This patch changes the prefetch API so that file systems must now
provide a set of block numbers, rather than a set of buffers. The
result is a leaner and more well-defined API; linear computation of
the range of blocks to prefetch; duplicates no longer interfering
with the prefetch process; guaranteed inclusion of the block needed
next into the prefetch range; and, limits and policy decisions better
established by libminixfs now actually being moved into libminixfs.
Change-Id: I7e44daf2d2d164bc5e2f1473ad717f3ff0f0a77f
- The lmfs_get_block*(3) API calls may now return an error. The idea
is to encourage a next generation of file system services to do a
better job at dealing with block read errors than the MFS-derived
implementations do. These existing file systems have been changed
to panic immediately upon getting a block read error, in order to
let unchecked errors cause corruption. Note that libbdev already
retries failing I/O operations a few times first.
- The libminixfs block device I/O module (bio.c) now deals properly
with end-of-file conditions on block devices. Since a device or
partition size may not be a multiple of the root file system's block
size, support for partial block retrival has been added, with a new
internal lmfs_get_partial_block(3) call. A new test program,
test85, tests the new handling of EOF conditions when reading,
writing, and memory-mapping a block device.
Change-Id: I05e35b6b8851488328a2679da635ebba0c6d08ce
There are currently no devices out there that require this change.
The change is merely needed to support subsequent changes.
Change-Id: I64214c5f46ff4a2260815d15c15e4a17709b9036
The new functionality aims to save each file system server from having
to implement its own block I/O routines just so that it can serve as a
root file system. The new source file (bio.c) lists the requirements
that file system servers have to fulfill in order to use the routines.
Change-Id: Ia0190fd5c30e8c2097ed8f4b0e3ccde1827e0b92
