This never was a logical block size, it always was a device specific
block size. Ideally the block size would change in accordance to
whatever the driver wants to use, but that is a change for the future.
For now, let's get rid of this confusing naming.
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.
These functions used to return booleans which withheld useful
error information for callers. Internally they would suppress
and convert Error objects. We now log or propagate these errors
up the stack.
We now use AK::Error and AK::ErrorOr<T> in both kernel and userspace!
This was a slightly tedious refactoring that took a long time, so it's
not unlikely that some bugs crept in.
Nevertheless, it does pass basic functionality testing, and it's just
real nice to finally see the same pattern in all contexts. :^)
Forcing the formatting to go through `Formatter<FormatString>` is
completely unnecessary, increases code size, performs a String
allocation and prevents us from using the formatting options available
on that type.
This commit also removes explicit formatters from
`BlockBasedFileSystem::BlockIndex` and `Kernel::InodeIndex`, as those
are already covered by the blanket implementation for all
`DistinctNumeric` types.
Create the disk cache up front, so we can verify it succeeds.
Make the KBuffer allocation fail-able, so we can properly handle
failure when the user asks up to mount a Ext2 filesystem under
OOM conditions.
The file system lock is meant to protect the file system metadata
(super blocks, bitmaps, etc.) Not protect processes from reading
independent parts of the disk at once.
This patch introduces a new lock to protect the *block cache* instead,
which is the real thing that needs synchronization.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
This way, if something goes wrong, we get to keep the actual error.
Also, KResults are nodiscard, so we have to deal with that in Ext2FS
instead of just silently ignoring I/O errors(!)
BlockBasedFileSystem::read_block method should get a reference of
a UserOrKernelBuffer.
If we need to force caching a block, we will call other method to do so.
Since the CPU already does almost all necessary validation steps
for us, we don't really need to attempt to do this. Doing it
ourselves doesn't really work very reliably, because we'd have to
account for other processors modifying virtual memory, and we'd
have to account for e.g. pages not being able to be allocated
due to insufficient resources.
So change the copy_to/from_user (and associated helper functions)
to use the new safe_memcpy, which will return whether it succeeded
or not. The only manual validation step needed (which the CPU
can't perform for us) is making sure the pointers provided by user
mode aren't pointing to kernel mappings.
To make it easier to read/write from/to either kernel or user mode
data add the UserOrKernelBuffer helper class, which will internally
either use copy_from/to_user or directly memcpy, or pass the data
through directly using a temporary buffer on the stack.
Last but not least we need to keep syscall params trivial as we
need to copy them from/to user mode using copy_from/to_user.
FileBackedFileSystem is one that's backed by (mounted from) a file, in other
words one that has a "source" of the mount; that doesn't mean it deals in
blocks. The hierarchy now becomes:
* FS
* ProcFS
* DevPtsFS
* TmpFS
* FileBackedFS
* (future) Plan9FS
* BlockBasedFS
* Ext2FS
