[Virtio-fs] [PATCH] fuse: implement FUSE_INIT map_alignment field
Vivek Goyal
vgoyal at redhat.com
Fri Jul 26 20:39:41 UTC 2019
On Fri, Jul 26, 2019 at 09:29:33AM +0100, Stefan Hajnoczi wrote:
> The device communicates FUSE_SETUPMAPPING/FUSE_REMOVMAPPING alignment
> constraints via the FUST_INIT map_alignment field. Parse this field and
> ensure our DAX mappings meet the alignment constraints.
Hi Stefan,
To meet alignment constraints, we also need to make sure dax window
start/end address is 2MB aligned as well?
Thanks
Vivek
>
> We don't actually align anything differently since our mappings are
> already 2MB aligned. Just check the value when the connection is
> established. If it becomes necessary to honor arbitrary alignments in
> the future we'll have to adjust how mappings are sized.
>
> The upshot of this commit is that we can be confident that mappings will
> work even when emulating x86 on Power and similar combinations where the
> host page sizes are different.
>
> Signed-off-by: Stefan Hajnoczi <stefanha at redhat.com>
> ---
> Please see separate virtiofsd patch for the server-side implementation.
>
> fs/fuse/fuse_i.h | 5 ++++-
> include/uapi/linux/fuse.h | 7 ++++++-
> fs/fuse/inode.c | 18 ++++++++++++++++--
> 3 files changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index edcc4a3e119b..988ea5c39d41 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -46,7 +46,10 @@
> /** Number of page pointers embedded in fuse_req */
> #define FUSE_REQ_INLINE_PAGES 1
>
> -/* Default memory range size, 2MB */
> +/*
> + * Default memory range size. A power of 2 so it agrees with common FUSE_INIT
> + * map_alignment values 4KB and 64KB.
> + */
> #define FUSE_DAX_MEM_RANGE_SZ (2*1024*1024)
> #define FUSE_DAX_MEM_RANGE_PAGES (FUSE_DAX_MEM_RANGE_SZ/PAGE_SIZE)
>
> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> index 0f4b69b9c751..41d384b189b6 100644
> --- a/include/uapi/linux/fuse.h
> +++ b/include/uapi/linux/fuse.h
> @@ -263,6 +263,9 @@ struct fuse_file_lock {
> * FUSE_MAX_PAGES: init_out.max_pages contains the max number of req pages
> * FUSE_CACHE_SYMLINKS: cache READLINK responses
> * FUSE_NO_OPENDIR_SUPPORT: kernel supports zero-message opendir
> + * FUSE_MAP_ALIGNMENT: init_out.map_alignment contains byte alignment for
> + * foffset and moffset fields in struct
> + * fuse_setupmapping_out and fuse_removemapping_one.
> */
> #define FUSE_ASYNC_READ (1 << 0)
> #define FUSE_POSIX_LOCKS (1 << 1)
> @@ -289,6 +292,7 @@ struct fuse_file_lock {
> #define FUSE_MAX_PAGES (1 << 22)
> #define FUSE_CACHE_SYMLINKS (1 << 23)
> #define FUSE_NO_OPENDIR_SUPPORT (1 << 24)
> +#define FUSE_MAP_ALIGNMENT (1 << 25)
>
> /**
> * CUSE INIT request/reply flags
> @@ -632,7 +636,8 @@ struct fuse_init_out {
> uint32_t time_gran;
> uint16_t max_pages;
> uint16_t padding;
> - uint32_t unused[8];
> + uint32_t map_alignment;
> + uint32_t unused[7];
> };
>
> #define CUSE_INIT_INFO_MAX 4096
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index ffa00caeea01..ecb47c65f514 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -969,9 +969,10 @@ static void process_init_limits(struct fuse_conn *fc, struct fuse_init_out *arg)
> static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
> {
> struct fuse_init_out *arg = &req->misc.init_out;
> + bool ok = true;
>
> if (req->out.h.error || arg->major != FUSE_KERNEL_VERSION)
> - fc->conn_error = 1;
> + ok = false;
> else {
> unsigned long ra_pages;
>
> @@ -1032,6 +1033,13 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
> min_t(unsigned int, FUSE_MAX_MAX_PAGES,
> max_t(unsigned int, arg->max_pages, 1));
> }
> + if ((arg->flags & FUSE_MAP_ALIGNMENT) &&
> + (FUSE_DAX_MEM_RANGE_SZ % arg->map_alignment)) {
> + printk(KERN_ERR "FUSE: map_alignment %u incompatible with dax mem range size %u\n",
> + arg->map_alignment,
> + FUSE_DAX_MEM_RANGE_SZ);
> + ok = false;
> + }
> } else {
> ra_pages = fc->max_read / PAGE_SIZE;
> fc->no_lock = 1;
> @@ -1045,6 +1053,12 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
> fc->max_write = max_t(unsigned, 4096, fc->max_write);
> fc->conn_init = 1;
> }
> +
> + if (!ok) {
> + fc->conn_init = 0;
> + fc->conn_error = 1;
> + }
> +
> fuse_set_initialized(fc);
> wake_up_all(&fc->blocked_waitq);
> }
> @@ -1064,7 +1078,7 @@ void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
> FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |
> FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
> FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
> - FUSE_NO_OPENDIR_SUPPORT;
> + FUSE_NO_OPENDIR_SUPPORT | FUSE_MAP_ALIGNMENT;
> req->in.h.opcode = FUSE_INIT;
> req->in.numargs = 1;
> req->in.args[0].size = sizeof(*arg);
> --
> 2.21.0
>
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