Thank you for addressing the symbolic link problems!
Additionally, I found an incompatibility with the no_open feature.
When the FUSE server has the no_open feature enabled, the atomic_open
FUSE request returns a d_entry with an empty file handler and open
option FOPEN_KEEP_CACHE (for files) or FOPEN_CACHE_DIR (for
directories). With this situation, if we can set fc->no_open = 1 or
fc->no_opendir = 1 after receiving the such FUSE reply, as follows,
will make the atomic_open compatible with no_open feature:
+ if (!inode) {
+ flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
+ fuse_sync_release(NULL, ff, flags);
+ fuse_queue_forget(fm->fc, forget, outentry.nodeid, 1);
+ err = -ENOMEM;
+ goto out_err;
+ }
+
+ if(ff->fh == 0) {
+ if(ff->open_flags & FOPEN_KEEP_CACHE)
+ fc->no_open = 1;
+ if(ff->open_flags & FOPEN_CACHE_DIR)
+ fc->no_opendir = 1;
+ }
+
+ /* prevent racing/parallel lookup on a negative hashed */
On Tue, Oct 24, 2023 at 3:41 AM Bernd Schubert <bschubert@xxxxxxx> wrote:
>
> From: Dharmendra Singh <dsingh@xxxxxxx>
>
> This adds full atomic open support, to avoid lookup before open/create.
> If the implementation (fuse server/daemon) does not support atomic open
> it falls back to non-atomic open.
>
> Co-developed-by: Bernd Schubert <bschubert@xxxxxxx>
> Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
> Signed-off-by: Dharmendra Singh <dsingh@xxxxxxx>
> Signed-off-by: Horst Birthelmer <hbirthelmer@xxxxxxx>
> Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Dharmendra Singh <dsingh@xxxxxxx>
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
> ---
> fs/fuse/dir.c | 214 +++++++++++++++++++++++++++++++++++++-
> fs/fuse/fuse_i.h | 3 +
> include/uapi/linux/fuse.h | 3 +
> 3 files changed, 219 insertions(+), 1 deletion(-)
>
> diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> index e1095852601c..61cdb8e5f68e 100644
> --- a/fs/fuse/dir.c
> +++ b/fs/fuse/dir.c
> @@ -716,7 +716,7 @@ static int _fuse_create_open(struct inode *dir, struct dentry *entry,
>
> static int fuse_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
> umode_t, dev_t);
> -static int fuse_atomic_open(struct inode *dir, struct dentry *entry,
> +static int fuse_create_open(struct inode *dir, struct dentry *entry,
> struct file *file, unsigned flags,
> umode_t mode)
> {
> @@ -763,6 +763,218 @@ static int fuse_atomic_open(struct inode *dir, struct dentry *entry,
> return finish_no_open(file, res);
> }
>
> +static int _fuse_atomic_open(struct inode *dir, struct dentry *entry,
> + struct file *file, unsigned int flags,
> + umode_t mode)
> +{
> + int err;
> + struct inode *inode;
> + FUSE_ARGS(args);
> + struct fuse_mount *fm = get_fuse_mount(dir);
> + struct fuse_conn *fc = fm->fc;
> + struct fuse_forget_link *forget;
> + struct fuse_create_in inarg;
> + struct fuse_open_out outopen;
> + struct fuse_entry_out outentry;
> + struct fuse_inode *fi;
> + struct fuse_file *ff;
> + struct dentry *switched_entry = NULL, *alias = NULL;
> + DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
> +
> + /* Expect a negative dentry */
> + if (unlikely(d_inode(entry)))
> + goto fallback;
> +
> + /* Userspace expects S_IFREG in create mode */
> + if ((flags & O_CREAT) && (mode & S_IFMT) != S_IFREG)
> + goto fallback;
> +
> + forget = fuse_alloc_forget();
> + err = -ENOMEM;
> + if (!forget)
> + goto out_err;
> +
> + err = -ENOMEM;
> + ff = fuse_file_alloc(fm);
> + if (!ff)
> + goto out_put_forget_req;
> +
> + if (!fc->dont_mask)
> + mode &= ~current_umask();
> +
> + flags &= ~O_NOCTTY;
> + memset(&inarg, 0, sizeof(inarg));
> + memset(&outentry, 0, sizeof(outentry));
> + inarg.flags = flags;
> + inarg.mode = mode;
> + inarg.umask = current_umask();
> +
> + if (fc->handle_killpriv_v2 && (flags & O_TRUNC) &&
> + !(flags & O_EXCL) && !capable(CAP_FSETID)) {
> + inarg.open_flags |= FUSE_OPEN_KILL_SUIDGID;
> + }
> +
> + args.opcode = FUSE_OPEN_ATOMIC;
> + args.nodeid = get_node_id(dir);
> + args.in_numargs = 2;
> + args.in_args[0].size = sizeof(inarg);
> + args.in_args[0].value = &inarg;
> + args.in_args[1].size = entry->d_name.len + 1;
> + args.in_args[1].value = entry->d_name.name;
> + args.out_numargs = 2;
> + args.out_args[0].size = sizeof(outentry);
> + args.out_args[0].value = &outentry;
> + args.out_args[1].size = sizeof(outopen);
> + args.out_args[1].value = &outopen;
> +
> + if (flags & O_CREAT) {
> + err = get_create_ext(&args, dir, entry, mode);
> + if (err)
> + goto out_free_ff;
> + }
> +
> + err = fuse_simple_request(fm, &args);
> + free_ext_value(&args);
> + if (err == -ENOSYS || err == -ELOOP) {
> + if (unlikely(err == -ENOSYS))
> + fc->no_open_atomic = 1;
> + goto free_and_fallback;
> + }
> +
> + if (!err && !outentry.nodeid)
> + err = -ENOENT;
> +
> + if (err)
> + goto out_free_ff;
> +
> + err = -EIO;
> + if (invalid_nodeid(outentry.nodeid) || fuse_invalid_attr(&outentry.attr))
> + goto out_free_ff;
> +
> + ff->fh = outopen.fh;
> + ff->nodeid = outentry.nodeid;
> + ff->open_flags = outopen.open_flags;
> + inode = fuse_iget(dir->i_sb, outentry.nodeid, outentry.generation,
> + &outentry.attr, ATTR_TIMEOUT(&outentry), 0);
> + if (!inode) {
> + flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
> + fuse_sync_release(NULL, ff, flags);
> + fuse_queue_forget(fm->fc, forget, outentry.nodeid, 1);
> + err = -ENOMEM;
> + goto out_err;
> + }
> +
> + /* prevent racing/parallel lookup on a negative hashed */
> + if (!(flags & O_CREAT) && !d_in_lookup(entry)) {
> + d_drop(entry);
> + switched_entry = d_alloc_parallel(entry->d_parent,
> + &entry->d_name, &wq);
> + if (IS_ERR(switched_entry)) {
> + err = PTR_ERR(switched_entry);
> + switched_entry = NULL;
> + goto out_free_ff;
> + }
> +
> + if (unlikely(!d_in_lookup(switched_entry))) {
> + /* fall back */
> + dput(switched_entry);
> + switched_entry = NULL;
> + goto free_and_fallback;
> + }
> +
> + entry = switched_entry;
> + }
> +
> + if (d_really_is_negative(entry)) {
> + d_drop(entry);
> + alias = d_exact_alias(entry, inode);
> + if (!alias) {
> + alias = d_splice_alias(inode, entry);
> + if (IS_ERR(alias)) {
> + /*
> + * Close the file in user space, but do not unlink it,
> + * if it was created - with network file systems other
> + * clients might have already accessed it.
> + */
> + fi = get_fuse_inode(inode);
> + fuse_sync_release(fi, ff, flags);
> + fuse_queue_forget(fm->fc, forget, outentry.nodeid, 1);
> + err = PTR_ERR(alias);
> + goto out_err;
> + }
> + }
> +
> + if (alias)
> + entry = alias;
> + }
> +
> + fuse_change_entry_timeout(entry, &outentry);
> +
> + /* File was indeed created */
> + if (outopen.open_flags & FOPEN_FILE_CREATED) {
> + if (!(flags & O_CREAT)) {
> + pr_debug("Server side bug, FOPEN_FILE_CREATED set "
> + "without O_CREAT, ignoring.");
> + } else {
> + /* This should be always set when the file is created */
> + fuse_dir_changed(dir);
> + file->f_mode |= FMODE_CREATED;
> + }
> + }
> +
> + if (S_ISDIR(mode))
> + ff->open_flags &= ~FOPEN_DIRECT_IO;
> + err = finish_open(file, entry, generic_file_open);
> + if (err) {
> + fi = get_fuse_inode(inode);
> + fuse_sync_release(fi, ff, flags);
> + } else {
> + file->private_data = ff;
> + fuse_finish_open(inode, file);
> + }
> +
> + kfree(forget);
> +
> + if (switched_entry) {
> + d_lookup_done(switched_entry);
> + dput(switched_entry);
> + }
> +
> + dput(alias);
> +
> + return err;
> +
> +out_free_ff:
> + fuse_file_free(ff);
> +out_put_forget_req:
> + kfree(forget);
> +out_err:
> + if (switched_entry) {
> + d_lookup_done(switched_entry);
> + dput(switched_entry);
> + }
> +
> + return err;
> +
> +free_and_fallback:
> + fuse_file_free(ff);
> + kfree(forget);
> +fallback:
> + return fuse_create_open(dir, entry, file, flags, mode);
> +}
> +
> +static int fuse_atomic_open(struct inode *dir, struct dentry *entry,
> + struct file *file, unsigned int flags,
> + umode_t mode)
> +{
> + struct fuse_conn *fc = get_fuse_conn(dir);
> +
> + if (fc->no_open_atomic)
> + return fuse_create_open(dir, entry, file, flags, mode);
> + else
> + return _fuse_atomic_open(dir, entry, file, flags, mode);
> +}
> +
> /*
> * Code shared between mknod, mkdir, symlink and link
> */
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index bf0b85d0b95c..af69578763ef 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -677,6 +677,9 @@ struct fuse_conn {
> /** Is open/release not implemented by fs? */
> unsigned no_open:1;
>
> + /** Is open atomic not implemented by fs? */
> + unsigned no_open_atomic:1;
> +
> /** Is opendir/releasedir not implemented by fs? */
> unsigned no_opendir:1;
>
> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> index db92a7202b34..1508afbd9446 100644
> --- a/include/uapi/linux/fuse.h
> +++ b/include/uapi/linux/fuse.h
> @@ -353,6 +353,7 @@ struct fuse_file_lock {
> * FOPEN_STREAM: the file is stream-like (no file position at all)
> * FOPEN_NOFLUSH: don't flush data cache on close (unless FUSE_WRITEBACK_CACHE)
> * FOPEN_PARALLEL_DIRECT_WRITES: Allow concurrent direct writes on the same inode
> + * FOPEN_FILE_CREATED: the file was indeed created
> */
> #define FOPEN_DIRECT_IO (1 << 0)
> #define FOPEN_KEEP_CACHE (1 << 1)
> @@ -361,6 +362,7 @@ struct fuse_file_lock {
> #define FOPEN_STREAM (1 << 4)
> #define FOPEN_NOFLUSH (1 << 5)
> #define FOPEN_PARALLEL_DIRECT_WRITES (1 << 6)
> +#define FOPEN_FILE_CREATED (1 << 7)
>
> /**
> * INIT request/reply flags
> @@ -617,6 +619,7 @@ enum fuse_opcode {
> FUSE_SYNCFS = 50,
> FUSE_TMPFILE = 51,
> FUSE_STATX = 52,
> + FUSE_OPEN_ATOMIC = 53,
>
> /* CUSE specific operations */
> CUSE_INIT = 4096,
> --
> 2.39.2
>
>
