I was looking into using stackable FSALs instead of the current mechanism
for creating FSAL_VFS (Linux), FSAL_VFS (freebsd), and FSAL_XFS. The
following functions are implemented differently for FSAL_VFS and FSAL_XFS
int vfs_fd_to_handle(int fd, struct fsal_filesystem *fs,
vfs_file_handle_t *fh);
This is only used by lookup_path, ultimately the best thing to do would
probably be to duplicate the lookup_path code in both under stacked FSALs.
int vfs_name_to_handle(int atfd,
struct fsal_filesystem *fs,
const char *name,
vfs_file_handle_t *fh);
This could be mapped to the FSAL lookup method.
int vfs_open_by_handle(struct vfs_filesystem *fs,
vfs_file_handle_t *fh, int openflags,
fsal_errors_t *fsal_error);
This could be mapped to the FSAL open2 method
int vfs_encode_dummy_handle(vfs_file_handle_t *fh,
struct fsal_filesystem *fs);
This is used to fabricate an object handle when we cross a filesystem mount
point into a filesystem not handled by the FSAL. It would somehow have to be
mapped to lookup, but that overloads the use of lookup for
vfs_name_to_handle.
bool vfs_is_dummy_handle(vfs_file_handle_t *fh);
This one is really internal to the guts of FSAL_VFS/XFS and has no analog in
the FSAL API.
bool vfs_valid_handle(struct gsh_buffdesc *desc);
This is called by vfs_check_handle and could maybe be mapped to the FSAL
wire_to_host method.
int vfs_readlink(struct vfs_fsal_obj_handle *myself,
fsal_errors_t *fsal_error);
This could be mapped to FSAL readlink method.
int vfs_extract_fsid(vfs_file_handle_t *fh,
enum fsid_type *fsid_type,
struct fsal_fsid__ *fsid);
This is also called by vfs_check_handle and maybe more of that function
could be moved into the FSAL wire_to_host method.
int vfs_get_root_handle(struct vfs_filesystem *vfs_fs,
struct vfs_fsal_export *exp);
int vfs_re_index(struct vfs_filesystem *vfs_fs,
struct vfs_fsal_export *exp);
These two are used in the process of claiming filesystems during
create_export, so perhaps could be mapped to FSAL create_export method.
All in all, these functions are not a great fit for the FSAL API so I'm not
sure it would be a good solution. Forcing some of the functions into FSAL
methods would require some code duplication that loses some of the advantage
of the mechanism. There would also be a question of how things like the file
descriptors and fsal_filesystems are shared between the main FSAL_ VFS and
the underlying stacked FSAL.
Frank
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