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virtiofs: implement FUSE_INIT map_alignment field

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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.

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@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Stefan Hajnoczi
2020-08-19 18:19:49 -04:00
committed by Miklos Szeredi
parent 45f2348ece
commit fd1a1dc6f5
4 changed files with 34 additions and 3 deletions
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4
include/uapi/linux/fuse.h
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@@ -313,7 +313,9 @@ struct fuse_file_lock {
* FUSE_CACHE_SYMLINKS: cache READLINK responses
* FUSE_NO_OPENDIR_SUPPORT: kernel supports zero-message opendir
* FUSE_EXPLICIT_INVAL_DATA: only invalidate cached pages on explicit request
* FUSE_MAP_ALIGNMENT: map_alignment field is valid
* FUSE_MAP_ALIGNMENT: init_out.map_alignment contains log2(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)