- do not allow live update for request and protocol free states if
there are any worker threads that have pending or active work;
- destroy all worker threads before such live updates and recreate
them afterwards, because transferring (the contents of) the
thread stacks is not an option at this time;
- recreate worker threads in the new instance only if they were
shut down before the state transfer, by letting RS provide the
original preparation state as initialization information.
Change-Id: I846225f5b7281f19e69175485f2c88a4b4891dc2
Since the heap is reconstructed upon state transfer, the old malloc
state is discarded. In order to avoid state transfer errors, we can
and in fact must discard the internal state of the malloc
implementation. This patch achieves this by using the sectionify
pass to mark the variables in the libminc malloc object as state that
must be skipped during state transfer.
Change-Id: Ie330f582c8bd45f37a878ea41fa0f9d4a18045e1
Due to changed VM internals, more elaborate preparation is required
before a live update with multiple components including VM can take
place. This patch adds the essential preparation infrastructure to
VM and adapts RS to make use of it. As a side effect, it is no
longer necessary to supply RS as the last component (if at all)
during the set-up of a multicomponent live update operation.
Change-Id: If069fd3f93f96f9d5433998e4615f861465ef448
The 'memory' service has holes in its data section, which causes
problems during state transfer. Since VM cannot handle page faults
during a multicomponent-with-VM live update, the state transfer must
ensure that no page faults occur during copying. Therefore, we now
query VM about the regions to copy, thus skipping holes. While the
solution is not ideal, it is sufficiently generic that it can be used
for the data section state transfer of all processes, and possibly
for state transfer of other regions in the future as well.
Change-Id: I2a71383a18643ebd36956c396fbd22c8fd137202
Edited by David van Moolenbroek to deallocate the guard page as well.
Note that while the new approach is better in theory (previously, the
hole could end up being filled by another allocated page), guard page
protection is now broken in practice, because VM does not support
setting specific page permissions (in this case, PROT_NONE).
Change-Id: I882624f5d152d3ebe82fca649cbad85aa4931780
VM used to call sendrec to send a boot-time RS_INIT reply to RS, but
RS could run into a pagefault at the same time, thus spawning a
message to VM, resulting in a deadlock. We resolve this situation by
making VM acknowledge RS_INIT asynchronously at boot time, while
retaining the synchronous sendrec for subsequent RS_INIT responses.
Change-Id: I3cb72d7f8d6b9bfdc59a85958ada739c37fa3bde
The following services have been updated to support stateful restarts:
- Drivers: tty
- Filesystems: isofs, mfs, pfs, libvtreefs-based file servers
- System servers: tty, ds, pm, vfs, vm
Change-Id: Ie84baa3ba1774047b3ae519808fe4116928edabb
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
This patch changes the libminixfs API and implementation such that the
library is at all times aware of how many total and used blocks there
are in the file system. This removes the last upcall of libminixfs
into file systems (fs_blockstats). In the process, make this part of
the libminixfs API a little prettier and more robust. Change file
systems accordingly. Since this change only adds to MFS being unable
to deal with zones and blocks having different sizes, fail to mount
such file systems immediately rather than triggering an assert later.
Change-Id: I078e589c7e1be1fa691cf391bf5dfddd1baf2c86
This removes an implicit requirement for the way the libminixfs API is
to be used, namely that a block is to be marked as dirty only once its
contents have been fully updated, within a single get_block/put_block
window. The requirement may not be appropriate for all file systems.
Change-Id: I6a129d51b1a5e9aec1572039dc7c1c82dd795db5
With this change, the lmfs_get_block*(3) functions allow the caller to
specify that it only wants the block if it is in the cache or the
secondary VM cache. If the block is not found there, the functions
return NULL. Previously, the PREFETCH method would be used to this
end instead, which was both abuse in name and less efficient.
Change-Id: Ieb5a15b67fa25d2008a8eeef9d126ac908fc2395
When VM asks a file system to provide a block to satisfy a page fault
on a file memory mapping, the file system previously had no way to
inform VM that the block is a hole, since there is no corresponding
block on the underlying device. To work around this, MFS and ext2
would actually allocate a block for the hole when asked by VM, which
not only defeats the point of holes in the first place, but also does
not work on read-only file systems. With this patch, a new libminixfs
call allows the file system to inform VM about holes. This issue does
raise the question as to whether the VM cache is using the right data
structures, since there are now two places where we have to fake a
device offset. This will have to be revisited in the future.
The patch changes file systems accordingly, and adds a test to test74.
Change-Id: Ib537d56b3f30a8eb05bc1f63c92b5c7428d18f4c
This patch employs one solution to resolve two independent but related
issues. Both issues are the result of one fundamental aspect of the
way VM's memory mapping works: VM uses its cache to map in blocks for
memory-mapped file regions, and for blocks already in the VM cache, VM
does not go to the file system before mapping them in. To preserve
consistency between the FS and VM caches, VM relies on being informed
about all updates to file contents through the block cache. The two
issues are both the result of VM not being properly informed about
such updates:
1. Once a file system provides libminixfs with an inode association
(inode number + inode offset) for a disk block, this association
is not broken until a new inode association is provided for it.
If a block is freed and reallocated as a metadata (non-inode)
block, its old association is maintained, and may be supplied to
VM's secondary cache. Due to reuse of inodes, it is possible
that the same inode association becomes valid for an actual file
block again. In that case, when that new file is memory-mapped,
under certain circumstances, VM may end up using the metadata
block to satisfy a page fault on the file, due to the stale inode
association. The result is a corrupted memory mapping, with the
application seeing data other than the current file contents
mapped in at the file block.
2. When a hole is created in a file, the underlying block is freed
from the device, but VM is not informed of this update, and thus,
if VM's cache contains the block with its previous inode
association, this block will remain there. As a result, if an
application subsequently memory-maps the file, VM will map in the
old block at the position of the hole, rather than an all-zeroes
block. Thus, again, the result is a corrupted memory mapping.
This patch resolves both issues by making the file system inform the
minixfs library about blocks being freed, so that libminixfs can
break the inode association for that block, both in its own cache and
in the VM cache. Since libminixfs does not know whether VM has the
block in its cache or not, it makes a call to VM for each block being
freed. Thus, this change introduces more calls to VM, but it solves
the correctness issues at hand; optimizations may be introduced
later. On the upside, all freed blocks are now marked as clean,
which should result in fewer blocks being written back to the device,
and the blocks are removed from the caches entirely, which should
result in slightly better cache usage.
This patch is necessary but not sufficient to resolve the situation
with respect to memory mapping of file holes in general. Therefore,
this patch extends test 74 with a (rather particular but effective)
test for the first issue, but not yet with a test for the second one.
This fixes#90.
Change-Id: Iad8b134d2f88a884f15d3fc303e463280749c467
There are currently no devices out there that require this change.
The change is merely needed to support subsequent changes.
Change-Id: I64214c5f46ff4a2260815d15c15e4a17709b9036
This barrier ensures that all fields of an asynchronously sent
message are properly initialized before the message is marked as
valid.
Change-Id: I7b9590c11c4e040c8f992f1dd2581e54201bf214
Previously, there was a tiny chance that tickdelay(3) would return
early or that it would fail to reinstate a previous alarm.
- sys_setalarm(2) now returns TMR_NEVER instead of 0 for the time
left if no previous alarm was set;
- sys_setalarm(2) now also returns the current time, to allow the
caller to determine whether it got an alarm notification for the
alarm it set or for a previous alarm that has just gone off;
- tickdelay(3) now makes use of these facilities.
Change-Id: Id4f8fe19a61ca8574f43131964e6f0317f613f49
Extended by David van Moolenbroek to continue using static buffers
for short inode names, so as to prevent important file system
services such as procfs from running out of memory at runtime.
Change-Id: I6f841741ee9944fc87dbdb78b5cdaa2abee9da76
As part of its built-in mmap emulation support for "none" file system
services, libfsdriver clears the VM cache upon exit. However, for
trivial file systems which do not even support reading from files, the
the VM cache need to be cleared either. With this patch, the VM cache
is cleared only when modified, so that such trivial file systems need
not be given CLEARCACHE permission.
Change-Id: I518c092443455302b9b9728f10a3f894d2c8036b
While putnode requests should always succeed, very simple file system
services may not care about reference counts and thus about putnode
requests at all. For this reason, we now default to an OK response if
no fdr_putnode implementation is given.
Change-Id: I01f6421abf4546a1f69d8c21900a92d6acc45745
The stat.st_ino field must always be filled with the inode number
given as part of the fdr_stat request anyway, so libfsdriver can
simply fill in the number and allow the file system not to bother.
Change-Id: Ia7a849d0b23dfc83010df0d48fa26e4225427694
