Unverified Commit 64a989db authored by Benjamin Coddington's avatar Benjamin Coddington Committed by Christian Brauner
Browse files

VFS/knfsd: Teach dentry_create() to use atomic_open() 



While knfsd offers combined exclusive create and open results to clients,
on some filesystems those results may not be atomic.  This behavior can be
observed.  For example, an open O_CREAT with mode 0 will succeed in creating
the file but unexpectedly return -EACCES from vfs_open().

Additionally reducing the number of remote RPC calls required for O_CREAT
on network filesystem provides a performance benefit in the open path.

Teach knfsd's helper dentry_create() to use atomic_open() for filesystems
that support it.  The previously const @path is passed up to atomic_open()
and may be modified depending on whether an existing entry was found or if
the atomic_open() returned an error and consumed the passed-in dentry.

Signed-off-by: default avatarBenjamin Coddington <bcodding@hammerspace.com>
Link: https://patch.msgid.link/8e449bfb64ab055abb9fd82641a171531415a88c.1764259052.git.bcodding@hammerspace.com


Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Reviewed-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 36411554

fs/namei.c

+42 −13
Original line number Diff line number Diff line
@@ -4953,25 +4953,54 @@ EXPORT_SYMBOL(start_creating_user_path); 
 * On success, returns a "struct file *". Otherwise a ERR_PTR

 * is returned.

 */

struct file *dentry_create(const struct path *path, int flags, umode_t mode,

struct file *dentry_create(struct path *path, int flags, umode_t mode,

			   const struct cred *cred)

{

	struct file *f;

	int error;

	struct file *file __free(fput) = NULL;

	struct dentry *dentry = path->dentry;

	struct dentry *dir = dentry->d_parent;

	struct inode *dir_inode = d_inode(dir);

	struct mnt_idmap *idmap;

	int error, create_error;



	file = alloc_empty_file(flags, cred);

	if (IS_ERR(file))

		return file;



	f = alloc_empty_file(flags, cred);

	if (IS_ERR(f))

		return f;

	idmap = mnt_idmap(path->mnt);



	if (dir_inode->i_op->atomic_open) {

		path->dentry = dir;

		mode = vfs_prepare_mode(idmap, dir_inode, mode, S_IALLUGO, S_IFREG);



		create_error = may_o_create(idmap, path, dentry, mode);

		if (create_error)

			flags &= ~O_CREAT;



		dentry = atomic_open(path, dentry, file, flags, mode);

		error = PTR_ERR_OR_ZERO(dentry);



		if (unlikely(create_error) && error == -ENOENT)

			error = create_error;



		if (!error) {

			if (file->f_mode & FMODE_CREATED)

				fsnotify_create(dir->d_inode, dentry);

			if (file->f_mode & FMODE_OPENED)

				fsnotify_open(file);

		}



		path->dentry = dentry;



	} else {

		error = vfs_create(mnt_idmap(path->mnt), path->dentry, mode, NULL);

		if (!error)

		error = vfs_open(path, f);



	if (unlikely(error)) {

		fput(f);

		return ERR_PTR(error);

			error = vfs_open(path, file);

	}

	return f;

	if (unlikely(error))

		return ERR_PTR(error);



	return no_free_ptr(file);

}

EXPORT_SYMBOL(dentry_create);

fs/nfsd/nfs4proc.c

+8 −3
Original line number Diff line number Diff line
@@ -194,7 +194,7 @@ static inline bool nfsd4_create_is_exclusive(int createmode) 
}



static __be32

nfsd4_vfs_create(struct svc_fh *fhp, struct dentry *child,

nfsd4_vfs_create(struct svc_fh *fhp, struct dentry **child,

		 struct nfsd4_open *open)

{

	struct file *filp;
@@ -202,6 +202,9 @@ nfsd4_vfs_create(struct svc_fh *fhp, struct dentry *child, 
	int oflags;



	oflags = O_CREAT | O_LARGEFILE;

	if (nfsd4_create_is_exclusive(open->op_createmode))

		oflags |= O_EXCL;



	switch (open->op_share_access & NFS4_SHARE_ACCESS_BOTH) {

	case NFS4_SHARE_ACCESS_WRITE:

		oflags |= O_WRONLY;
@@ -214,9 +217,11 @@ nfsd4_vfs_create(struct svc_fh *fhp, struct dentry *child, 
	}



	path.mnt = fhp->fh_export->ex_path.mnt;

	path.dentry = child;

	path.dentry = *child;

	filp = dentry_create(&path, oflags, open->op_iattr.ia_mode,

			     current_cred());

	*child = path.dentry;



	if (IS_ERR(filp))

		return nfserrno(PTR_ERR(filp));
@@ -350,7 +355,7 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp, 
	status = fh_fill_pre_attrs(fhp);

	if (status != nfs_ok)

		goto out;

	status = nfsd4_vfs_create(fhp, child, open);

	status = nfsd4_vfs_create(fhp, &child, open);

	if (status != nfs_ok)

		goto out;

	open->op_created = true;

include/linux/fs.h

+1 −1
Original line number Diff line number Diff line
@@ -2457,7 +2457,7 @@ struct file *dentry_open(const struct path *path, int flags, 
			 const struct cred *creds);

struct file *dentry_open_nonotify(const struct path *path, int flags,

				  const struct cred *cred);

struct file *dentry_create(const struct path *path, int flags, umode_t mode,

struct file *dentry_create(struct path *path, int flags, umode_t mode,

			   const struct cred *cred);

const struct path *backing_file_user_path(const struct file *f);