Reimplement fsfs private operations required by `svnfsfs` (stats, dump index, load index) as "ioctls".
Technically we achieve this by introducing the new svn_fs_ioctl() API that adds a generic way of performing backend-specific I/O operations.
This change serves two purposes:
- It allows us to properly expose FS-specific details and invoke FS-specific operations everywhere without necessarily promoting them into a proper public API (the ioctl code itself may be made either public or private, depending on the requirements).
- It solves a potential dependency/linking problem where tools like `svnfsfs` work through the libsvn_fs's loader, but also have to load and call private APIs from libsvn_fs_fs thus ignoring the loader. The latter part may potentially cause issues with the global shared state, etc. With the patch, all such operations always go through the FS loader.
* subversion/include/svn_error_codes.h (SVN_ERR_FS_UNRECOGNIZED_IOCTL_CODE): New error code.
* subversion/include/private/svn_fs_fs_private.h (svn_fs_fs__get_stats, svn_fs_fs__dump_index, svn_fs_fs__load_index): These functions are now implemented as... (SVN_FS_FS__IOCTL_GET_STATS, SVN_FS_FS__IOCTL_DUMP_INDEX, SVN_FS_FS__IOCTL_LOAD_INDEX): ...these new ioctls, which ... (svn_fs_fs__ioctl_get_stats_input_t, svn_fs_fs__ioctl_get_stats_output_t, svn_fs_fs__ioctl_dump_index_input_t, svn_fs_fs__ioctl_load_index_input_t): ...use these new structures.
* subversion/libsvn_fs/fs-loader.h (fs_library_vtable_t.ioctl, fs_vtable_t.ioctl): New vtable members.
* subversion/libsvn_fs/fs-loader.c (svn_fs_ioctl): Implement the new API by forwarding it to an appropriate vtable member.
* subversion/libsvn_fs_fs/fs_fs.h (svn_fs_fs__get_stats, svn_fs_fs__dump_index, svn_fs_fs__load_index): These functions are now declared here.
* subversion/libsvn_fs_fs/fs.c (): Include `svn_fs_fs_private.h`. (fs_ioctl): Implement the ioctl dispatcher for three current fsfs-specific operations. (fs_vtable): Initialize the `ioctl` field. (library_vtable): Initialize the `ioctl` field to NULL.