13 +118,13 @@ struct v9fs_inode {
 
 static inline struct v9fs_inode *V9FS_I(const struct inode *inode)
 {
-	return container_of(inode, struct v9fs_inode, vfs_inode);
+	return container_of(inode, struct v9fs_inode, netfs.inode);
 }
 
 static inline struct fscache_cookie *v9fs_inode_cookie(struct v9fs_inode *v9inode)
 {
 #ifdef CONFIG_9P_FSCACHE
-	return netfs_i_cookie(&v9inode->vfs_inode);
+	return netfs_i_cookie(&v9inode->netfs.inode);
 #else
 	return NULL;
 #endif

fs/9p/vfs_addr.c

@@ -140,7 +140,7 @@ static void v9fs_write_to_cache_done(void *priv, ssize_t transferred_or_error,
 	    transferred_or_error != -ENOBUFS) {
 		version = cpu_to_le32(v9inode->qid.version);
 		fscache_invalidate(v9fs_inode_cookie(v9inode), &version,
-				   i_size_read(&v9inode->vfs_inode), 0);
+				   i_size_read(&v9inode->netfs.inode), 0);
 	}
 }
 

fs/9p/vfs_inode.c

@@ -234,7 +234,7 @@ struct inode *v9fs_alloc_inode(struct super_block *sb)
 	v9inode->writeback_fid = NULL;
 	v9inode->cache_validity = 0;
 	mutex_init(&v9inode->v_mutex);
-	return &v9inode->vfs_inode;
+	return &v9inode->netfs.inode;
 }
 
 /**
@@ -252,7 +252,7 @@ void v9fs_free_inode(struct inode *inode)
  */
 static void v9fs_set_netfs_context(struct inode *inode)
 {
-	netfs_i_context_init(inode, &v9fs_req_ops);
+	netfs_inode_init(inode, &v9fs_req_ops);
 }
 
 int v9fs_init_inode(struct v9fs_session_info *v9ses,

fs/afs/callback.c

@@ -30,7 +30,7 @@ void afs_invalidate_mmap_work(struct work_struct *work)
 {
 	struct afs_vnode *vnode = container_of(work, struct afs_vnode, cb_work);
 
-	unmap_mapping_pages(vnode->vfs_inode.i_mapping, 0, 0, false);
+	unmap_mapping_pages(vnode->netfs.inode.i_mapping, 0, 0, false);
 }
 
 void afs_server_init_callback_work(struct work_struct *work)

fs/afs/dir.c

@@ -109,7 +109,7 @@ struct afs_lookup_cookie {
  */
 static void afs_dir_read_cleanup(struct afs_read *req)
 {
-	struct address_space *mapping = req->vnode->vfs_inode.i_mapping;
+	struct address_space *mapping = req->vnode->netfs.inode.i_mapping;
 	struct folio *folio;
 	pgoff_t last = req->nr_pages - 1;
 
@@ -153,7 +153,7 @@ static bool afs_dir_check_folio(struct afs_vnode *dvnode, struct folio *folio,
 		block = kmap_local_folio(folio, offset);
 		if (block->hdr.magic != AFS_DIR_MAGIC) {
 			printk("kAFS: %s(%lx): [%llx] bad magic %zx/%zx is %04hx\n",
-			       __func__, dvnode->vfs_inode.i_ino,
+			       __func__, dvnode->netfs.inode.i_ino,
 			       pos, offset, size, ntohs(block->hdr.magic));
 			trace_afs_dir_check_failed(dvnode, pos + offset, i_size);
 			kunmap_local(block);
@@ -183,7 +183,7 @@ static bool afs_dir_check_folio(struct afs_vnode *dvnode, struct folio *folio,
 static void afs_dir_dump(struct afs_vnode *dvnode, struct afs_read *req)
 {
 	union afs_xdr_dir_block *block;
-	struct address_space *mapping = dvnode->vfs_inode.i_mapping;
+	struct address_space *mapping = dvnode->netfs.inode.i_mapping;
 	struct folio *folio;
 	pgoff_t last = req->nr_pages - 1;
 	size_t offset, size;
@@ -217,7 +217,7 @@ static void afs_dir_dump(struct afs_vnode *dvnode, struct afs_read *req)
  */
 static int afs_dir_check(struct afs_vnode *dvnode, struct afs_read *req)
 {
-	struct address_space *mapping = dvnode->vfs_inode.i_mapping;
+	struct address_space *mapping = dvnode->netfs.inode.i_mapping;
 	struct folio *folio;
 	pgoff_t last = req->nr_pages - 1;
 	int ret = 0;
@@ -269,7 +269,7 @@ static int afs_dir_open(struct inode *inode, struct file *file)
 static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 	__acquires(&dvnode->validate_lock)
 {
-	struct address_space *mapping = dvnode->vfs_inode.i_mapping;
+	struct address_space *mapping = dvnode->netfs.inode.i_mapping;
 	struct afs_read *req;
 	loff_t i_size;
 	int nr_pages, i;
@@ -287,7 +287,7 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 	req->cleanup = afs_dir_read_cleanup;
 
 expand:
-	i_size = i_size_read(&dvnode->vfs_inode);
+	i_size = i_size_read(&dvnode->netfs.inode);
 	if (i_size < 2048) {
 		ret = afs_bad(dvnode, afs_file_error_dir_small);
 		goto error;
@@ -305,7 +305,7 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
 	req->actual_len = i_size; /* May change */
 	req->len = nr_pages * PAGE_SIZE; /* We can ask for more than there is */
 	req->data_version = dvnode->status.data_version; /* May change */
-	iov_iter_xarray(&req->def_iter, READ, &dvnode->vfs_inode.i_mapping->i_pages,
+	iov_iter_xarray(&req->def_iter, READ, &dvnode->netfs.inode.i_mapping->i_pages,
 			0, i_size);
 	req->iter = &req->def_iter;
 
@@ -897,7 +897,7 @@ static struct inode *afs_do_lookup(struct inode *dir, struct dentry *dentry,
 
 out_op:
 	if (op->error == 0) {
-		inode = &op->file[1].vnode->vfs_inode;
+		inode = &op->file[1].vnode->netfs.inode;
 		op->file[1].vnode = NULL;
 	}
 
@@ -1139,7 +1139,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
 	afs_stat_v(dir, n_reval);
 
 	/* search the directory for this vnode */
-	ret = afs_do_lookup_one(&dir->vfs_inode, dentry, &fid, key, &dir_version);
+	ret = afs_do_lookup_one(&dir->netfs.inode, dentry, &fid, key, &dir_version);
 	switch (ret) {
 	case 0:
 		/* the filename maps to something */
@@ -1170,7 +1170,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
 			_debug("%pd: file deleted (uq %u -> %u I:%u)",
 			       dentry, fid.unique,
 			       vnode->fid.unique,
-			       vnode->vfs_inode.i_generation);
+			       vnode->netfs.inode.i_generation);
 			goto not_found;
 		}
 		goto out_valid;
@@ -1368,7 +1368,7 @@ static void afs_dir_remove_subdir(struct dentry *dentry)
 	if (d_really_is_positive(dentry)) {
 		struct afs_vnode *vnode = AFS_FS_I(d_inode(dentry));
 
-		clear_nlink(&vnode->vfs_inode);
+		clear_nlink(&vnode->netfs.inode);
 		set_bit(AFS_VNODE_DELETED, &vnode->flags);
 		clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
 		clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
@@ -1487,8 +1487,8 @@ static void afs_dir_remove_link(struct afs_operation *op)
 		/* Already done */
 	} else if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags)) {
 		write_seqlock(&vnode->cb_lock);
-		drop_nlink(&vnode->vfs_inode);
-		if (vnode->vfs_inode.i_nlink == 0) {
+		drop_nlink(&vnode->netfs.inode);
+		if (vnode->netfs.inode.i_nlink == 0) {
 			set_bit(AFS_VNODE_DELETED, &vnode->flags);
 			__afs_break_callback(vnode, afs_cb_break_for_unlink);
 		}
@@ -1504,7 +1504,7 @@ static void afs_dir_remove_link(struct afs_operation *op)
 			op->error = ret;
 	}
 
-	_debug("nlink %d [val %d]", vnode->vfs_inode.i_nlink, op->error);
+	_debug("nlink %d [val %d]", vnode->netfs.inode.i_nlink, op->error);
 }
 
 static void afs_unlink_success(struct afs_operation *op)
@@ -1680,8 +1680,8 @@ static void afs_link_success(struct afs_operation *op)
 	afs_update_dentry_version(op, dvp, op->dentry);
 	if (op->dentry_2->d_parent == op->dentry->d_parent)
 		afs_update_dentry_version(op, dvp, op->dentry_2);
-	ihold(&vp->vnode->vfs_inode);
-	d_instantiate(op->dentry, &vp->vnode->vfs_inode);
+	ihold(&vp->vnode->netfs.inode);
+	d_instantiate(op->dentry, &vp->vnode->netfs.inode);
 }
 
 static void afs_link_put(struct afs_operation *op)

fs/afs/dir_edit.c

@@ -109,7 +109,7 @@ static void afs_clear_contig_bits(union afs_xdr_dir_block *block,
  */
 static struct folio *afs_dir_get_folio(struct afs_vnode *vnode, pgoff_t index)
 {
-	struct address_space *mapping = vnode->vfs_inode.i_mapping;
+	struct address_space *mapping = vnode->netfs.inode.i_mapping;
 	struct folio *folio;
 
 	folio = __filemap_get_folio(mapping, index,
@@ -216,7 +216,7 @@ void afs_edit_dir_add(struct afs_vnode *vnode,
 
 	_enter(",,{%d,%s},", name->len, name->name);
 
-	i_size = i_size_read(&vnode->vfs_inode);
+	i_size = i_size_read(&vnode->netfs.inode);
 	if (i_size > AFS_DIR_BLOCK_SIZE * AFS_DIR_MAX_BLOCKS ||
 	    (i_size & (AFS_DIR_BLOCK_SIZE - 1))) {
 		clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
@@ -336,7 +336,7 @@ void afs_edit_dir_add(struct afs_vnode *vnode,
 	if (b < AFS_DIR_BLOCKS_WITH_CTR)
 		meta->meta.alloc_ctrs[b] -= need_slots;
 
-	inode_inc_iversion_raw(&vnode->vfs_inode);
+	inode_inc_iversion_raw(&vnode->netfs.inode);
 	afs_stat_v(vnode, n_dir_cr);
 	_debug("Insert %s in %u[%u]", name->name, b, slot);
 
@@ -383,7 +383,7 @@ void afs_edit_dir_remove(struct afs_vnode *vnode,
 
 	_enter(",,{%d,%s},", name->len, name->name);
 
-	i_size = i_size_read(&vnode->vfs_inode);
+	i_size = i_size_read(&vnode->netfs.inode);
 	if (i_size < AFS_DIR_BLOCK_SIZE ||
 	    i_size > AFS_DIR_BLOCK_SIZE * AFS_DIR_MAX_BLOCKS ||
 	    (i_size & (AFS_DIR_BLOCK_SIZE - 1))) {
@@ -463,7 +463,7 @@ void afs_edit_dir_remove(struct afs_vnode *vnode,
 	if (b < AFS_DIR_BLOCKS_WITH_CTR)
 		meta->meta.alloc_ctrs[b] += need_slots;
 
-	inode_set_iversion_raw(&vnode->vfs_inode, vnode->status.data_version);
+	inode_set_iversion_raw(&vnode->netfs.inode, vnode->status.data_version);
 	afs_stat_v(vnode, n_dir_rm);
 	_debug("Remove %s from %u[%u]", name->name, b, slot);
 

fs/afs/dir_silly.c

@@ -131,7 +131,7 @@ int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
 			goto out;
 	} while (!d_is_negative(sdentry));
 
-	ihold(&vnode->vfs_inode);
+	ihold(&vnode->netfs.inode);
 
 	ret = afs_do_silly_rename(dvnode, vnode, dentry, sdentry, key);
 	switch (ret) {
@@ -148,7 +148,7 @@ int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
 		d_drop(sdentry);
 	}
 
-	iput(&vnode->vfs_inode);
+	iput(&vnode->netfs.inode);
 	dput(sdentry);
 out:
 	_leave(" = %d", ret);

fs/afs/dynroot.c

@@ -76,7 +76,7 @@ struct inode *afs_iget_pseudo_dir(struct super_block *sb, bool root)
 	/* there shouldn't be an existing inode */
 	BUG_ON(!(inode->i_state & I_NEW));
 
-	netfs_i_context_init(inode, NULL);
+	netfs_inode_init(inode, NULL);
 	inode->i_size		= 0;
 	inode->i_mode		= S_IFDIR | S_IRUGO | S_IXUGO;
 	if (root) {

fs/afs/file.c

@@ -194,7 +194,7 @@ int afs_release(struct inode *inode, struct file *file)
 		afs_put_wb_key(af->wb);
 
 	if ((file->f_mode & FMODE_WRITE)) {
-		i_size = i_size_read(&vnode->vfs_inode);
+		i_size = i_size_read(&vnode->netfs.inode);
 		afs_set_cache_aux(vnode, &aux);
 		fscache_unuse_cookie(afs_vnode_cache(vnode), &aux, &i_size);
 	} else {
@@ -325,7 +325,7 @@ static void afs_issue_read(struct netfs_io_subrequest *subreq)
 	fsreq->iter	= &fsreq->def_iter;
 
 	iov_iter_xarray(&fsreq->def_iter, READ,
-			&fsreq->vnode->vfs_inode.i_mapping->i_pages,
+			&fsreq->vnode->netfs.inode.i_mapping->i_pages,
 			fsreq->pos, fsreq->len);
 
 	afs_fetch_data(fsreq->vnode, fsreq);

fs/afs/fs_operation.c

@@ -232,14 +232,14 @@ int afs_put_operation(struct afs_operation *op)
 	if (op->file[1].modification && op->file[1].vnode != op->file[0].vnode)
 		clear_bit(AFS_VNODE_MODIFYING, &op->file[1].vnode->flags);
 	if (op->file[0].put_vnode)
-		iput(&op->file[0].vnode->vfs_inode);
+		iput(&op->file[0].vnode->netfs.inode);
 	if (op->file[1].put_vnode)
-		iput(&op->file[1].vnode->vfs_inode);
+		iput(&op->file[1].vnode->netfs.inode);
 
 	if (op->more_files) {
 		for (i = 0; i < op->nr_files - 2; i++)
 			if (op->more_files[i].put_vnode)
-				iput(&op->more_files[i].vnode->vfs_inode);
+				iput(&op->more_files[i].vnode->netfs.inode);
 		kfree(op->more_files);
 	}