Commit 9a87907d authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

ovl: implement tmpfile 



Combine inode creation with opening a file.

There are six separate objects that are being set up: the backing inode,
dentry and file, and the overlay inode, dentry and file.  Cleanup in case
of an error is a bit of a challenge and is difficult to test, so careful
review is needed.

All tmpfile testcases except generic/509 now run/pass, and no regressions
are observed with full xfstests.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Reviewed-by: default avatarAmir Goldstein <amir73il@gmail.com>
parent ed30a4a5

fs/backing-file.c

+23 −0
Original line number Diff line number Diff line
@@ -52,6 +52,29 @@ struct file *backing_file_open(const struct path *user_path, int flags, 
}

EXPORT_SYMBOL_GPL(backing_file_open);



struct file *backing_tmpfile_open(const struct path *user_path, int flags,

				  const struct path *real_parentpath,

				  umode_t mode, const struct cred *cred)

{

	struct mnt_idmap *real_idmap = mnt_idmap(real_parentpath->mnt);

	struct file *f;

	int error;



	f = alloc_empty_backing_file(flags, cred);

	if (IS_ERR(f))

		return f;



	path_get(user_path);

	*backing_file_user_path(f) = *user_path;

	error = vfs_tmpfile(real_idmap, real_parentpath, f, mode);

	if (error) {

		fput(f);

		f = ERR_PTR(error);

	}

	return f;

}

EXPORT_SYMBOL(backing_tmpfile_open);



struct backing_aio {

	struct kiocb iocb;

	refcount_t ref;

fs/internal.h

+3 −0
Original line number Diff line number Diff line
@@ -62,6 +62,9 @@ int do_mkdirat(int dfd, struct filename *name, umode_t mode); 
int do_symlinkat(struct filename *from, int newdfd, struct filename *to);

int do_linkat(int olddfd, struct filename *old, int newdfd,

			struct filename *new, int flags);

int vfs_tmpfile(struct mnt_idmap *idmap,

		const struct path *parentpath,

		struct file *file, umode_t mode);



/*

 * namespace.c

fs/namei.c

+3 −3
Original line number Diff line number Diff line
@@ -3668,7 +3668,7 @@ static int do_open(struct nameidata *nd, 
 * On non-idmapped mounts or if permission checking is to be performed on the

 * raw inode simply pass @nop_mnt_idmap.

 */

static int vfs_tmpfile(struct mnt_idmap *idmap,

int vfs_tmpfile(struct mnt_idmap *idmap,

		const struct path *parentpath,

		struct file *file, umode_t mode)

{

fs/overlayfs/dir.c

+130 −19
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/posix_acl_xattr.h>

#include <linux/atomic.h>

#include <linux/ratelimit.h>

#include <linux/backing-file.h>

#include "overlayfs.h"



static unsigned short ovl_redirect_max = 256;
@@ -260,14 +261,13 @@ static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry) 
 * may not use to instantiate the new dentry.

 */

static int ovl_instantiate(struct dentry *dentry, struct inode *inode,

			   struct dentry *newdentry, bool hardlink)

			   struct dentry *newdentry, bool hardlink, struct file *tmpfile)

{

	struct ovl_inode_params oip = {

		.upperdentry = newdentry,

		.newinode = inode,

	};



	ovl_dir_modified(dentry->d_parent, false);

	ovl_dentry_set_upper_alias(dentry);

	ovl_dentry_init_reval(dentry, newdentry, NULL);
@@ -295,6 +295,9 @@ static int ovl_instantiate(struct dentry *dentry, struct inode *inode, 
		inc_nlink(inode);

	}



	if (tmpfile)

		d_mark_tmpfile(tmpfile, inode);



	d_instantiate(dentry, inode);

	if (inode != oip.newinode) {

		pr_warn_ratelimited("newly created inode found in cache (%pd2)\n",
@@ -345,7 +348,8 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode, 
		ovl_set_opaque(dentry, newdentry);

	}



	err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink);

	ovl_dir_modified(dentry->d_parent, false);

	err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink, NULL);

	if (err)

		goto out_cleanup;

out_unlock:
@@ -529,7 +533,8 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode, 
		if (err)

			goto out_cleanup;

	}

	err = ovl_instantiate(dentry, inode, newdentry, hardlink);

	ovl_dir_modified(dentry->d_parent, false);

	err = ovl_instantiate(dentry, inode, newdentry, hardlink, NULL);

	if (err) {

		ovl_cleanup(ofs, udir, newdentry);

		dput(newdentry);
@@ -551,12 +556,35 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode, 
	goto out_dput;

}



static int ovl_setup_cred_for_create(struct dentry *dentry, struct inode *inode,

				     umode_t mode, const struct cred *old_cred)

{

	int err;

	struct cred *override_cred;



	override_cred = prepare_creds();

	if (!override_cred)

		return -ENOMEM;



	override_cred->fsuid = inode->i_uid;

	override_cred->fsgid = inode->i_gid;

	err = security_dentry_create_files_as(dentry, mode, &dentry->d_name,

					      old_cred, override_cred);

	if (err) {

		put_cred(override_cred);

		return err;

	}

	put_cred(override_creds(override_cred));

	put_cred(override_cred);



	return 0;

}



static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,

			      struct ovl_cattr *attr, bool origin)

{

	int err;

	const struct cred *old_cred;

	struct cred *override_cred;

	struct dentry *parent = dentry->d_parent;



	old_cred = ovl_override_creds(dentry->d_sb);
@@ -572,10 +600,6 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode, 
	}



	if (!attr->hardlink) {

		err = -ENOMEM;

		override_cred = prepare_creds();

		if (!override_cred)

			goto out_revert_creds;

		/*

		 * In the creation cases(create, mkdir, mknod, symlink),

		 * ovl should transfer current's fs{u,g}id to underlying
@@ -589,18 +613,10 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode, 
		 * create a new inode, so just use the ovl mounter's

		 * fs{u,g}id.

		 */

		override_cred->fsuid = inode->i_uid;

		override_cred->fsgid = inode->i_gid;

		err = security_dentry_create_files_as(dentry,

				attr->mode, &dentry->d_name, old_cred,

				override_cred);

		if (err) {

			put_cred(override_cred);

		err = ovl_setup_cred_for_create(dentry, inode, attr->mode, old_cred);

		if (err)

			goto out_revert_creds;

	}

		put_cred(override_creds(override_cred));

		put_cred(override_cred);

	}



	if (!ovl_dentry_is_whiteout(dentry))

		err = ovl_create_upper(dentry, inode, attr);
@@ -1290,6 +1306,100 @@ static int ovl_rename(struct mnt_idmap *idmap, struct inode *olddir, 
	return err;

}



static int ovl_create_tmpfile(struct file *file, struct dentry *dentry,

			      struct inode *inode, umode_t mode)

{

	const struct cred *old_cred;

	struct path realparentpath;

	struct file *realfile;

	struct dentry *newdentry;

	/* It's okay to set O_NOATIME, since the owner will be current fsuid */

	int flags = file->f_flags | OVL_OPEN_FLAGS;

	int err;



	err = ovl_copy_up(dentry->d_parent);

	if (err)

		return err;



	old_cred = ovl_override_creds(dentry->d_sb);

	err = ovl_setup_cred_for_create(dentry, inode, mode, old_cred);

	if (err)

		goto out_revert_creds;



	ovl_path_upper(dentry->d_parent, &realparentpath);

	realfile = backing_tmpfile_open(&file->f_path, flags, &realparentpath,

					mode, current_cred());

	err = PTR_ERR_OR_ZERO(realfile);

	pr_debug("tmpfile/open(%pd2, 0%o) = %i\n", realparentpath.dentry, mode, err);

	if (err)

		goto out_revert_creds;



	/* ovl_instantiate() consumes the newdentry reference on success */

	newdentry = dget(realfile->f_path.dentry);

	err = ovl_instantiate(dentry, inode, newdentry, false, file);

	if (!err) {

		file->private_data = realfile;

	} else {

		dput(newdentry);

		fput(realfile);

	}

out_revert_creds:

	revert_creds(old_cred);

	return err;

}



static int ovl_dummy_open(struct inode *inode, struct file *file)

{

	return 0;

}



static int ovl_tmpfile(struct mnt_idmap *idmap, struct inode *dir,

		       struct file *file, umode_t mode)

{

	int err;

	struct dentry *dentry = file->f_path.dentry;

	struct inode *inode;



	if (!OVL_FS(dentry->d_sb)->tmpfile)

		return -EOPNOTSUPP;



	err = ovl_want_write(dentry);

	if (err)

		return err;



	err = -ENOMEM;

	inode = ovl_new_inode(dentry->d_sb, mode, 0);

	if (!inode)

		goto drop_write;



	inode_init_owner(&nop_mnt_idmap, inode, dir, mode);

	err = ovl_create_tmpfile(file, dentry, inode, inode->i_mode);

	if (err)

		goto put_inode;



	/*

	 * Check if the preallocated inode was actually used.  Having something

	 * else assigned to the dentry shouldn't happen as that would indicate

	 * that the backing tmpfile "leaked" out of overlayfs.

	 */

	err = -EIO;

	if (WARN_ON(inode != d_inode(dentry)))

		goto put_realfile;



	/* inode reference was transferred to dentry */

	inode = NULL;

	err = finish_open(file, dentry, ovl_dummy_open);

put_realfile:

	/* Without FMODE_OPENED ->release() won't be called on @file */

	if (!(file->f_mode & FMODE_OPENED))

		fput(file->private_data);

put_inode:

	iput(inode);

drop_write:

	ovl_drop_write(dentry);

	return err;

}



const struct inode_operations ovl_dir_inode_operations = {

	.lookup		= ovl_lookup,

	.mkdir		= ovl_mkdir,
@@ -1310,4 +1420,5 @@ const struct inode_operations ovl_dir_inode_operations = { 
	.update_time	= ovl_update_time,

	.fileattr_get	= ovl_fileattr_get,

	.fileattr_set	= ovl_fileattr_set,

	.tmpfile	= ovl_tmpfile,

};

fs/overlayfs/file.c

+0 −3
Original line number Diff line number Diff line
@@ -24,9 +24,6 @@ static char ovl_whatisit(struct inode *inode, struct inode *realinode) 
		return 'm';

}



/* No atime modification on underlying */

#define OVL_OPEN_FLAGS (O_NOATIME)



static struct file *ovl_open_realfile(const struct file *file,

				      const struct path *realpath)

{