TmpFS

[bugaevc]

This is an FS that stores all of its contents directly in memory.
It's mounted on /tmp by default.

[awesomekling]

This is really cool! Let's improve some things :)

[awesomekling]

This can just be

void TmpFS::register_inode(TmpFSInode& inode)

We're not passing ownership of the TmpFSInode, it just needs to be a live, non-null object.

[bugaevc]

Ah, right, I was thinking of a different refcounting scheme (where refcount is stored by the smart pointer outside of the object)

[awesomekling]

This can also be written as

return m_inodes.get(identifier.index()).value_or(nullptr);

[bugaevc]

That's a nice shortcut, but it doesn't seem to work here; m_inodes stores NonullRefPtr<Inode>s, so we cannot use nullptr as a default value; the conversion to RefPtr<Inode> is happening after we get it from the map.

[awesomekling]

No need to default-initialize objects like this:

Suggested change

	InodeMetadata metadata {};
	InodeMetadata metadata;

[awesomekling]

Let's add an override for fs() in TmpFSInode that does the casting for us:

TmpFS& fs() { return static_cast<TmpFS&>(Inode::fs()); }
const TmpFS& fs() const { return static_cast<const TmpFS&>(Inode::fs()); }

That way we'll always get the right type when we call fs() inside TmpFSInode

[awesomekling]

No need to initialize this explicitly; a RefPtr is always nullptr by default.

[awesomekling]

Here's the most important change to make: this should be a KBuffer.
ByteBuffer uses kmalloc() for its storage, taking memory from the tiny little kernel heap.
KBuffer takes memory from the global page allocator, which has lots more of it :)

[bugaevc]

Done, plus some other tweaks, please review again 😄

[awesomekling]

I think this look good enough to merge, but we'll probably need to rethink how truncation works if we have multiple processes mmapping the file.