BAN: Implement Ext2 file unlinking

Ext2 inodes can now be unlinked from directories and after last
inode closes (destructor gets called) we check if link count is 0
and cleanup the inode from filesystem

kernel/include/kernel/FS/Ext2/FileSystem.h

@@ -58,7 +58,7 @@ namespace Kernel
 		BAN::ErrorOr<void> initialize_root_inode();
 
 		BAN::ErrorOr<uint32_t> create_inode(const Ext2::Inode&);
-		BAN::ErrorOr<void> delete_inode(uint32_t);
+		void delete_inode(uint32_t);
 		BAN::ErrorOr<void> resize_inode(uint32_t, size_t);
 
 		void read_block(uint32_t, BlockBufferWrapper&);
@@ -68,6 +68,7 @@ namespace Kernel
 		BlockBufferWrapper get_block_buffer();
 
 		BAN::ErrorOr<uint32_t> reserve_free_block(uint32_t primary_bgd);
+		void release_block(uint32_t block);
 
 		BAN::HashMap<ino_t, BAN::RefPtr<Ext2Inode>>& inode_cache() { return m_inode_cache; }
 

kernel/include/kernel/FS/Ext2/Inode.h

@@ -13,6 +13,8 @@ namespace Kernel
 	class Ext2Inode final : public Inode
 	{
 	public:
+		~Ext2Inode();
+
 		virtual ino_t ino() const override { return m_ino; };
 		virtual Mode mode() const override { return { m_inode.mode }; }
 		virtual nlink_t nlink() const override { return m_inode.links_count; }
@@ -32,6 +34,7 @@ namespace Kernel
 		virtual BAN::ErrorOr<void> list_next_inodes_impl(off_t, DirectoryEntryList*, size_t) override;
 		virtual BAN::ErrorOr<void> create_file_impl(BAN::StringView, mode_t, uid_t, gid_t) override;
 		virtual BAN::ErrorOr<void> create_directory_impl(BAN::StringView, mode_t, uid_t, gid_t) override;
+		virtual BAN::ErrorOr<void> unlink_impl(BAN::StringView) override;
 		
 		virtual BAN::ErrorOr<BAN::String> link_target_impl() override;
 
@@ -45,6 +48,8 @@ namespace Kernel
 
 		BAN::ErrorOr<void> link_inode_to_directory(Ext2Inode&, BAN::StringView name);
 
+		void cleanup_from_fs();
+
 		BAN::ErrorOr<uint32_t> allocate_new_block();
 		BAN::ErrorOr<void> sync();
 

kernel/include/kernel/FS/Inode.h

@@ -91,7 +91,7 @@ namespace Kernel
 		BAN::ErrorOr<void> list_next_inodes(off_t, DirectoryEntryList*, size_t);
 		BAN::ErrorOr<void> create_file(BAN::StringView, mode_t, uid_t, gid_t);
 		BAN::ErrorOr<void> create_directory(BAN::StringView, mode_t, uid_t, gid_t);
-		BAN::ErrorOr<void> delete_inode(BAN::StringView);
+		BAN::ErrorOr<void> unlink(BAN::StringView);
 
 		// Link API
 		BAN::ErrorOr<BAN::String> link_target();
@@ -109,7 +109,7 @@ namespace Kernel
 		virtual BAN::ErrorOr<void> list_next_inodes_impl(off_t, DirectoryEntryList*, size_t)	{ return BAN::Error::from_errno(ENOTSUP); }
 		virtual BAN::ErrorOr<void> create_file_impl(BAN::StringView, mode_t, uid_t, gid_t)		{ return BAN::Error::from_errno(ENOTSUP); }
 		virtual BAN::ErrorOr<void> create_directory_impl(BAN::StringView, mode_t, uid_t, gid_t)	{ return BAN::Error::from_errno(ENOTSUP); }
-		virtual BAN::ErrorOr<void> delete_inode_impl(BAN::StringView)							{ return BAN::Error::from_errno(ENOTSUP); }
+		virtual BAN::ErrorOr<void> unlink_impl(BAN::StringView)									{ return BAN::Error::from_errno(ENOTSUP); }
 
 		// Link API
 		virtual BAN::ErrorOr<BAN::String> link_target_impl()				{ return BAN::Error::from_errno(ENOTSUP); }

kernel/include/kernel/FS/RamFS/Inode.h

@@ -97,7 +97,7 @@ namespace Kernel
 		virtual BAN::ErrorOr<void> list_next_inodes_impl(off_t, DirectoryEntryList*, size_t) override;
 		virtual BAN::ErrorOr<void> create_file_impl(BAN::StringView, mode_t, uid_t, gid_t) override;
 		virtual BAN::ErrorOr<void> create_directory_impl(BAN::StringView, mode_t, uid_t, gid_t) override;
-		virtual BAN::ErrorOr<void> delete_inode_impl(BAN::StringView) override;
+		virtual BAN::ErrorOr<void> unlink_impl(BAN::StringView) override;
 
 	private:
 		static constexpr size_t m_name_max = NAME_MAX;

kernel/kernel/FS/Ext2/FileSystem.cpp

@@ -212,6 +212,40 @@ namespace Kernel
 		return BAN::Error::from_error_code(ErrorCode::Ext2_Corrupted);
 	}
 
+	void Ext2FS::delete_inode(uint32_t ino)
+	{
+		LockGuard _(m_lock);
+
+		ASSERT(ino <= superblock().inodes_count);
+
+		auto bgd_buffer = get_block_buffer();
+		auto bitmap_buffer = get_block_buffer();
+
+		const uint32_t inode_group = (ino - 1) / superblock().inodes_per_group;
+		const uint32_t inode_index = (ino - 1) % superblock().inodes_per_group;
+
+		auto bgd_location = locate_block_group_descriptior(inode_group);
+		read_block(bgd_location.block, bgd_buffer);
+
+		auto& bgd = bgd_buffer.span().slice(bgd_location.offset).as<Ext2::BlockGroupDescriptor>();
+		read_block(bgd.inode_bitmap, bitmap_buffer);
+
+		const uint32_t byte = inode_index / 8;
+		const uint32_t bit = inode_index % 8;
+		ASSERT(bitmap_buffer[byte] & (1 << bit));
+
+		bitmap_buffer[byte] &= ~(1 << bit);
+		write_block(bgd.inode_bitmap, bitmap_buffer);
+
+		bgd.free_inodes_count++;
+		write_block(bgd_location.block, bgd_buffer);
+
+		if (m_inode_cache.contains(ino))
+			m_inode_cache.remove(ino);
+
+		dprintln("succesfully deleted inode {}", ino);
+	}
+
 	void Ext2FS::read_block(uint32_t block, BlockBufferWrapper& buffer)
 	{
 		LockGuard _(m_lock);
@@ -255,8 +289,7 @@ namespace Kernel
 		const uint32_t lba = 1024 / sector_size;
 		const uint32_t sector_count = BAN::Math::div_round_up<uint32_t>(superblock_bytes, sector_size);
 
-		BAN::Vector<uint8_t> superblock_buffer;
+		auto superblock_buffer = get_block_buffer();
-		MUST(superblock_buffer.resize(sector_count * sector_size));
 
 		MUST(m_partition.read_sectors(lba, sector_count, superblock_buffer.span()));
 		if (memcmp(superblock_buffer.data(), &m_superblock, superblock_bytes))
@@ -266,7 +299,6 @@ namespace Kernel
 		}
 	}
 
-
 	Ext2FS::BlockBufferWrapper Ext2FS::get_block_buffer()
 	{
 		LockGuard _(m_lock);
@@ -334,6 +366,38 @@ namespace Kernel
 		return BAN::Error::from_error_code(ErrorCode::Ext2_Corrupted);
 	}
 
+	void Ext2FS::release_block(uint32_t block)
+	{
+		LockGuard _(m_lock);
+
+		ASSERT(block >= m_superblock.first_data_block);
+		ASSERT(block < m_superblock.blocks_count);
+
+		const uint32_t block_group = (block - m_superblock.first_data_block) / m_superblock.blocks_per_group;
+		const uint32_t block_offset = (block - m_superblock.first_data_block) % m_superblock.blocks_per_group;
+
+		auto bgd_buffer = get_block_buffer();
+		auto bitmap_buffer = get_block_buffer();
+
+		auto bgd_location = locate_block_group_descriptior(block_group);
+		read_block(bgd_location.block, bgd_buffer);
+
+		auto& bgd = bgd_buffer.span().slice(bgd_location.offset).as<Ext2::BlockGroupDescriptor>();
+		read_block(bgd.block_bitmap, bitmap_buffer);
+
+		const uint32_t byte = block_offset / 8;
+		const uint32_t bit  = block_offset % 8;
+		ASSERT(bitmap_buffer[byte] & (1 << bit));
+
+		bitmap_buffer[byte] &= ~(1 << bit);
+		write_block(bgd.block_bitmap, bitmap_buffer);
+
+		bgd.free_blocks_count++;
+		write_block(bgd_location.block, bgd_buffer);
+
+		dprintln("successfully freed block {}", block);
+	}
+
 	Ext2FS::BlockLocation Ext2FS::locate_inode(uint32_t ino)
 	{
 		LockGuard _(m_lock);

kernel/kernel/FS/Ext2/Inode.cpp

@@ -41,6 +41,12 @@ namespace Kernel
 		return result;
 	}
 
+	Ext2Inode::~Ext2Inode()
+	{
+		if ((mode().ifdir() && m_inode.links_count == 1) || m_inode.links_count == 0)
+			cleanup_from_fs();
+	}
+
 #define VERIFY_AND_READ_BLOCK(expr) do { const uint32_t block_index = expr; ASSERT(block_index); m_fs.read_block(block_index, block_buffer); } while (false)
 #define VERIFY_AND_RETURN(expr) ({ const uint32_t result = expr; ASSERT(result); return result; })
 
@@ -252,6 +258,21 @@ namespace Kernel
 		return {};
 	}
 
+	void Ext2Inode::cleanup_from_fs()
+	{
+		if (mode().ifdir())
+		{
+			// FIXME: cleanup entires '.' and '..' and verify
+			//        there are no other entries
+			ASSERT_NOT_REACHED();
+		}
+
+		ASSERT(m_inode.links_count == 0);
+		for (uint32_t i = 0; i < blocks(); i++)
+			m_fs.release_block(fs_block_of_data_block_index(i));
+		m_fs.delete_inode(ino());
+	}
+
 	BAN::ErrorOr<void> Ext2Inode::list_next_inodes_impl(off_t offset, DirectoryEntryList* list, size_t list_size)
 	{
 		ASSERT(mode().ifdir());
@@ -371,9 +392,16 @@ namespace Kernel
 
 		const uint32_t new_ino = TRY(m_fs.create_inode(initialize_new_inode_info(mode, uid, gid)));
 
-		auto inode = MUST(Ext2Inode::create(m_fs, new_ino));
+		auto inode_or_error = Ext2Inode::create(m_fs, new_ino);
+		if (inode_or_error.is_error())
+		{
+			m_fs.delete_inode(new_ino);
+			return inode_or_error.release_error();
+		}
 
-		MUST(link_inode_to_directory(*inode, name));
+		auto inode = inode_or_error.release_value();
+
+		TRY(link_inode_to_directory(*inode, name));
 
 		return {};
 	}
@@ -387,11 +415,18 @@ namespace Kernel
 
 		const uint32_t new_ino = TRY(m_fs.create_inode(initialize_new_inode_info(mode, uid, gid)));
 
-		auto inode = MUST(Ext2Inode::create(m_fs, new_ino));
+		auto inode_or_error = Ext2Inode::create(m_fs, new_ino);
-		MUST(inode->link_inode_to_directory(*inode, "."sv));
+		if (inode_or_error.is_error())
-		MUST(inode->link_inode_to_directory(*this, ".."sv));
+		{
+			m_fs.delete_inode(new_ino);
+			return inode_or_error.release_error();
+		}
 
-		MUST(link_inode_to_directory(*inode, name));
+		auto inode = inode_or_error.release_value();
+		TRY(inode->link_inode_to_directory(*inode, "."sv));
+		TRY(inode->link_inode_to_directory(*this, ".."sv));
+		
+		TRY(link_inode_to_directory(*inode, name));
 
 		return {};
 	}
@@ -496,6 +531,42 @@ needs_new_block:
 		return {};
 	}
 
+	BAN::ErrorOr<void> Ext2Inode::unlink_impl(BAN::StringView name)
+	{
+		ASSERT(mode().ifdir());
+
+		auto block_buffer = m_fs.get_block_buffer();
+
+		for (uint32_t i = 0; i < blocks(); i++)
+		{
+			const uint32_t block = fs_block_of_data_block_index(i);
+			m_fs.read_block(block, block_buffer);
+
+			blksize_t offset = 0;
+			while (offset < blksize())
+			{
+				auto& entry = block_buffer.span().slice(offset).as<Ext2::LinkedDirectoryEntry>();
+				if (entry.inode && name == entry.name)
+				{
+					auto inode = TRY(Ext2Inode::create(m_fs, entry.inode));
+					if (inode->nlink() == 0)
+						dprintln("Corrupted filesystem. Deleting inode with 0 links");
+					else
+						inode->m_inode.links_count--;
+
+					TRY(sync());
+
+					// FIXME: This should expand the last inode if exists
+					entry.inode = 0;
+					m_fs.write_block(block, block_buffer);					
+				}
+				offset += entry.rec_len;
+			}
+		}
+
+		return {};
+	}
+
 #define READ_OR_ALLOCATE_BASE_BLOCK(index_)											\
 	do {																			\
 		if (m_inode.block[index_] != 0)												\

kernel/kernel/FS/Inode.cpp

@@ -97,13 +97,13 @@ namespace Kernel
 		return create_directory_impl(name, mode, uid, gid);
 	}
 
-	BAN::ErrorOr<void> Inode::delete_inode(BAN::StringView name)
+	BAN::ErrorOr<void> Inode::unlink(BAN::StringView name)
 	{
 		LockGuard _(m_lock);
 		Thread::TerminateBlocker blocker(Thread::current());
 		if (!mode().ifdir())
 			return BAN::Error::from_errno(ENOTDIR);
-		return delete_inode_impl(name);
+		return unlink_impl(name);
 	}
 
 	BAN::ErrorOr<BAN::String> Inode::link_target()

kernel/kernel/FS/ProcFS/FileSystem.cpp

@@ -40,7 +40,7 @@ namespace Kernel
 	void ProcFileSystem::on_process_delete(Process& process)
 	{
 		auto path = BAN::String::formatted("{}", process.pid());
-		MUST(m_root_inode->delete_inode(path));
+		MUST(m_root_inode->unlink(path));
 	}
 
 }

kernel/kernel/FS/RamFS/Inode.cpp

@@ -263,8 +263,9 @@ namespace Kernel
 		return {};
 	}
 
-	BAN::ErrorOr<void> RamDirectoryInode::delete_inode_impl(BAN::StringView name)
+	BAN::ErrorOr<void> RamDirectoryInode::unlink_impl(BAN::StringView name)
 	{
+		// FIXME: delete inodes contents only after they are closed
 		for (size_t i = 0; i < m_entries.size(); i++)
 		{
 			if (name == m_entries[i].name)