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 <[email protected]> > --- > 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 >
