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068fc8f914
Currently struct btrfs_inode has a key member, named "location", that is either: 1) The key of the inode's item. In this case the objectid is the number of the inode; 2) A key stored in a dir entry with a type of BTRFS_ROOT_ITEM_KEY, for the case where we have a root that is a snapshot of a subvolume that points to other subvolumes. In this case the objectid is the ID of a subvolume inside the snapshotted parent subvolume. The key is only used to lookup the inode item for the first case, while for the second it's never used since it corresponds to directory stubs created with new_simple_dir() and which are marked as dummy, so there's no actual inode item to ever update. In the second case we only check the key type at btrfs_ino() for 32 bits platforms and its objectid is only needed for unlink. Instead of using a key we can do fine with just the objectid, since we can generate the key whenever we need it having only the objectid, as in all use cases the type is always BTRFS_INODE_ITEM_KEY and the offset is always 0. So use only an objectid instead of a full key. This reduces the size of struct btrfs_inode from 1048 bytes down to 1040 bytes on a release kernel. Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.