Primary purpose of change: to support the mmap implementation, VM must
know both (a) about some block metadata for FS cache blocks, i.e. inode
numbers and inode offsets where applicable; and (b) know about *all*
cache blocks, i.e. also of the FS primary caches and not just the
blocks that spill into the secondary one. This changes the interface and
VM data structures.
This change is only for the interface (libminixfs) and VM data
structures; the filesystem code is unmodified, so although the secondary
cache will be used as normal, blocks will not be annotated with inode
information until the FS is modified to provide this information. Until
it is modified, mmap of files will fail gracefully on such filesystems.
This is indicated to VFS/VM by returning ENOSYS for REQ_PEEK.
Change-Id: I5ddf51a27e3b85b87a10556be87fc33bb92b1090
REQ_PEEK behaves just like REQ_READ except that it does not copy
data anywhere, just obtains the blocks from the FS into the cache.
To be used by the future mmap implementation.
Change-Id: I1b56de304f0a7152b69a72c8962d04258adb44f9
The "bdev" library provides basic primitives for file systems to talk
to block device drivers, hiding the details of the underlying protocol
and interaction model.
This version of libbdev is rather basic. It is planned to support the
following features in the long run:
- asynchronous requests and replies;
- recovery support for underlying block drivers;
- retrying of failed I/O requests.
The commit also changes our block-based file systems (mfs, ext2, isofs)
to make use of libbdev.
