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Kernel: Deemphasize inode identifiers

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These APIs were clearly modeled after Ext2FS internals, and make perfect sense
in Ext2FS context. The new APIs are more generic, and map better to the
semantics exported to the userspace, where inode identifiers only appear in
stat() and readdir() output, but never in any input.

This will also hopefully reduce the potential for races (see commit c44b4d61f3).

Lastly, this makes it way more viable to implement a filesystem that only
synthesizes its inodes lazily when queried, and destroys them when they are no
longer in use. With inode identifiers being used to reference inodes, the only
choice for such a filesystem is to persist any inode it has given out the
identifier for, because it might be queried at any later time. With direct
references to inodes, the filesystem will know when the last reference is
dropped and the inode can be safely destroyed.
This commit is contained in:
Sergey Bugaev 2020-06-24 23:35:56 +03:00 • committed by Andreas Kling
parent c689be0dbc
commit df66c28479
Notes: sideshowbarker 2024-07-19 05:23:53 +09:00
12 changed files with 133 additions and 160 deletions
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37
Kernel/FileSystem/Ext2FileSystem.cpp
View file

@ -150,9 +150,9 @@ const char* Ext2FS::class_name() const
return "Ext2FS";
}
InodeIdentifier Ext2FS::root_inode() const
NonnullRefPtr<Inode> Ext2FS::root_inode() const
{
return { fsid(), EXT2_ROOT_INO };
return *get_inode({ fsid(), EXT2_ROOT_INO });
}
bool Ext2FS::find_block_containing_inode(unsigned inode, unsigned& block_index, unsigned& offset) const
@ -935,7 +935,14 @@ bool Ext2FSInode::write_directory(const Vector<FS::DirectoryEntry>& entries)
return static_cast<size_t>(nwritten) == directory_data.size();
}
KResult Ext2FSInode::add_child(InodeIdentifier child_id, const StringView& name, mode_t mode)
KResultOr<NonnullRefPtr<Inode>> Ext2FSInode::create_child(const String& name, mode_t mode, dev_t dev, uid_t uid, gid_t gid)
{
if (mode & S_IFDIR)
return fs().create_directory(identifier(), name, mode, uid, gid);
return fs().create_inode(identifier(), name, mode, 0, dev, uid, gid);
}
KResult Ext2FSInode::add_child(Inode& child, const StringView& name, mode_t mode)
{
LOCKER(m_lock);
ASSERT(is_directory());
@ -944,7 +951,7 @@ KResult Ext2FSInode::add_child(InodeIdentifier child_id, const StringView& name,
return KResult(-ENAMETOOLONG);
#ifdef EXT2_DEBUG
dbg() << "Ext2FSInode::add_child(): Adding inode " << child_id.index() << " with name '" << name << "' and mode " << mode << " to directory " << index();
dbg() << "Ext2FSInode::add_child(): Adding inode " << child.index() << " with name '" << name << "' and mode " << mode << " to directory " << index();
#endif
Vector<FS::DirectoryEntry> entries;
@ -966,17 +973,14 @@ KResult Ext2FSInode::add_child(InodeIdentifier child_id, const StringView& name,
return KResult(-EEXIST);
}
auto child_inode = fs().get_inode(child_id);
if (child_inode) {
result = child_inode->increment_link_count();
if (result.is_error())
return result;
}
result = child.increment_link_count();
if (result.is_error())
return result;
entries.empend(name.characters_without_null_termination(), name.length(), child_id, to_ext2_file_type(mode));
entries.empend(name.characters_without_null_termination(), name.length(), child.identifier(), to_ext2_file_type(mode));
bool success = write_directory(entries);
if (success)
m_lookup_cache.set(name, child_id.index());
m_lookup_cache.set(name, child.index());
return KSuccess;
}
@ -1405,11 +1409,6 @@ KResultOr<NonnullRefPtr<Inode>> Ext2FS::create_inode(InodeIdentifier parent_id,
return KResult(-ENOSPC);
}
// Try adding it to the directory first, in case the name is already in use.
auto result = parent_inode->add_child({ fsid(), inode_id }, name, mode);
if (result.is_error())
return result;
auto blocks = allocate_blocks(group_index_from_inode(inode_id), needed_blocks);
ASSERT(blocks.size() == needed_blocks);
@ -1458,6 +1457,10 @@ KResultOr<NonnullRefPtr<Inode>> Ext2FS::create_inode(InodeIdentifier parent_id,
auto inode = get_inode({ fsid(), inode_id });
// If we've already computed a block list, no sense in throwing it away.
static_cast<Ext2FSInode&>(*inode).m_block_list = move(blocks);
auto result = parent_inode->add_child(*inode, name, mode);
ASSERT(result.is_success());
return inode.release_nonnull();
}