* Jeffle Xu (jefflexu@xxxxxxxxxxxxxxxxx) wrote:
> For passthrough, when the corresponding virtiofs in guest is mounted
> with '-o dax=inode', advertise that the file is capable of per-file
> DAX if the inode in the backend fs is marked with FS_DAX_FL flag.
>
> Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
> ---
> tools/virtiofsd/passthrough_ll.c | 43 ++++++++++++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
>
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 5b6228210f..4cbd904248 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -171,6 +171,7 @@ struct lo_data {
> int allow_direct_io;
> int announce_submounts;
> int perfile_dax_cap; /* capability of backend fs */
> + bool perfile_dax; /* enable per-file DAX or not */
> bool use_statx;
> struct lo_inode root;
> GHashTable *inodes; /* protected by lo->mutex */
> @@ -716,6 +717,10 @@ static void lo_init(void *userdata, struct fuse_conn_info *conn)
>
> if (conn->capable & FUSE_CAP_PERFILE_DAX && lo->perfile_dax_cap ) {
> conn->want |= FUSE_CAP_PERFILE_DAX;
> + lo->perfile_dax = 1;
> + }
> + else {
> + lo->perfile_dax = 0;
> }
> }
>
> @@ -983,6 +988,41 @@ static int do_statx(struct lo_data *lo, int dirfd, const char *pathname,
> return 0;
> }
>
> +/*
> + * If the file is marked with FS_DAX_FL or FS_XFLAG_DAX, then DAX should be
> + * enabled for this file.
> + */
> +static bool lo_should_enable_dax(struct lo_data *lo, struct lo_inode *dir,
> + const char *name)
> +{
> + int res, fd;
> + int ret = false;;
> + unsigned int attr;
> + struct fsxattr xattr;
> +
> + if (!lo->perfile_dax)
> + return false;
> +
> + /* Open file without O_PATH, so that ioctl can be called. */
> + fd = openat(dir->fd, name, O_NOFOLLOW);
> + if (fd == -1)
> + return false;
Doesn't that defeat the whole benefit of using O_PATH - i.e. that we
might stumble into a /dev node or something else we're not allowed to
open?
> + if (lo->perfile_dax_cap == DAX_CAP_FLAGS) {
> + res = ioctl(fd, FS_IOC_GETFLAGS, &attr);
> + if (!res && (attr & FS_DAX_FL))
> + ret = true;
> + }
> + else if (lo->perfile_dax_cap == DAX_CAP_XATTR) {
> + res = ioctl(fd, FS_IOC_FSGETXATTR, &xattr);
> + if (!res && (xattr.fsx_xflags & FS_XFLAG_DAX))
> + ret = true;
> + }
This all looks pretty expensive for each lookup.
Dave
> + close(fd);
> + return ret;
> +}
> +
> /*
> * Increments nlookup on the inode on success. unref_inode_lolocked() must be
> * called eventually to decrement nlookup again. If inodep is non-NULL, the
> @@ -1038,6 +1078,9 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
> e->attr_flags |= FUSE_ATTR_SUBMOUNT;
> }
>
> + if (lo_should_enable_dax(lo, dir, name))
> + e->attr_flags |= FUSE_ATTR_DAX;
> +
> inode = lo_find(lo, &e->attr, mnt_id);
> if (inode) {
> close(newfd);
> --
> 2.27.0
>
> _______________________________________________
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> Virtio-fs@xxxxxxxxxx
> https://listman.redhat.com/mailman/listinfo/virtio-fs
>
--
Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
