On Fri, Jul 18, 2025 at 1:36 AM Darrick J. Wong <djwong@xxxxxxxxxx> wrote:
>
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> Create new fuse_reply_{attr,create,entry}_iflags functions so that we
> can send FUSE_ATTR_* flags to the kernel when instantiating an inode.
> Servers are expected to send FUSE_IFLAG_* values, which will be
> translated into what the kernel can understand.
>
> Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
> ---
> include/fuse_common.h | 3 ++
> include/fuse_lowlevel.h | 87 +++++++++++++++++++++++++++++++++++++++++++++--
> lib/fuse_lowlevel.c | 69 ++++++++++++++++++++++++++++++-------
> lib/fuse_versionscript | 4 ++
> 4 files changed, 146 insertions(+), 17 deletions(-)
>
>
> diff --git a/include/fuse_common.h b/include/fuse_common.h
> index 66c25afe15ec76..11eb22d011896c 100644
> --- a/include/fuse_common.h
> +++ b/include/fuse_common.h
> @@ -1210,6 +1210,9 @@ struct fuse_iomap {
> /* is append ioend */
> #define FUSE_IOMAP_IOEND_APPEND (1U << 15)
>
> +/* enable fsdax */
> +#define FUSE_IFLAG_DAX (1U << 0)
> +
> #endif /* FUSE_USE_VERSION >= 318 */
>
> /* ----------------------------------------------------------- *
> diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
> index 1b856431de0a60..07748abcf079cf 100644
> --- a/include/fuse_lowlevel.h
> +++ b/include/fuse_lowlevel.h
> @@ -240,6 +240,7 @@ struct fuse_lowlevel_ops {
> *
> * Valid replies:
> * fuse_reply_entry
> + * fuse_reply_entry_iflags
> * fuse_reply_err
> *
> * @param req request handle
> @@ -299,6 +300,7 @@ struct fuse_lowlevel_ops {
> *
> * Valid replies:
> * fuse_reply_attr
> + * fuse_reply_attr_iflags
> * fuse_reply_err
> *
> * @param req request handle
> @@ -334,6 +336,7 @@ struct fuse_lowlevel_ops {
> *
> * Valid replies:
> * fuse_reply_attr
> + * fuse_reply_attr_iflags
> * fuse_reply_err
> *
> * @param req request handle
> @@ -364,7 +367,7 @@ struct fuse_lowlevel_ops {
> * socket node.
> *
> * Valid replies:
> - * fuse_reply_entry
> + * fuse_reply_entry_iflags
> * fuse_reply_err
> *
> * @param req request handle
> @@ -380,7 +383,7 @@ struct fuse_lowlevel_ops {
> * Create a directory
> *
> * Valid replies:
> - * fuse_reply_entry
> + * fuse_reply_entry_iflags
> * fuse_reply_err
> *
> * @param req request handle
> @@ -429,7 +432,7 @@ struct fuse_lowlevel_ops {
> * Create a symbolic link
> *
> * Valid replies:
> - * fuse_reply_entry
> + * fuse_reply_entry_iflags
> * fuse_reply_err
> *
> * @param req request handle
> @@ -477,7 +480,7 @@ struct fuse_lowlevel_ops {
> * Create a hard link
> *
> * Valid replies:
> - * fuse_reply_entry
> + * fuse_reply_entry_iflags
> * fuse_reply_err
> *
> * @param req request handle
> @@ -969,6 +972,7 @@ struct fuse_lowlevel_ops {
> *
> * Valid replies:
> * fuse_reply_create
> + * fuse_reply_create_iflags
> * fuse_reply_err
> *
> * @param req request handle
> @@ -1315,6 +1319,7 @@ struct fuse_lowlevel_ops {
> *
> * Valid replies:
> * fuse_reply_create
> + * fuse_reply_create_iflags
> * fuse_reply_err
> *
> * @param req request handle
> @@ -1435,6 +1440,23 @@ void fuse_reply_none(fuse_req_t req);
> */
> int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e);
>
> +/**
> + * Reply with a directory entry and FUSE_IFLAG_*
> + *
> + * Possible requests:
> + * lookup, mknod, mkdir, symlink, link
> + *
> + * Side effects:
> + * increments the lookup count on success
> + *
> + * @param req request handle
> + * @param e the entry parameters
> + * @param iflags FUSE_IFLAG_*
> + * @return zero for success, -errno for failure to send reply
> + */
> +int fuse_reply_entry_iflags(fuse_req_t req, const struct fuse_entry_param *e,
> + unsigned int iflags);
> +
> /**
> * Reply with a directory entry and open parameters
> *
> @@ -1456,6 +1478,29 @@ int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e);
> int fuse_reply_create(fuse_req_t req, const struct fuse_entry_param *e,
> const struct fuse_file_info *fi);
>
> +/**
> + * Reply with a directory entry, open parameters and FUSE_IFLAG_*
> + *
> + * currently the following members of 'fi' are used:
> + * fh, direct_io, keep_cache, cache_readdir, nonseekable, noflush,
> + * parallel_direct_writes
> + *
> + * Possible requests:
> + * create
> + *
> + * Side effects:
> + * increments the lookup count on success
> + *
> + * @param req request handle
> + * @param e the entry parameters
> + * @param iflags FUSE_IFLAG_*
> + * @param fi file information
> + * @return zero for success, -errno for failure to send reply
> + */
> +int fuse_reply_create_iflags(fuse_req_t req, const struct fuse_entry_param *e,
> + unsigned int iflags,
> + const struct fuse_file_info *fi);
> +
> /**
> * Reply with attributes
> *
> @@ -1470,6 +1515,21 @@ int fuse_reply_create(fuse_req_t req, const struct fuse_entry_param *e,
> int fuse_reply_attr(fuse_req_t req, const struct stat *attr,
> double attr_timeout);
>
> +/**
> + * Reply with attributes and FUSE_IFLAG_* flags
> + *
> + * Possible requests:
> + * getattr, setattr
> + *
> + * @param req request handle
> + * @param attr the attributes
> + * @param attr_timeout validity timeout (in seconds) for the attributes
> + * @param iflags set of FUSE_IFLAG_* flags
> + * @return zero for success, -errno for failure to send reply
> + */
> +int fuse_reply_attr_iflags(fuse_req_t req, const struct stat *attr,
> + unsigned int iflags, double attr_timeout);
> +
> /**
> * Reply with the contents of a symbolic link
> *
> @@ -1697,6 +1757,25 @@ size_t fuse_add_direntry_plus(fuse_req_t req, char *buf, size_t bufsize,
> const char *name,
> const struct fuse_entry_param *e, off_t off);
>
> +/**
> + * Add a directory entry and FUSE_IFLAG_* to the buffer with the attributes
> + *
> + * See documentation of `fuse_add_direntry_plus()` for more details.
> + *
> + * @param req request handle
> + * @param buf the point where the new entry will be added to the buffer
> + * @param bufsize remaining size of the buffer
> + * @param name the name of the entry
> + * @param iflags FUSE_IFLAG_*
> + * @param e the directory entry
> + * @param off the offset of the next entry
> + * @return the space needed for the entry
> + */
> +size_t fuse_add_direntry_plus_iflags(fuse_req_t req, char *buf, size_t bufsize,
> + const char *name, unsigned int iflags,
> + const struct fuse_entry_param *e,
> + off_t off);
> +
> /**
> * Reply to ask for data fetch and output buffer preparation. ioctl
> * will be retried with the specified input data fetched and output
> diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
> index d26043fa54c036..568db13502a7d7 100644
> --- a/lib/fuse_lowlevel.c
> +++ b/lib/fuse_lowlevel.c
> @@ -102,7 +102,8 @@ static void trace_request_reply(uint64_t unique, unsigned int len,
> }
> #endif
>
> -static void convert_stat(const struct stat *stbuf, struct fuse_attr *attr)
> +static void convert_stat(const struct stat *stbuf, struct fuse_attr *attr,
> + unsigned int iflags)
> {
> attr->ino = stbuf->st_ino;
> attr->mode = stbuf->st_mode;
> @@ -119,6 +120,10 @@ static void convert_stat(const struct stat *stbuf, struct fuse_attr *attr)
> attr->atimensec = ST_ATIM_NSEC(stbuf);
> attr->mtimensec = ST_MTIM_NSEC(stbuf);
> attr->ctimensec = ST_CTIM_NSEC(stbuf);
> +
> + attr->flags = 0;
> + if (iflags & FUSE_IFLAG_DAX)
> + attr->flags |= FUSE_ATTR_DAX;
> }
>
> static void convert_attr(const struct fuse_setattr_in *attr, struct stat *stbuf)
> @@ -438,7 +443,8 @@ static unsigned int calc_timeout_nsec(double t)
> }
>
> static void fill_entry(struct fuse_entry_out *arg,
> - const struct fuse_entry_param *e)
> + const struct fuse_entry_param *e,
> + unsigned int iflags)
> {
> arg->nodeid = e->ino;
> arg->generation = e->generation;
> @@ -446,14 +452,15 @@ static void fill_entry(struct fuse_entry_out *arg,
> arg->entry_valid_nsec = calc_timeout_nsec(e->entry_timeout);
> arg->attr_valid = calc_timeout_sec(e->attr_timeout);
> arg->attr_valid_nsec = calc_timeout_nsec(e->attr_timeout);
> - convert_stat(&e->attr, &arg->attr);
> + convert_stat(&e->attr, &arg->attr, iflags);
> }
>
> /* `buf` is allowed to be empty so that the proper size may be
> allocated by the caller */
> -size_t fuse_add_direntry_plus(fuse_req_t req, char *buf, size_t bufsize,
> - const char *name,
> - const struct fuse_entry_param *e, off_t off)
> +size_t fuse_add_direntry_plus_iflags(fuse_req_t req, char *buf, size_t bufsize,
> + const char *name, unsigned int iflags,
> + const struct fuse_entry_param *e,
> + off_t off)
> {
> (void)req;
> size_t namelen;
> @@ -468,7 +475,7 @@ size_t fuse_add_direntry_plus(fuse_req_t req, char *buf, size_t bufsize,
>
> struct fuse_direntplus *dp = (struct fuse_direntplus *) buf;
> memset(&dp->entry_out, 0, sizeof(dp->entry_out));
> - fill_entry(&dp->entry_out, e);
> + fill_entry(&dp->entry_out, e, iflags);
>
> struct fuse_dirent *dirent = &dp->dirent;
> dirent->ino = e->attr.st_ino;
> @@ -481,6 +488,14 @@ size_t fuse_add_direntry_plus(fuse_req_t req, char *buf, size_t bufsize,
> return entlen_padded;
> }
>
> +size_t fuse_add_direntry_plus(fuse_req_t req, char *buf, size_t bufsize,
> + const char *name,
> + const struct fuse_entry_param *e, off_t off)
> +{
> + return fuse_add_direntry_plus_iflags(req, buf, bufsize, name, 0, e,
> + off);
> +}
> +
> static void fill_open(struct fuse_open_out *arg,
> const struct fuse_file_info *f)
> {
> @@ -503,7 +518,8 @@ static void fill_open(struct fuse_open_out *arg,
> arg->open_flags |= FOPEN_PARALLEL_DIRECT_WRITES;
> }
>
> -int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e)
> +int fuse_reply_entry_iflags(fuse_req_t req, const struct fuse_entry_param *e,
> + unsigned int iflags)
> {
> struct fuse_entry_out arg;
> size_t size = req->se->conn.proto_minor < 9 ?
> @@ -515,12 +531,18 @@ int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e)
> return fuse_reply_err(req, ENOENT);
>
> memset(&arg, 0, sizeof(arg));
> - fill_entry(&arg, e);
> + fill_entry(&arg, e, iflags);
> return send_reply_ok(req, &arg, size);
> }
>
> -int fuse_reply_create(fuse_req_t req, const struct fuse_entry_param *e,
> - const struct fuse_file_info *f)
> +int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e)
> +{
> + return fuse_reply_entry_iflags(req, e, 0);
> +}
> +
> +int fuse_reply_create_iflags(fuse_req_t req, const struct fuse_entry_param *e,
> + unsigned int iflags,
> + const struct fuse_file_info *f)
> {
> alignas(uint64_t) char buf[sizeof(struct fuse_entry_out) + sizeof(struct fuse_open_out)];
> size_t entrysize = req->se->conn.proto_minor < 9 ?
> @@ -529,12 +551,18 @@ int fuse_reply_create(fuse_req_t req, const struct fuse_entry_param *e,
> struct fuse_open_out *oarg = (struct fuse_open_out *) (buf + entrysize);
>
> memset(buf, 0, sizeof(buf));
> - fill_entry(earg, e);
> + fill_entry(earg, e, iflags);
> fill_open(oarg, f);
> return send_reply_ok(req, buf,
> entrysize + sizeof(struct fuse_open_out));
> }
>
> +int fuse_reply_create(fuse_req_t req, const struct fuse_entry_param *e,
> + const struct fuse_file_info *f)
> +{
> + return fuse_reply_create_iflags(req, e, 0, f);
> +}
> +
> int fuse_reply_attr(fuse_req_t req, const struct stat *attr,
> double attr_timeout)
> {
> @@ -545,7 +573,22 @@ int fuse_reply_attr(fuse_req_t req, const struct stat *attr,
> memset(&arg, 0, sizeof(arg));
> arg.attr_valid = calc_timeout_sec(attr_timeout);
> arg.attr_valid_nsec = calc_timeout_nsec(attr_timeout);
> - convert_stat(attr, &arg.attr);
> + convert_stat(attr, &arg.attr, 0);
> +
> + return send_reply_ok(req, &arg, size);
> +}
> +
> +int fuse_reply_attr_iflags(fuse_req_t req, const struct stat *attr,
> + unsigned int iflags, double attr_timeout)
> +{
> + struct fuse_attr_out arg;
> + size_t size = req->se->conn.proto_minor < 9 ?
> + FUSE_COMPAT_ATTR_OUT_SIZE : sizeof(arg);
> +
> + memset(&arg, 0, sizeof(arg));
> + arg.attr_valid = calc_timeout_sec(attr_timeout);
> + arg.attr_valid_nsec = calc_timeout_nsec(attr_timeout);
> + convert_stat(attr, &arg.attr, iflags);
>
> return send_reply_ok(req, &arg, size);
> }
I wonder why fuse_reply_attr() is not implemented as a wrapper to
fuse_reply_attr_iflags()?
FWIW, the flags field was added in minor version 23 for
FUSE_ATTR_SUBMOUNT, but I guess that doesn't matter here.
Thanks,
Amir.
