On Thu, Jul 3, 2025 at 8:51 PM John Groves <j...@groves.net> wrote:
>
> * FUSE_DAX_FMAP flag in INIT request/reply
>
> * fuse_conn->famfs_iomap (enable famfs-mapped files) to denote a
> famfs-enabled connection
>
> Signed-off-by: John Groves <j...@groves.net>
> ---
> fs/fuse/fuse_i.h | 3 +++
> fs/fuse/inode.c | 14 ++++++++++++++
> include/uapi/linux/fuse.h | 4 ++++
> 3 files changed, 21 insertions(+)
>
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index 9d87ac48d724..a592c1002861 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -873,6 +873,9 @@ struct fuse_conn {
> /* Use io_uring for communication */
> unsigned int io_uring;
>
> + /* dev_dax_iomap support for famfs */
> + unsigned int famfs_iomap:1;
> +
pls move up to the bit fields members.
> /** Maximum stack depth for passthrough backing files */
> int max_stack_depth;
>
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 29147657a99f..e48e11c3f9f3 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1392,6 +1392,18 @@ static void process_init_reply(struct fuse_mount *fm,
> struct fuse_args *args,
> }
> if (flags & FUSE_OVER_IO_URING &&
> fuse_uring_enabled())
> fc->io_uring = 1;
> + if (IS_ENABLED(CONFIG_FUSE_FAMFS_DAX) &&
> + flags & FUSE_DAX_FMAP) {
> + /* XXX: Should also check that fuse server
> + * has CAP_SYS_RAWIO and/or CAP_SYS_ADMIN,
> + * since it is directing the kernel to access
> + * dax memory directly - but this function
> + * appears not to be called in fuse server
> + * process context (b/c even if it drops
> + * those capabilities, they are held here).
> + */
> + fc->famfs_iomap = 1;
> + }
1. As long as the mapping requests are checking capabilities we should be ok
Right?
2. What's the deal with capable(CAP_SYS_ADMIN) in process_init_limits then?
3. Darrick mentioned the need for a synchronic INIT variant for his work on
blockdev iomap support [1]
I also wonder how much of your patches and Darrick's patches end up
being an overlap?
Thanks,
Amir.
[1] https://lore.kernel.org/linux-fsdevel/20250613174413.GM6138@frogsfrogsfrogs/
