This commit reached that goal of "safely discarding" a filesystem by
doing the following:
1. Stop using the s_file_system_map HashMap as it was an unsafe measure
to access pointers of FileSystems. Instead, make sure to register all
FileSystems at the VFS layer, with an IntrusiveList, to avoid problems
related to OOM conditions.
2. Make sure to cleanly remove the DiskCache object from a BlockBased
filesystem, so the destructor of such object will not need to do that in
the destruction point.
3. For ext2 filesystems, don't cache the root inode at m_inode_cache
HashMap. The reason for this is that when unmounting an ext2 filesystem,
we lookup at the cache to see if there's a reference to a cached inode
and if that's the case, we fail with EBUSY. If we keep the m_root_inode
also being referenced at the m_inode_cache map, we have 2 references to
that object, which will lead to fail with EBUSY. Also, it's much simpler
to always ask for a root inode and get it immediately from m_root_inode,
instead of looking up the cache for that inode.
The idea is to enable mounting FileSystem objects across multiple mounts
in contrast to what happened until now - each mount has its own unique
FileSystem object being attached to it.
Considering a situation of mounting a block device at 2 different mount
points at in system, there were a couple of critical flaws due to how
the previous "design" worked:
1. BlockBasedFileSystem(s) that pointed to the same actual device had a
separate DiskCache object being attached to them. Because both instances
were not synchronized by any means, corruption of the filesystem is most
likely achieveable by a simple cache flush of either of the instances.
2. For superblock-oriented filesystems (such as the ext2 filesystem),
lack of synchronization between both instances can lead to severe
corruption in the superblock, which could render the entire filesystem
unusable.
3. Flags of a specific filesystem implementation (for example, with xfs
on Linux, one can instruct to mount it with the discard option) must be
honored across multiple mounts, to ensure expected behavior against a
particular filesystem.
This patch put the foundations to start fix the issues mentioned above.
However, there are still major issues to solve, so this is only a start.
We now have a seperately allocated structure for the bookkeeping
information in the QueueHead and TransferDescriptor UHCI strucutres.
This way, we can support 64-bit pointers in UHCI, fixing a problem where
32-bit pointers would truncate the upper 32-bits of the (virtual)
address of the descriptor, causing a crash.
Co-authored-by: b14ckcat <b14ckcat@protonmail.com>
In theory our peer process could die between the call to getsockopt()
and Core::system::stat() and another process could end up with the same
PID which would result in us incorrectly launching the service as
another user (e.g. root).
For SystemServer, we simply ensure that the /dev mount is now mounted
with MS_NOREGULAR flag to ensure only non-regular files are created,
thus, achieving what DevTmpFS provided in its implementation, but in a
much more sane and clean way than how DevTmpFS did that.
For other userland applications, we simply make them being aware of this
flag so they can show an indication about this flag being used to the
user.
This flag doesn't conform to any POSIX standard nor is found in any OS
out there. The idea behind this mount flag is to ensure that only
non-regular files will be placed in a filesystem, which includes device
nodes, symbolic links, directories, FIFOs and sockets. Currently, the
only valid case for using this mount flag is for TmpFS instances, where
we want to mount a TmpFS but disallow any kind of regular file and only
allow other types of files on the filesystem.
Although this code worked quite well, it is considered to be a code
duplication with the TmpFS code which is more tested and works quite
well for a variety of cases. The only valid reason to keep this
filesystem was that it enforces that no regular files will be created at
all in the filesystem. Later on, we will re-introduce this feature in a
sane manner. Therefore, this can be safely removed after SystemServer no
longer uses this filesystem type anymore.
The implementations for these methods is manually defined in the .cpp
file for `int` and `float`, meaning that other `T` values would fail -
but only once we got to the linking stage. This patch makes the error
happen much earlier, so it's more obvious.
Putting the implementations in the .cpp file meant that they only
existed for `IntRect` and `FloatRect`, since those were instantiated at
the bottom of the file. Now they work for other types. :^)
A couple of places in WindowServer had to be modified to disambiguate
between the two `Rect::intersected()` overloads.
Co-authored-by: davidot <davidot@serenityos.org>
Homebrew does not add upstream LLVM's install location to $PATH so as
not to conflict with XCode tools, so we need to run `brew --prefix llvm`
to figure out its install path.
I originally missed this while handling the upgrade to LLVM 15 (as it
only affects the on-serenity port), so the patch gets to be here with a
bit of a delay.
Co-Authored-By: sin-ack <sin-ack@users.noreply.github.com>
