72a69cd030
Currently we use u16 bitmap to make 4k sectorsize work for 64K page size. But this u16 bitmap is not large enough to contain larger page size like 128K, nor is space efficient for 16K page size. To handle both cases, here we pack all subpage bitmaps into a larger bitmap, now btrfs_subpage::bitmaps[] will be the ultimate bitmap for subpage usage. Each sub-bitmap will has its start bit number recorded in btrfs_subpage_info::*_start, and its bitmap length will be recorded in btrfs_subpage_info::bitmap_nr_bits. All subpage bitmap operations will be converted from using direct u16 operations to bitmap operations, with above *_start calculated. For 64K page size with 4K sectorsize, this should not cause much difference. While for 16K page size, we will only need 1 unsigned long (u32) to store all the bitmaps, which saves quite some space. Furthermore, this allows us to support larger page size like 128K and 258K. Signed-off-by: Qu Wenruo <wqu@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 Restructured Text 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.